CA2407161A1 - Devices for physiological fluid sampling and methods of using the same - Google Patents

Abstract

Methods and devices are provided for determining a suitable site for sampling physiological fluid. In the subject methods, a potentially suitable physiological sampling site is selected, the fluid flow of the site is characterized and the site is then determined to be suitable based on the whether the site has high or low flow. Suitability may also be determined based on the type of sample obtainable firm the silt, where the order of the above-described steps may be altered. The subject devices include at least one silo flow characterization element for determining the flow characteristics of a potential physiological sampling site and/or at least one sample type characterization element for determining whether the vasculature is arterial, venous or neither, i.c., an interstitial fluid sampling site.
The subject methods and devices are particularly suited for use in the detection of physiological sampling sifts in the fingers, arms, legs, earlobes, heels, feet, nose: and toes.
Also provided are kits that include the subject devices for use in practicing the subject methods.

Description

!1 CA 02407161 2002-10-09 DEVICES lv'4R THYSf4LOGICAI, h't.UiD SAMPLING AND METHODS Oh' USING THE SAME
IN 1'RODZJ(:TIAN
f~iBLD Ol: T~IR INVENTION
The field of this invention is physiological fluid sampling and more particulsriy devices and methods of use thereof for non-invasively determining suitable physiological ftuid sampling sites.
HACKGR4UND OF Tlil; INVENTION
Analyze concentration characterization in physiological samplos is of ever increasing importance to today's society. Such assays find use in a variety of application settings, 1S including clinical laboratory testing, home testing, ere., where the results of such testing play a rromincnt role in the diagnosis and management of a vat7ety of disease conditions.
Analyzes of interest include glucose for diahetes management, cholesterol for monitoring cardiovascular conditions, and the lire. In response to this growing importance of analyte concentration charactc~ization, a variety of analyze cuncenlration characterization protocols and devices for both clinical and home testing have been developed.
1'o determine the concentration of an analyte in a physiological sample, a physiological sample must first be obtained from a site suitable for the particular lest to be performed on the sample. For example, certain tests t~equire a specific volume of interstitial fluid as the sample and olhem require a specific volume of blood, blood derivatives and the ~S tike as the sample. As such, depending on the type of sample required by the test, a site which expresses the requisite volume oC the particular sample type must first be located.
The curtcnt processes of physiological fluid sample collection have certain drawbacks. First and foremost, such processes or techniques are associated with a significant amount of pain, hurthermore, a patient may need to cndum multiple skin-piercings in order ~0 to find one suitable sampling site or enough sites to collect the requisite amount of sample.
The pain associated wish sample collection may have serious adverse consequences for those who require analyze characterizations tea be performed, e.g., analyle detection and/or concentration determinations. Fc~r instance, patients who require frequent analyze concentration determinations may not adhere to their requisite testing protocols due t~ this associated pain and it is not uncommon for patients who require frequent monitoring of an r~nalyte to simply avoid monitoring the analyze of interest because of the pain involved in sample collection. With diabetics, for example, the failure to measure. their glucose level on a prescribed basis results in a lack of infonnation necessary to properly control the Icvel of S slucose. Uncontrolled glucose levels can be very dangerous and even life threatening.
1 ypically, and more typically for those perfonrting home testing protocols, common sampling sites include the fingers. Recently however, the sum has become a popular alternative sampling site bEcause its nerve beds alt= sparser than in the fingers, thus minimizing paint somewhat. However, collecting a physiological fluid sample from the arm !0 has disadvantages as welt. Most notably, there are pttrticular anatomical and physiological aspect, of the arm which make pltysioiogical fluid collection from it difficult.
Small veins and arteries typically reach to within about 1 mm of the surface of the skin; arterioles ascend vertically Irom these to within about O.S mm of the surface where they branch out and become capiilarics which reach to within about 0.25 mm of the surface.
15 The capillaries terminate in venuole.~ which carry blood back to veins.
Each ascending artc~~iole feeds a maze of bt~dnched arteriolc;s, capillaries and vcnuoles, where each groupings of capillaries, venuoles and arterioles have horizontal dimensions on the order of about 2-7 mm. Skin pieraing to obtain brood from these stntctures is usually done to a depth of about 1 mm or less. Spaces exist between these areas when the arterioles, venuolcs and capilladcs 2U at~c non-existent, spt<rse or not sufficiently engorged with blood.
When randomly choosing a sampling site, a patient may encounter a substantially high fluid flow arcs or a substantially low fluid flow area, Oftentimes, an adequate or minimum volume of sample is required in order to peuonn a particular test accurately. Thus, t f such a minimum volume were not collected from a first skin piercing, the patient would be 25 required to continually pierce the skin until the minimum volume were obtained. It can be appreciated that this process of multiple skin piercings would contribute to more pain to the patient.
Furthermore, certain tests require a particular sample type in order to perform an accurate test. tfowcver, when randomly choosing a site to pierce the skin, a patient may 30 encoumer ( 1 ) a region with substantially few or no artcrlcs or veins, and thus a good source of interstitial fluid, but not a good source of arterial or venous blood, (2) a region rich in arteries and thus a good source of arterial blood, but not a good source of venous blood ctr interstitial fluid, (3) a region rich in veins and thus a good source of venous blood, but not a good source of arteria) blood or interstitial fluid, and (A) a combination of l-3 which may not _z.

be suitable for any test. Blood from capillaries tends to be arterial in nature. Thus, if sample is ultimately obtained from a site such as site (!) above for a test which reduires a blood sample, l.c., a site with few or no sources of arterial ~r venous blood, the sample may be diluted with or composed entirely of intcrstidal fluid which may skew results of the pasticular test. hor instance, it is known that arterial samples, venous samples and interstitial Cluid sarnplcs may have different analyte concentrations, e.g., arterial blood can have as much as 7 mg/dl higher gluc;osc levels than does venous blood. 2'hus, it can be appreciated that the ability to choose a suitable sampling site is very important, furthermore, if a type of sample is obtained that is not appropriate for a particular testing protocol, the patient may be required to pierce the skin achlitional times, again contributing more pain to the patient.
As such, there is continued interest in the development of new devices and methods for use for non-invasively determining whether, once the skin is pierced, the patient will be able to obtain the appropriate sample volume from the site for the particular test to be performed and also whether an appropriate sample type can be obtained from the site. O!
pzt~tic;ular interest would be the development of such devices, and methods of use thereof, which r,re efficient and simple to use. Such devices integrated with at least one skin-pici~cing element for piercing the skin once an appropriate sampling site has been non-invasively determined andlor integrated with a magent test strip for determining the concentration of an analytc in the sample would also be of particular interest.
I3clcvant I.iteraturc References of interest include: Bcrwdcsca et al., Bloengineerirtg of the Skin:
Cutanevus Blood Tlow and Frythrnca, CRC Press, (I995); C.R. Skoglund, Vasodilatation irt llttrrran Skin Induced by Low-Arnplittccfe High-Frequency Vlbratiort, Clin.
Phys. pp. 36t-372 (1989); Van Asscndclft, O.W., Spectrophotnmehy ofHmttoglobiu Derivatives, Charles Thomas> pub,, 1970 arid Nilsson, G., et a1. laser Doppler Flowrrzetry A New Technique for Nnnlnvasive Assessment of Skirt Rlovd Flnw> Cosmetics & Toiletries, vol. 99, pp. 97-108, Mar. 1984.
StJMMAItY Ot' TNt: INVENTION
Methods and devices are provided fur determining a suitable site far sampling physiological fluid. In the subject methods, a potentially suitable physiological sampling site is selected, the fluid t7ow of the site is characterized and the site is then dEtermirtcd to be suitsible based on the whether the sift has high or low flow. Suitability may also be CA 02407'161 2002-10-09 dctennined based on the type of sample obtainable from the site, where the order of the above-described steps may be altared. The subject devices include at least one site flow characterisation element for determining the flow characteristics of a potential physiological sampling site andlor at (cast one sample type characterisation element for dctennining whether the vasculature is arterial, venous or neither, i.c., an interstitial fluid sampling site, The subject methods and devices are particularly suited for use in the detection of physiological sampling sites in the fingers, arms, legs, earlobes, heels, feet, nose and toes.
Also provided are kits that include the subject devices for use in practicing the subject methods.
!U
.BRIEF DESCRIpTiON$ OF 1 HE DRAWINGS
Figure 1 shows a schematic block diagram representing the subjcxt methods.
Figtn~e 2 shows a graph of optimal measurements of the subject invention correlated to specific sample type obtainable.
higure 3 shows an embodiment of an exemplary device of the subject invention showing a cut-away view of the proximal portion of the device.
rigure 4 shows an embodiment of an exemplary proximal portion of a device of subject invention.
~0 Figure 5 shows a graph correlating temperature at a site to the amount of sample expressed therefrom.
DETAiLtab DL~SCRIt"TrON OF THR INVENT10N
Methods and devices are provided for determining a suitable site for sampling physiological fluid. In the subject methods, a potentially suitable physiological sampling sift is selected, the fluid flow of the site is characterized and the site is then determined to be suitable based on the whether the site has high or low flow. Suitability may also be determined based on the type of sample obtainable from the site, where the order of the above-described steps may be altemd. The subject devicos include at least ono site flow characterization clement for determining the flow characaeristics of a potential physiohgical sampling site andlor at Icast one sample type characterization element for determining whether the vasculature is arterial, venous ar neither, i.c., an interstitial fluid sampling site.
The subject methods and devices sre particularly suited for use in the detection of physiological sampling sites in the fingers, arms, legs, earlobe', heels, feet, nose and toes.
-a-Also provided are kits that include the subject devices for use in practicing the subject methods. Tn further descilbing the subject invention, the subject methods will be described first, followed by a review of the subject devices for use in practicing the subject methods.
Before the present invention is described, it is to be understood that this invention is not limited to the particular embodiments described, as such may, of course, vary. It is also to be a»derstood that the terminology used herein is for the putrose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower Limit unless the context cicarly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention.1'he upper and lower limits of these smaller ranbes may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits ate also included in the invention, Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understcwd by one of ordinary skill in the art to which this invention belongs, Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.
1t must be noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.
Thus, fc>r example, reference to "a vessel" includes a plurality of such vessels and reference 2S to "the device" includes referc:nee to one or morn devices and equivalents thet~eof known to those skilled i» the art, and s~ forth.
All publications mentioned herein are incorporated herein by reference to disclose and describe the rttethods andJor mateaals in connection with which the publications are cited. The Publications discussed herein arc provided solely for their disclosure prior to the fitins date of the present application. Nothing herein is to be constmed as an admission that the prcaent invention is not entitled to antedate such publication by vinue of prior invention.
rutthcr, the dates of publication provided may be different from the actual publication dates which may need to be independently confirnted.

nt~rHn».s As summarized above, the subject invention provides methods for determining a suitable site far sampling physiological fluid and in some embodiments also provides methods for piercing the skin at the suitable site and further determining the presence and/or concentration of at least one analytr~ in a sample collected from the site, usually automatically. The subject methods find use in the sampling of a wide variety of physiological fluids, where such physiological fluids include, but are not limited to, interstitial fluids, blood, blood Fractions and constituents thereof, and the like. When the determination of analyze concentration is employed, the subject methods find use in the determination of a wide variety of different analyte concentrations, where representative analytes include glucose, cholesterol, lactate, alcohol, and the like. In many embodiments, the subject methods are employed to determine the glucose concentration in physiological fluid.
The subject methods detetlnine a suitable sampling site, where suitable sites may be located on various regions of the body, including, but not limited to, the fingers, arms, legs, earlobos> heels, feet, nose and toes. Where, for example, blood is the targeted physiological sample, a potential sampling site is characterized as suitable if the site has a high flow of arterial or venous blood. Iiowever, where interstitial fluid or the like is the target physiological sample, a potential sampling site is characterized as suitable if the site has no or substantially no or low amount of arterial or venous blood, Alternatively, the site may be determined la be unsuitable for sratnpling either blood or interstitial fluid.
rigure 1 provides a schematic block diagram representing the methods of the pre~cent invention.1t will be apparent that the steps recited herein may be practiced in any order and certain steps may be subtracted or added, as deemed appropriate for a particular intended use. I=ar example, it may be appropriate to only characterize the flow of the potential site or it may be appropriate to only characterize the type of sample obtainable from the site, Still further, it might be appropuate to characterize the type of sample obtainable from the site first, followed by a characterisation of the flow, etc. The subject methods will be described herein as serial, i.e., performing site flow characterization first and/or performing sample 3~U type characterization second, where such a s~;rial description is by way of example only and not limitation. It is to be understood, and will he apparent, that any seduence of steps or subtractions and/or additions of such stops is contemplated by this invention.
Turning now to the Figures, Figure 1 is a flow chatrt of the subject methods used to determine a suitable sampling site. The first step in the subject methods is t4 select a _(_ potentially suitable physiological fluid sampling site (step 1). As described above, the potentially suitable situ is typically on the fingers, arms, legs, earlobes, hxls, feet, nose and toes, usually on the fingers or arms. Flow characterization is then performed, in other wows, a determination of whether the site is a high flow site or a low flow site is made (step 2). The appropriateness of the site for a particular test is then determined (steps 3 and 4). Tf the site is found inappropriate, another potentially suitable site is then selected (return to step 1). lif appropriate, sample type characterisation may then be performed (steps 5 and 6). More specifically, a potential site is then characterized as having the ability to produce or exprcas substantially arterial sample, substantially venous sample or neither, i.e., substantially interstitial fluid.11~e appmpriatcncss of the sample type for a particular test is then determined (step 7). If the site is found inappropriate, another potentially suitable sire is then selected (re;turn to step I). In certain embodiments, once the site is deterzrrined to be suitable for a particular testing protocol, the target physiological sample is accessed and collected from the site (steps 8 and 9). The prrsence and/or concentration of one or more analytes in the sample may also be determined by the subject methods, often times automatically (step 10).
1. aIITE ~'I~W CIIAJ~G'T~'Rl9rITll)N
As described above, the subject methods include the flow charncterizalion of a pat~ntially suitable sampling site.1n other words, the flow or flow rate or velocity of the potential site is characterized, where a high flow rata will yield relatively larger sample volumes as compared to a low flow rate site. A variety of methodx rnay be used to determine the flow characteristics of a potential site, where temperature determination andlor red blood cell ("RBC") characterization such as RBC flux, as will be described below, are of particular interest. Using temperature, for cxatnple, high temperature is associated with high flow and tow temperature is associated with low flow. In the case of RBC
characterization, e.g., RBC
flux, a high RRC flux is associated with high flow and tow RBC
characterisation, e.g., RBC
flux, is associated with low flow. Each of these methods will now be described in greater detail.
A. Ten:oer~rtu~e C~g~r~~,terizatin~
1n many embodiments of the subject methods, flow characterization, i.e., characterising the flow or flow rRte or velocity of s potential site, is detezmined by measuring the temperature of a potential site, on the principle that higher fluid flow is associated with higher temperature than a relatively lower flow of fluid would be.
Accordingly, the temperature of a site is determined, where such a temperature may include one or more measurements, c.g., a plurality of measurements may be made and a statistically relevant value (mean, median, etc.) may be determined. Regardless of the number of S mcasurcmerrts made at a potential site, a temperature value or signal relating to the Lemperatui~c is determined, where the temperature or value or signal associated therewith may then be Compared to a predetermined value. Per example, if a temperature were determined to be above a predetermined value typically ranging fram about 30.5°C to 35°C, usually from about 31 °C to 32°C, for example, the site would be determined to have a high (low. Alternatively, if the temperature were to fall below a predetermined value, such as below a range that is typically from about 29°C to 30.5°C and usually from about 29°C to 30°C, the site would be determined to have a low flow. Alternatively, or in addition to the above method employing a predetermined value to which the measured value is compared, in those instances where the best avt~ilable site is sought amongst a plurality of sites tested, 1S i.e., the most appropriate site in relation to other sites tested, the temperature value may be compared to other sites' temperatures.
This temperature measurement method may be in place of, or in addition to, other flow characterization methods, e.g., red blood cell flux, as will be described below. 1n those embodiments where the temp~,~rature measurement is in addition to other flow characterization methods, the temperature measurement may be performed before, during or at the same time as the other method(s).
Typically, this temperature characterization occurs in about O.S to 180 seconds and mare usually in about 0.75 to 60 seconds, but usually takes no mot~c than about 10 seconds.
More specifically, a temperature sensor such as a thermocouple, c.g., a thertnocouplc 2S associated with the subject devices 1s will be descubed below, measures the temperature of the sampling site. Such a measurement may be processed by a mictbproccssor working under the control of to software program. The measurement is made, communicated to the InlCropfOCCSSOr and the microprocessor may perform all the steps, calculations and comparisons necessary to determine the flow characteristics of a site.

N. X !3C Charactert;~a~inn In place of, or in addition tn, the above described temperature methods, the flow of a potential site may be characteri~cd by determining the RBC character of the site, e.g., 1:13C
_g.

flux of the site.1n other words, a determination of a high RHC flux corresponds to high flow and a determination of a low RBC flux corresponds to row flow, as mentioned above.
'ho determine flow based on RBC characteristics, techniques based upon the frequencies of light or more pru-ticularly the change in the frequencies of lisht as the light encounters objects in its path such as RBCs, may be used. Far example, techniques employing I~appler flowmetry method..s may be employed, where I>oppler flowmetry is well known in the alt and includes the transmission and measurement of light, i.e., laser Doppler flawmetry {sec for example t3erar~lesca et al., l3io~enganeerin~ of tJre Skin:
Cutaneous Blood Flow a~rcf Erytfunea, CRC Press, (1995)). RBC characterization may be in addition to, or in place of, other site flow characterization methods. Where RBC charactcr7zation is in addition to other methods, the methods may be performed at the same or different times.
As mentioned, generally the subject RBC characte»ration methods measure the change in frequency of light waves, i.e., the change in frequency that light waves undergo when reflected by moving oUjects such as RBCs. Typically, skin is irradiated with coherent, single wavelength light which penetrates to a depth dependent on the wavelength of the light (the longer the wavelength, the deeper the penetration). A shoat distance away, light scattered back from the underlying tissue is detected by a broadband photodetector (the larger the distance between the source and detector, the deeper the tissue being observed).
light which has scattered back from immobile objects is the same frequency as the original illuminating beam. Light which is scattered back tram moving objects, such as Rl3Cs hawing in blood vessels, has a slightly shitted wavelength, with the shift dependant on the velocity of the: moving objects. 'the shifted and unshifted light returning to the photodetector interacts in such a manner as to produce a low frequency (typically 0-20 kHz) oscillation or beat in the detected sisnal. The oscillating or AC component of the signal thus contains information about the velocity of flow of blood cells, while the average (DC) magnitude of the signal contains information about the total amount of light absorption and scaue»ng in the tissue (which may correlate with the tott~l amount of bland, both flowing and static, if the wavelength used is one where hcrnoglobin absorbs strongly).
'Thus, a large average absorbance of light in ranges from about 450 nm to 600 nm or 3U 854 nm to 950 nm indicates a high concentration of reel blood cell-containing vessels, whether or not there was I7ow, where such a high concentration of red blood cell-containing vessels indicates a high concentration of arterioles, vcnuoles or capillaries.
The AC signal is processed so that its power versus its frequency relationship is detennined.
The integral of this relationship between some lower and upper frc;quency bounds (e.g., 5 and 20 kHx) is _9_ determined, where the rate of flow increases as this integral increases. This integral is not completely linear with respect to flow, since higher frequencies are more sensitive to flow than lower ones. Therefore, outputs proportional to flow arc employed, such as RBC flux.
ror example, formulas such as the formula r RI3C flux = ~fE'(f)df -N /i2 where f represents the shifted frequency, ft and f" represent the lower and upper cutoff frequeneiec, P(1~ is the power at frequency f, N is a voltage offset and i is the mean photocurrent. RBC flux, as is known in the an (sec for example Bcrardcsca et al., Dioertgirrcerireg of the Skin: Cutmtrous 131nad Flow and Eryrhmea, CRC Press, (1995)), may be used to generate outputs proportional to flow. The quamity or rather the magnitude of the RBC flux, as defined by the above-described formula, is substantially proportional to flow rate, where a high RBC flux corresponds to a high flow rate and a low RBC flux concsponds to a low RI3C flux.
AccoWingly, in the present invention, light at a wavelength in the range from about 400 nm to about 1?OU nm, usually from about 450 nm to 800 nm is emitted from a light source such as a laser or the like and directed at the sample site, where such sources of light may be activated manually or automatically. The intensil:y of reflected light (the light reflected tram n;d blood cells), and more specifically the change with time of the light, is measured and a value related to the character of the RBCs of the site, such as RBC flux, is determined. Such measurements may be fed into a microprocessor working under the contml of a software program, where the microprocessor then determines the value related to the character of the RBCs of the site, such as RBC flux, which is proportional to the flow rate of a Cluid in a vessel.
Tn one instance, the RBC characlcrixation value, e.g., the RBC flux value or a statistically relevant value corresponding to the 12BC flux value may be compared to a predetermined value, e,g., by means of a microprocessor. A comparison may then be made such that of the RBC value is above the predetermined value, the; silo is characta~zed as having a high flow rate and if the RBC value is below the predetermined value, the site is clt~racteri~ed as having a low flow rate. Alternatively, the best site (a highly appropriate site) amongst a plurality of potential siteR tested may he determined by comparing RBC values of other tasted riles.

_ . . __-; ; - ~, ., Typically, RBC characterization is performed in about 1 to 180 seconds, usually in about 2 to 90 seconds and more usually in about 3 to b0 seconds.
1l. SAMFLl! I~YPKCHARACI'BRIZ~tTION
As described, the subject methods include sample type characterization, where such methods determine whether a site is capable of expressing or producing substantially artciial sample, substantially venous sample or substantially interstitial fluid. More specifically, when used in conjunction with the above described methods for characterizing flow, the plriicular sample type obtainable from a potential site can be charactcriz~d in regards to flow rotes and sample type. Tn other words, a potential sampling site can be characterized as (1) high flow rate, arterial/capillary, (5a of Figure 1) (2) high flaw rate, vinous, (5b of Figure 1), (3) law flow rate, artcrial/capillary or venous, (6b of Figure 1) or (4) low flow rate, interstitial t7uid (6a of Figure 1). As noted above, the sample type charac;leriration may be in addition to, or in place of, flow characterization, where the order of these may be changed or 1 S altered.
A variety of tnethods may be used to characterize the sample type obtainable from a potential sarnpling site, where pulse characterization and hetnoglobin charactcuzation are of particular interest, For example, if a high flow site is characterized as having a high pulse and/or a high oxygenated hemoglobin/deoxygenated hemoglobin ratio (where heroin IlbO
represents oxygenated hemoglobin and hlb represents deoxygenated hemoglobin and Hb0/Hb represents the ratio thereof), it is determined to be a site having substantially high flowing arterial sample (5a of rigurc 1) and if a high flow site is characterized as having low Pulse or law Hb0/Hb ratio, it is determined to be a site having substantially high flowing venous sample (5b of Figure 1 ). Furthermore, it a law flow sire is characterised as having a high total hemoglobin level or value it is determined to be a site of low flow at~terial, capillary or venous sample (lib of Figure 1) and if a low flow site is characterized as having a low total hemoglobin level or value it is determined to be a site of interstitial fluid (6a of Figure 1)_ Thus, the subject invention provides methods that enable an individual to select a sampling site according to the amount or volume and/or type of sample obtainable from the 3(1 site.
Any canvenient method may be used to characteriTe the pulse and/or hemoglobin values or levels of a potential site, where RBC characterizations and hemoglobin C11;t1';lCtCl'IZiltlOns (total hemoglobin and IlbO/llb ratio) are of particular interest. Each of these methods will now be described in greater detail.

l CA 02407161 2002-10-09 A. Pulse Characferizafion As described abave, once the flow of a site has bcxn characterized, the detetznination of whether the pulse of such a site is relatively or substantially high or low will further enable characterization of the type of sample obtainable from the site. Toe example, if a site is characterized as having high flow, a high pulse characterization correlates to a substantially arierial/capillary site and a low pulse characterization correlates to a substantially venous site, a relatively lower or substantially no pulse site con~clatcs to an interstitial fluid site.
1n certain embodiments, pulse can be determined by determining the RBC
characteristics oC a site, e.g., RBC flux, as described above. The methods for determining itl3C characteristics such as RBC flux have been described above and will not be repeated here. Once the R13C flux is determined, further characterizing pulsations (from the RBC
flux) corre3sponding to cardiac pulse indicates whether the site is arterial or venous, based on the principle that an arteriaUcapitlary site will have a greater pulse than a venous site.
Cardiac pulsations are observed as oscillations with a frequency of typically between 60 and 100 pulses per minute in the R13C flux vs. time relationship, as described about (it will be apparent to one of skill in the art that certain clinical conditions may result in higher or Lower frequencies). The pulsations result from flow surges in arteries and capillaries.
U l3CCilusC UC the resistance to flow of the capillaries, flow pulsations do not occur in veins.
More specifically, if pulsations ranging from about 0.33 to about 3.3 Hz, usually from about 0.67 to 2.50 liz and more usually from about 0.85 to 1.67 Hz are characterized at the site, the site is ch~mctcrizcd as arterial. Alternatively, if pulsation in this frequency range is not detected or is very weak, the sift is characterised as venous, where pulsations less than the arterial/capillary pulsation levels indicates a site devoid or substantially devoid of vasculature. Thus, if a site is determined to have a high RBC flux (high flow) and is also highly pulsatile, the sift is characterized as arterial/capillary, l.c., high flow and arterial/capillary, rather than venous. If tho RBC flux is determined to have low or substantially no pulsatile slow, the silo may either be devoid of va~culature or may be venous, l.c., an interstitial fluid site or a high flow and venous site.
13. Herrro,~~lobln Charactsr~tz_aflon In other methods of the present invention, sample type charaetcrization is determined by characterising the hemoglobin character of the site, for example a characterisation of the total hemoglobin of the site will enable a determination of whether the sire is capable of expressing arierial/capillary or venous sample or interstitial fluid, based on the principle that a site having substantially intemtitial fluid will have little or no hemoglobin. Also, as an atterial/capillary site will have a gtrater amount of Hb0 than a venous site, characterizing a site's Hb0/Ilb ratio will enable a determination of whether the site is capable of expressing substantially artcrial/capillary sample ear substantially venous sample.
Accordingly, methods to measure optical properties of the potential site arc used to dctcrtnine the hemoglobin characterization of the potential site.1n ether words, the absorbance, e.g., the light reflected from, or transmitted through, the potential site is detected lU and measured, i.e., an external portion of skin is irradiated with light (where light in this context does not necessarily refer to visible light, but may also include infrared light, etc.), and the absorbanec of the light is detected, where such absorptions are indicative of hemoglobin characteristics of the site. In certain embodiments of the subject methods, the measured value is compared to a predetermined value to characterize the site.
In other I ~ embodiments, it is compared to other hemoglobin values of other tested sites.
As dcscubcd above, a site is irradiated with light and the light absorbed by the site, or rather the light reflected by or transmitted through the area of interest, is detected, where such detecting involves collecting the reflected or transmitted light or a statistically relevant value thereof, for example by at least one light detector of an optics clement, and processing 2U the detected data to determine the hemoglobin character of the site. For example, the detected light or a respective signal may be transferred to a microprocessor for further processing, where the microprocessor works under the control of a software program. In other words, the program code in the software program instructs the microprocessor to carry out all the steps necessary to accomplish the particular task. Regardless of whether 25 performed manually or automatically, the amount, magnitude or quantity of the reflected or transmitted light or a signal or relevant statistical value themof may be compared to a predetermined value. For example, if the signal were to be above a pmdctcrmined value, the site might be determined to have a high total hemoglobin Ievcl or high Hb0/Hb ratio.
Alternatively, if the signal were to full below a Predetermined value, the site might be 30 dctennined to have a substantially low hemoglobin level or low I360/Hb ratio. Alternatively, or in addition to, the above method employing a prcdctcrmincd value to which the measured value is compared, in those instances where the best available sift is sought, l.c., the most appropriate site in relation to other sites tested, the measured value or statistically relevant value thereof may be compared to measured values of other tested sites.
Typically, this optical irradiation and detection takers about 0.1 to 1$0 seconds and more usually about 0.1 to GO seconds, and more typically about 0.1 to 20 seconcLs.
Thus, in practice, light ftbm at Icast one light source, i.e., an optics clement, e.~., at least one LED, laser emitting diode, light enutter, bispectral emitter, dual spectral emitter, S photoemitter, photodiode, a semiconductor die or the like at a wavelength in the range from about 400 to 1200 nm, irradiates the site, where in some embodiments more than one wavelength is used from the same or diffemnt light sources, where the different wavelengths may irradiate the site at the same or different times. Usually, the site will be irradiated for about 0.1 to 180 seconds, typically about 0.1 to GO seconds and more typically about 0.1 to 20 seconds :u~d then the absorbed light will be detected by a suitable detector such as at least one of the following: a photodiode, a photoelectric receiver, a photodetector, a semiconductor die, or the like. The detected signal is then related to hemoglobin concentration, i.e., total hemoglobin or a component or suitable ratio thereof. In certain embodiments, the detected light is then communicated to a suitable microprocessor for further processing such as computational ptbcessing and the like.
By way of background, generally when the skin is illuminated by light, if the light were to enter the skin, reflect off the collagen at the bottom of the dcrmis and m-emerge from the skin without absorption by an chromophorcs, (c.g., melanin or hemoglobin), the signal (remittance) detected and thus generated by the photodetector could be defined as R~.
When chromophorcs in the cpidcnnis (tnclanin) and the dcrmis (hemoglobin) intervene, the reflectance is attenuated, giving a signal defined as Rc"t. Thus, an equation representative of the signal received is defined as:
( 1 ) Rm~'1'm2 ~ ~'E~hoz . Tp~n2 . Rr W here:
'1'~,rcprcsents the fraction of light allowed to pass through the epidermis without berg ahsorbed by melanin.
Tnno r~:Presents the fraction of light allowed to pass through the dermis to the collagen layer without heing absorhed by oxyhemoglobin.
T",, represents the fraction of light allowed to pass through the dmmis to the collagen layer without being absorbed by deoxyhem«globin.
Thus, the Beers-Lambent formulation (i.e., the equation representing the punciple that the degree of absorption of light varies exponentially with the thickness of the layer of the absorbing medium, its molar concentration and extinction coefficient) of equation 1 above is;

(2) A= -In(R,o,/ R~ = 2{IE.[M]eM + lp(IlbO]Ei~ +Tn[Hb]crib}
Where:
A represents the absoi~ance at the site.
I represents the effective path length of the cone rePresentcd by the subscript.
)E:, D rcpc~csents dermis and epidermis, respectively.
[ ] rc;prescnts molar concentration, iU M, HbU, Hb represent melanin, oxyhemoglobin and deoxyhcmoglobin, respectively.
a represents the molar extinction coefficient (unique for each wavelength).
Thus, it will be apparent that if blood is substantially Prevented from entering a potential sampling site while an optical reading is taking place, the ai'~orbanc~ in equation 2 above is a function only of the melanin absorbance such that:

(3) A=-In(Rr",/ It~)=Zl,~(M]aM or (4) In(Rco~) = In(>~)-2h[M]EM = C, where C represents the melanin absorbance or background signal. Thus, the light absorbance resulting from hemoglobin can be represented by:

(5) In(Hm~)=C-2] Itr[Hb0]~tao +In[Hb]Ean1 Again, Rc", is the signal received by the photodetect~r. Thus, to obtain the background signal, a site having substantially no blood flow, i.e., a sire where pressure is applied has been applied thereto to substantially prevent blood flow to the site, the absorbancc due to hemoglobin only can be determined by first determining C
from equation 4 above, where R,ot is the signal obtained from the first occluded optical measurement, and then solving for hernoglobin terms in equation S using Rtor from the second optical measurement where blood was not pr~cventcd from entering the site.
As such, since the molar extinction coefficients for both oxy and deoxygenated hcrnoglobin are known for all wavelengths in the visible and near infrared range (sec for example 4. W. Van Assendelft, Specrroph«tometry vfHE~rno~lvbin Derivatives, Charles 1'hornas, pub., 1970), oxy and deoxygenated hemoglobin can both be dctcrrnined by using more than one wavelength. Accordingly:

. CA 02407161 2002-10-09 (6) In[iib0] = (Ci-ln(Rwth - (Crln(Rte~t)( Etibl~~l~b2)~ (grtnouEttnt) (7) I"(IIbO] ~ (Cl-ln(R~1- Ip[HbU] (~t"pt~e,~t) Subscripts 1 and 2 represent wavelengths 1 and 2. 1n using the subject methods to charactct~ize the hemoglobin of a potential site, the wavelengths arc typically chosen so as to have very diffcmnt extinction coefficients, i.e., wavelengths fire usually chosen to make equations 6 and 7 as orthogonal as possibly.
Accordingly, the first step in the subject methods to the eharacteri~e hemoglobin of a site is to determine the backgrow~d signal at the site,13y background is meant the absorbancc of the situ not related to hemoglobin, for example the absorbance related to mctanin and the like. As such, light of two different wavelengths irradiates a potential site and the brtckground signal is defected, More specifically, wavelengths of light are chosen such that the molar extinction Coefficient deltas of the oxy and deoxygenated hcmoglobins am different for the different wavelengths chosen, i.e., as one molar extinction coefficient goes up the other molar extinction coefficient goes down, where such molar extinction coefficient deltas of oxy and deoxygenated hemoglobin are known in the art. Thus, to determine the background signal, the potential sift is tctnporarily substantially occluded or rather blood is temporarily substantially stopped or prevented from entering the site, for exarnplc by ptcssing against the tile, e.g., by pressing or applying pnessurc by the aperture of the device described below onto the surface of tile skin with enough farce as to substantially stop blcx~d flow to the site. Tn this way, the site is substantially devoid of any hemoglobin and thus any absorbance will be attributed to background or the absorbance of various chromophorcs at the site such as melanin. Once signal is detected from such an occluded potential site, the background value is then datc;rmined based upon the above described equations, typically automatically. More 2S specifically, the signal detected by such a background dctern~ining method is communicated to a microprocessor, where such ti tnicroprocESSOr computes the background level or value of the site.
Following the background reading from the occluded site, a second reading at the site is taken. More: specifically, light of two different wavelengths irradiates the site, where such wavelengths fine chosen such that there is a large and opposite delta of the extinction coefficients of the two wavelengths. Once the signals from the two wavelengths are detected, the various components ~f hemoglobin can be determined from the above described equations, i.e., equations G and 7, typically automatically by a microprocessor tts described above. In other words, oxygenated hemoglobin, deoxygenated hemoglobin and total hemoglobin (the sum of the oxygenated and deoxygenated hemoglobin components) can be deterniincd, where such a determination can then be compared to a predetermined or cut-off value such that a total hemoglobin value ancUor a hemoglobin ratio value, i.e., a ratio value defined by Hb0/Hb, above the predetermined value is designated as a high hemoglabin value and a hcmoglabin value below the predetermined value is designated as a low hemoglobin value. As noted above, altennatively, the values may be compared to other tested sites such that the best site among those tested is chosen.
Rcfcrrind again to Figure 1, if a cite has been characterized as having low flow, a further dctetmination regarding total hemoglobin level will enable characterization of the site as having substantial vasculaturc (high total Hb) (6b of figure 1) or substantially devoid of vascutature, i.e., interstitial fluid (low total I-lb) (ba of Figure 1).
Once vasculature versus intct~stitial fluid or substantially no vasculature is determined, the site is then further characterized as being apptropriate or not for a particular test (7 of Figure 1). In other words, if the particular test requires intcmtitial fluid, the potential sampling site will be determined to be appropriate if the total hemoglobin site is found to be low, thus detcimined to be capablo of expressing interstitial fluid. Site apprupuatencss will be described in greater detail below.
if the site has been characterized as having high flow according to the above described methods, a IIbOBb ratio can then be determined, when such a ratio enables charac;teriiation of a site as either high flow and arterial/capillary (5a of Figure 1) ar high flow and venous (5b of Figure 1). 1n other words, a site having a relatively or substantially high cancentration of llb0 to Hb is indicative of an arterial/capihary site and a site having a relatively or substantially low concentration of ,T-1b0 to Hb is indicative of a vcnotts site.
.SPecifically, a hemoglobin ratio is determined bard upon the above described equations, typically automatically by a microprocessor, where such a determination can then be compared to a predetermined ar cut-off value such that a ratio value about the predetermined value is designated as a high ratio value and a ratio value lxlow the Predetermined value is designated as a low ratio value. As noted above, altentatively, the values may be compared to other tested sites such that the best site among those tested is chosen.
Once artcrial/capillary versus venous is determined, the site is then further characterized as being appropriate or not for a Particular test (7 of Pigut~c 1). In other words, if the particular test requires arterial/capillary sample, the potential sampling site will be determined to be appropuate if the 1-Ib0/Hb ratio is found to 1~ high, thus it is determined to be capable of expressing substantially ar~crial/eapillary sample, particularly high flow arterial/capillaty sample. However, if the particular test requires venous sample, the potential sampling site will be determined to be appropriate if the 1-~b0/Hib ratio is found to be low, thus it is determined to be capable of expressing substantially venous sample, particularly high flow venous sample, Site appmpriatcncss will be described in greater detail bElow, As described in detail above, in practicing the subject methods for hemoglobin eharaetenzation, whether ~~IbO, )<!b or total hemoglobin, light sources such as LIrD's, laser diodes, ere., in~adiato a site, where the licht sources irradiate the site with at least two different wavelengths, each of which ranges from about 400 to 1200 nm. A
photodetector detects the absarkx;d tight and the amount of c;ach hemoglobin component can then be 1(f determined based on the specific absorbances of the wavelengths of interest, where such ttbsoWanees arc then related to the particular hemoglobin component. More particularly, a device having the above described optical components, such as a device described in detail below, may be used to practice the subject methods, As such, the device also is typically operatively coupled to a micropmcessor working under the control of a soflwme program such that the microprocessor is capable of performing all of the steps and functions nccessa~y to characterize the hemoglobin of the site and also determine the appropriateness of the site for a particular test, for example the microprocessor is capable of performing all of the computations and/or comparisons necessary to determine oxygenated, deoxygenated and/or total hemoglobin values. As mentioned above, the above-described methods, the total hemoglobin and/or h160/Hb ratio may be compared to a predetermined value or may be used as a comparison against other values from other tested sites to determine the best site amongst a plurality of sites testes. Additionally, the optical determination described herein may he in addition lo, or instesd of, other sample type characterization methods.
1n certain other embodiments of thv subject methods, hemoglobin characterization may lx derived according to the methods described below, where the below described methods arc of particular use where the path lengths and melanin concentrations are substantially constant from site to site and it is desirable to characterise the total hemoglobin concentralian 4f a potential site, Again by way of background, at a number of wavelengths such as 506.5, 522, 54$,5, 586 and 815, Hb0 and Hb have the same molar extinction coefficients. If lt~o, is measured at any of the wavelengths where Hb0 and I-ib have the same molar extinction cocfl'icicnts, the magnitude of )Etto~ will inctrase or decrease as total hemoglobin decreases ar increases, respectively, based on the principle that C is substantially constant from site to site. Thus, in certain embodiments, total hemoglobin can be determined using the following equation:
-l8-(7) ln(kto~)rC-2{ InIIIbO](~rho = ~Hb) +InC~Ib)(~n~o ~ enn) }
=C~Z Iu (Erl,,o ~ Eira) ([HbH) + [Hb)) Thus, for this particular embodiment, light of one wavelength irradiates a site, where .S such wavelength is chosen such that Hb0 and fIb have the same molar extinction coefficient. The absorbancc or signal is then detected from the site and the total hemoglobin at the site is determined based upon the above described equation, where oftentimes the total hemoglobin concentration is determined automatically by a microprocessor. More particularly, light from a light source such as an LED, laser diode, or the like in~adiates a site lU with light of one wavelength, where the extinction coefficients of both HBO
and Hb are the same. The absorbanec or signal of the site is detected by a suitable photodctcctor or the Iikc, where such absorbance is related to the total hemoglobin level of the site, Once total hemoglobin has been determined, the site is then further characterized as being appropriate or not for a particular test. In other words, for example, if the particular lest requires 1 S interstitial fluid, the potential sampling site will be determined to be appropriate if the total hemoglobin site is found to be low, and the site is thus detetZrtined to be capable of expressing interstitial fluid. Site appropriateness wilt be described in greater detaril below.
!n yet another embodiment of the subject methods, hemoglobin characterization may be derived according to the methods described below, where the below described methods 2U aide of pauicular use where the path lengths and melanin concentrations are substantially constant from site to site and it is desirable to characterize a hemoglobin ratio of a potential site, e.g., llbO/Hb.
In this particular embodiment, two wavelengths arc chosen to irradiate a site, when, al each wavelength, the two hemoglobin species have substantially different extinction 2S coefficients, i.e., oxygenated hemoglobin and deoxygenated hemoglobin have different extinction coefficients. For example, suitable wavelengths where Mb0 and hIb have substantially different extinction coefficients include, but arc not lirnitcd to, 431, 415, SSS, 700 and 940 nm. That is, a first wavelength and a second wavelength are chosen, where each wavelength may be selected from the above described set of wavelengths so that Hb0 and 30 Hb wilt have substantially different wavelength coefficients. The extinction coefficients at such suitable wavelength pairs have opposite deltas between the two wavelengths, l.c., as one increases between the first and second wavelengths, the other decreases between the first and second wavelengths. As such, the difference in In{R~t) between the two wavelengths wit) increase as one hemoglobin component increases and will decrease as the other hemoglobin component decreases. In other words, for example, for each suitable chosen wavelength pair, as Hb0 increases, the difference in ln(R~ between the two wavelengths will increase and as Hh decreases, the difference in In(lt~"i) between the two wavelengths will decrease.
More specifically, from equation 5 above, modified for two wavelengths:
In(Rto~)t=Cr2( InIHbO]i;lmot +lnIHbIEtrni~
In(R~oc)~z=Cz-2t Inf~'Ib0)Etioo2 +TnIHb]~uua~
($) In(Ke~~i - ln(R,~Jz = W - ~=x -a Iu ( IilbO](t=rmoi-a?rrooi) +IHbI(Eitm-I O EIIb2)?
'fhua, if (eHbO~-l;Hb02) > 0 and (rHb~-sHbz) < 0, then ln(Rtot)~ - In(Rtot)t increases as [Hb0] increases or [IIb] decreases. For example, if the extinction coefficient of Hb0 is greater at wavelength 1 than wavelength 2, and Hb has an extinction coefficient that is Icss at wavelength 1 than wavelength 2, then as the difference between the signals (i_e., the 1 S di ffemncc between wavelength 1 - wavelength 2) increases, the ratio of IIbO to Hb will increase;. In many embodiments, this method of characterizing total hemoglobin concentration is performed first, such that this method of characterizing HbO/Hb ratios is performed on a site having a high hemoglobin concentration. In other words, because the total hemoglobin concentration affects the difference calculation, charactcri2ing Hb0/Hh 2C1 ratios should be performed on a site having a substantially high total hemoglobin concentration.
Specifically, a potential site is illuminated with two wavelengths from two light sources, where such light sottrecs may include one or more LED, one or more laser diode, etc. The wavelengths are chosen such that the molar extinction coefficient deltas of Hb0 and 25 Hb are different between the two wavelengths, i.e., as one goes up the other goes down, as described above. At lease one photodctector detects the signal from the site, i.e., the absorhance of the tisht, where such signal is related to an Hb0/Hh ratio, according to the alwve described equations. The site is then further characterized as being appropriate or not far a particular test. Site appropriateness will be described in greater detail below.
.Ill. Uet~rnt~iretns tha Annrnt~riu~teness of a .Sile~nr a Partic~lacr Test As mentioned above, the appropriateness of a site for a pazticular test is determined by the subject methods. Referring now to steps 3, 4 and 7 of Pigurc I, as described above, once t~ site is characterized by flow and/or sample type, its appropriateness in regards to the particular test to be performed is evaluated. Such appropriateness is best described in reference to Figunr 2, which shows certain sample test parameters and their correlation to particular samples obtainable from a site. For example, certain tests require a minimum ~;ampte volume. 'Thus, a site which is characterized as being capable of producing or expressing a gicatcr volume of sample (a site having higher flow mte) would be preferable to a site not so capable, e.g., hi$h flow of arterial/capillary and/or venous would be moro appropriate versus a low flow site of arterial/eapillary and/or venous, unless the particular test required interstitial fluid as opposed to arterlal/capillary or venous blood. As such, test results meeting the requirements of such samples would be determined to be appropriate.
Also, certain tests such as glucose tests calibrated to whole blood may require a certain type of sample such as blood, blood constituents or the like as the appropriate fluid sample and as such a site will be determined appropriate for such a test if the site is characterized as arterial/capillaiy and/or venous and likewise inappropriate if it is charactct7zcd as having interstitial fluid. I~owever, certain other tests such as glucose tests calibrated to interstitial fluid may, accordingly, require interstitial fluid as the appropriate fluid aarnpIe and as such a sire will be determined appropriate if the site is charactcriaed as having interstitial fluid and likewise inappropnatc if it does not.
Furthermore, some tests may require arterial blood instead of venous blood, or vice versa, and as such wilt be determined appropriate if the site is charactcuzed as having the requisite arterial or vcnaus blood and inappropriate if it does not. In other words, a test that requires artcrial/capillary ansLor venous blood would thus correlate to a high flow tuterial/capilIary and/or high flow venous site. A test that requires interstitial fluid would thus correlate to a Iow flow interstitial fluid sire. A site characterized as low flow artcital/capillary ar venous site would thus likely not be appropriate for any test.
?5 As described above, in many emboduncnts of the subject methods, appropriateness of a site for a particular test is typically accomplished automatically by a microprocessor, where the microprocessor works under the control of a software program and includes all the code necessary for it to cry out the steps requirc?d to determine if a site is appropriate for a particular test.

1 V.~irt !'~ercir:F
Once an appropriate site has been determined, sample is then accessed and collected (steps 8 and 9 of Figure 1). Typically, sample is collected from the dermis and epidermis. In certain methods, the sampling site may be stimulated to incmase the volume andlor rate of sample produced or expressed at the sampling site, Accordingly, in some embodiments, at least one skin-piercing element is inserted into the skin of a patient or user of the subject invention to access physiological fluid.
S Depending on the type of physiological sample to be obt<~incd, the at least one skin-piercing clement may penetrate to a particulrtr skin layer, such as the dcrmis and epidermis layers.
Typically, the at least one skin-piercing element is inserted into the skin for about 0.X01 to GO seconds, usually about 0.0005 to 30 seconds and more usually from about O.OOI to 15 seconds so as to ensure an adequate sampling volume of the targeted physiological fluid is oblained_ The ut least one skin-piercing element may lx activated manually by the user by releasing an actuating element associated with the at least one skin-piercing clement, e.~., by depressing a button or the like on a device which activates the spying-loaded element towards the skin, or may be automatically activated to pierce the skin, for example triggered automatically when a suitable sampling site is located.
In certain embodiments of the subject methods, the at least one skin-piercing clement, or one or more elements operatively associated therewith, stimulates the site to produce or express a greater volume and/or rate of the physiological fluid desired of the physiological fluid desired, i.e., increases the rate of expression of physiological fluid. For example a fluid enhancing element, e.g., an ultrasonic clement or the like, may be used to create vibt~ations at the site during fluid access and collection, where such vibrations stimulate fluid expression. In certain embodiments, the fluid enhancing means may include, in addition to or in place of other fluid stimulating elements, a tcmperatut~e element to increase the temperature of the site to stimulate fluid expression. The fluid enhancing clement may be operatively associated with the at least ono skin-pict~cing element such that the at least one skin-piercing element stimulates fluid expression itself whIlc it accesses the fluid from the site, in any event, in those embodiments employing an ultrasonic element to stimulate sample expression from a site, such an ultrasonic element typically vibrates at a frcducncy in the range from about 10 to 1000 Hz, where such vibrations stimulate the 3U expression of physiological fluid, e.g., increase the volume and/or rate of sample production.
V. Analyse !'orr~c~g,tr~u Many embodiments of the subject methods also include determining the concentration of at least one analyte in the physiological sample (step 10 of Figure 1)_ As such, once a suitable sampling site is found and sample is accesses and collected therefrom, the concentration of at least one analyze of the sample may be determined using any appropriate analyze concentration determination method, as ale known in the an.
In certain embodiments of the subject mothods, the sample is then transferred to a standard analyze concentration determination reagent test strip, e.g., a glucose test strip or the like, which is in communication with the device, where oftentimes the test strip may be directly integrated into the device.1n those embodiments where the test strip is dit~ectly integrated into the device, the test strip may be loaded directly into the device before, during or after the physiological sarnplc is extracted, and in many instances may be manufactured with the test step already integrated with the device.
Once sample is transferred to a test strip, l.c., delivered to the reaction area of the tact strip, the concentration of at least one analyze of interest is determined.
Sample may be transferred to a test strip by a variety of mechanisms, where such mechanisms include, but arc not limited to, vacuum, capillary forces and the like. As will lx apparent to one of skill in IS the art, a variety of anaiyte determination methods may be employed, e.g., electrochemical and colorimetric, where both methocLs will be described below.
hor an cIcctrochcmical analyze concentration determination assay, an electrochemical measurement is made using reference and working electrodes, as is known in the art. "!'he electrochemical me:asuremcnt that is made may vary depending on the particular nature of the assay and the device with which the electrochemical test strip is employed, e.g., depending on whether the assay is eoulomctric, araperotnetric or potentiometric. Generally, the electrc~ehc:mieal measurement will measure charge (coulomctric), current (umperometric) or potentiat (Potentiometric), usually over a given period of time following sample inttnduction into the reaction arcs. Methods for making the above described electrochemical 2S measurement are further described in U.S. Patent Nos. 4,224,125; 4,545,382;
and 5,266,179;
as well as WO 97118465; WO 99/49307; the disclosures of which are herein incorporated by referc;nce. Regardless of the type of measurement, an electrochemical measurement or signal is made in the reaction zone of the test strip.
hallowing detection of the clectrochemicat measurement or signal generated in the reaction zone as described above, the amount of the analyze present in the sample introduced inw the reaction zone is thon determined by relating the electrochemical signal to the amount of analyte in the sample.
Generally, for colorimetric assays, the sample is allowed to react with a reagent system, e~.g., members of a signal producing system, to produce a detectable product that is present in an amount proportional to the initial amount p~rscrtt in the sample.1n one such system, e.g., in a system used to determine the presence andlor concentration of glucose in a physiological sample, the signal producing system is an analyte oxidation signal producing system. lay analytc oxidation signal producing system is meant that in generating the detectable signal from which the analyze concentration in the sample is derived, the analytc is oxidized by a suitable enzyme to produce an oxidized form of the analyse and a corresponding or proportional amount of hydrogen peroxide. The hydrogen pv,,roxlde is then employed, in turn, to generate the detectable product from one or more indicator compounds, where the amount of detectable product generated by the signal measuring system, i.e. the signal, is then related to the amount of analyte in the initial sample. The amount of detectable product, i,e., signal produced by the signal producing system, is then determined and related to the amount of analyze in the initial sample. Of course, any type of colorimetrie assay, i,e., vcuious colorimetric chemistries, may be used with the present invention.
Tn many embodiments, the above described characterization and relation processes arc pc~fortnad by an automated device, e. g., a meter, as is well known in the relevant art.
Representative meters for automatically practicing these steps arc further described in copending 17,5, Application Serial Nos. 09/333,793; 09/497,304; 09/497,269;
09/736,788 and 09/746,116, and iJ,S. Patent Nos. 4,734,360; 4,900,666; 4,935,346;
S,OS9,394;
5,304,468; S,30G,623; 5,418,142; 5,426,032; 5,515,170; 5,526,120; 5,563,042;
5,620,863;
5,753,429; 5,573,452; 5,780,304; 5,789,255; 5,843,691; 5,846,486; 5,968,836 and 5,972,294; the disclosures of which are herein incorporated by reference, 1)~VIC
As summarised above, the invention provides devices for delem~ining $ suitable site fir sampling physiological fluid, by way of a site flow characterization element and/or a sample lyre characterisation element. The devices may also include al least one skin-piercing element for piercing the skin at the appropriate sampling site and/or include an operatively associated means for determining the presence andlor concentration of at least one unalyte in a physiological srample extracted or expressed from the appropriate sampling site. The subject devices find use in the location of suitable physiological fluid sampling Sites on various areas of the body, including, hut not limited to, the fingers, arms, legs, ~arlobca, heels, feet, nose and toes, Furthermore, the subject devices find use in the location and collection of a wide variety of physiological samples, where such samples include, but arc not limited to, interstitial fluids, blood, blood fractions and constituents thereof, and the lil,c.
As described above, the subject invention includes at Least one sift flow characterization clement andlor at least one sample type characterization clement, where one or both types of the elements may be integrated into a housing or may otherwise be a single unit, i.e., an integrated device, usually with at least one skin piercing element and/or test strip. The unit, i.e.., the housing, may be manufactured from a wide variety of materials including, but not limited to, polystyrene, palypropylcne, polyethylene, polyacryonitr-ile, holycarbonatc, trnd the Like. The unit may be re-usable or single use.
The housing is intended to be easily held by the user, l.c., a hand-held device, and as such i5 sufficiently compact to enable portability and case-of-use.
Accordingly, the housing may take a number of different shapes, as lung as the shape enables the functionability of the device, e.g., facilitates portability and grasping by the user and positioning on an appropriate sampling site area, such as a surface area of the skin. For example, the shape may be l 5 substantially irregular or may assume a substantially regular shape such as a parallelogram, rhombus, circle, oval and the like. Regardless of the shape, the unit and associated elements typically have a length in the range from about 1 to 20 inches, usually in the range from about 2 to 15 inches and more usually in the range from about 3 to 10 inches.
The width of the unit is usually in the range from about 0.1 to 10 inches, usually in the range from about 2U 0.2 to 5 inches and rnore usually in the range from about 0.5 to 3 inches.
The height is usually in the range Pram about 0.1 to 10 inches, usually in the range from about 0.2 to S
inches and more usually in the range from about 0.5 to 3 inches.1'he weight of the subject device is usually in the r.~npe from about 0.02 to 10 pounds and more usually in the range from about 0.04 to 5 pounds, but in most cases is less than about 2 pounds.
The proximal cad 25 of the device, l.c., the end of the device which is in close proximity to or in dirt,~et contact with the skin when in use, typically includes a proximal orifice, where such an orifice usually has a diameter less than about S rnillimctcrs, and is in the range from about 1 to 4 millimeter, and man; usually iii the range from about I la 2 millimeters.
Typically, the visible surface of the unit will include a display or screen on which 3t) messages, instn~ctions, ewer warnings, and nu~st importantly, results, l.c., whether a site is suitable and/or the cancenh~rtion of an anaiyte, may be displayed by means such as liquid crystal displays, as are knawn in the art. Such information m$y be conveyed by alphanurneric digits ur units ar pictorial icons. In certain embodiments, an audio means may also be present in or en the device for audibly conveying information to the user.

Additionally, the subject device may include a power switch for manually activating the device.
l,~srTC~ l~row~',tr:rtr~nrz~
As described above, in certain embodiments of the subject invention, the housing includes art least one site flow characterization clement which charracterizes the flow of a potential site, i.e., the flow rate or velocity of the site. A wido variety of elements or components may be employed to determine the flow characterizations of a particular sampling site, where particular embodiments of interest will now he described.
A. Temverature Characte_r~u_trion l~le In certain embodiments, the flow characterization element includes an element capable of characterising the temperature of a pcnential site. For example, a temperature element or sensor such as a thermocouple or the like may be employed, where such thermocouples arc known in the art. Such a tet»perature element may be in place of or in addition to, other elements used to characterize the flow of a site, such as the RBC
characterization clement described below, whom one or more site characteri2ation elements arc capable of being activated at the same or different times, e.g., a temperature element is capable of being activated at the same or different time as a light detecting element, etc.
The temperature element of the present invention is one which is capable of measuring the temperature of the site, where such a temperature is an indication of the l7ow character of the site. In other words, the temperature of the skin increases as blood flow increases due to factors such as the velocity of the flow of fluid at the site.
Accardingiy, the temperature sensor is capable of measuring infrared radiation or tcmperatums in the range from about 0 to 100°C, usually from about 10 to 75°C and more usually from about 10 to 50°C. Typically, the temperatut~e clement will be positioned in close proximity to the proximal aperture of the device or housing; however, other positions tray be employed as well depending upon the configuration of the device, the particular temperature sensor used and the specifc body area to be tested.
B. RJ3C Char~l~cte 'r_~a_tion glen:ent fn other embodiments, the flow characterization element is an element capablo of characterizing the RBCs of the site, e.g., RBC flux characterization. RBC
characterization elements may be in addition to, or in place of, other flow characterization elements, as described herein. Where the 1ZBC characterization clement is in addition to other elements, the elements may be capable of being activated at the same or at di fferent times.
'Typically, an element configured to perform RBC characterization, e.g., RBC
flux determination as described above, usually includes at least one light source capable of emitting light, usually coherent, single wavelength light, at a wavelength ranging from about 400 to 1200 nm, usually from about 450 to 800 nm such as a laser as is commonly known in the art, and a sensor or detector, typically a broadbactd sensor or detector, for detecting the intensity of light reflected from the RF3Cs, The at least one light source may thus include one or mare: light emitting diode (LFT~), laser diode, light emitter, bispectral emitter, dual spectral emiuer, photoemitter, photodiode, semiconductor die, or the like, and the detector may include one or more: photodiode, photoelectric receiver, photodetector such as a broadband photodetector, semiconductor die, or the like.
Lxamplcs of commercially available elements capable of RHC characterisation or RBC flux characterisation, e.g., Doppler tlowrneters, adaptable for use with the present invention include, but are not limited to, flowmeter models LD-5000 and LD-manufactured by Medpaciftc of Seattle, WA; flowmctcr models Prl, and models PF2 and PI~3 manufactured by Perimed of Stockholm, Sweden.
The RBC characterization element may be operatively associated with a microprocessor under the control of a software program that is capable of processing signal ?0 from the site :end determining the RBC character, e.g., RIiC flux, or a statistically relevant value thereof, of the site based upon the measured intensities of reflected Iight and may also Ixrform the steps necessary to compare such a RBC characterization value or measurement such as RBC flux value to a predetermined value or to RBC characterization values of various tested sites.
J~'. ~AMPLG 1'YPL~ E( ~,~T~ l2ATlON ~'LEMENT
As mentioned above, the subject devices may also includes one or more sample type;
characterization element, whEre such an element is capable of characterizing a site as either primarily or generally (1) artcrial/capillary, (2) venous or (3) interstitial fluid, and more :~0 specifically is capable of characterizing the type of sample at a site a.S
either primarily or gencruhy anetaal/capillary, venous or interstitial fluid. A variety of elements may be used to characterise the type of sample at a site. ror example, elements include those capable of characterising the pulse of ~ site and/or charactctYZin ; the Hb of the site, ac will now be described in grater detail.

A. Pulse Cl~a~racte ' tion Element The pulse characterization clement is an clement capable of characterising the pulse of a site. Pulse characterization may be in addition to, or in place of, other sample type charucteriration elements, as described herein. Where the pulse characterization element is in addition to other elements, the elements may be capable of being activated at the same or at different timc;s.
Typically, an element configured to perform pulse characterisation usually includes at (cast one light source capable of emittins light, usually coherent, single wavelength light at a wavclcn,gth from about 400 to 1200 nrn, usually from about 450 to 800 nm such as a laser ac is commonly known in the art, and a sensor, typically a broadband sensor or dctecaor for defecting the intensity of light reflected from the Rl3Cs. The light soumc may include one or more: light emitting diode (LED), a laser diode, a light emiuer, a bispectral emitter, a dual spectral emitter, a photocrnittcr, a photodiode, a semiconductor die, or the like, and the detector may include a photodiode, a photoelectric receiver, a photodetector such as a broadband photodetector, a semiconductor die, or the like.
The light source and detector may the same as or in addition to the above described elements used for RBC characterization. Examples of commercially available Pulse characterization elements, e.g., Doppler flowmeters, adaptable far use with the present invention to determine flow characterization include, but are not limited to, flowmeter rnode)s LD-5000 and LD-b000 manufacaured by Medpacific of Seattle, WA;
flowmeter modals PF1, and models PF2 anti PF3 manufsetured by Perimed of Stockholm, Sweden, The pulse characterization clement may be operatively may be associated with a microprocessor under the control of a software program that is capable of processing signal 2S from the site and determining the pulse or determining a magnitude associated with the pulse, or a statistically relevant value thereof, of the site based upon the rncasured intensities of the reflected light and may also perform the steps necessary to compare such a pulse value to a predetermined value or to pulse values of various tested sites.
3() B, lle»to~,lobin Charaeterizalin~e Ele»~ent 1n certain embodiments of the subject invention, the sample type characterization clement includes a hemoglobin characterization element capable of determining the characteristic of hemoglobin of a site 1n p;irticul~rr, the hemoglobin eharaeterix~tion element is configured to determine the total hemoglobin level of the site and/or determine the amount of oxygenated hemoglobin to deoxygenated hemoglobin yr the 1lbU/Irib ratio.
1'he hemoglobin characterization element is typically an optics element, where such an optics element contains (I) at least one light source such as at least one of the following: a light emitting diode (i.ED), a light emitter, a bispcctral emitter, a dual spectral emitter, a photoemitter, a photodiode, a semiconductor die, laser, or the lilve, and (2) at least one detector capable of measuring light absorbed by the site, i.e., intercepting light transmitted through yr reflected tram a surface upon which the light source is focused, and which may also capable of converting such light into measurable electrical signals, e.
g., voltage, current, lC~ etc.), where auitable detectors include, but are not limited to, at least one of the following: a Phatodiode, a photoelectric receiver, a photodetector, a semiconductor die, or the like. As noted above, light sources and detectors arc commonly known in the art, when examples of suitable light sources and detectors suitable far use with the present invention include those disclosed in U.S. Patent Nos. 6,241,680 and G,233,2GG, the disclosuna of which are herein incorrarated by reference.
Typically, the at least one light source of relatively narrow wavelength distribution, e.g., at least one I,ED or laser, will be capable of in~adiating a prospective sampling site with at least one wavelength, typically at (cast two wavelengths ranging from about 4~-1200 nm.
In other wards, if one light source is used and more than one wavelength is required, the one light source will be capable of producing or emittins light at more than one wavelength. If more than one light source is used, at least two of such light sources will be capable of trrrnsmiuing light at different wavelengths either serially or simultaneously with respect to each other. 1'he at least one light source and/or the associated detectors) may be positioned at or near the proximal end of the housing, l.c., the portion of the housing in close proximity to or in direct contact with the skin of the user. In other words, the light sources) and/or detuctor(s) m:.ry be located near the proximal orifice of the device; however, the light sources) and /or detector(s) may be positioned elsewhere in the device as wc;ll.
1'he hemoglobin characterization element may be operatively associated with a microprocessor under the control of a software program that is capable of processing signal tram the site and detenrining total hemoglobin or the components thereof (oxygenated yr deoxygenated Iib) or the I3b0/hIb ratio, or a statistically relevant value thereof, of the site based upon the measured absorbances of the light and may also be operatively associated with 11~C1SUrem~nt processing means for performing the steps necessary to compare such hemoglobin values to a predetermined value or to hemoglobin values of various tested sites.

Ill. Me~surern~r~Procarssi"~t; Compgnents 1'he device also includes associated electronics for proeessin$ the measurements or signals produced by the site flow characterization element and/or the sample type characterization element artdJor may be used to automatically determine the concentration of an analytc in the sample, as described below. For example, in many embodiments the device may also includes a current to voltage converter unit and an analog to digital converter, where such electronics arc known in the art.
Fuil,hennore, the device includes a micmptncessor working under the control of a software program, whore such a software program contains the entire code necessary for the microprocessor to petfortn all of the tasks required by the device, e.g., the microprocessor contains all the code necessary for determining the suitability of a sampling site and/or the concentration of an analyte. In other words, the program code of the software instructs dtc microprocessor to Cathy out all the steps which are necessary for it to determine one or mom l5 of the site's functions, such as the flow characteristics of the site, ancUar the sample type characteristics, l.c., whether the site include primarily arlcdal/capillary, venous or interstitial fluid, the appropriateness of the site far a particular test and the concentration of at least one antlyte in the sample, among other functions such as automatically activating the device, ere.
IV .Skin Piercir:g Element The device may further include at Icast one skin-piercing element, e.g., a needle or the like, far accessing and withdrawing or collecting the targeted sample fluid. The at least one skin-piercing clement may be associated wish an actuating mechanism, such as a srring-loaded mechanism, for manually actuating the at least one skin-piercing element towards the ?5 skin; however, the at least one skin-piercing clement may also be capable of being activated automatically. Representative lancing elements adaptable for use with the present invention include, hut arc not limited to, those disclosed in U.S. Patent Nos.
4,449,529; 4,892,097;
5,314,441; 5,318,54; 5,366,469; 5,395,388; 5,439,473; 5,454,828 5,540,709, 6,197,040;
G,071,?94; 6,045,567 and 6,036,924, the diselo5ure of which arc heroin incorporated by reference. fiurtltcnnore, the Pcnietm brand Blood Samplers manufactured by LifeSean, lnc.
arc also adaptable for use with the present invention. The at least one skin-piercing clement may further include a fluid pathway or channel operatively associated with, e.g., either within, concentric with or adjacent to, the at least one skin-piercing element for transporting fluid accessed by the clement.

The at least one skin-piercing element may also include one or more fluid enhancing elements for stimulating the production or expression of physiological fluid from the site.
For Example, a vibration element may be operatively associated with the present device or with the at least one skin-piercing element of the device, where such a vibration device is capable of vibrating al a frequency in the range of about 10 to 1000 Hz.1n certain embodiments, the fluid enhancing means may include, in addition to or in place of other fluid stimulating elements, a temperature element to increase the temperature of the site to stimulate fluid expression.
Y. 'I'ect Strit~s 'The device may be adapted to receive or otherwise be operatively associated or in communica~ian with standard analyze concentration determination test strips, e.g., glucose reagent test strips. In many devices of the subject methods, one or more test strips arc capable of being loaded directly into the device, i.e., the present device is configured to receive at least one test strip, before, during cm after the physiological sample is extracted.
Examples of such a reagent test strips suitable for use with the subject invention include those described in capending U.S. Application Serial Nos_ 09/333,793;
09/497,304;
09/497,269; 09/736,788 and 09/746,116, and U.S, Patent Nos. 5,563,042;
5,753,452;
5,789,255, the disclosures of which are herein incorporated by rcfctcnee.
1n those embodiments where a reagent test strip is in communication with the device, an element for automatically determining the cancentration of an analyte in a physiological sample may also be included in the device, where such automatic elements, e.g., automatic meters, are well known in the art. F;xamples of such automatic elements adaptable for use with the present invention include those described in U.S. Patent Nos.
4,734,360; 4,900,666;
4,935,346; 5,059,394; 5,304,468; 5,306,623; 5,418,142; 5,426,032; 5,515,170;
5,526,120;
5,563,042; 5,620,863; 5,753,429; 5,573,452; 5,780,304; 5,789,255; 5,843,691;
5,846,486;
5,968,836; 5,972,294 and described in copending U.S. Application Serial Nos.
09/333,793;
09/497,304; 09/497,269; 09/736,788 and 09/746,116, the disclosures of which are herein incorparated by reference.
Referring now to the drawings, Figure 3 provides a representation of an exemplary device of the subject invention showing a cut-away view of the proximal portion of the device, rigure 3 shows device 2 made;-up oC an outer housing 18, which includes a visual display or liquid crystal display 4 for displaying results to a user of the device (as mentioned abave, infarmttion may also be audibly communicated to the user in stead or in addition to being visually displayed) and a proximal orifice 10, where the proximal otYfice of the device 2 is in communication with, or is in close proximity to, an area of skin S. A
cut-away view of the proximal portion 8 of the device 2 reveals the inner components of the subject device.
Accordingly, device 2 includes flow characterization element 12, sample type chat~ac;tcriiation element 14, temperature sensor 16 and microprocessor 6.
t~igure 4 provides a representation of an exemplary proximal portion of the subject device, showing a cut-away view of the proximal portion. In this patrticular embodiment, the proximal portion 32 of the device 30 is shown, where a proximal portion 32 of device 30 includes a flow characterization element made up of temperature characterization element 22 and a sample type characterization element which includes laser diode 24 and laser diode 21 and detectors 23 and 25. Further included in this embodiment is at least one skin-piercing clement 24, olxratively associated with spring mechanists 2G. Device 30 includes reagent test strip 28, where test snip 28 may be in communication with an internal lumen of the at least one skin-piercing element 24 (not shown) or some other elongated tube or transfer cle~ncnt, th roubh which sample is drawn to the test stop Z8. It will ix;
apparent, however, that lest step 28 may be separate from and/or otherwise adjacent to the skin-piercing element 24.
KITS
Also Provided by the subject invention are kits for use in practicing the subject methods. The kits of the subject invention include at least one subject device, where such a device includes at least one flow characterization element for characterizing the flow of a potential physiological sampling sits and/or may include a sample type characterization element for determining the type of fluidic contents of the site. Oftentimes the kits of the subject invention include a plurality of such devices. The kits tray also include a reusable or disposable lancing element, if not already integrated into the device.
Furthermore, the kit may also include a reusable or disposable meter, if not already integrated into the device, that may be used with reusable or disposable test strips used with the subject invention.
Ccnain kits may include various typc;s of lest strips, e.g., where various test strips contain the same or different rca,gcnts, e.8., electrochemical ancUor colorimettic test strips. Finally, the kits may further include instructions for using the subject devices for detennining a suitable physiological fluid sampling site and/or for determining the concentration of at least one unalyte in a physiological sample. The instructions may be printed on a substrate, such as paper ur plastic, etc. As such, the instructions may be rresent in the kits as a package insert, in the labeling of the container of the kit or components thereof (i.e., associated with the packaging or sub-packaging) rte. In other embodiments, the instructions are present as an electronic storage data file present on a buitable computer readable storage medium, e.g., CU-iZOM, diskette, etc.
FXPEXIM~NTAL
The following example correlating skin temperature with t7uid volume is ofFered by way of illustration and not by way of limitation.
A fine thermocouple (0.002 inch type CHAL from Omega Technologies Corp.), associated at the end of a PenletC~ Plus Dlood Sampler using a FiuePointT"d lancet from LifcScan , Inc., was used to measure the temperature of a sampling site and to access and obtain sample therefrom. As such, the thermocouple was positioned in the center of the orifice of the Blood Sampler having a variable depth setting fixed to G. A
location on the upper forearm of a subject was chosen as a sampling site. The temperature of the site was measured and the site was lanced substantially immediately thereafter. Sample which was readily expressed for a period of about 30 seconds was collected and the weight thereof was determined. 'this procedure was repeated for a sample size of 21.
Figure S shows the results of the amount of blood volume, represented by sample weight, collected far each temperature, The graph shows that there is a clear correlation between temperature of a site and the weight or volume of sample obtainable therefrom.
'There is one out(ier at about 29.1°C, which may be attributed to a deeper lancing depth or the like.
It is evident from the above description and discussion that the above described invention provides a simple, quick and convenient way to locate a suitable physiolosical fluid sampling site, obtain a physiological sample from the suitable site and determine an analyte concentration thereof. 1'he above described invention provides a number of advantages, including ease of use, a single skin-piercing event, non-invasiveness and compatibility with both electrochemical and colorimetric analyte concentration characterivation assays. As such, the subject invention represents ct signil'tcant contribution W thv art.
All publications and patents cited in this specification arc; herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference. '1'hc citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention.
Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes :end modifications may be made thereto without departing from the spirit or scope of the appended claims.

Claims (15)

1. A device for determining a suitable site for sampling physiological fluid, said device comprising:
(a) at least one flow characterization element for determining the flow of said site; and (b) at least one skin-piercing element for accessing said physiological fluid at said site.

2. The device according to claim 1, wherein said at least one flow characterization element comprises an element capable of determining the temperature of said site.

3, The device according to claim 1, wherein said at least one flow characterization element comprises an clement capable of determining red blood cell character of said site.

4. The device according to claim 1, wherein said at least one flow characterization element comprises at least one light source for irradiating tissue wish light and at least one detector for detecting the light absorbed by said tissue.

5. The device recording to claim 4, wherein at least one light source is capable of emitting light at a wavelength in the range from about 400 nm to 1200 nm.

6. The device according to claim 1, wherein said at least one glow characterization element comprises an element capable of performing Doppler flowmetry.

7. The device according to claim 1, further comprising a microprocessor for processing measurements obtained by said flow characterization element.

8, The device according to claim 1, further comprising an analyze concentration determination reagent test strip.

9. The device according to claim 8, wherein said lost strip is an electrochemical test strip.

10. The device according to claim 8, wherein said test strip is a colorimetric test strip.

11. The device according to claim 1, further comprising a means for automatically determining the concentration of at least one analyze in said physiological sample.

12. The device according to claim 1, further comprising at least one fluid enhancing element.

13. The device according to claim 1, further comprising at Least one sample type characterization element.

14. The device according to claim 13, wherein said at least one sample type characterization element comprises a pulse characterization element.

15, The device according to claim 13, wherein said at least one sample type characterization element comprises a hemoglobin characterization element.