CA2032796C - Personal spirometer - Google Patents
Personal spirometer Download PDFInfo
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- CA2032796C CA2032796C CA002032796A CA2032796A CA2032796C CA 2032796 C CA2032796 C CA 2032796C CA 002032796 A CA002032796 A CA 002032796A CA 2032796 A CA2032796 A CA 2032796A CA 2032796 C CA2032796 C CA 2032796C
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- Prior art keywords
- spirometer
- microprocessor
- air
- housing
- orifice
- Prior art date
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/087—Measuring breath flow
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/087—Measuring breath flow
- A61B5/09—Measuring breath flow using an element rotated by the flow
Abstract
A self-contained portable spirometer includes a housing and an air tube with an orifice. Within the housing there is a transducer and microprocessor-based circuitry for generating standard exhaled air measurements such as FEV1 and PFER. These measurements are displayed on a screen disposed on the housing.
Description
A PERSON~.I. BPIROMETER
BACKGROUND OF TFIE dNVEEdTIO~T
a. Field of Invention This invention pertains to an apparatus for automatic measure of the volume and flow rate of air exhaled by a person, and more particularly, to a personal spirometer small enough so that it can be carried unobtrusively in a pocket so that person can use it easily with maximum convenience and minimum embarrassment.
b. Description of the Prior Art Spirometers are devices used to measure the volume and flow rate of air exhaled by a person. These measurements are important for general physiological studies and for diagnostic analysis of particular patients. For example, the effects of various medicines used to treat patients with pulmonary or asthmatic problems can be best analyzed by monitoring the volume and flow rate of air exhaled at regular intervals before and after the administration of medication.
In general, spirometers make their measurement by one of two means. One type collects the exhaled volume from the subject into a bellows or other container, the displacement of which corresponds to the volume of exhaled air. These devices are by their nature large to allow sufficient air collection volume and hence are not easily made portable. A second type measures the rate of air flow through a flow measurement device. Exhaled volume is derived by integration of the air flow rate over some period of time.
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., ".~ l, 8( ; 3 Until the present invention, spirometers were rather bulky and expensive devices found mostly in clinics and laboratories. Their operation required a trained technician. Furthermore, most such devices were complicated so that they could net be made small enough to be carried in a pocket. For example, there are several devices available in the market known as pneumotachs, such as the Fleisch Pneumotach. These devices depend on a laminar air flow past a resistance element. Such devices need additional means for insuring that the flow remains laminar even at high air velocities. Therefore, these type of devices are inherently complex and relatively large. Furthermore the resistance element frequently includes a screen disposed directly in the air path. This screen , intercepts impurities which clog the screen and change the response of the device and in addition are unsanitary. The pneumotach also includes pressure measurement ports which frequently become occluded from moisture or impurities, thus adversely altering the accuracy of measurement.
osJECTxeES Ago sur~r~ax o~ ~x~ xrrv~N~~orr An objective of the present invention is to provide an apparatus which may be used for an accurate and instantaneous measurement of exhaled air.
A further objective is to provide a self-contained apparatus which can be made small enough to fit in a person's pocket.
Another objective is to provide an apparatus which 3o is simple enough to be used by the subject and is reliable without special care from the user.
Yet another objective is to provide an apparatus which can be adapted for data recording.
BACKGROUND OF TFIE dNVEEdTIO~T
a. Field of Invention This invention pertains to an apparatus for automatic measure of the volume and flow rate of air exhaled by a person, and more particularly, to a personal spirometer small enough so that it can be carried unobtrusively in a pocket so that person can use it easily with maximum convenience and minimum embarrassment.
b. Description of the Prior Art Spirometers are devices used to measure the volume and flow rate of air exhaled by a person. These measurements are important for general physiological studies and for diagnostic analysis of particular patients. For example, the effects of various medicines used to treat patients with pulmonary or asthmatic problems can be best analyzed by monitoring the volume and flow rate of air exhaled at regular intervals before and after the administration of medication.
In general, spirometers make their measurement by one of two means. One type collects the exhaled volume from the subject into a bellows or other container, the displacement of which corresponds to the volume of exhaled air. These devices are by their nature large to allow sufficient air collection volume and hence are not easily made portable. A second type measures the rate of air flow through a flow measurement device. Exhaled volume is derived by integration of the air flow rate over some period of time.
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., ".~ l, 8( ; 3 Until the present invention, spirometers were rather bulky and expensive devices found mostly in clinics and laboratories. Their operation required a trained technician. Furthermore, most such devices were complicated so that they could net be made small enough to be carried in a pocket. For example, there are several devices available in the market known as pneumotachs, such as the Fleisch Pneumotach. These devices depend on a laminar air flow past a resistance element. Such devices need additional means for insuring that the flow remains laminar even at high air velocities. Therefore, these type of devices are inherently complex and relatively large. Furthermore the resistance element frequently includes a screen disposed directly in the air path. This screen , intercepts impurities which clog the screen and change the response of the device and in addition are unsanitary. The pneumotach also includes pressure measurement ports which frequently become occluded from moisture or impurities, thus adversely altering the accuracy of measurement.
osJECTxeES Ago sur~r~ax o~ ~x~ xrrv~N~~orr An objective of the present invention is to provide an apparatus which may be used for an accurate and instantaneous measurement of exhaled air.
A further objective is to provide a self-contained apparatus which can be made small enough to fit in a person's pocket.
Another objective is to provide an apparatus which 3o is simple enough to be used by the subject and is reliable without special care from the user.
Yet another objective is to provide an apparatus which can be adapted for data recording.
Other objectives and advantages of the invention shall become apparent from the following description of the invention.
Accordingly, the present invention relates to a portable spirometer comprising a housing, an air tube coupled to the housing and including a substantially linear air passage with a reduced diameter orifice for generating a turbulence in the air passage, and pressure sensing means for sensing a differential pressure across the orifice when a person exhales through the air tube. Filter means are disposed at an interface between the tube and the pressure sensing means for protecting the pressure sensing means. The filter means is made of a material permeable to gases and impermeable to liquids. Electronic circuitry means is disposed in the housing and coupled to the pressure sensing means for generating electric input signals corresponding to the differential pressure. The electronic circuitry means includes calculating means for calculating performance signals from the electric input signals. Display means are also provided for displaying the performance signals.
Preferably, the spirometer displays two parameters known as FEV1 (the volume of air exhaled in one second in liters) and PEFR (peak expiratory flow rate in liters per second).
Optionally the results of several measurements may be recorded in a memory for later down-loading to a data processing system.
An adaptive start algorithm is used to detect a true test, using a statistical approach rather than a preset threshold level. More particularly, the device calculates the average and the variance of a window formed of four consecutive samples and flow rate and volume calculations are started only if a progressive increase in the measurements is detected. This approach is found to provide good sensitivity and, at the same time, it is relatively immune to noise.
Furthermore, the spirometer taxes aavanLage oL Lne cm~-linear characteristics of the air tube to increase sensitivity without expensive high resolution A/D converters. Separate look-up tables for high and low ~~~~~1~~' flow rates are used to convert pressure differential samples into actual flow rates.
BRIEF DESCRIPTION OF THE DRA69ZN(~8 Figure 1 shows a side view of a personal spirometer constructed in accordance with the invention;
Figure 2 shows a front view of the spirometer of Figure 1;
Figure 3 shows a cross-sectional view of the air tube of Figures 1 and 3;
Figure 4 shows an end view of the air tube of Figure 3;
Figure 5 shows somewhat schematic block diagram for the elements of the spirometer constructed in accordance with this invention;
Figures 6A and 6B show an elementary wiring diagram of a preferred embodiment of the invention; and Figures 7A, 7B and 7C show flow charts for the operation of the microprocessor for the spirometer.
DETAILED DESCRIPTTON OF THE TNi,ENTION
2o Referring now to the drawings, a personal spirometer 10 constructed in accordance with this invention includes a housing 12 with a generally square section 14 and an air tube 16 disposed on one side of the section 14. The spirometer is sized and shaped so that it can fit in a pocket. Furthermore, the spirometer is shaped and sized so that it can be held comfortably in one hand while air is exhaled through it as described more fully below. The section 14 has a flat surface 18. A control panel 20 is 3o imbedded in surface 18 and it includes a start button 22' and an LCD display screen 24. Air tube 16 has an annular mouth piece 26 at one end sized to fit in a person's mouth. A cylindrical hole 28 passes through the air tube 16. Hole 28 has a substantially constant '~~~~~y~~~i' ~~ z3 ,~ l a t~
diameter except at an annular wall 30. This annular wall 30 forms a sharp-edged orifice within hole 28.
Two small openings 32, 34 are spaced on either side of the wall 30 and extend into section 14 for measuring 5 the differential pressure within the air tube due to a flow of exhaled air.
As shown more clearly in Figure 4 each of the openings 32, 34 is provided with a plug 36, 36' (only one orifice being shown in Figure 4). This plug holds a filter 38 at the interface with hole 28. The filter 38 may be made of a porous material which is permeable to air but impermeable to liquids. In this manner, saliva or other materials from the exhaled air of a person will be limited to the tube and will not contaminate the remainder of the spirometer 10.
Furthermore since filter 38 is impermeable to water the spirometer may be immersed in or sprayed with water for cleaning and sanitary purposes. Filter 38 maybe made for example of a hydraphobic filter media such as a 1/16" thick hydrophobic polyethylene with a 10 micron pore size, and about 40~ porosity.
As shown more clearly in Figure 5, the plugs are connected by two tubes 40, 42 to a differential pressure transducer 44, which may be for example a MPX
2010D made by Motorola.
The transducer 44 generates an electrical signal on a pair of output wires 46, which ,signal is proportional to the differential pressure between tubes 40, 42. This signal is amplified by a differential amplifier stage 48 and fed into an analog-to-digital converter 50 which converts the amplifier output into digital signals. The converter output is fed to a microprocessor 52. The microprocessor 52 uses an algorithm stored in a R.OM 54 f f.°
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to perform several calculations on the signal from converter 50, and to display the results (i.e. volume and rate of flow) on display 24. Switch 22 activated by button 22' initiates the operation of spirometer 10 through microprocessor 52. The results obtained during each measurement may be stored in a RAM 56 for future reference. An input/output port 58 may also be provided to allow for changing the programming of the microprocessor. Furthermore the microprocessor may be programmed so that on command it can down-load the results accumulated in RAM 56 through port 58 to a printer or a desl~-top computer.
A preferred diagram for implementing the circuit shown in Figure 5 is shown in Figures 6A and 6B. It should be understood that the various circuit elements (such as resistance and capacitance values) are shown in the Figures merely for illustrative purposes and do not limit the scope of this invention in any fashion.
In the embodiment of Figures 6A and 6B, differential air pressure in the air tube is sensed by the pressure transducer 44 schematically shown as a resistive bridge. The output of the transducer is processed by an amplifier analog circuit 48 consisting of amplifiers 60, 62, 64 and 66 which may be, for example, Motorola MC 34074 op amps. These amplifiers are used for a relatively high air flow. For low air flows a further amplifier 68 is also used. The outputs of these amplifiers 66, 68 are fed 'to a multiple channel A/D converter 50, which may be for example a 68FiC68A2 manufactured by RCA Harris. The A/D converter 50 feeds its output to microprocessor 52 which may be for example a MC68HC804C4 made by Motorola. After performing the necessary calculations, the microprocessor 52 displays the ~~ ~ ," s~ r, ~~ .:a > > °~
results on the LCD screen 24. (Display screen 24 may also include LCD display drivers not shown in the Figures for the sake of convenience).
As shown in Figure 6A, the circuit also includes a power supply 70 which provides the required power to the various circuit elements from a battery 72. The operation of the power supply is also controlled by wires W2, W3 by the microprocessor 52. More particularly, the analog section consisting of the amplifiers, the transducer and. the digital-to-analog converter is turned on last (when measurements are started) and turned off first (when the measurements are completed) to conserve power. The power to the display screen is independently controlled.
Preferably, the display is on whenever the microprocessor is on.
The spirometer 10 further includes a beeper 80 controlled by the microprocessor for generating audible signals for the user.
A further feature of the invention is an automatic offset compensation circuit consisting of a plurality of resistors 74 and an amplifier 76. The resistors 74 are coupled to microprocessor 52 by a plurality of lines 78. This offset compensation circuit operates as follows. During the initialization of the spirometer (described mare fully below), the microprocessor checks the output of the pressure transducer to insure that it essentially corresponds to no air flow. If the transducer output is non-zero (due for example to a temperature drift, a variation in the output of the power supply 70, the offset voltages of amplifiers 62, 64, 66, 68 and so on) the microprocessor 52 sends a compensating signal ~x °.;) ~~ Jv - nd ~J Z.~ ' J ~'~ iJ
through lines 78 to resistors 74. Resistors 74 and amplifier 76 cooperate in effect to form a digital-to-analog converter used by the microprocessor 52 to produce a DC offset. This DC offset is added by amplifier 62 to the output of transducer 44. During the initialization period when no air is blown through the air tube, the microprocessor sequentially changes the signals on lines 78 until the offset signal from amplifier 76 compensates for the error signal from transducer 44.
OPEgtATION
The device requires no user adjustment or calibration. To make a measurement, the user pushes the START button 22'. This turns the unit on and initiates a self-test routine. During this self test, all segments on the liquid-crystal display (LCD) are turned on to allow the user to confirm proper operation of the unit. Upon completion of self-test (approximately 5 seconds), the display is blanked except for a READY annunciatora the unit beeps by activity beeper 80 and is now ready for a measurement.
The user inhales as much as he can, places his lips around the mouthpiece 26, and blows as hard as possible. The device senses the start of exhalation, measures flow for one second, then displays the volume and maximum rate of air flow for the person (cammonly known as FEV1 and PEFR respectively) measurements on display screen 24.
The parameter FEV1 and the criteria for measuring this parameter is described in the Official Statement of American Thoracic Society, Medical Section of the American Lung Association --Standardization of Spirometry--1987 Update found in Respiratory Care, November °87, vol. 32, No. 11, pgs. 1039-1060. The ~r: , c ~a .-; -,~
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parameter PEFR is identical to the FEFmax parameter in the same Statement.
The display will persist for 45 seconds, and then the unit will turn itself off, unless the START button 22' is pushed to initiate another measurement cycle.
If no breath is detected within 15 seconds of the READY signal, the unit beeps twice and shuts itself off.
PRINCIPLE OF ME.~SiJREMENI' 1o The spirometer 10 determines the flow rate of air by measuring the differences in pressure developed across a restricting orifice. This pressure difference is related to the flow rate by a well-known equation based on Bernoulli's equation for non-compressible flow. (See for instance Binder, R.C., Fluid Mechanics, 5th Edition, Prentice Hall Inc., Englewood Cliffs, N.J., pgs. 23f-237.) Tn the case of the sharp-edged orifice used in this device, the flow rate is equal to a coefficient (found empirically) multiplied by the square-root of the pressure difference measured between a point upstream of the orifice and a point downstream of the orifice. The value of the coefficient is predominantly determined by the physical design of the device, including the ratio of the area of the flow tuba to the area of the orifice, the size of the orifice, and the location of the pressure measurement ports. Ideally, if these physical parameters were held canstant, the pressure difference would be dependent only upon the flow rate and density of the fluid being measured. ~Iowever, there is also some influence of Reynolds Number upon the value of the coefficient, which introduces an error if the coefficient is treated as a constant over a large range of flows.
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The pressure difference across the orifice is a function of the square of the flow rate. Therefore, an orifice size must be chosen that does not offer excessive back-pressure to the highest flows to be 5 measured, yet has an adequate, measurable pressure difference at low flow rates.
THEORY OF a~ERI~TION
The air tube 16 contains the sharp-edged orifice (defined by wall 32) that provides a pressure 1o difference which is approximately proportional to the flow rate squared. Preferably, the diameter is about 5/8" and tube 16 has a diameter of about 7/8". This size represents a reasonable compromise between back-pressure at higher flows and at low flows. The outside diameter of the tube 16 is approximately 1", and the length is' approximately 3.5". Again, the dimensions represent a compromise; an attempt has been made to keep the overall size small enough to fit a pocket or handbag, yet large enough so that an extraneous mouthpiece is unnecessary. Tiowever, a tapered profile is provided on the inlet end of the tube so that a disposable mouthpiece may be added (26' in Figure 1) if desired. The pressure ports are covered with a disk of hydrophobic falter material (as described above) inset flush with the floor of the tube. This material allows air and water vapor to pass freely, but blocks dirt and liquid. 7a is made of a 7./16" thick rigid plastic and is not easily damaged, allowing the interior of the tube to be 3o cleaned with gently running water or wiped with a soft, lint-free cloth.
The pressure is transmitted via the 1/16" i.d.
pipes 40, 42 to the solid-state, piezo-resistive, differential pressure transducer 44. This transducer fi~",E~r~~~a .-~ ~.J z.~ ~ ti is provided with a reduced amount of silicon isolation gel coating its diaphragm as compared with the standard transducers used for other measurements.
This coating improves the transient response and reduces the sensitivity of the transducer to the position and motion of the spirometer. The differential pressure transducer provides an output signal proportional to the pressure difference between the two openings 32, 34.
The signal from the transducer is amplified and filtered by the 4-stage analog amplifier circuit shown in Figures 6A and 6B. Two outputs are produced by this amplifier circuit. The first circuit generated by amplifier 66 has a total gain of 808. The second circuit generated by amplifier 68 has a total gain of 3,232. The offset voltage of this circuit is adjusted to 300 +/- 50 mV at the first output as described above.
Two filter stages (including amplifiers 64, 66) are included in the analog amplifier circuitry providing a low-pass transfer function with a cut-off frequency of l0hz. The first and second outputs from the analog circuitry are fad to two channels marked CH1, CH3 of the 10-bit A/D converter 50. A signal proportional to the voltage of battery 72 is fed to channel CH2 on the A/D converter 50.
The microprocessor controls all aspects of device function. It is able to independently control power to the display, the pressure transducer and analog circuitry, and itself. Timing pulses are provided by a 3.59 MHz crystal 53. The microprocessor receives the digital values representing pressure, does all necessary calculations, arid generates the codes for the liquid-crystal display circuitry.
a ~v>_~~~~' The liquid-crystal display shows the measured values for FEV1 and Peak Expiratory flow Rate (PEER).
It also includes a BATTERY annunciator to indicate when the battery needs replacement and a READY
annunciator to indicate when the device is ready to make a measurement.
MEASUREMENT SEQUENCE
The sequence of operation for the spirometer is now described in conjunction with the flow charts of Figures 7A, 7B and 7C. Details of the operations are found in the program listing attached hereto. P7hen the start switch is depressed, the microprocessor 52 is reset and loads its program, which is stored in its Read-Only Memory (ROM) 54. It begins by running a self-test and initialization routine step S1 which checks for internal consistency. It else measures the voltage of battery 72 through input channel CH2 of the A/D converter 52. If the voltage is below a lower limit such that an accurate measurement cannot be made, the microprocessor will not continue. If the voltage is low, but does not exceed this operational limit, the BATTERY annunciator on the LCD is turned on and will not extinguish until the unit turns itself off. If the internal checkout is completed without error, the microprocessor then turns on all segments of the display to allow the user to see if any segments are non-functional. Next, it starts sampling the input on channel CH1 of the A/D converter so as to decide which bits of the digital-to-analog converter (I/O lines 78) to turn an or off and to adjust the offset voltage at channel CH1 to 300 +/- 50 mV. This sequence takes about 2 seconds.
At the end of offset adjustment, the display is blanked (except for the battery annunciator, if F ;
il ~l ;'r .~ c~ se voltage is low) and then analog circuitry is allowed to stabilize. The microprocessor in step S2 begins to sample both CH1 and CH3 inputs of the A/D converter signals at a rate of about 100Hz and fills its history array as described below.
The subroutines for step S2 are shown in Figures 7B and 7C. The unit continues to sample both the CH1 and CH4 channels at 100Hz each. It continuously calculates the average and variance of the past four l0 measurements X1, X2, X3 and X4 from the CH3 channel (Steps 521, 22 and 23). It then compares the next sample (X5) to this average and variance in Steps 524, S26. If the current value is higher than the average by more than 2 standard deviations, the unit branches to a start detection routine (Step 27). If the value is more than 2 volts higher than the average, the microprocessor 52 switches over to the CH1 channel (Step 28) and scales the reading (Step 29) . If the current value is lower than the average or is less than 2 standard deviations higher than the average, the current value becomes the new 4th sample in the average and variance calculation and the loop continues (Steps 22, 30, 39). This loop will continue for a maximum of 15 seconds. If no start is detected (as described below) in this time, the unit will beep twice and turn itself off in step S8.
If the current sample value is high enough to cause branching to the start detection routine, the old average and variance are saved. In Steps 31, 32 3o the next sample is now checked to see if it is also above a threshold level 128 (Step 32) or the 2 standard deviation threshold (using either the CH3 or CH1 channel, depending on how large the input an channel CH3 is), and also to see if it is higher than the previous sample (Step 33). :If both of these conditions are met, a third sample is obtained and checked in the same way (Step 34). (It must be larger than second sample.) If either the second or third sample fails either test, the average and variance are updated using the new sample values and the program returns to the loop above (Steps 35, 35, 37, 38, 39).
If three samples in a row are larger than the threshold value 128 or the average plus 2 standard deviations, and each is larger than the one preceding it, then start is detected (Steps 40, 41, 42, 43).
The saved average is stored as the offset to be subtracted from all samples and the 3 samples are converted to flow values and summed as the first three volume increments (Step 41). The actual conversion from the measurement pressure differential samples to volumes is accomplished by using two look-up tables stored in ROM 54. One look-up table correlates samples from the low flow channel CH3 (i.e. 0-2 volts) while the second look-up table correlates the samples from the high flow rate channel CH1 (i.e. 0-4 volts).
The values on these look-up tables are determined empirically. As previously mentioned, the orifice used to measure flow rate has a non-linear response, i.e. the pressure differential across the openings 32, 34 due to turbulent flow is non-linear. The present spirometer takes advantage of this non-lineality by separating the pressure differential samples into two ranges based on the flow rate, and then using a look-up table fo~c each. By switching gains, the microprocessor has expanded resolution at low flows.
This would be analogous to an equivalent linear range of 16 volts at 10 bits of resolution, or 4 volts at 12 bits of resolution. This feature is made possible by ,~Y C~ : W ;~ !d ~~~N~~ ~;.~3f~~
the non-linear cr~aracter.istic of the orifice. To conserve microprocessor memory space, rather than store a value for every possible A/D code, the microprocessor extrapolates between the two closest 5 stored values. Enough samples are stored to keep the extrapolation error small. In this manner, a less-discriminating (having lower resolution) A/D converter can be used without sacrificing accuracy and sensitivity.
10 Once start is detected and integration of flow values has begun, the unit begins to look for the maximum slope of the volume curve (step S3). If the slope determined by several consecutive samples is low or negative, the whole measurement is reported as a 15 false start. The maximum positive slope is determined over seven flow samples and, when found, is back extrapolated to determine the start of the first second timing for FEV1 determination in accordance with the standards set by the American Thoracic Society identified above (step S4). Meantime, each 10 cosec. the CH1 and CH3 channels are sampled (step S5).
If the CH3 output is less than 2 volts above the offset, it is converted to flow and summed. If the CH3 input is more than 2 volts, the input from channel CH1 is used instead. The unit also looks for, and stores the highest flow sample (step 6).
When the FEV1 timing has been determined, flow samples have been collected and integrated as volume, and the peak flow value has been stored, the unit displays the measured FEV1 and REFR (step S7) and it turns off the analog circuitry to save battery life.
The display is maintained for 45 seconds (or until the START button 22' is pushed to initiate another measurement cycle). After 45 seconds, the microprocessor powers down (step S8) to an idle made.
The operation and circuitry described above and in Figures 6A, 6B and 7 pertain to a basic spirometer.
For more advanced modes additional features may be incorporated mostly by modifying the programming of microprocessor 52. For example, before the unit goes into the idle mode, each measurement may be stored into RAM 54 with a time stamp and/or date stamp indicating the time and day on which the measurements were made. The measurements are then recalled and reviewed on the display screen sequentially by activating switch 22. As an incentive, the instantaneous flow measurements could be displayed as the person blows through air tube 26, and when certain mile stones are reached, the beeper could be sounded.
Obviously numerous other modifications can be made to the invention without departing from its scope as defined in the appended claims.
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Accordingly, the present invention relates to a portable spirometer comprising a housing, an air tube coupled to the housing and including a substantially linear air passage with a reduced diameter orifice for generating a turbulence in the air passage, and pressure sensing means for sensing a differential pressure across the orifice when a person exhales through the air tube. Filter means are disposed at an interface between the tube and the pressure sensing means for protecting the pressure sensing means. The filter means is made of a material permeable to gases and impermeable to liquids. Electronic circuitry means is disposed in the housing and coupled to the pressure sensing means for generating electric input signals corresponding to the differential pressure. The electronic circuitry means includes calculating means for calculating performance signals from the electric input signals. Display means are also provided for displaying the performance signals.
Preferably, the spirometer displays two parameters known as FEV1 (the volume of air exhaled in one second in liters) and PEFR (peak expiratory flow rate in liters per second).
Optionally the results of several measurements may be recorded in a memory for later down-loading to a data processing system.
An adaptive start algorithm is used to detect a true test, using a statistical approach rather than a preset threshold level. More particularly, the device calculates the average and the variance of a window formed of four consecutive samples and flow rate and volume calculations are started only if a progressive increase in the measurements is detected. This approach is found to provide good sensitivity and, at the same time, it is relatively immune to noise.
Furthermore, the spirometer taxes aavanLage oL Lne cm~-linear characteristics of the air tube to increase sensitivity without expensive high resolution A/D converters. Separate look-up tables for high and low ~~~~~1~~' flow rates are used to convert pressure differential samples into actual flow rates.
BRIEF DESCRIPTION OF THE DRA69ZN(~8 Figure 1 shows a side view of a personal spirometer constructed in accordance with the invention;
Figure 2 shows a front view of the spirometer of Figure 1;
Figure 3 shows a cross-sectional view of the air tube of Figures 1 and 3;
Figure 4 shows an end view of the air tube of Figure 3;
Figure 5 shows somewhat schematic block diagram for the elements of the spirometer constructed in accordance with this invention;
Figures 6A and 6B show an elementary wiring diagram of a preferred embodiment of the invention; and Figures 7A, 7B and 7C show flow charts for the operation of the microprocessor for the spirometer.
DETAILED DESCRIPTTON OF THE TNi,ENTION
2o Referring now to the drawings, a personal spirometer 10 constructed in accordance with this invention includes a housing 12 with a generally square section 14 and an air tube 16 disposed on one side of the section 14. The spirometer is sized and shaped so that it can fit in a pocket. Furthermore, the spirometer is shaped and sized so that it can be held comfortably in one hand while air is exhaled through it as described more fully below. The section 14 has a flat surface 18. A control panel 20 is 3o imbedded in surface 18 and it includes a start button 22' and an LCD display screen 24. Air tube 16 has an annular mouth piece 26 at one end sized to fit in a person's mouth. A cylindrical hole 28 passes through the air tube 16. Hole 28 has a substantially constant '~~~~~y~~~i' ~~ z3 ,~ l a t~
diameter except at an annular wall 30. This annular wall 30 forms a sharp-edged orifice within hole 28.
Two small openings 32, 34 are spaced on either side of the wall 30 and extend into section 14 for measuring 5 the differential pressure within the air tube due to a flow of exhaled air.
As shown more clearly in Figure 4 each of the openings 32, 34 is provided with a plug 36, 36' (only one orifice being shown in Figure 4). This plug holds a filter 38 at the interface with hole 28. The filter 38 may be made of a porous material which is permeable to air but impermeable to liquids. In this manner, saliva or other materials from the exhaled air of a person will be limited to the tube and will not contaminate the remainder of the spirometer 10.
Furthermore since filter 38 is impermeable to water the spirometer may be immersed in or sprayed with water for cleaning and sanitary purposes. Filter 38 maybe made for example of a hydraphobic filter media such as a 1/16" thick hydrophobic polyethylene with a 10 micron pore size, and about 40~ porosity.
As shown more clearly in Figure 5, the plugs are connected by two tubes 40, 42 to a differential pressure transducer 44, which may be for example a MPX
2010D made by Motorola.
The transducer 44 generates an electrical signal on a pair of output wires 46, which ,signal is proportional to the differential pressure between tubes 40, 42. This signal is amplified by a differential amplifier stage 48 and fed into an analog-to-digital converter 50 which converts the amplifier output into digital signals. The converter output is fed to a microprocessor 52. The microprocessor 52 uses an algorithm stored in a R.OM 54 f f.°
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to perform several calculations on the signal from converter 50, and to display the results (i.e. volume and rate of flow) on display 24. Switch 22 activated by button 22' initiates the operation of spirometer 10 through microprocessor 52. The results obtained during each measurement may be stored in a RAM 56 for future reference. An input/output port 58 may also be provided to allow for changing the programming of the microprocessor. Furthermore the microprocessor may be programmed so that on command it can down-load the results accumulated in RAM 56 through port 58 to a printer or a desl~-top computer.
A preferred diagram for implementing the circuit shown in Figure 5 is shown in Figures 6A and 6B. It should be understood that the various circuit elements (such as resistance and capacitance values) are shown in the Figures merely for illustrative purposes and do not limit the scope of this invention in any fashion.
In the embodiment of Figures 6A and 6B, differential air pressure in the air tube is sensed by the pressure transducer 44 schematically shown as a resistive bridge. The output of the transducer is processed by an amplifier analog circuit 48 consisting of amplifiers 60, 62, 64 and 66 which may be, for example, Motorola MC 34074 op amps. These amplifiers are used for a relatively high air flow. For low air flows a further amplifier 68 is also used. The outputs of these amplifiers 66, 68 are fed 'to a multiple channel A/D converter 50, which may be for example a 68FiC68A2 manufactured by RCA Harris. The A/D converter 50 feeds its output to microprocessor 52 which may be for example a MC68HC804C4 made by Motorola. After performing the necessary calculations, the microprocessor 52 displays the ~~ ~ ," s~ r, ~~ .:a > > °~
results on the LCD screen 24. (Display screen 24 may also include LCD display drivers not shown in the Figures for the sake of convenience).
As shown in Figure 6A, the circuit also includes a power supply 70 which provides the required power to the various circuit elements from a battery 72. The operation of the power supply is also controlled by wires W2, W3 by the microprocessor 52. More particularly, the analog section consisting of the amplifiers, the transducer and. the digital-to-analog converter is turned on last (when measurements are started) and turned off first (when the measurements are completed) to conserve power. The power to the display screen is independently controlled.
Preferably, the display is on whenever the microprocessor is on.
The spirometer 10 further includes a beeper 80 controlled by the microprocessor for generating audible signals for the user.
A further feature of the invention is an automatic offset compensation circuit consisting of a plurality of resistors 74 and an amplifier 76. The resistors 74 are coupled to microprocessor 52 by a plurality of lines 78. This offset compensation circuit operates as follows. During the initialization of the spirometer (described mare fully below), the microprocessor checks the output of the pressure transducer to insure that it essentially corresponds to no air flow. If the transducer output is non-zero (due for example to a temperature drift, a variation in the output of the power supply 70, the offset voltages of amplifiers 62, 64, 66, 68 and so on) the microprocessor 52 sends a compensating signal ~x °.;) ~~ Jv - nd ~J Z.~ ' J ~'~ iJ
through lines 78 to resistors 74. Resistors 74 and amplifier 76 cooperate in effect to form a digital-to-analog converter used by the microprocessor 52 to produce a DC offset. This DC offset is added by amplifier 62 to the output of transducer 44. During the initialization period when no air is blown through the air tube, the microprocessor sequentially changes the signals on lines 78 until the offset signal from amplifier 76 compensates for the error signal from transducer 44.
OPEgtATION
The device requires no user adjustment or calibration. To make a measurement, the user pushes the START button 22'. This turns the unit on and initiates a self-test routine. During this self test, all segments on the liquid-crystal display (LCD) are turned on to allow the user to confirm proper operation of the unit. Upon completion of self-test (approximately 5 seconds), the display is blanked except for a READY annunciatora the unit beeps by activity beeper 80 and is now ready for a measurement.
The user inhales as much as he can, places his lips around the mouthpiece 26, and blows as hard as possible. The device senses the start of exhalation, measures flow for one second, then displays the volume and maximum rate of air flow for the person (cammonly known as FEV1 and PEFR respectively) measurements on display screen 24.
The parameter FEV1 and the criteria for measuring this parameter is described in the Official Statement of American Thoracic Society, Medical Section of the American Lung Association --Standardization of Spirometry--1987 Update found in Respiratory Care, November °87, vol. 32, No. 11, pgs. 1039-1060. The ~r: , c ~a .-; -,~
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parameter PEFR is identical to the FEFmax parameter in the same Statement.
The display will persist for 45 seconds, and then the unit will turn itself off, unless the START button 22' is pushed to initiate another measurement cycle.
If no breath is detected within 15 seconds of the READY signal, the unit beeps twice and shuts itself off.
PRINCIPLE OF ME.~SiJREMENI' 1o The spirometer 10 determines the flow rate of air by measuring the differences in pressure developed across a restricting orifice. This pressure difference is related to the flow rate by a well-known equation based on Bernoulli's equation for non-compressible flow. (See for instance Binder, R.C., Fluid Mechanics, 5th Edition, Prentice Hall Inc., Englewood Cliffs, N.J., pgs. 23f-237.) Tn the case of the sharp-edged orifice used in this device, the flow rate is equal to a coefficient (found empirically) multiplied by the square-root of the pressure difference measured between a point upstream of the orifice and a point downstream of the orifice. The value of the coefficient is predominantly determined by the physical design of the device, including the ratio of the area of the flow tuba to the area of the orifice, the size of the orifice, and the location of the pressure measurement ports. Ideally, if these physical parameters were held canstant, the pressure difference would be dependent only upon the flow rate and density of the fluid being measured. ~Iowever, there is also some influence of Reynolds Number upon the value of the coefficient, which introduces an error if the coefficient is treated as a constant over a large range of flows.
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The pressure difference across the orifice is a function of the square of the flow rate. Therefore, an orifice size must be chosen that does not offer excessive back-pressure to the highest flows to be 5 measured, yet has an adequate, measurable pressure difference at low flow rates.
THEORY OF a~ERI~TION
The air tube 16 contains the sharp-edged orifice (defined by wall 32) that provides a pressure 1o difference which is approximately proportional to the flow rate squared. Preferably, the diameter is about 5/8" and tube 16 has a diameter of about 7/8". This size represents a reasonable compromise between back-pressure at higher flows and at low flows. The outside diameter of the tube 16 is approximately 1", and the length is' approximately 3.5". Again, the dimensions represent a compromise; an attempt has been made to keep the overall size small enough to fit a pocket or handbag, yet large enough so that an extraneous mouthpiece is unnecessary. Tiowever, a tapered profile is provided on the inlet end of the tube so that a disposable mouthpiece may be added (26' in Figure 1) if desired. The pressure ports are covered with a disk of hydrophobic falter material (as described above) inset flush with the floor of the tube. This material allows air and water vapor to pass freely, but blocks dirt and liquid. 7a is made of a 7./16" thick rigid plastic and is not easily damaged, allowing the interior of the tube to be 3o cleaned with gently running water or wiped with a soft, lint-free cloth.
The pressure is transmitted via the 1/16" i.d.
pipes 40, 42 to the solid-state, piezo-resistive, differential pressure transducer 44. This transducer fi~",E~r~~~a .-~ ~.J z.~ ~ ti is provided with a reduced amount of silicon isolation gel coating its diaphragm as compared with the standard transducers used for other measurements.
This coating improves the transient response and reduces the sensitivity of the transducer to the position and motion of the spirometer. The differential pressure transducer provides an output signal proportional to the pressure difference between the two openings 32, 34.
The signal from the transducer is amplified and filtered by the 4-stage analog amplifier circuit shown in Figures 6A and 6B. Two outputs are produced by this amplifier circuit. The first circuit generated by amplifier 66 has a total gain of 808. The second circuit generated by amplifier 68 has a total gain of 3,232. The offset voltage of this circuit is adjusted to 300 +/- 50 mV at the first output as described above.
Two filter stages (including amplifiers 64, 66) are included in the analog amplifier circuitry providing a low-pass transfer function with a cut-off frequency of l0hz. The first and second outputs from the analog circuitry are fad to two channels marked CH1, CH3 of the 10-bit A/D converter 50. A signal proportional to the voltage of battery 72 is fed to channel CH2 on the A/D converter 50.
The microprocessor controls all aspects of device function. It is able to independently control power to the display, the pressure transducer and analog circuitry, and itself. Timing pulses are provided by a 3.59 MHz crystal 53. The microprocessor receives the digital values representing pressure, does all necessary calculations, arid generates the codes for the liquid-crystal display circuitry.
a ~v>_~~~~' The liquid-crystal display shows the measured values for FEV1 and Peak Expiratory flow Rate (PEER).
It also includes a BATTERY annunciator to indicate when the battery needs replacement and a READY
annunciator to indicate when the device is ready to make a measurement.
MEASUREMENT SEQUENCE
The sequence of operation for the spirometer is now described in conjunction with the flow charts of Figures 7A, 7B and 7C. Details of the operations are found in the program listing attached hereto. P7hen the start switch is depressed, the microprocessor 52 is reset and loads its program, which is stored in its Read-Only Memory (ROM) 54. It begins by running a self-test and initialization routine step S1 which checks for internal consistency. It else measures the voltage of battery 72 through input channel CH2 of the A/D converter 52. If the voltage is below a lower limit such that an accurate measurement cannot be made, the microprocessor will not continue. If the voltage is low, but does not exceed this operational limit, the BATTERY annunciator on the LCD is turned on and will not extinguish until the unit turns itself off. If the internal checkout is completed without error, the microprocessor then turns on all segments of the display to allow the user to see if any segments are non-functional. Next, it starts sampling the input on channel CH1 of the A/D converter so as to decide which bits of the digital-to-analog converter (I/O lines 78) to turn an or off and to adjust the offset voltage at channel CH1 to 300 +/- 50 mV. This sequence takes about 2 seconds.
At the end of offset adjustment, the display is blanked (except for the battery annunciator, if F ;
il ~l ;'r .~ c~ se voltage is low) and then analog circuitry is allowed to stabilize. The microprocessor in step S2 begins to sample both CH1 and CH3 inputs of the A/D converter signals at a rate of about 100Hz and fills its history array as described below.
The subroutines for step S2 are shown in Figures 7B and 7C. The unit continues to sample both the CH1 and CH4 channels at 100Hz each. It continuously calculates the average and variance of the past four l0 measurements X1, X2, X3 and X4 from the CH3 channel (Steps 521, 22 and 23). It then compares the next sample (X5) to this average and variance in Steps 524, S26. If the current value is higher than the average by more than 2 standard deviations, the unit branches to a start detection routine (Step 27). If the value is more than 2 volts higher than the average, the microprocessor 52 switches over to the CH1 channel (Step 28) and scales the reading (Step 29) . If the current value is lower than the average or is less than 2 standard deviations higher than the average, the current value becomes the new 4th sample in the average and variance calculation and the loop continues (Steps 22, 30, 39). This loop will continue for a maximum of 15 seconds. If no start is detected (as described below) in this time, the unit will beep twice and turn itself off in step S8.
If the current sample value is high enough to cause branching to the start detection routine, the old average and variance are saved. In Steps 31, 32 3o the next sample is now checked to see if it is also above a threshold level 128 (Step 32) or the 2 standard deviation threshold (using either the CH3 or CH1 channel, depending on how large the input an channel CH3 is), and also to see if it is higher than the previous sample (Step 33). :If both of these conditions are met, a third sample is obtained and checked in the same way (Step 34). (It must be larger than second sample.) If either the second or third sample fails either test, the average and variance are updated using the new sample values and the program returns to the loop above (Steps 35, 35, 37, 38, 39).
If three samples in a row are larger than the threshold value 128 or the average plus 2 standard deviations, and each is larger than the one preceding it, then start is detected (Steps 40, 41, 42, 43).
The saved average is stored as the offset to be subtracted from all samples and the 3 samples are converted to flow values and summed as the first three volume increments (Step 41). The actual conversion from the measurement pressure differential samples to volumes is accomplished by using two look-up tables stored in ROM 54. One look-up table correlates samples from the low flow channel CH3 (i.e. 0-2 volts) while the second look-up table correlates the samples from the high flow rate channel CH1 (i.e. 0-4 volts).
The values on these look-up tables are determined empirically. As previously mentioned, the orifice used to measure flow rate has a non-linear response, i.e. the pressure differential across the openings 32, 34 due to turbulent flow is non-linear. The present spirometer takes advantage of this non-lineality by separating the pressure differential samples into two ranges based on the flow rate, and then using a look-up table fo~c each. By switching gains, the microprocessor has expanded resolution at low flows.
This would be analogous to an equivalent linear range of 16 volts at 10 bits of resolution, or 4 volts at 12 bits of resolution. This feature is made possible by ,~Y C~ : W ;~ !d ~~~N~~ ~;.~3f~~
the non-linear cr~aracter.istic of the orifice. To conserve microprocessor memory space, rather than store a value for every possible A/D code, the microprocessor extrapolates between the two closest 5 stored values. Enough samples are stored to keep the extrapolation error small. In this manner, a less-discriminating (having lower resolution) A/D converter can be used without sacrificing accuracy and sensitivity.
10 Once start is detected and integration of flow values has begun, the unit begins to look for the maximum slope of the volume curve (step S3). If the slope determined by several consecutive samples is low or negative, the whole measurement is reported as a 15 false start. The maximum positive slope is determined over seven flow samples and, when found, is back extrapolated to determine the start of the first second timing for FEV1 determination in accordance with the standards set by the American Thoracic Society identified above (step S4). Meantime, each 10 cosec. the CH1 and CH3 channels are sampled (step S5).
If the CH3 output is less than 2 volts above the offset, it is converted to flow and summed. If the CH3 input is more than 2 volts, the input from channel CH1 is used instead. The unit also looks for, and stores the highest flow sample (step 6).
When the FEV1 timing has been determined, flow samples have been collected and integrated as volume, and the peak flow value has been stored, the unit displays the measured FEV1 and REFR (step S7) and it turns off the analog circuitry to save battery life.
The display is maintained for 45 seconds (or until the START button 22' is pushed to initiate another measurement cycle). After 45 seconds, the microprocessor powers down (step S8) to an idle made.
The operation and circuitry described above and in Figures 6A, 6B and 7 pertain to a basic spirometer.
For more advanced modes additional features may be incorporated mostly by modifying the programming of microprocessor 52. For example, before the unit goes into the idle mode, each measurement may be stored into RAM 54 with a time stamp and/or date stamp indicating the time and day on which the measurements were made. The measurements are then recalled and reviewed on the display screen sequentially by activating switch 22. As an incentive, the instantaneous flow measurements could be displayed as the person blows through air tube 26, and when certain mile stones are reached, the beeper could be sounded.
Obviously numerous other modifications can be made to the invention without departing from its scope as defined in the appended claims.
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1.5 -, U..!iEr~~~tJT:NE THAT CA!CU! aTfS i!iE v7nRIANCe ,~ THE SIGNAL AND iETECTi 15 ; ~F ;Hf 'IALUE IS LARGER 1NAN THIS VAR;~NCE
t7 ;tttdttttttdtdttdttdtttttttdttdtttlt8ttdtitdddtdttittdtdddtttittdtttttdtttttait "EF:'.IE c.'ITR'I nN0 ERIT POIN1S F!R iU9a0UTiNES
:1 _LOBAL START ; 90UTINE DETECTS START ~'..F 9REAT~1 j SL:)9~L CAL 'JAR . :A! :~JI~TE's VAAIENCE
y :;
~5 f:iTEn:NAL 9ETDATA ; 5=i5 DATA FROA 50URCE
:5 27 EtTEiiNA! DIVIDE
sg EbiERNAL MULTlPll1 jp ;,..,.,. " ... "
..,........................,.,......,...............,........,..
3l g OEFIIIES ~1ND 'J~RIA9LES IN FILE: aEFaIES.SRC
j~ !15T OFF
3qg ;.........,....,. " ......,............... " .,...,................,.,....
" .....
399 .
~ODt:;~;TtrtiS
it)1 A)i lQj s;)a ;ttatm cattttsstv tttttttttttw ttsttstttttttttttatdttddddttt:tcn tstciattattt .:'!': ,:_°:a':,:' :. __ . _ ::.i:v .';~ORMATI°'~ :', ' : _~::__ 'vA6E
a~i7 ; JOITAGE
4iiq , .............................................................................
i .
4ll 41' ; HAIN S S1ATISTiCS A!D 1E5TS, 'JALUE, CALCIiLA~E
41:; ; START T BEEPS AND TURNS OFF
IH l5 SECONDS.
OTHERNISE
( 41s el; STAR1 CLR FCDUNT ; :;.EAR LODP CGUN1ER
~i3~i0 :~F
415 :.F CLR HEO_SLOP
41: ......... ...............................
420 ~;~;~aCD 00 hAIHLGOP GETDATA ; SET AH INPUT VAIU
00 ~SR OF VOLTAGF_ ~1~, 4~; ; TES1 TOG BI6 USE VOLTtI !GRIN I1 iF 'JGLTt4AND IF
:.
d5 i'i0?86 AE LuA 'JGLT4l0 : TEbT %~AB tDLTAGE
' FROH SEHSGR
d25 . Ais SU8 iBJQ
yp~)~yp a_7 0008B5 AF !DA :'OLt4H0 48 :iQ'iCA: 0: S8C 9f~)'s 4_~
i;C OOOF25 10 BCS VALU uK : n~N~:F LNG USE GAiH
4 JAIiJES
4.:1 43? OOItB6 A1 i9A VOt.TII
~
_:: Ot:l3B7 AE STA VGlT4L0 434 00158b Ci !DA 'JOllIH
a.350017B7 AF 5TA 'JOLT4H0 a~.ti a i~il9'B AE ! 5L aGLTau ; H~:T iF:u ~~; 4 TO
; OFFSET FDR 7fiiH ~sF
~ , .i9 ROl VOl.T4H0 ; 4 4'3 OOIBAF
43 OOID:3 AE !SL 'JULT4L0 440 OO1F39 aF ~ ROl 'JOlT4N0 a41 s.2 a4: ;....... ......... .......................
00:13D b5 VALU OK FCOUHT ; TEST CGUNT GF POSITIVE
151 AT1E!4PT5 445 00:x7 03 BEG STAT ; ?ERO, CALCULATE STATISTICS
4 ~ CAL
4 . CC 00 JHP _ ; FDUNO ONE ALREADY, OOiS8A i DETECTED TEST THI~ lNFUT
a49 450 ;.............. ........ "
,.,...........,.....................
" ........,.......
FIROT CALCULATE
THE VARIEHCE
f4 ail d SAf9PlES
45a ;
454 ~i0r9CD O1 CAL STAT CAL VAR ; RETURNS VARIANCE
OF JSA
i TO !II'lIHUH
; VALUE
ERO
456 . . , 45, ,iu2B:,p 1ST 'JARNCE
96 ii s5= a,:~:, OC BNB TEST _(t _;:.:F96 35 =rA 'J",n!iCE_L. :a F _=SS THA;i :a: ..:'::A4 Ifl i~JB :Ih :.; ':::~5 ~: .:8 EE; ! J~o :..'. =0 .a t=;. .:.: T
. _.
.
~~~~~~~~J
454 SET lOH 4Is Ab a55 5TA
BI
4b7 468 ; . " . . . . . , . , . " . . . , .
. . . . . " . , . . . . . .
. . .
, 47g " . . TEST (S RESIDUAL CF 'lOLTO
IF BREATH IS 6AEATEA THAN 'JARIANCE
STARTED
-472 ; F1RST REASE IN 'lCLTA6E - LAA6ER
TEST IF THAN OFFSET
CHAhc~
IS ~N
INC
474 Bb 87 TEST_IT ~':5 ; 5E1 aVERA6E OFFSET AND
0038 LDA OFD:
475 80 AE SUB 'r~iLT4L4. 'J6iRACT NE4d VOLTAGE
476 B7 72 STA TE:9P!
471 95 88 LDA n'i6 0041 OFF'tl 478 B2 AF SBC ';;=.'4t10 479 8711 STA TC;!t'H
aeD
ail ?4 29 BCC ~E:v~F ; '~i,B 'JOLTA6E SHALLER
0041 OR n?!JhL
aa2 a84 ;. , . . , . , . . . , . . . . . , . . . . . . . . .
i85 .. . TEST
IF LAA6E~
'9~N ~~AIAtICc - ~:AL:,U~.'~E
vESIDUAL
JALUE
, . , . . .
. . .
48i 488 3F 67 CLR 5=_GF . :L:;R NE6 SLOFE CCUttiEA
a94 Bb AE LDA '1~:_T:I_;), ;':i;LTfj - A'J6 OFFSrT!Bt2 491 87 12 'STA
492 B5 AF LDA _! i 004F at!0 49:. B1 71 STA '="N
494 CD O1 3SR _:_iASC . ;=I!JRNS iiESIOI~AL
0053 8F IN FLOiIH.
49b Bb 85 LDA 'i;wNCs :~ ~:E~ID!JAL i at'JARIANCE
005b '..
a9l 80 74 5UB F'_'?w~ ; ei: a'JARIANCE - RESIDUAL
005A 86 86 lDA 'I~RNCE
a98 ti -499 B2 73 SBC FLDiIN
50i 24 OD 8CC NsT JK ; RESULT IEAO OR P95ITI'JE
503 3C 66 'JAL INC F.U4; : ur.. ':ALUE LAR6ER, 0060 OK ADVANCE Ct7UNT
509 Bb 14 _ FLDHL ; 5A'JE RESIDUAL FOR TESTING
505 87 85 5TA 'J~RNCE
OOb~ i 50b Bb T3 LDA P~_CUH
006b 507 87 86 5TA '.'wh.NCE
508 CC 00 dNP 'SS1I'!E; D i? TEST IF TINE (~P
OObA D2 511 3F bb HOT OK FCCUNT ; nESET COUNT AND
OObD CLR
5t2 CC 00 aNP T~iTIHE .
00bF 02 515 ;...... ......,......... " .,.,...........
~ l.i , yE!iaTl'JE5i'.F __. :F ' .__. _: IV a h.GI H!~0 idEtt ~:V:<E
5I' ,. , _ ._ _. _.
5t6 7 v'tlT ?!C1I.:~;.aiT:t =aLSn Sr;' ':v~
LN ~_ .v'~
;1a :e~m~: .._' . _._ ._u ')t~i2 CLn .~
:'D
y PAGE
%~~:
r y G t~ ~ ~a ~~.~e~~ l s~~j 522 ; TE51 IS GREATER
ruAH ~
;.
2;
524 0074 B6 LDa TEMPL
'2 525 4075 A~i SUD 404 52b 4076 i5 HCS SKIPCNT
'i8 ~C ~57 1NC NEG SLOP . ~u'JriNCE CDUH1 528 407A _ 530 007C :5 LDA NE6 SLOP ; T:ST lF t TI!!E5 of !H A RON
531 007E ~I CNP 94 532 0090 :~ 6HE EXITIT
i5 534 0082 ;_ LDT X401 ; HETURH AITH EFcROR
:.I CODE
535 0094 2: RTS
53b 531 0085 'c Sk:IPCN1 NEG SLOP ; F.ESET COUNT
, . ~'!) D_ EXITIT TESTINE . 7 TO TEST IF tIHE
538 U087 . ~)NP OF
5i9 54!
i42 ;..............................................................................
544 ; . PRE'JICJS ':c; ve:lT 4 iiNES
T1ME PERIODS . . . . . . . . .
:UCCSSF:JL . . . .
, 546 ; FIR5T VOLTAGE VALUE
TE71 IF 1FL04RATE) :'JERY LARGE:
> 128 AID
UNITS
548 OOBA ~ OETECTEO'LDAVOLT4L0 . :Tt.aCT vJOLT FROM
vE A'JERA6E OFFSET
549 008C 2) SU8 AVG OFFL
s5W009E A' yiA TEMPL . :;':.-- FESULT
' 55I 0090 Ha LOA 'JOLT4H0 AF
553 ')094 ~' StA TEMPH
't i2 ~30 557 009A 66 LDA iEMPH
7t 558 009C A2 SDC i00 i)0 9E 24 lA BCC BIGGER ; IHE 'JOLTAGE FR9H
THE SENSOR 1S 'JER'!
560 00 : DlG 50 ASSURE 11 5bl ; THAN THE VAFIANCE
Sb2 564 ;....... ........... ...................., 56b .; SENSOR GE GhALL THE RESIDUAL
VOLTA SO CALCULAtE
5b7 DA VOLT4L0 ; CALCULATE RESIDUAL
' OF NEH DATA
5b8 OOAO Bh JAL OK
AE L
5b9 90A2 di STA TEHPI .
aF
51l OOAb R' STA 1EMPH
7l ~'%OLT9 - A'JE OFFSETItt2, IFLONL.H!
572 ')'A$ .. J5R fELTASO ;
)I :F
:..5 :-c . . . 'E:iLAAGEn IN:iN:: ''c =;:'~IOn: ':;?:
IF :iEal2~'JaL ~En'.~u -" - ~.~~ ,':.L UE - ,!
' :ro ~ia~ 9 !r'_t=
iC=
.;yA._ := _ .
_i ~'a5t r ,3 578 QUAD 80 74 S9B FLOat 51? OOAF Bb B6 LDA VAFItCE~t ~Bl 582 l~OB3 :5 45 6CS B16E_ ; BRa IF hE~ :~,U:E -OLS VHLnE
585 ;. E!7UAl. UPDATE THE ST:~TIStiCS
OR WHALLEN . . . . . . . . . .
50 ~:E~ET
AND ue 587 0085 3F 6b CLR FCUUNT ; CLEAR CUUNTFs 588 OUB7 CC 00 28 JNP CAL :TAT ; AND CAICIiIATE STATISTICS
FOR THIS
589 ; T1HE PERi~ID
59t 592 ;. . . . . . . . . . . . . . . . . .
. . . . . . . .
S?4 ;. . . ER '.)N ;:ST !F DUNE. . . . .
VALUE THIS TR'i . . . . . . . . . .
I.ARfi au .
5'35 595 Ur)BA 3C 56 ~I96ER FC.~_'.'' :lis, 5?7 009C 85 65 lDA FCU~_V' ; TEST IF )thE
599 r)OCO ~7 OB BEO RESET
501 : iOT DUNE,THE FF:ESENT
SAVE RESt~'!~L
w.R NE%T
~w~E:i;.
. . .
. . .
. . .
. .
,5r).2 503 OOC2 86 74 LDA FLDaL
.an4 Or)C4 Bl 85 STA VARNCE
505 OOC6 Bb 73 .LDA F!ti~N
,505 OOCB ii _ NF T=:'il! : ErIT AND '_T IF TI"ER
' D9NE
508 OQCA CC ~)0 D2 ~.
.
5r)9 oI0 611 OOCD 3F 66 RESET CLR FCJU!IT
512 OOCF CC 00 DE JqP CAl !.'ut.; DON - CHL:'I~a~E 40sUHE
NEsT
5l3 6l4 ;.................................................,..,...............,..,......
6l6 11 ; TEST R 15 SEC
FU
599 r)OCO ~7 OB BEO RESET
501 : iOT DUNE,THE FF:ESENT
SAVE RESt~'!~L
w.R NE%T
~w~E:i;.
. . .
. . .
. . .
. .
,5r).2 503 OOC2 86 74 LDA FLDaL
.an4 Or)C4 Bl 85 STA VARNCE
505 OOC6 Bb 73 .LDA F!ti~N
,505 OOCB ii _ NF T=:'il! : ErIT AND '_T IF TI"ER
' D9NE
508 OQCA CC ~)0 D2 ~.
.
5r)9 oI0 611 OOCD 3F 66 RESET CLR FCJU!IT
512 OOCF CC 00 DE JqP CAl !.'ut.; DON - CHL:'I~a~E 40sUHE
NEsT
5l3 6l4 ;.................................................,..,...............,..,......
6l6 11 ; TEST R 15 SEC
FU
UN i IlIE tEST UN T i;',: iU aiE
619 OOD2 Bb 5t TESTINE ;
LOA
621 OOD6 25 A3 RCS TIH uUT ; TIME UP, ElI1 ROUTINE
522 0008 CC 00 04 ,INP HAlNt.OUP ; LOOP 9ACY, AND RETRY
b23 b24 OODB AE 00 TIN OUT 1600 l01( RTS ; E1IT SYSTE19 NI1H ERROR
= 0 525 OODD 8l :ttttttlt8ttittttttttlit6tt161fltttlttttltlBtttitttlllttttttttlttttttttttttitit START PETE:':D, a?L.:_:~:' -:~__ :~i,~, -;t:'_ :-dF .:_:":
~5 ':~: ;'U :';F':i.v'_a__, .E. :vEw_, -~;.T;C
_ _ _ ;:~~DE to a:Et =_aa=
_ _ ~ _ .
:s ,.,r .
c i: a c, v ~.
. ~~~~~~ ~z~L3 5:5 OQE4 ~4 LSR FLDN H:;H ; CALCULATE FH312 9:
h35 u9E: ~6 ROR FLON H3L
iii 5:5 '.':lE4 LDA FLAN H;L ; aOC 14 Fn2 Bb 94 59 :)OE5 9B ADD FLON_H2L
~7 .i4; :)QEA LDA FLON_H3H
B5 9:
542 40EC B9 ADC FLON h2H
54' OQEE 87 STA 'lOLUhEH
;45 OOFO B6 LOA VOLUHEL ; ADD iH FHi 546 OOF2 BB ADD FLAN Hll 4i OOF4 B7 5TA VOLUHEL
.543 OOFb eb LOA 'JOLUNEH
530 ')OF9 Ba AOC FLON_H1H
550 Qi)FA B7 STA VOLUHEH
lb 55OOFC 35 9D LDA FLON :)H ; ~.ALCUIAiE FLON/2 .;;:; 0:)F= LSRA
~a TA% : AIiD SAVE l~t X REGISTER
~'4 OOFF '1 5~5 s!V)~) LDA FLON_eL
55 ~?;: :.5 ~ORA
55i .558 OIO.i ADO volunEL ; A60 TO VOLiillE
559 ' O105 STA 'IOLUHEL
81 il b50 :)107 ?F T1A
,5bi 0108 89 ~ pDC 'IOLUHEH
7b 55~ ')l0A 81 STA 'JOLUpEH
5.5.3 i)2 LD!I 4102 ; EXIT aITH ~K. GODE
,5ha :)li)C
gE
DOIIE RTS ; AHG EI1T 'START
565 i)10E 8l .~59 bli) ss4ttaatsitats~taatt~att:eta:c~sasatactttgataaratt~tt~atsat::::4sa><uscsaa bll ;
.... CALCULATE
OFFSET
A'JERHSE
ANO VARIANCE
STATISTIC
,.,.................
51.s I....
, FIRST
CALCULATE
AVERAGE
OFFSET
I
, 57b CAL 'JAR VOLT4Ll ; CALCULATE AVERAGE
LOA OFFSET 'JALUE
bil OtOF Bb ~ ADO VOLT4L2 ; Vl + V2 + V3 + V4 BO
b79 Olt~ B7 5TA AV6 OFFL
bd0 OllS 86 LDA VOLT4Hl bd1 0111 B9 AOC VOlT4H2 b8Oll9 87 88 STA AV6 OFFH
5a~
5d4 uilB Bb LOA AV6 AFFL
a85 )110 BB ADO VOLT4L.3 -5.: ~tt: 37 SiA AV6 OFFL
iti 5 38 LCA AV6 ~FFH
'.' . ar~~ VOLT;hJ
...
~ B5 .,' .~I; ' ii: AV6!)FF;i _ . ': i~ ._ . C;w nL's_.~F'_ W
' ~~~~~~~~;9 :?3 0128 B7 87 9TA AV6 ~7FFL
,as OI:D B6 99 LDA VG OFFH
aye OI~F 89 B7 'dDC VOLT4H4 5ab i)I;1 81 STA A'7G!)FFH
5~~
b4g Ot.33 34 LSR AV6 OFFH ; :~'JIuE ey 4 ~?? 013.5 ib OR AVG_OFFL
';):i 0137 34 LSR AV8_OFFH
013? 3b 97 ROR AVG OFFL
70l _ .,)' -;)3 ;, , CALCULATE . . .
'dARIANCE
VALUE
. . .
619 OOD2 Bb 5t TESTINE ;
LOA
621 OOD6 25 A3 RCS TIH uUT ; TIME UP, ElI1 ROUTINE
522 0008 CC 00 04 ,INP HAlNt.OUP ; LOOP 9ACY, AND RETRY
b23 b24 OODB AE 00 TIN OUT 1600 l01( RTS ; E1IT SYSTE19 NI1H ERROR
= 0 525 OODD 8l :ttttttlt8ttittttttttlit6tt161fltttlttttltlBtttitttlllttttttttlttttttttttttitit START PETE:':D, a?L.:_:~:' -:~__ :~i,~, -;t:'_ :-dF .:_:":
~5 ':~: ;'U :';F':i.v'_a__, .E. :vEw_, -~;.T;C
_ _ _ ;:~~DE to a:Et =_aa=
_ _ ~ _ .
:s ,.,r .
c i: a c, v ~.
. ~~~~~~ ~z~L3 5:5 OQE4 ~4 LSR FLDN H:;H ; CALCULATE FH312 9:
h35 u9E: ~6 ROR FLON H3L
iii 5:5 '.':lE4 LDA FLAN H;L ; aOC 14 Fn2 Bb 94 59 :)OE5 9B ADD FLON_H2L
~7 .i4; :)QEA LDA FLON_H3H
B5 9:
542 40EC B9 ADC FLON h2H
54' OQEE 87 STA 'lOLUhEH
;45 OOFO B6 LOA VOLUHEL ; ADD iH FHi 546 OOF2 BB ADD FLAN Hll 4i OOF4 B7 5TA VOLUHEL
.543 OOFb eb LOA 'JOLUNEH
530 ')OF9 Ba AOC FLON_H1H
550 Qi)FA B7 STA VOLUHEH
lb 55OOFC 35 9D LDA FLON :)H ; ~.ALCUIAiE FLON/2 .;;:; 0:)F= LSRA
~a TA% : AIiD SAVE l~t X REGISTER
~'4 OOFF '1 5~5 s!V)~) LDA FLON_eL
55 ~?;: :.5 ~ORA
55i .558 OIO.i ADO volunEL ; A60 TO VOLiillE
559 ' O105 STA 'IOLUHEL
81 il b50 :)107 ?F T1A
,5bi 0108 89 ~ pDC 'IOLUHEH
7b 55~ ')l0A 81 STA 'JOLUpEH
5.5.3 i)2 LD!I 4102 ; EXIT aITH ~K. GODE
,5ha :)li)C
gE
DOIIE RTS ; AHG EI1T 'START
565 i)10E 8l .~59 bli) ss4ttaatsitats~taatt~att:eta:c~sasatactttgataaratt~tt~atsat::::4sa><uscsaa bll ;
.... CALCULATE
OFFSET
A'JERHSE
ANO VARIANCE
STATISTIC
,.,.................
51.s I....
, FIRST
CALCULATE
AVERAGE
OFFSET
I
, 57b CAL 'JAR VOLT4Ll ; CALCULATE AVERAGE
LOA OFFSET 'JALUE
bil OtOF Bb ~ ADO VOLT4L2 ; Vl + V2 + V3 + V4 BO
b79 Olt~ B7 5TA AV6 OFFL
bd0 OllS 86 LDA VOLT4Hl bd1 0111 B9 AOC VOlT4H2 b8Oll9 87 88 STA AV6 OFFH
5a~
5d4 uilB Bb LOA AV6 AFFL
a85 )110 BB ADO VOLT4L.3 -5.: ~tt: 37 SiA AV6 OFFL
iti 5 38 LCA AV6 ~FFH
'.' . ar~~ VOLT;hJ
...
~ B5 .,' .~I; ' ii: AV6!)FF;i _ . ': i~ ._ . C;w nL's_.~F'_ W
' ~~~~~~~~;9 :?3 0128 B7 87 9TA AV6 ~7FFL
,as OI:D B6 99 LDA VG OFFH
aye OI~F 89 B7 'dDC VOLT4H4 5ab i)I;1 81 STA A'7G!)FFH
5~~
b4g Ot.33 34 LSR AV6 OFFH ; :~'JIuE ey 4 ~?? 013.5 ib OR AVG_OFFL
';):i 0137 34 LSR AV8_OFFH
013? 3b 97 ROR AVG OFFL
70l _ .,)' -;)3 ;, , CALCULATE . . .
'dARIANCE
VALUE
. . .
7')4 05 Old B6 80 LOA VOLT4L1 ; :L~:!.ILATE t'dDLTt-OFFSET)4Z:
7!)b Olio B7 STA TEdPI
~07 013F 9b B1 LDA 'dOLT4H1 '08 Ot41 87 71 STA TENPH
:09 0143 CD Ol JSR DELTASO
BF
.':') 0145 Bb LDA FLONL
:it 4148 B7 85 STA VAfNCE
L
~t? :)14A Bb LDA FLD14H
B7 86 STA iAF'HCE
';OIsC H
-its ;t5 OIdE B6 B2 LOA VOLT4l2 :~:!J!~TE (~:~!
T2-ciFF3ET~tl~
i!b 0150 B7 72 STA TLHPL
i17 0152 86 B3 LDA VOLT4H2 7t9 0154 97 71 STA TE;1PH
~
'1? OlSb CO 01 JSR DELTASO
BF
i)t59 95 i4 LDA FL OIiL
'! 0158 BB 85 ADD 6'ARHCE
!.
??. OlSD B7 85 STA 'JARNCE
!_ 'i 015F B6 73 LDA FLOiiH
,)l.sl B9 8.4 ADC VARNCE
H
i5 H
-i11 0155 86 B4 LDA VOLTslL3 ; !:nLC!lLATE t'JGLT3-OFFSETi442 i28 0161 B7 72 STA TENPL
72? 0164 B6 85 LOA VOLT4H3 70 0168 Bl 71 STA TENPH
BF
-32 Oi70 B6 74 LDA FL061L
L
734 0174 87 85 STA 'JARNCE
L
13b 0178 B9 86 ADC VARNCE
H
Bl 86 STA VARNCE
-LDA VOLT4L4 ; :ALCULATE IVOLT4-OFFSET1112 140 O11E 87 12 STA TENPL , '41 0180 B6 B7 LDA VOLT4H4 '42 0182 B7 71 STA TENFH
'43 0184 CD O1 JSR DELTASD
NF
!)l87 85 i4 LDA FLObL
'': ~):=4 BB DD 'lARHCE
n' ~
~'ta3 d7 35 i'A '~anN;:E_!
. ~:te) 3b ~'. !_cH F!'_'xH
:~t3F .4 8b ADC .~nN~::_ PAGE
'4 a H
~50 ;:1 -;l ,. . TEST nND AttO
!F ZERO IF SO
EIII
'S3 .'S4 Ot9~ 30 TS1 VARHCE
i55 0195 25 8NE tIATH
45 4.3 'S6 0197 30 iST VARNCE
?57 Ot99 25 6NE MATH 43 758 0198 :0 BRA DDNE_CAL
2l ?59 ?5ti NULTIF'LY 8Y 4 AND
; Di'lIDE
. . .
7.;1 75019D 39 55 MATH d3 VARNCE ; NUL11PLY BY 4 75.019F 39 ROL VARNCE
'03 OIAI 38 LSL VARNCE
OlA3 39 8b ROL VARHCE
-"a i "6i 01A5 8b LOA 'lARHCE_L
..i3 OIA7 87 STA TENFL
'b9 OtA9 B5 LOA VARNCE
'?~) OlAB 67 5TA THFN
7l '? 1 O1A0 A5 03 LOA 13 ; 5Ei UP OIVI50R
... sSTA DIVSORL
773 OtAF 87 ;l~
v75 4163 CO J5R DPJtOE : 00 THE OI'JI50t1 ;77 778 0185 Hb LOA TEHFL RESTORE VALUE IN 'JAFANCE
''9 Ot9S 87 STA VARNCE
"3!) 018A H5 LUA TEtiFH
1 t 87 9b 5TA VARNC
-7~
1H3 O18E 31 GONE CAL ; AND E><1T CAL VaR' RTS
?85 ;,...,...,....,.......,...............,........................................
-8g ; SUBROUTINECALCULATEVAV6)112 CALLED THE RESIDUAL
TD tVOLT ' a~ ; USES HULTIPLYROUTINE, ANSdER
RETURNED
iH 'FLDaH,FLObL' 791 018F Bb DELTASD TENPL ; SUBTRACT VOLT FROM AVERAGE
9'. OICt 80 SU8 AV6 OFFL
703 OtC3 87 5TA TEHPL ; SAVE RESULT
7a; OtCS 8b LOA TEHPH
7t i95 OICT 82 S8C AV6 OFFN
79b OlC9 87 ST A TENPH
It 798 OICB 86 LOA TEtIPL ; T51 FOR ZERO RHSULT
9 ~!I~:D 5 8NE HOT IERD , c;') O1CF 56 Li~A TENPH
::,: :)t~; 8NE NOT_ERO
; ~5 ... ~?;:: . iLn FL'Ja~_ : OLTPUT ~ :_9:J RE3UL' "~4 ~:1?: 'F .. CL9 FLC~BH
.. STS ' ... ~?::' ':
PGn~
'~~'E~r~y~~~'~jf, ~ ~, r~ a ~~ (h 807 ;. . , , . . . . . , . . . . . . .
. , , , . . . . .
E09OlDB3D11 NOT_iEFO TENPH , ..'~ 1~ FOS(TI'IE AND
TST ~.uIITi!It;E
912OtDC3372 COH TENPL :.~rz: CDN~JERT TO POSItl9E
'IALUE
9t3OIDE337l CON 1EHPH
815OLEO9672 OK CAL TEtiPL
LDA
9laOlE5877.: STA FLOAH
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Claims (12)
1. A portable spirometer comprising:
a housing;
an air tube coupled to said housing and including a substantially linear air passage with a reduced diameter orifice for generating a turbulence in the air passage;
pressure sensing means for sensing a differential pressure across said orifice when a person exhales through said air tube;
filter means disposed at an interface between said tube and said pressure sensing means for protecting said pressure sensing means, said filter means being made of a material permeable to gases and impermeable to liquids;
electronic circuitry means disposed in said housing and coupled to said pressure sensing means for generating electric input signals corresponding to said differential pressure, said electronic circuitry means including calculating means for calculating performance signals from said electric input signals; and display means for displaying said performance signals.
a housing;
an air tube coupled to said housing and including a substantially linear air passage with a reduced diameter orifice for generating a turbulence in the air passage;
pressure sensing means for sensing a differential pressure across said orifice when a person exhales through said air tube;
filter means disposed at an interface between said tube and said pressure sensing means for protecting said pressure sensing means, said filter means being made of a material permeable to gases and impermeable to liquids;
electronic circuitry means disposed in said housing and coupled to said pressure sensing means for generating electric input signals corresponding to said differential pressure, said electronic circuitry means including calculating means for calculating performance signals from said electric input signals; and display means for displaying said performance signals.
2. The spirometer of claim 1, wherein said pressure sensing means includes:
access holes disposed in said air tube and spaced from said orifice; and transducer means coupled to said access holes for generating a transducer output corresponding to said differential pressure.
access holes disposed in said air tube and spaced from said orifice; and transducer means coupled to said access holes for generating a transducer output corresponding to said differential pressure.
3. The spirometer of claim 1 or 2, further comprising power supply means disposed in said housing for supplying said circuitry means with electrical power, said circuitry means deactivating said power supply means when said spirometer is in an idle mode.
4. The spirometer of claim 3, wherein said electronic circuitry means includes analog circuit means and digital circuit means, and wherein said power supply means provides power to said analog circuit means when said spirometer is not in said idle mode.
5. The spirometer of claim 3, wherein said power supply means includes a battery to make said spirometer self-contained.
6. The spirometer of any one of claims 1 to 5, further comprising voltage offset compensation means for offsetting voltage offsets in said circuitry means.
7. The spirometer of claim 6, wherein said voltage offset compensation means includes digital-to-analog convertor means for receiving an error signal from said means corresponding to said voltage offset and said converter means generating a convertor output.
8. The spirometer of any one of claims 1 to 7, wherein said electronic circuitry means includes:
first amplifier means for amplifying said electric input signals by a first factor to generate a first amplified output;
second amplifier means for amplifying said electric input signals by a second factor to generate a second amplified output; and microprocessor means being coupled to first and second amplified output, said microprocessor means being programmed to select one of said first and second amplified outputs to calculate said performance signals.
first amplifier means for amplifying said electric input signals by a first factor to generate a first amplified output;
second amplifier means for amplifying said electric input signals by a second factor to generate a second amplified output; and microprocessor means being coupled to first and second amplified output, said microprocessor means being programmed to select one of said first and second amplified outputs to calculate said performance signals.
9. The spirometer of claim 8, wherein said electronic circuitry means further includes analog-to-digital converter means for converting said first and second amplified output for said microprocessor means.
10. The spirometer of claim 8 or 9, wherein said air passage has a non-linear response to air flow;
wherein said microprocessor means includes select means which selects said first amplified output in response to a first air flow below a threshold level; and wherein said select means selects said second amplified output in response to a high air flow above said threshold level.
wherein said microprocessor means includes select means which selects said first amplified output in response to a first air flow below a threshold level; and wherein said select means selects said second amplified output in response to a high air flow above said threshold level.
11. The spirometer of claim 8, 9 or 10, wherein said microprocessor means includes sampling means which samples the air flow through said air passage and which calculates a running average signal.
12. The spirometer of claim 11, wherein said microprocessor means includes monitoring means which monitors said average signal to discriminate a test from noise.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US461,089 | 1990-01-04 | ||
| US07/461,089 US5137026A (en) | 1990-01-04 | 1990-01-04 | Personal spirometer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2032796A1 CA2032796A1 (en) | 1991-07-05 |
| CA2032796C true CA2032796C (en) | 2000-12-05 |
Family
ID=23831180
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002032796A Expired - Fee Related CA2032796C (en) | 1990-01-04 | 1990-12-20 | Personal spirometer |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US5137026A (en) |
| EP (1) | EP0437055B1 (en) |
| JP (1) | JP3102898B2 (en) |
| AT (1) | ATE120944T1 (en) |
| AU (1) | AU636183B2 (en) |
| CA (1) | CA2032796C (en) |
| DE (1) | DE69018602T2 (en) |
| DK (1) | DK0437055T3 (en) |
| ES (1) | ES2073542T3 (en) |
| NZ (1) | NZ236575A (en) |
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| USD848620S1 (en) * | 2016-11-28 | 2019-05-14 | Spirosure, Inc. | Mouthpiece for a respiratory monitor |
| USD833014S1 (en) * | 2017-01-25 | 2018-11-06 | Healthup Sp. z.o.o. | Portable spirometer |
| AU2019254665A1 (en) * | 2018-04-19 | 2020-10-15 | Healthup Sp. Z O.O. | Portable handheld electronic spirometer |
| KR102039984B1 (en) * | 2019-05-10 | 2019-11-04 | 브레싱스 주식회사 | Measuring device of breath |
| US11672934B2 (en) | 2020-05-12 | 2023-06-13 | Covidien Lp | Remote ventilator adjustment |
| USD1021096S1 (en) * | 2022-05-06 | 2024-04-02 | Ulrich Gmbh & Co. Kg | Spirometer for medical purposes |
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-
1990
- 1990-01-04 US US07/461,089 patent/US5137026A/en not_active Expired - Lifetime
- 1990-12-12 AU AU67994/90A patent/AU636183B2/en not_active Ceased
- 1990-12-13 EP EP90313554A patent/EP0437055B1/en not_active Expired - Lifetime
- 1990-12-13 DK DK90313554.9T patent/DK0437055T3/en active
- 1990-12-13 DE DE69018602T patent/DE69018602T2/en not_active Expired - Fee Related
- 1990-12-13 ES ES90313554T patent/ES2073542T3/en not_active Expired - Lifetime
- 1990-12-13 AT AT90313554T patent/ATE120944T1/en not_active IP Right Cessation
- 1990-12-20 CA CA002032796A patent/CA2032796C/en not_active Expired - Fee Related
- 1990-12-20 NZ NZ236575A patent/NZ236575A/en unknown
- 1990-12-27 JP JP02408252A patent/JP3102898B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE69018602T2 (en) | 1995-10-26 |
| ATE120944T1 (en) | 1995-04-15 |
| CA2032796A1 (en) | 1991-07-05 |
| DE69018602D1 (en) | 1995-05-18 |
| AU6799490A (en) | 1991-07-11 |
| US5137026A (en) | 1992-08-11 |
| DK0437055T3 (en) | 1995-07-10 |
| AU636183B2 (en) | 1993-04-22 |
| JPH0428350A (en) | 1992-01-30 |
| ES2073542T3 (en) | 1995-08-16 |
| JP3102898B2 (en) | 2000-10-23 |
| NZ236575A (en) | 1994-01-26 |
| EP0437055A1 (en) | 1991-07-17 |
| EP0437055B1 (en) | 1995-04-12 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed |