US 2915056 A
Abstract available in
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Description (OCR text may contain errors)
Dec. 1, 1959 A. s. J. LEE
RESPIRABLE GAS ADMINISTRATION APPARATUS 2 Sheets-Sheet 1 Filed May 18, 1956 mUdDOm mdnmmmda MUKDOW 5535;
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Dec. l, 1959 A. s. J. LEE
RESPIRABLT: cAs ADMINISTRATION APPARATUS Filed may 18', 195e 2 Sheets-Sheet 2 xNvEN-roR ARNOLD S. J. L EE BY @MMM H IS ATTORNEYS This invention-relates `-generally to apparatus for ad- -ministering a respirable gas to a living subject, animal or human. More particularly, the invention relates to apparatus of this character adapted 4to automatically exert `a form of control over the gas to thereby automatically render a bodily state of functioning of the subject in accordance with apre-selected standard therefor.
This-application isa continuation-in-part of my co. Vpendingapplication Serial No. 484,460 iiled lanuary27,
`In connection `with the description of the present invention, unless the .context otherwise requires, the following words andphrases Yare to be taken in the senses indicated as follows. The phrase respirable gas is used to denote `a fluid substance which may be an anaesthetic,
therapeutic'or-experimentalpure gas or mixtures of gases Aand/onvapors and/or gas-borne suspensions of liquid and/ or solids. A respirable gas of any of these sorts will be referred to as an input gas. when subject to inhalation by the patient, and asan output gas when the consequence of exhalation by the subject. More specifically, output gas will refer to that portion of the'breathed out gases from the lungs of a patient which is last breathed out just before the patient starts to breathe in again; that is, the gaseous contents of the lung which were in intimate contact with the blood. In speaking of a property or properties ofga gas, the Word property is used to denote one or more of the sum total of the characteristics of the gas Whichserve to identify the givengas by differentiating it'from all other gases. A referred to'property ymaybe physical or chemical in nature and may either represent a simple characteristic or a composite of characteristics which are all physical, Vall chemical or part physical and part chemical. i
As further considerations, the Word analyze is used to denote the action of continuously or semi-continuously measuring somel substance in .order to determine the value of one or more vproperties thereof. Also, the word automatic is usedto denote continuous or semi-continuous operation of a device yor system, essentially without the intervention of a human operator. The bodily state of functioning of a subject is to be taken to mean what is either usuallyjconsidered `a bodily .function fsuch as rate of respiration or a bodily condition such as depth of anaesthesia, `or degree of lbalance between oxygen intake and metabolism.
While from the above it will be seen that the purview of the presentjinventon comprehends a wide variety of forms o'f respirable gas administration apparatus, for convenience the shortcomings of the prior art in this field will be discussed in connection .with that form of such apparatus which is used to produce anaesthesia in a living subject. y The usual form of anaesthetc Iadministration apparatus depends upon a human operator for its control. In operating the apparatus the anaesthetist conventionally must .rely entirely upon the data 4`directly presented to his 2,915,056 "'atentedDec. 1, 1959 Vsenses in theform o'f-external symptoms manifested by depth deemed desirable inview yof the circumstances, the `'.anaesthetist,corrects for this discrepancy by manipulating his apparatusto change the current depth of anaesthesia in the appropriate direction.
From the above it will be seen thaty a number of'factors may enter into the operation of a human controlled anaesthetic Vadministration apparatus torender this operation an unreliable onefor reaching the result desired. One such factorarises outof a possibly incompleteilow of data from 4the external. symptoms of condition manifested by the subject to the sense receiving organs of the anaesthetist. Another such factor productive of unreliability may reside in theinexperience or otherpsychologicalinability of the anesthetist to correctly interpret the sense data received by him. A third such factor which should be mentionedis thertotal time-lag occurring between the time that an incorrect depth of anaesthesia .-iirst'occursand the time When'.the depth is brought back fully to its desired value. This total time lag represents an accumulation of the respective times necessary for the-incorrect depthof `anaesthesia to'be first manifested asan externalsymptom by the subject, the time necessary for the anaesthetist to iirst observe this symptom, the timerequire-d for interpretation ofthe symptom in the mind `of the anaesthetist, and the time required, after the-anaesthetist, has reached his `mental conclusion of the proper corrective measure, 'for the anaesthetist to manually carry out this corrective measure. lt will be seen that the factors contributing to this total time lag each represent an inherent slownessof response of the hu- `man body or brain, and that hence the time lag is unavoidable infthe conventional anaesthetic administration technlque.
It has been proposed heretofore to circumventthese shortcomings by providing anvautomatic anaesthetic administration system. This prior art system, however,.is designed to determinethe depth of 'anaesthesia of the subject by means of electric signals which are generated either within the body of the subject or as the result oi a direct sensing, by probes or the like in contactwith the body of the subject, of the body functioning of the subject. Thus, the mentioned prior art system-proposes to use electro-encephalographic or electrocardiographic signals as indications of the depth of anaesthesia of the subject. These signals are in themselves complex in form, and, moreover, the functional relation between the signals and the depth of anaesthesia is relatively complex. Accordingly,A it is necessary in the mentioned prior art system to have an unusually complicated system of electric circuits and electronic tubes. This large-scale electrical organization is, of course, undesirable because of the expense, bulk, liability to failure, and difficulty o'f maintenance involved.
It is accordingly Van object of the invention to pro- .vide respirable gas administration apparatus which is lfree of the disadvantages noted above.
Itis another object of this invention to provide apparatus of the above noted character which operates by virtue of a relatively simple indication of the bodily state of functioning of the subject.
A further object of the invention ,is to provide `apparatus of 'the `above noted character .requiring a `minimum number of electric circuit and other organizational components.
These and other objects are realized in accordance with the present invention by providing a uid flow system carrying alternate ow of input and output gas to and from a living subject, and by providing an adjustable gas regulator mechanism connected in this system in regulating relation with the input gas to exercise a form of control thereover affecting the bodily state of functioning of the subject. Further, a gas analyzer means is connected in the mentioned fluid How system in responsive relation with the output gas to automatically analyze the same by a mode of analysis providing signals indicative of the bodily response of the subject to the input gas. The signals so developed by the analyzer means are received by an automatic means which, responsive to these signals, adjust the regulator mechanism to automatically control the input gas to render the bodily state of functioning of the subject accordant to a preselected standard.
The invention may be better understood from the following detailed description of typical embodiments thereof, taken in conjunction with the accompanying drawings, in which:
Fig. l is a schematic diagram of a respirator-anaesthetizing apparatus constructed according to the invention;
Fig. 2 is a diagram of details of the apparatus of Fig. 1; and
Fig. 3 is a schematic diagram of an anaestheti'c administration apparatus constructed in accordance with the invention.
In the description to follow it will be understood that analogous elements in the two embodiments will be designated by the same number, with such elements in the second embodiment being further designated by a prime sux for the number. Further, analogous elements in the same embodiment will be designated by the same. number with different letter suffixes.
Referring now to Figs. 1 and 2 which show a respirator-anaesthetizing apparatus for inducing forced breathing of a living subject along with administration of anaesthesia thereto, as a part of the apparatus there is shown a fluid ow system permitting alternate ow of input and output gas to and from a subject during, respectively, the inhalation and the exhalation phase of each recurring respiration of the subject. More speciiically, this uid flow system includes a gas distributing manifold having an inlet port 11, an outlet port 12, and an exhaust port 13. An adapter 14 is coupled to manifold 1t) for the purpose of guiding gas between the manifold and the respiratory tract of the subject.
The inlet port 11 has connected thereto a tirst conduit means comprised of apair of conduits 20, 21 respectively communicating with sources (not shown) of anaesthetic gas (as, say, nitrous oxide at 50 p.s.i.) and a source of oxygen (at, say, 50 p.s.i.). The mentioned conduit means is also comprised of a third conduit 23 coupled directly at one end with the inlet port 11 and coupled at the other end through a mixer 24 with the conduits 20, 21.
The conduits 20, 21 in the usual manner have respectively interposed therein the manually set pressure regulators 26, 27. Each of these regulators is adapted to accept gas at high pressure from the source coupled therewith by way of the conduits, and to deliver this gas at some lower preset constant pressure essentially independent of the rate of gas flow. For indications of this lower preset pressure, the conduits 2i), 21 are respectively equipped with the pressure gauges 28, 29.
.The mixer 24 is a conventional gas ow device for mixing two gases in a constant preset proportion essentially independent of the rate of flow of the mixture of the gases. Thus, from the input of nitrous oxide and oxygen respectively received from the conduits 20, 21,
the mixer 24 is adapted to flow into conduit 23 an anaesthetic mixture of fixed composition as, say, 70% nitrous oxide and 30% oxygen. By virtue of the construction of mixer 24, the percentage composition of this intermixture remains constant irrespective of pressure changes in conduit 23.
To provide for control of the input gas, the conduit 23 has interposed therein a variable regulator mechanism 30. In the present instance the input gas is controlled with regard to the specific property of the preslsure thereof, and hence the regulator mechanism 30 is a variable pressure regulator which is adjustable in its regulating action by appropriate movement of a controller arm 31. In essence, the variable pressure regulator 30 receives gas owing at medium pressure through conduit 23 from mixer 24, the regulator delivering this gas at some lower pressure determined by the position of control arm 31. The described regulator may be of the type commonly employed on acetylene and oxygen tanks for welding purposes, the regulator control arm being adapted to motor drive. The lower pressure output gas from the regulator is delivered into conduit 23 for flow thereof to inlet port 11 and from thence through manifold 10, adapter 14, and into the respiratory tract of the subject. For convenience in measuring the pressure of the regulated input gas, the portion of conduit 23 between regulator 30 and inlet port 11 may be equipped with the pressure gauges 32, 33 adapted respectively, to give exact pressure readings over a limited scale and approximate pressure readings over a wider scale.
The outlet port 12 has connected thereto a second conduit means in the form of a conduit 40 running between the outlet port and an exit 41 permitting venting of gas in the conduit to the atmosphere. The conduit 40 has connected therein a gas analyzer means 42 (to be later described in further detail) and a sampling means 43 disposed in the conduit between the gas analyzer means and the outlet port 12. The sampling means in its essential components comprises a collapsible, but somewhat stift' and resilient tube 44 (fabricated from say, rubber), a larger diameter rigid tube 45 enclosing the major extent of tube 44 in a pressure-tight chamber, and valve means in the form of a check valve 46 disposed in conduit 40 between manifold 10 and tube 44 to permit ow of gas in the conduit only from the manifold towards the analyzer 42. The sampling means 43 may also desirably include a second check valve 47 disposed in conduit 40 between tube 44 and analyzer 42 to preclude any substantial backward iiow of gas from the atmosphere through the exit 41 and thence into the analyzer.
As stated, the presently described apparatus is in part a respirator apparatus adapted to produce forced breathing in a subject. To this end the apparatus is provided with a two-way breathing valve wherein a valve plug 50 is adapted to be reciprocated back-and-forth between an upward seated position covering the exhaust port 13 and a lower seated position covering the inlet port 11. In this reciprocation the valve plug 50 is moved downwardly by a spring 51 disposed above the plug to act in compression thereagainst from a xed support for the spring. Conveniently, the spring 51 may be positioned within an exhaust conduit 52 leading from exhaust port 13 to the atmosphere, the fixed support in this case being in the form of a bracket 53 extending radially inward of conduit 52 to hold the spring in alignment with the axis of the conduit. For better guidance of valve plug 50 in its reciprocating movement, preferably the compression spring S1 encircles an upper guiding stem 54 which extends from a juncture with plug S0 upwardly through bracket 53 by way of a bore (not shown) therein serving to constrain the stem to up and down movement only.
To provide upward movement in reciprocation of the valve 50, a fluid pressure cylinder 60 is mounted by an internal bracket 61 within and in alignment with the axis of a vertical section of conduit 23 adjacent to the inlet .frptfV 1 1. cylinder l6th-containswithinv itsbore; a-,piston E1.62` connected to the `valve plug :.50 :by` alowen valve stem ,163. Thus,-intthe presence of increased pressure inicyl- ,inder 60, suflicient force willbeexertedon thelpiston to drivevalve plug 50 against thecompression of springiSl 1 ygtoan upwardly seated position sealing exhaust `port 13. .t Conversely, when the pressuregin cylinder 60 is per- @mitted to decrease, the ccmpressivefforce `of spring 51 overcomes the upwardly directed `piston-force. Accordingly, both valve plug 50 and-piston62fare driven downward with the respective consequences that the plug is seated to seal off inlet port-lLwhilethe interior of cylinder is emptied of fluid by the downward movementof the piston.
Reciprocation of the described breathing valve isv established by a timing means (Fig..2) comprised of a constant speed motor 70, a breathingcontrol cam 71a and sampling control cam 71b commonly driven by the motor- 70, and a breathing controlA slide vak/e720:V and sarnpling control slide valve '72b actuated, respectively, from the cams 71a and 71b. Since the two valves mentioned are essentially similar in construction, it is only necessary ,for the most part to describe slide valve 72a, it being understood, that, unless -otherwise noted, the description of a given number element in valve 72a applies as prop- `erly to ,the element designated by the same number in valve 72b.
The slide valve 72a comprises a cylinder 75a,\a piston 76a, slidable in tight-fitting relation within this cylinder,
j a cam follower 71a mounted on piston 76a to ride on cam 77a .to thereby translate the .variation in contour vthereof into up and down piston movement, and a compression spring 78a acting on 4piston 76a to maintain cam follower 77a in iirm contact with its cam. Within cylinder 75, the piston 76a is cut away -circumferentially tohave formed therein anannular groove 79a. The groove 79a performs the function of furnishing a fluid ow coupling between either a middle conduit 85a and a lower conduit 86a coupled to a high pressure uid source, or between the middle conduit 85a and anupper conduit 87a venting to the atmosphere. The middle conduit 85a is itself coupled with the interior of driving cylinder 60 for the breathing valve.
As` stated, the sampling control valve 72b is essentially similar in construction to the breathing control valve 72a with the following exceptions. First, the cam 7117 which operates valve 72b is of different contour than the cam 71a for valve 72a. Second, in valve 72b it is the upper conduit 37b which is connected to the high pressure fluid source, and it is the lower conduit 86a which opens to the atmosphere. Third, the middle conduit 85b of Valve 72b furnishes a iiuid ilow coupling from the valve to the interior of the outside tube 45 (Figures 1 and 2) in the sampling means 43.
Considering for the time being the `action of breathing control valve 72a only, the contour of the cam is subdivided into a lowered arc 90 of smaller angular extent and a raised are 91 of larger angular extent. When cam follower 77a rides in lower arc 90, the piston 76a YVpositions groove 79a to provide for flow of high pressure 'uid from conduit 86a through conduit 85a lto the interior of cylinder du. The valve plug 50 will be accordingly moved upwand to uncover inlet port11 and to seal exhaust port 13. Responsive to this valve plug movement, a ow of input gas under slight pressure will ensue from conduit 2,3 into manifold lo and from thence through adapter 14 into the respiratory tract of the subject. Within the respiratory tract, the slight pressure of the input gas causes the subjects lungs to expand, the net effect being an inhalation by the subject which is forcibly induced. I
The changeover from inhalation to exhalation in the Auforced respiration of the subject is effected by rotation of the yearn 71a raising the cam follower 77a up upon the arc .'91 of the cam contour. Piston 76a is accordvingly moved-upward to 'disconnect `heginterior ofcylin- .der 60 (Figujrelyffromlthe uidppressure conduitv'da (Figure v2) ;an,d`-to1establish` an exhaustpath for the cylinder thronghconduit 8,5,z,:valveg groove 79a, and ex- 10'are respectivelyuncovered and,sealed. With the respective changes in condition takingplaceas torthese two ports, the lungs of the-subjectfare freeof the pressure effect ofthe input gas. Freed of this pressure .,efect, `the' subjectslungs contract `elastically to exhale output gas through adapter 14,f-manifold 10, exhaust port 13, and exhaust conduit 52.
-lt is thus seen that theqdescribed apparatus develops recurring forced respirations of Ythesubject consisting alternately., of inhalationsand-exhalations. An apparatus performing this function iscommonly used, for example, where for medical reasons it is desirable to anaesthetize da subject who has been completely paralyzed by the action of a drug or the like. Y
It is well known, in the normabphysiological control of respiration, that the `amount of lair. taken into a subjects lung is'so adjusted by thesubjects body that the carbon dioxide level remains constant at the subjects physiological level. The Ycarbon dioxide normally present exerts a tension of 40mm. of mercury. vThis -amount of air is then usually adequate to provide a proper voxygen availability to the bloodin the subjects lungs.
In natural respiration, this amount of air taken in is ordinarily controlled by a physiological process wherein involuntary nerve centers of the human body respond `to the percentage of carbon dioxide in the blood stream `to adjust the rate and/ or depth of respiration. Thus, where the carbon dioxide in the blood stream increases, the mentioned nerve centers act to increase the involuntary `depth and rate of breathing or to createafeeling oi shortness of breath in the subject. Also, when the carbon dioxide inthe blood streamdecreases, the mentioned nerve centers adjust .the involuntary `breathing of the subject to the proper rate, and depth.
It will be evident, however, thatwith complete paralysis of the subject, the described involuntary self-adjustment of the state of bodily functioning of the subject is `no longer effective because of paralysis of the lungs. Unless the carbon dioxide tension is carefully controlled by accomplishment of the required tidal exchange,vimpor tant consequences result. Thus, reducing the alveolar tension to say 2O mm. mercury induces a general vasoconstriction, especially in the cerebral blood vessels and diminishment of the respiratory drive as the respiratory center is made less sensitive. Still lower carbon dioxide tension, such as l0 mm. of mercury, produces syncopy or fainting. Higher carbon dioxide arterial blood tensions than normal, such as about `50 mm. of mercury, cause increased respiratory drive, dilate the cerebral blood vessels, and often cause increased blood pressure and pulse rate. It is, accordingly, necessary that some artificial substitute be provided for the involuntary control over respiration normally provided within the body of the subject when the subject is anaesthetized.
In accordance with the present invention, to provide for this substitute control over respiration, the cam 71b is shaped in contour to have radially raised and lowered portions lill) and 101 which are respectively of such angular extent and phase with respect to the contour of cam 71a (which establishes the periods of inhalations and exhalations) that the cam follower 775 rides on lowered arc 101 only during a short intervalat the end of each exhalation. Thus, during a major interval of a respiration induced in the subject, the piston '76b of the sampling control valve is positioned upward to establish a uid flow coupling from pressure conduit 87h through valve groove 79h and conduit SSbto the interiorof 7 the outside tube 45 of sampling means 43. In consequence, there is produced within this outside tube a high pressure condition which collapses the inner tube 44 during inhalation by the subject and during most of the time of exhalation thereby. At the end of exhalation, however, the cam follower 7712 drops momentarily into the lowered arc 101 of cam 71b with the consequence that piston 76b drops downward to vent the interior of tube 45 to the atmosphere through conduit 85h, valve groove 79b and exhaust conduit 86b. With the pressure within tube 45 so released, the inner tube 44 springs back into uncollapsed shape to thereby produce a vacuum in i-ts interior. Responsive to this vacuum, the check valve 46 opens to permit a sample of end-of-exhalation output gas to liow from manifold 10 to within tube 44. When,
aty the beginning of the next inhalation, the cam follower 77b is once again raised up on the arc 101 of cam 71h, the resulting higher pressure condition re-established -within tube 45 causes the tube 44 to again collapse to thus force the contained sample of end-of-exhalation output gas through the check valve 47 to fiow through the analyzer 42.
As is known, over the whole interval of an exhalation, the carbon dioxide content of the output gas undergoes a wide fluctuation in value, the spread in values in this fluctuation not being of substantial significance as a measure of the carbon dioxide level in the blood of the subject. Considering the succession of individual fluctuations occuring from exhalation to exhalation, however, there may be discerned therein a trend in value representing a measure of the carbon dioxide content of the blood stream. The course of this trend may be established in various ways, as by taking the average value of each fiuctuation or the highest value thereof, or the lowest value thereof, or the value thereof at some fixed phase in time of the exhalaton period. It has been found, however, that a very satisfactory measure is obtained of richness of the blood in carbon dioxide if a sampling means like that described is utilized to sample the output gas by taking end-of-exhalation samples thereof which are, of course, alveolar gas. Since no carbon dioxide is administered, it has a zero concentration in the input gas. Therefore, the difference between arterial carbon dioxide concentration and venous carbon dioxide concentration will be small, even when there are appreciable areas of atelectasis. The carbon dioxide output gas tension accordingly will about equal the arterial blood carbon dioxide tension. Since the output gas, i.e., the last portion of the expelled or alveolar gas, normally has a carbon dioxide tension of 40 mm. of mercury the arterial tension in carbon dioxide will be about the same figure.
The output gas samples which pass through analyzer 42 are analyzed therein for the specific property of the output gas of its carbon dioxide content. Preferably the analyzer 42 is in the form of an infra-red spectrophotomer analyzer such as is described in further detail on pages 1021 and 1036 of Medical Physics, Volume II, by Otto Glasser and published by the Yearbook Publishers, Inc., Chicago, Illinois. An analyzer of this type is adapted to provide on an output lead 165 an electrical voltage signal which is roughly proportional to (or, at least in direct correspondence to) the percentage of carbon dioxide in the gas mixture fed to it. For the purpose of generating such signal, the analyzer has a selfcontained amplifying system.
The analyzer signals on lead 105 are fed to an automatic means which responds to these signals to automatically adjust the setting of or maintain a given setting of the variable pressure regulator 30. This automatic means may take the form in a broad sense of a means for generating a reference signal representing a preselected Value for the end-of-exhalation carbon dioxide content of the output gas (and thus a preselected value for the richness of carbon dioxide in the blood stream), a means for comparing the analyzer signals in value with this reference signal, and a means responsive to a change in value of the analyzer signals away from the reference signal for adjusting the pressure regulator 30 to ultimately cause the analyzer signals to follow the reference signal. While the reference signal may, of course, be a signal which changes in value over time in a preselected manner, in most cases it suffices for the referenceV signal to have a steady value over time in the absence of manual intervention to change the value of the signal.
As a specific example, the automatic means referred to may take the form shown in Figure 1 wherein the reference signal is generated as the steady voltage output of a reference signal generating means 109. This means may take such form that the output thereof appears on a movable tap of a potentiometer resistor 111 connected across a voltage source shown as the battery 112. As stated, this reference signal represents a preselected value for the end-of-exhalation carbide dioxide content of the output gas, the signal thus being indicative of a preselected value for the richness in carbon dioxide in the blood stream of the subject being administered to by the apparatus. Selection of such value or a change in the selected value from one to another value is effected by manually sliding tap 110 over resistor 111. A meter 113 may, for convenience, be connected with a signal carrying lead 114 from tap 110, the meter indicating the voltage of the reference signal.
The analyzer signals on lead 105 and the reference signal on lead 114 are fed as respective inputs to a servo system such assay, a servo-system comprised of the components manufactured by the Brown Instrument Division of the Minneapolis Honeywell Company of a continuous balancing amplifier (catalog number 351921 and a balancing motor (catalog number 767504). As shown in Figure 1 this servo system is comprised essentially of a servo amplifier 119 (consisting 'of a subtracting chopper amplifier 120, and a power amplifier 1'21) and a servo motor 122 in the form of a two-phase induction motor characterized by a first phase winding 123 and a second phase winding 124 which is spatially in quadrature relation with phase winding 123. The phase winding 123 may be energized in a conventional manner from an alternating current power source 125, which also acts, as will now be described, as a synchronizing signal source for the subtracting chopper amplifier 1120.
The subtracting chopper amplifier is of a Well known type, which, in the presence of a difference in voltage between the analyzer signals and the reference signal inputs, is adapted to produce an error signal form of the analyzer signals. This error signal represents by its amplitude and polarity the amplitude and polarity of the voltage difference between the input analyzer and reference signals. As another function, the subtracting chopper amplifier 120 is adapted to render this error signal of alternating form by chopping the error signal at the frequency and phase of a synchronizing signal received by the amplifier. In the present instance, this synchronizing signal is a signal originating with alternating source 125 which is thereafter impressed with a 90 phase shift by a phase shifting device 126. Accordingly, if there is no dilference in voltage between the analyzer signals and reference signal inputs to amplifier 120, the amplifier will produce zero output. On the other hand, a voltage difference between the input signal will be represented at the output of the amplifier by an alternating error signal of the same frequency as the current which excites phase winding 123. In dependence on Whether the analyzer signals are greater or less than the reference signal, the error signal output from amplifier 120 will have one or the other of opposite phases, both of these phases being electrically displaced 90 from the phase of the current energizing winding 123.
The error signal output from amplifier 120 is fed to 19 il firepower-amplifier 121 which-.amplifes 'the signalbysan t amount suicient toprovide forproper energization ofthe :phase .winding 124the amplied error 1signal being applied to this winding. AAs` is known, the motor 122 :rwillnot rotate when only phasewinding 123 is energized. 1
.In the presence, however, of an error signal which'energizes winding 124 in 90 phase relation to the current inwinding 123, the motor 122 will rotate in one direction of rotation or the other in dependence on whether the @error signal leads or lags by"90i the exciting current for .Winding 123.
.The mechanical angular output of motor 122`is couipled to the control arm 31 of pressure regulator 30 .by a linkage consisting of the arms 128 and 129. .There is I thus established in the respirator apparatus a closed loop ttcausal sequence wherein a series of responses are inter- Arelated as follows:
'i If ythe quantity of gaseous intake by the subject'is lower than optimum, this fact is manifested in the physiological functioning of the subject by an increase inthe` vvhale more deeply, the carbon dioxide-content of the sub-H jectls blood stream is diminished until the proper balance is once again restored between vthe quantity ofgaseous intake and the carbon dioxide level of the subject. Conversely, if the-quantity of gaseous intake by the subject is greater than optimum, the carbon dioxide content of this blood stream drops to create a difference between the analyzer signals and the reference signal to thus stimulate t thedescribed servo system to adjust vthe regulator 30 to decrease the pressure of the input gas fed to the subject.
As la result, the forced respiration of thesubject will be2 less deep, and the carbon dioxide content ofthe blood stream will rise to its proper level.
By means of this invention actual` tests have` maintained arterial blood carbon dioxide tension within 3 mm.
of `40 mm. of mercury, the normal tension, for aslong as three hours during surgical operations.
kInstead of controlling respiration on the basis of carbon dioxide, the same thing may be accomplished by analyz- `ing the oxygen content of the outputgas and adjusting .jthe oxygen or air given to the patient to maintain a normal arterial oxygen tension of about 105 mm. of mercury. The alveolar gas oxygen tension is normally about V110 mm. of mercury. The gradient between arterial and .alveolar oxygen tensions is ordinarily about mm. of mercury although errors in ventilation or dilfusion may make for increases in the gradient. For the purpose of Icontrolling respiration by oxygen analysis it is convenient to base the respiration control system on the normal venous oxygen tension of 40 mm. of mercury. Using this as Athe standard, a sample of output gas taken at the end of exhalation may be analyzed for oxygen content, cornpared with the standard and the input gas adjusted accordingly to maintain proper administration of oxygen. uIn such a system it is generally desirable to maintain an `input oxygen tension of below 250 mm. of mercury since nonrapparent errors may arise `due to the characteristics of hemoglobin-oxygen dissociation.
1"Referring now to Figure 3, there isshown therein another example of the present invention in the form of an apparatus for administering anaesthetics to a subject. In this apparatus a manifold 10' has an inlet port 11',and an outlet port 12', and has joined therewith an adapter '.14' in the form of a mask .which fits over thenose .and mouth of the subject. The adapter 14', asv before,y performs the lfunction of furnishinga guidewayforafow of I zfgasfbetween manifold v10' and Ithe respiratorytract =of the subject.
Coupled with the inlet port 11' is a first conduit means vconsisting of .the separate conduits 20', 21', respectively 1 coupled to a source. of anaesthetic gas (as, say, cyclopropane) at above atmospheric pressure and a source of oxygen at above atmospheric pressure. The first-con- 4,duit :means is also comprised of a mixing conduit v coupled between a gas flow junction 131 and a junction of the conduits 21', 20', a conduit 23' coupled directly to the inlet port 11', and a breathing purier 132 coupled in Aterms of gas ow between the gas ow junction 131and the conduit 23'. The conduits 20', 21' have conventional :rate of flow meters 135, 136, respectively connected therein to regulate the ow of gas in each of these conduits. Further control over these gas Hows is afforded by a manually operated needle valve 137 connected in conduit 21' and by a needle valve 138 in conduit 20 ywhich permits a iiow of cyclopropane therethrough in accordance 20` .ftheneedle Valve.
with the setting in adjustment of a control arm 139'for The cyclopropane in conduit 20 and the oxygen in conduit 21' ow into conduit 130 to be intermixed therein to form the input gas administered to the subject. This input gas has a relative percentage composition of pure anesthetic gas and of oxygen gas wherein the relative percentages of these two components are determined by the respective settings of the needle valves 137 and 138. From rconduit 130 the input gas ows through junction 131,;purifier 132, conduit 23,`inlet port 11', manifold 10', and adapter 14' into the respiratory tract of the subject during inhalation thereby.
The outlet port 12' for the manifold has connected therewith a secondconduit means in the form. ofa conduit 40' running between the outlet port and the gas oW junction 131. The output gas exhaled by the patient -is conveyed by conduit 4b' from manifold 10' to junction 131 from whence the output gas passes through the purifier 132 which is` a carbon dioxide absorber. The output gas after being freed of most of its carbon dioxide content by passing through the purifier is recircuiated back through conduit 23 to the subject. In this connection it will be noted that while there may be a considerable volume of circulating gas, the quantity of gas iiowing out of conduit 130 just balances with the quantity of gas which is inhaled and absorbed by the subject. Thus there is a ow of input gas to the subject although this flow is accomplished through the intermediary of a volurne of circulating gas.
To assure a proper gas circulation of the sort 'described, the apparatus is provided with valve means consisting of the check valve 140 disposed in conduit 23' to Vpermit gas iiow only toward inlet port 11' and `also the check valve 141 disposed in conduit 40' to permit gas ow in this conduit only away from the outlet port12.
The apparatus,v of Figure 3 as so far described (with the exception of the mechanically adjustable needle valve 138) represents a closed circle anesthesia system such as is disclosed on page 24 of the afore-inentioned text by Otto Glasser. Such system is characterized by continuous circulation of the anesthetic gas around the loop formed by conduit 23', manifold 1d', conduit 40', and purilier 132. The fraction of oxygen `and cyclopropane l.absorbed by the subject from the circulating anesthetic mixture during inhalation is continuously replenished -yfrom the oxygen and cyclopropane flows in the conduits 21' and 20'. Further, in the circulating mixture, the 'waste product ofcarbon dioxide exhaled by the subject `is`continuously removed by a soda lime mixture in 'the purifier :132. To permit closed loop circulation of the `anesthetic mixture without the introduction of pressure conditions varying widely from those normal for respiration, the described apparatus includes a accid balloon 145 connected to the purier 132. As theV pressure in the circulating ,mixture rises and falls, the balloon-145 1`l responsively expands and contracts to tend to maintain the pressure at atmospheric value.
When a subject is under anaesthesia, the depth of anesthesia of the subject at any time, although usually ascertained by indirect symptoms thereof such as rate of respiration or rate of heartbeat, is in fact in direct relation to the percentage content of anesthetic gas in the blood stream of the subject. This blood stream content of anesthetic gas is reflected in the percentage of anesthetic gas appearing in the output gas exhaled by the subject.
As in the case of the carbon dioxide content of the output gas in the Figure l apparatus, however, the content of anesthetic gas in the output gas of the Figure 3 apparatus is characterized by a short term iuctuation in value over the period of each exhalation and by a trend of the uctuations from exhalation to exhalation. Of these two factors, only the trend in anesthetic gas content from exhalation to exhalation is a satisfactory indication of the depth of anesthesia of the subject. Accordingly in the operation of the Figure 3 apparatus, to automatically bring the subject to or maintain the subject at a preselected depth of anesthesia, it is necessary that the trend in this percentage content be dissociated from the short term uctuations therein.
To provide for automatic control of depth of anesthesia, the apparatus of Figure 3 includes a gas analyzer 42' connected in conduit 40 between the outlet port 12' of the manifold and the mentioned gas flow junction 13-1. The analyzer 42 may be an analyzer generally like the analyzer 42 of the Figure l apparatus except that analyzer 42 is adapted to analyze the output gas for a percentage content of cyclopropane rather than for a percentage content of carbon dioxide. It will be noted that the aforementioned text by Otto Glasser describes on page 1024 and on page 1036 the details of analyzers suitable for both such purposes.
As is to be expected, cyclopropane analyzer 42' represents the outcome of its analysis for this gas in the form of electrical signals.
The Figure 3 apparatus, like the Figure l apparatus includes an automatic means responsive to the signals of the analyzer for adjusting the regulator mechanism for the input gas to produce a preselected bodily state of functioning of the subject. Thus in the present instance the automatic means adjusts the setting of the adjustable needle valve 138 to govern the relative percentages of cyclopropane and oxygen injected into the circulating anesthetic mixture to thus bring the subject to or maintain the subject at a preselected depth of anesthesia. This automatic means is analogous to that previously described for the Figure 1 apparatus in that it is comprised of the components of a reference signal generating means 109', a subtracting chopper amplifier 120', a power amplitier 121', the mentioned components being constructed and mutually cooperative in a manner alike to the corresponding components of the Figure l apparatus. The automati-c means of the Figure 3 apparatus differs, however, in one important respect, now to be described, from the automatic means of the Figure l apparatus.
It will be noted in the Figure 3 apparatus that the conduit 40', which serves among other uses to couple the cyclopropane analyzer 42 'in responsive relation with the output gas, permits the free flow of output gas during the Whole of each exhalation period by the subject. This free flow of output gas in conduit 40 is preferable in a closed loop anesthetic administering system (of which conduit 40' represents a section of the loop) vin order to avoid the setting up of pressure stresses in the circulating anesthetic mixture as a result of interruption of the free circulation. It follows, however, that with free flow of output gas through conduit 40 during the whole of each exhalation, the output signals from analyzer 42 will also extend over the whole of each a servomotor 122 and a phase shifter 126',
exhalation. Thus these analyzer signals will, as the unmodified output of the analyzer, be indicative of both the intra-exhalation fluctuations and the inter-exhalation trend in percentage content of anesthetic gas in the output gas, rather than being the desired indication of the trend in percentage content dissociated from the fluctuations thereof.
For the purpose of rendering the Figure 3 apparatus responsive primarily to this trend in percentage content. the apparatus is provided with a sampling means in the form of a pressure sensitive switch and a sampling relay 151. Considering first the switch, this component comprises a gas tight container 152, a resilient diaphragm 153 of electrically conducting material dividing the interior of container 152 into left hand and right hand gas tight chambers 154, 155, a contact 156 mounted on diaphragm 153, and a pair of fixed contacts 157, 158 respectively located within chambers 154 and 15S to respectively close with contact 156 when diaphragm 153 is in an expanded and a contracted condition. Normally diaphragm 153 is in contracted condition so that the contact 156 of the diaphragm is electrically closed with the right hand xed Contact 158.
For control of the expansion and contraction of diaphragm 153, the left-hand chamber 154 of container 152 is connected by a conduit to a junction 161 of this conduit with a section of conduit 40' between manifold 10 and analyzer 42'. The right-hand chamber 155 of container 152 is connected by a conduit 162 with the gas iiow junction 131. During the major time interval of a respiration by the subject, the fluid pressure in conduit 40 at the junction 161 is either greater than or substantially equal to the fluid pressure at junction 131. These relative pressure conditions are duplicated by the relative conditions of the pressures within chambers 154 and 155 to maintain diaphragm 153 in contracted state to thus keep contact 156 closed with Contact 158. At the beginning of inhalation, however, the initial indrawing of breadth by the subject reduces the pressure at junction 161 below the pressure at gas junction 131, the mentioned pressure reduction being augmented by the action of check valve 141 in preventing ow of gas from junction 131 towards the other junction. The resulting pressure reduction in chamber 154 of container 152, relative to the pressure in chamber 155 thereof, causes diaphragm 153 to expand so that contact 156 moves leftward to momentarily close with contact 157. At this.time the output gas within analyzer 42 is that fraction of the output gas expelled by the subject substantially at the end of exhalation. Of course, the described momentary pressure drop is speedily relieved by iiow of gas from conduit 23 through manifold 10 into conduit 40', the diaphragm 153 hence recontractng after a short interval to break the contact of elements 156, 157 and to reestablish the contact of elements 156 and 158.
The contacts 156 and 153 are in a condenser charging circuit consisting, in series connection, of contact 156, the diaphragm 153, a capacitor 165, a charging source shown as the battery 166, a resistor 167, and the contact 158. When contacts 156 and 158 are closed, the condenser charges up through the described circuit to output voltage value of the battery 166. The contact 156 is also in a discharging circuit for capacitor 165, this discharging circuit consisting of the upper side of the capacitor, the diaphragm 153, contact 156, contact 157, a relay winding of sampling relay 151, and a return through ground to the lower side of capacitor 165. When contact 156 momentarily closes with Contact 157, the previously charged capacitor discharges through the circuit just described to produce a momentary energization of relay winding 170. This energization occurs at the beginning of inhalation when, -it will be recalled, the output gas within analyzer 42' is substantially of endof-exhalation nature.
The relay winding 170 of sampling relay 151 operates 'gerente motor 122 in its action of` adjusting needle valve 138 is thus made responsive to the inter-exhalation trend" in the mentioned percentage content Arather than to the intraexhalation fluctuations thereof. From the foregoing the operation `ot" the apparatus in Figure 3 will beilargely selfevident; I The" reference signal generatingf means 109 provides a referenceY signal of a value representingla preselected depth of anesthesia for the subject. If the subject isV or becomes under-anesthetized with respect to this depth, the resulting lack of cycl'opropane inthe blood stream of the patient will lie-manifested at the end of exhalationr by* a low or lowered percentage content of cyclopropane inthe output gas. YThis under value of cyclopropane has the effect, by the` respective actions of the; analyzer 42', the subtracting chopper amplier 120', the poweramplifer 12,1, the sampling` relay 151 andthe servomotor 122', of producing a setting in adjustment of needlevalve` 138 to increase the ow of cyclopropane through conduit 20 to thereby bring the subject to or restore the subject to the preselected depth ofv anesthesia. In like manner, if the subject is or becomes over-anesthetized, the excess of cyclopropane in the blood stream ofthe subject initiates a` sequence of events in the operation of the apparatus which brings' the subject to or `restores' the subject to the preseiected depth of anesthesia.
1n the administration of anesthetic gases such as ethyl ether, chloroform and cyclopropane, which are essentially not consumed or changed by the body, concentrations of such gases are usually administered which the. patient may well tolerate until anesthesized to the desired level, after which time the administration must be continued at such concentrations so as to maintain an equilibrium between Vthe anesthetic input and anesthetic output. `The apparatus of this invention maintains the necessary equilibrium. For lirst plane anesthesiay (surgical), or slightly lighter, the following concentrations may `be used:
A rterial Plood, Conc. mgnL/lOO ce.
Substance Itf is assumed for such `concentrations to vcreate the 'd esired equilibrium that the so-called Ventilation/ perfusion T4 aboveior below that required' forv thesdesiredtanesthesia; the automatic means responds thereto and 'causes 7the needle valve to increase or decrease the concentration of anesthetic in the input gas.- Theconcentrations of typical anesthesia gases which, when present `in the output gas,fgive various depths of anesthesia are as follows:
Depth of Anesthesia Analgesic Light. Deep i Percent Percent Percent Dethyl ether 5 1Q Chloroform 0.2 0. S 1: .3 Cyclopropanc 5 1:5 la Ethyl chloride V' l ath 0.2 2 5 65 SO 0. 3 0.5 0. 8
When one of these gasesis administered an analyzer is used which is capable of analyzing for the particular anesthetic gas administered. Thus, a chloroform anallyzer is usedwhen chloroform is administered, and an ethyl ether analyzer is used when ethyl ether is the anesthetic gas administered.
In cases Where the anesthetic induces anethesia while the patient continues to breathe, as with cyclopropane, not only may the administration to one patient of cycloy propaneV be regulated by this invention but, also, the
total volume exchange of respired gases. This is accomplished by analyzing alternate exhalations for cyclopropane and either oxygen or carbon dioxide. By
varranging'the apparatus in a suitable manner each exhalation say 'be analyzedifor the content of both such gases. The sampling arrangement may be set up as desired.
The above-described embodiments beingV exemplary only, it `will be understood that the present invention comprehends organizations dilering in form or detail Vfrom the presently described embodiments. Accordingly, the invention is not to be considered as limited save as is consonant with the scope of the followingclaims,
1. Apparatus for administering a respirable gas to a living subject comprising, a fluid flow system providing forfalternate ow of input and output gas to and from said'subject during the inhalations and exhalations there.- of, adjustable gas regulating mechanism connected in said system in regulatingrelation with said input gas to thereby quantitatively control a bodily state offunctioning of said subject, gas analyzer means connected in said systeni'in responsive relation with said output gas, said apparatus being adapted by automatically analyzing said V output gas to produce signals` indicative of the bodily reratio is about unity, i.e., there are no signicantportension is thefcontrolling determinant of the depth o f anesthesia Where the ventilation/ perfusion ratio is about unity the anesthetic partial pressure in the input `gas is the controlling determinant of the depth of anesthesia. Where the ventilation/perfusion ratio is not `close to unity, the input concentration of the anesthetic gas must be raised in accor-dance with the defect tor maintain the same arterialanesthetic blood level.
Thel administration of an anesthetic gas is regulated by the concentration of such gas in the outputgas or exhalation as determined by the analyzer, which then signals the automatic means for adjusting the needle valve for controlling input of the anesthetic gas. The automatic means is pre-set and controllable. lf the ,analyzer sponse ofsaid subject to said input gas, and automatic means responsive to said signals for adjusting said regulatping' mechanism to render saidvbodily state of functioning of said' subject accordant with a preselected standard therefor.
2. Apparatus as in claim 1 wherein said apparatus is a respirator apparatus adapted to produce forced respiration of said subject. 3. Apparatus as iu claim 1 wherein said apparatus is an anaesthetic administration apparatus.
4. Apparatus for administering a respirable gas to a `living subject comprising, a uid ow system providing for alternate flow of input and output gas to and from said subject during the inhalations and exhalations thereof, adjustable gas regulating mechanism connected in said system in regulating relation with said input gas to quantitatively control a property thereof serving -to quantitatively control a bodily state of functioning of said subject, gas analyzer means connected in said system Vin responsive relation with said outputgas to automatically analyze the same for a property thereof characterized in quantitative valuegbyshorttetmfflucwatltlls and allonger term'trend, said uctuations and Itrend being manifested, respectively, within individual exhalations and from eX- halation to exhalation, and being, respectively, extraneous to and indicative of the bodily response of said subject to said input gas, said analyzer means being adapted to generate signals as the outcome of said analysis, sampling means operable by repetitively sampling said fluctuations to render said analysis indicative in terms of said signals of said trend dissociated from said fluctuations, and automatic means responsive -to said signals for adjusting said regulating mechanism to produce a following by said trend of a preselected standard of value therefor, said apparatus being accordingly adapted to automatically render said bodily state of functioning of said subject accordant with a preselected standard therefor.
5. Apparatus as in claim 4 wherein said sampling means establishes said trend by rendering said analysis indicative in terms of said signals of an end-of-exhalation sampling of said output gas.
6. Apparatus for administering a respirable gas to a living7 subject comprising, a fluid fiow system providing for alternate flow of input and output gas to and from said subject during the inhalations and exhalations thereof, adjustable gas regulating mechanism connected in said system in regulating relation with said input gas to quantitatively control a property thereof serving to quantitatively control a bodily state of functioning of said subject, gas analyzer means connected in said system in responsive relation with said output gas to automatically analyze the same for a property thereof indicative of the bodily response of said subject to said property of said input gas, said analyzer being adapted to generate signals indicative of the value of said property of said output gas, means adapted to develop a reference signal representing a preselected standard of value for said lastnamed property, means for comparing said analyzer signals with said reference signal, and means responsive to a change established by said comparison of said analyzer signals away from said reference signal for adjusting said regulating mechanism -to restore said analyzer signals to conformity with said reference signal, said apparatus being accordingly adapted to automatically render said bodily state of functioning of said subject accordant with a preselected standard therefor. A
7. Apparatus for administering a respirable gas to a living subject comprising, a fluid ow system providing for alternate flow of input and output gas to and from said subject during the inhalations and exhalations thereof, adjustable gas regulating mechanism connected in said system in regulating relation with said input gas to quantitatively control a property thereof serving to quantitatively control a bodily state of functioning of said subject, gas analyzer means connected in said systemin responsive relation with said output gas to automatically analyze the same during said respirations for a property thereof indicative of the bodily response of said subject to said property of said input gas, said analyzer being adapted to generate electric voltage signals indicative of the value of said property, of said output gas, electrical means for developing an electrical reference signal having a steady voltage representing a preselected value for said property of said output gas, servo-amplifier means responsive to inputs of said analyzer signals and said reference signal for producing an output of an error signal indicative of a change in voltage of said analyzer signals away from said reference signal, and servo-motor means responsive to said error signal for adjusting said regulating mechanism to restore said analyzer signals to equality with said reference signal by the causal sequence described herein as following onV said adjustment, said apparatus being accordingly adapted to automatically render said bodily state of functioning of said subject accordant with a preselected standard therefor.
8. IApparatus as in claim 7 wherein said electrical means permits adjustment between one value and an-l other of the steady voltage of said reference signal,
9. Apparatus as in claim 7 wherein said servo-motor means is an electric motor adapted to receive a first input of alternating current at a fixed phase and frequency, said servo-amplifier means is synchronized by said current to develop an alternating error signal at said frequency and of opposite phases for oppositely `going changes of said analyzer signals away from said reference signal, and said motor is connected with said servoamplifier to receive any error signal developed thereby as a second input to said motor, said motor being adapted to rotate in opposite directions in the presence, respectively of alternating error signals of opposite phases.
10. Apparatus for furnishing a living subject with respirable gas in the nature of input gas and output gas during, respectively, the inhalations and exhalations of said subject, said apparatus comprising, a gas distributing manifold having first and second ports, adapter means for guiding gas between said manifold and the respiratory tract of said subject, first conduit means connected with said first port to supply input gas through said manifold to said subject, an'adjustable gas regulating device connected in said conduit means 4to regulate said input gas to thereby quantitatively control a bodily state of functioning of said subject, second conduit means connected with said second port, a gas analyzer device connected in said second conduit means to receivev output gas from said subject by way bf said manifold, said analyzer device being adapted by automatically analyzing said output gas to produce signals indicative of the bodily response of said subject to said input gas, and automatic means responsive to said signals for adjusting said regulating mechanism to render said bodily state of functioning of said subject accordant with a preselected standard therefor. Y ll. Apparatus for furnishing a living subject with respirable gas in the nature of input gas and outputgas during, respectively, the inhalations and exhalations of said subject, said apparatus comprising, a gas distributing manifold having first and second ports, adapter means for guiding gas between said manifold and the respiratory tract of said subject,'rst conduit means connected with said second port to supply input gas by way of said manifold to said subject, an adjustable gas regulating device connected in said conduit means to quantitatively control said input gas as to a property thereof serving to quantitatively control a bodily state of functioning of said subject, a gas analyzer device connected in said second conduit means to receive said output gas from said subject by way of said manifold, said analyzer device being adapted to automatically analyze said output gas for a property thereof characterized in quantitative value by short term fluctuations and a longer term trend, said fluctuations and trend being manifested, respectively, within individual exhalations and from exhalation to eX- halation, and being, respectively, extraneous to and indicative in degree of the bodily response of said subject to said property of said input gas, said analyzer being further adapted to generate electric signals as the outcome of said analysis, a sampling device operable by repetitive- .ly Sampling said fluctuations to render said analysis indicative interms of said signals of said trend dissoc iated from said uctuations, electrical means for developingan electrical reference signal representing a preselected standard of value for said property of said output gas, a servo-amplifier responsive to inputs of said analyzer signals and said reference signal for producing an output of an error signal indicative of change in said analyzer signals away from said reference signal, and servo-motor means responsive to said error signal for adjusting said lregulating vmechanism to produce a restoration of said analyzer signals with said reference signal by thecausal sequence described herein as following on said adjustment, said apparatus being accordingly adapted to render ,said bodily state of functioning of said subject accordant with a preselected standard therefor.
12. Apparatus for furnishing a living subject with respirable gas in the nature of input gas and output gas Y .fr-,cinese manifold having nrst and' second ports, adapter means for guiding 'gas between said manifold and the respiratory tract ofsaidfsubject, rst conduit 'meansconnected with said iirst port to supply input gas by way of said manifold to said' subject, an adjustable gas regulating device connected in saidrst conduitmeans to quantitatively control said input gas as to` a property thereofserving-to quantitatively control a bodilystate of'functioningof'said subject, second conduit means connected Withsaid second port, a gas 'analyzer device 'connected in said second conduit means tol receive said output gaefromy said subject by way of saidy manifold, said 1analyzer devicebeing adapted-torautomatically analyze 4said output gas for a property 'thereof characterizedv in` quantitative `value by short termv uctuations and a-longer term trend, said uctuatons and trend being manifested, respectively,
within individual exhalations and from exhalation to exhalation, and being, respectively, extraneous to and indic ative of the bodily response of said subject to said property of said input gas, said analyzer being further adapted to generate electric signals as the outcome ofsaid analysis, a sampling device operable in timed relation with changeover in respiration of said subject from exhalation to inhalation for rendering said analysis indicative in terms of said signals of an end-of-exhalation sampling of said output gas for said property thereof, said sampling means thereby rendering said signals indicative of said trend dissociated from said fluctuations, electrical means for developing an electrical reference signal having a steady voltage representing a preselected value for said property of said output gas, a servo amplifier responsive to inputs of said analyzer signals, said reference signal, and an alternating chopping signal of xed frequency and phase for producing an output of an'alter nating error signal of said frequency and of opposite phases when said analyzer signals change in one and the other direction away from said reference signal, and an electric motor mechanically coupled with said regulator device to adjust the same, electrically coupled with said amplifier to receive said error signal as one input, and
electrically coupled to receive an alternating current of said frequency and of xed phase as another input, said motor being respectively responsive to error signals of opposite phases to produce opposite direction adjustments of said regulator device serving to equalize said analyzer signals with said reference signal, said apparatus being accordingly adapted to automatically render said bodily state of functioning of said subject accordant with a preselected standard therefor.
13. Apparatus for administering respirable gas to a living subject comprising, la source of input gas under pressure, a manifold having an inlet port and an outlet port, adapter means for guiding the flow of gas between said manifold and the respiratory tract of said subject, first conduit means disposed between said source and said inlet port to supply input gas to said manifold, valve means for opening said inlet port, timing means for `actuating said valve means to open said inlet port intermittently to thereby induce respirations in said subject consisting of Ialternate inhalations of input gas responsive to the pressure thereof, and of exhalations of output gas, an adjustable pressure regulator for said input gas disposed in said conduit means between said source and said inlet port, second conduit means connected with said outlet port, an analyzing device connected in said second conduit means and adapted to provide electric signals as` a lfunction of the carbon dioxide content of said output gas, sampling means connected in said second conduit means between said manifold and said analyzing device,
r`18 matie means .responsivejtofsaid signal for adjusting said; regulatorio maintain it preselected depth of respiration for said subject; Y
14. Apparatus for administeringianaestlieticto aliv-y ing subject comprising, a manifoldY having ati-"inlet port and an outlet port, adapter means for guiding gas'between said manifold' and the respiratory tract of 'said subject, first conduit means comprised both of a'y pair of conduits respectively adapted Vtocarry. anaesthetic gas and oxygen and of aithird'conduit connected 'between said inlet port andboth of said pair of'foondu'its'to rniJt` said anaesthetic gas andfox'ygen, the intermixture there-f` of being the input gas for saidjsubject,-an` adjustable regulator connected in said'conduit carrying anaesthetic gas to meter the amount thereof'owing to saidthird conduit to vthereby control-the percentage"thereofI present in said input gas, second conduit? meansfconnectedwith said outlet port,kvalve means for directing into said second conduit means the ow of output gasfrom said subject into said manifold, an analyzer device connected in said second conduit means to generate electric voltage signals as a function of the content of anaesthetic gas in said output gas, electric circuit means adapted to develop a steady reference voltage representing a preselected depth of anaesthesia for said subject, servo-amplifier means responsive to` inputs of said analyzer signals and said reference signal to develop an output of an error signal indicative of change in said analyzer signals away from said reference signal, switch means responsive to the pressure drop in said manifold during changeover in the respiration of said subject from exhalation to inhalation to close a circuit for said error signal as a consequence of said pressure drop, said error signal being thus rendered indicative of an end-of-exhalation sampling from the patient and gas analysis means directly com-v municating therewith for analyzing the undiluted exhalations from the patient, and means actuated by the gas analysis means for controlling the means for administering the chemicalto the patient.
16. Apparatus comprising means for administering a therapeutic treatment to a patient, means for directly receiving exhalations from the patient and gas analysis means directly communicating therewith for analyzing the yundiluted exhalations from the patient, and means actuated by the gas analysis means for controlling the means for administering the therapeutic treatment to the patient.
R17. Apparatus comprising means for supplying an inhalation gas to a patient, means for directly receiving `exhalation from a lung of the patient and gas analysis means directly communicating therewith for analyzing theundiluted exhalations fromv the patient, and means actuated by the gas analysis means for controlling the means for supplying the inhalation gas to the patient.
18. Apparatus comprising means for supplying an r`inhalation gas to a patient, means for directly receiving exhalations from a lung of a patient and gas analysis said sampling means being controlled by said timing means'to draw oi a sample of the output gas present in said manifold at the end of exhalation and to thereafter discharge said sample into said analyzer means, and automeans directly communicating therewith for analyzing the undiluted exhalations from the patient, and means actuated by the gas analysis means for automatically controlling the means for supplying the inhalation gas toY `regulate the composition of the inhalation gas to the patient.
` 19. Apparatus comprising means for supplying an inhalation gas to a patient, means for directly receiving exhalations from a lung of a patient and gas analysis means directly communicating therewith for. analyzing:v
the undiluted, exhalatidns-,fromfthe patient, andmeans actuated by the gas analysis means for controlling the meansfor `supplying;the-inhalation gas to regulate the compositionof an inhalation gas to the patient. H
r2 0. Apparatus comprising means for supplying an 2l; The apparatus of claimvZO in whichthe gas ana-v lysis means analyzes cyclopropane. Y
22.. Apparatus comprising means .for administering a therapeutic gas to apatient, means for directlyreceiving exhalationV from fal unlg of the patientand-.gas analysis.;
means directly communicatingl therewith for analyzing the` undilutedy exhalation from lthepatient, ,and means actuated by the gas analysis means vfor controllingy the means forsupplying'the therapeutic gas so that admnistration of the therapeutic gas may be regulated.v
23. The apparatus of claim 22 in whichv the gas analysis means analyzes carbon dioxide. y
24. The apparatus of claim 22 in which the gas an- 1D alysis means analyzes oxygen.
References Cited in thcile of this patent UNITED STATES 'PATENTS 2,754,819 Kirschbaum. ..v- July f 17, 1956 j UNlTED STATES' PATENT FFTCE CERTIFICATE OF CORRECTION Patent No. 2915O56 December 1q 1959 Arnold S. L Lee It is herebr certified that error appears in theprinted specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 5-q` line 30(I for "713" read' 77a wline 31l for 77a readl 71a column 'Xq line 57., for "photomer" read m photometer eg column SQ. line 20,? for `"carbide" read M4 carbon wm; line 36(I for "351921" read m 351921) ma.
Signed and sealed this 23rd day of August 1960.
( SEAL) Attest:
KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents