CA2238530A1 - Abnormal dyspnea perception detection system - Google Patents
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Abstract
Apparatus and methods to test respiratory patients for altered dyspnea awareness. The device imposes a defined inspiratory resistive load (3, 24) under controlled breathing conditions and records the patient's subjective sensation of dyspnea (10, 14) over time by incrementally increasing (18, 29) the inspiratory resistive load. In a preferred embodiment, the patient breathes in a controlled manner with visual biofeedback prompting (19, 11, 14, 6), having predetermined respiratory rate, inspiration to expiration time ratio and inspiration and expiration respiratory waveforms.
Description
WO 98/1411r, PCTIUS96/15643 ABNORMAL DYSPNEA PE~CEPTION DETECTION SYSTEM
E3ACICGROUND OF THE~ INVENTION
This invention relates to improved methods and apparatus to detect patients with an abnormally altered perception of dyspnea. Of particular concern5 are asthma patients at risk for fatal asthmatic attaclcs. An unexpected risingincidence of fatal asthmatic attaclcs in recent years has been of concern to themedical profession.
The sensitivity of the testing procedure is enhanced by the test being performed under controlled conditions by having the patient breathe in a 0 precisely defined manner by visual biofeedback means, with the subject following a preclet.o~nined breathing pattern on a computer CRT or similar means. Hillsman incorporates by reference his U.S. Patent No. 3,991,304 which describes a sophisticated method to prompt patients to desired breathing patterns by visual biofeedback means.
Prior art has indicated patients who have survived a near fatal asthma attack have decreased dyspnea awareness to increased inspiratory resistance (See:
LOWERED CHEMOSENSITIVITY AND PERCEPTION OF DYSPNEA IN
PATIENTS WIT~I NEAR-F~TALASTHMA - Mlcuchi, ~. et all, Respiratory and Critical Care Medicine, Supplement, Volume l 49, Number 4, April 1994). The 20 cited investigators demonstrated decreased dyspnea awareness in near fatal asthma patients by imposing graded inspiratory respiratory resistance from zero to minus 30 cm. water/liter/second gauge pressure. But no attempt was made b~
these investigators to further control the experimental conditions by defining the testing tidal volume to the patient's available lung volume as reflected in the WO 98/1411~; PCT/US96/15643 patient's vital capacity, or the testing inspiratory resistance load to the patient's available maximum inspiratory pressure capability. Further, no attempt was made to otherwise precisely control the patient's breathing pattern or the precise timing of the breathing stages under the testing conditions, or to otherwise detect 5 whether or not the subjects were performing as required under the testing conditions. The~crol~, absent col~ chensive controlled breathing conditions the testing achieved was relatively crude and therefore less sensitive to defining and detecting dyspnea awareness as measured by the commonly used Borg scale of dyspnea, and likewise there was no assurance as to patient performance and 0 therefore data reliability.
~ n addition, there are many patients vvith Hyperventilation Syndrome, who perceive they ha~e dyspnea when in fact their respiratory function is normal, and definition and quantifying this abnormality and normalization with treatment is of value in the patient therapeutic program.
Further, many patients with dyspnea related to Chronic Obstructive Pulmonary Disease (Emphysema and Chronic Bronchitis) and other respiratory conditions undergo comprehensive Pulmonary Rehabilitation, including various measures to improve dyspnea distress. These measures include various medications, breathing exercises and breathing retraining in proper breathing 2 o patterns, respiratory muscle reconditioning and strengthening by various means, and general body reconditioning and strengthening. Present methodology to quantify dyspnea and measure improvement with the various treatment modalities has generally been controversial and unsa~isfactory. Therefore, thereis a need to properly define and quantify the dyspnea abnormality and an~
WO 98/1411~ PCTIUS96115643 normalization with the various treatments in the patient therapeutic program7 both to guide therapy and to document improvement for administrative needs.
The instant invention to comprehensively define the testing conditions relative to the patient's vital capacity and~or maximum inspiratory pressure 5 capability, and to further define the testing conditions by having the patientbreathe in a precisely controlled manner using predefined breathing patterns by visual biofee~1h~flc means, and to precisely control the sequence and timing of the testing events. Therefore, by establishing the breathing testing conditions the sensitivity, accuracy and reproducibility of the diagnostic methodology will be 0 enhanced. In addition, by placing definable plus and minus error limits abo~reand below the desired breathing analogs, with suitable audio and~or visual alarms to indicate if the patient breathing performance is outside acceptable limits, the diagnostician may determine whether or not the subject is performing in an acceptable manner to the testing methodology as defined by the operator Çor the 5 particular subject and thereby generating reliable testing data.
CA 02238~30 1998-0~-2~
WO 98/14115 PCT/US9611~i643 SUMMAR~ OF TH}~ INVENTION
It is therefore one object of the present invention to enhance the sensitivity of testing for dyspnea awareness by the testing procedures being precisely controlled as to breathing patterns with defined elements of respiratory 5 rate, inspiration to expiration time ratio, and inspiration and expiration breathing waveforrn analogs by visual biofeedback prompting means.
It is another object of the invention to enhance testing sensitivity in a first mode of operation by relating the testing tidal volume breath to a defined percentage of the patient's vital capacity capability, and to observe the patients 0 dyspnea awareness under controlled respiratory stress conditions to detect abnormal response.
It is yet another object of the invention to enhance testing sensitivity in a first mode of operation by relating the testing inspiratory restive load to a defined percentage of the patient's maximum inspiratory pressure capability. A
15 variable resistive load can be imposed by either a so-called non-linear adjustable "pinhole" orifice restrictive device or a so-called inspiratory "threshold" loading device, the non-linear resistive device being ~rcrcllcd in the present embodiment.
It is still another object of the invention to insure data integrity in all testing procedures by having the patient's breathing performance during testing 2 o tal~e place between definable percentage plus and minus tidal volume error limits, and to indicate on the patient's breathing signal what zone of reliabilit~ they are operating within, and to indicate with alarm means when breathing performance is unsatisfactory.
CA 02238530 l998-05-25 WO 98/14115 PCT/US96/Lr,643 It is a further object of the invention to have the patient indicate freely on a sliding electro-mecnanical device their Borg Unit level of dyspnea awareness, on a scale of zero to ten (0 to l0), with automatic input of same to computer J display and storage means.
It is an additional objective of the invention to perrnit testing other perceptual abnormality of patients for excessive dyspnea awareness, such as may occur in the Hyperventilation Syndrome.
It is a further additional objective of the invention to permit testing other perceptual abnormality of patients for excessive dyspnea awareness, such as may occur in Chronic Obstructive Pulmonary Disease7 such as Emphysema and/or Chronic Bronchitis, and/or other respiratory conditions.
It is a final object of the invention to enhance testing sensitivity in a second mode of operation b~ controlling the testing breathing pattern by visual biofrr-lh~rlc means while introducing progressive inspiratory loads precisely and automatically at prt .~et~rrnined time intervals.
These objectives are achieved by a computer based controlling system that displays the desired patient breathing patterns and real time patient pclr~lmance for patient biofeedback breathing control, and the patient indication of Borg defined units of dyspnea level. Inspiratory pressure is sensed7 input to the computer and automatically adjusted to prr-let-ormined levels. Data integrity isassured by automated detection of the patient's ~reathing pattern exceeding plusor minus tidal volume percentage error limits, with a~ riate indicating alarms.
CA 02238530 l998-05-25 In the first mode of operation the patient follows the prescribed breathing pattern and tidal volume based on a percentage of the patient's vital capacity at a constant inspirato~r pressure predetermined as a percentage of the patient's n~xim~l inspiratory pressure. The resultant data is plotted on a graph with the 5 ~3org IJnit dyspnea level plotted on the vertical "y" ordinate axis verslls Tirne on the horizontal "x" abscissa axis. Also numerically indicated at one minute intervals are the number of times the patient's breathing performance failed to remain within acceptable plus and minus defined parameter error limits.
In the second mode of operation the patient follows the prescribed 10 breathing pattern and tidal volume based on a percentage of the patient's vital capacity at progressively increasing inspiratol~ resistive loads, starting a zero load and then automatically increasing by suitable increments, e.g. minus 5 cm. waterpressure at suitable time intervals, e.g. every two mimltes. The resultant data is plotted on a graph with the Borg Unit dyspnea level on the vertical "y" ordinate5 axis versus Time on the Horizontal "~" abscissa axis, and in addition the inspiratory pressures are plotted on the vertical "y" axis. Also numerically indicated at one minute inter~rals are the number of times the patient's breathing performance failed to remain within acceptable plus and minus defined parameter error limits.
These and other objects of the invention will be seen in the following description and in the drawing.
WO 98/14115 PCT/US96/1~;643 T~IE D~WING
Fig. l is a simple schematic diagram of the overall system;
Fig. 2 is a schematic diagram of the system and patient interactive devices;
Fig. 3 is a schematic diagram of the Inspiratory Resistive Device, where 5 Fig. 3a is a side view of the Airway Resistor/Stepping Motor Assembly, and Fig. 3b is a top view of the ~irway Resistive Device, and Fig. 3c is a side view of the Airway Resistor/Stepping Motor Assembly;
Fig. 4 is a schematic diagram of the breathing Visual Biofeedbaclc Display, where Fig. 4a is a display of the patient ~ Ling program breathing analogs, and 10 Fig. 4b is a display of proper patient breathing performance matching the prompting analog display, and Fig. 4c is a display of inadeqllate patient breathing performance, not achievingthe cursor prompted analog display~ and Fig. 4d is a display of plus and minus Phantom Line error limits, and the 15 detection of inadequate patient performance, and Fig. 4e is a display of the prompting breathing analog and the patient real timebreathing performance, with changing symbols and!or color depending on which error limit the patient's breathing is operative, and Fig. 4f is display of an exhausted patient ~mable to maintain performance 2 o requirements and therefore termination of the test;
Fig. 5 is a display of the patient data, where Fig. 5a is a display of Constant Inspiratory Resistance plotting the Borg Dyspnea Scale and Inspiratory Pressure against time~ and Fig. 5b is a display of Incremental Inspiratory ~esistance plotting the Borg ~ 2~ Dyspnea Scale and Inspiratory Pressure against time.
CA 02238530 l998-05-25 WO 98/1411~; PCTIUS96/15643 DESC~IPTION OF P~EF~ED EMBODIMENTS
In the following description, metric units and standard respiratory terminology as defined by the American College of Chest Physicians are employed unless othervvise stated. Particular attention is directed toward the 5 testing of human subjects for susceptibility to fatal asthmatic attaclcs by detecting a decreased awareness of dyspnea distress during the imposition of an inspiratory resistance load. This has been found to be a valid method to test asthmatic patients in this regard, but the lcnown ~nethods have employed relatively simplemethodology that fails to standardize the testing conditions adequately. The 10 method and apparatus may alternatively be used to test subiects for e~cessive dyspnea awareness as may be present in the abnormal perception-related condition of Hyperventilation Syndrome, or to define and quantify the dyspnea of patients with Chronic Obstructive Pulmonary Disease and!or other respiratory conditions.
The underlying ob~ect of this invention is to define testing conditions for all a~ iate pulmonaIy function testing procedures in a more precise manner by visual biofeedbadc means, where the subject is encouraged to follow preciselydefined inspiration and expiration visual analogs and thereby malce the sensitivity, accuracy and reproducibility of the tested parameter optimally 2 o standardized. This is based on the general observation that the sophistication of modern pulmonary function testing equipment is usually more accurate than the methodology and the physiologic parameter being tested, due to the natural variability of native patient breathing pattems, and the alteration of these breathing patterns under testing conditions. Therefore, to improve the accuracy 2 5 of the relevant pulmonary function test, the variable patient breathing patterns must be standardized and quality controlled in order the measuring equipment CA 02238=730 lsss-o=7-2=7 and the measuring methodology produce more valid data on the tested patient functional parameter.
The underlying concept of the instant invention relates to precise breathing control using defined visual inspiration and expiration analogs for the 5 subject to follow7 with the subject's respiratory Tidal Volume defined as a pref~et~orrnined ~-elltage of their Vital Capacity, and the Inspiratory Resistance load a pr~let.orn~ined percentage of the subject's Maximum Inspiratory Pressure;or alternatively the Inspiratory Resistance being predetermined time incrementalsteps of predetermined resistance loads7 and to automate the procedure.
0 In the ~lere~led embodiment the patient sees a visual analog of inspiration and expiration on a computer CRT or TV display7 and with a simultaneous display also visualizes their real time breathing performance analog7 with the Tidal Volume breath indicated on the vertical ~lly~l ordinate axis plotted against Time on the horizontal ~Ixll abscissa axis. The patient is instructed to match their real time breathing performance to the desired performance analog as indicated by flashing cursor means in the a~ropfiate time domain using so-called visual biofeedback means; thereby conforming the patientls breathing to a defined standard breathing pattern. The Tidal Volume breath is determined as a defined standard percentage7 generally between 25% and 50% of an independently 2 o measured Vital Capacity breath. The Inspiratory Resistive negative pressure load is determined as a defined standard percentage7 generally between 25% and 75%
of an independently measured Maximum Inspiratory Pressure. I'he ~espiratory Rate is defined generally between 5 and l 5 breaths per minute. The Inspiration to Expiration Time Ratio is defined generally between 1: l and l :3. The Inspiratory Pause Time is defined as a percentage of the Inspiratory Time WO 9811411S PCT/US96tl5643 generally between zero and l 0%, and the Expiratory Pause Time is defined as a percentage of the Expiratory Time generally between zero and 25%. The Inspiration and ~ild~ion waveforms are defined as linear or various curvilinear forms. Thus all the components of the breathing cycle may be defined precisel~
5 and displayed as a visual analog of breath volume plotted against time, and with the patient following the breathing analog at the flashing cursor the method therefore becomes an instantaneous breath flow controller as dictated by the fundamental ec~uation Volume = Flow X Time. In another mode of operation multiple plus and minus analog error limits as a percentage of the Tidal Volume 10 may be defined and optionally displayed, to detect patient performance falling outside defined limits, with suitable auditory and/or visual alarms to indicate deficient performance. Optionall~ the error limit analogs ma~ be hidden from display, with the displayed patient breathing signal changing shape andlor colordepending on wnich error limit the patient's breathing performance is operative.
In the ~refc~l~cd embodiment the Inspiratory ~esistive Load remains constant, with the patient attempting to maintain the desired breathing pattern until unable to maintain said standardized breathing pattern due to fatigue or excessive r~spir~tory distress. At one minute intervals the patient is prompted to indicate their perceived dyspnea level in standard Borg numeric units on a scale2 o of zero to ten (0 to 10), zero indicative of no perceived dyspnea and ten being indicative of maximal perceived dyspnea, by sliding a pointer along a linear potentiometer or similar device for data input. In an alternate mode of operation the Inspiratory Resistive Load is progressively incremented in predetermined negative pressure loads ~ressed as cm. water, for example zero, -2, -S, -10, -15, -20, -25, -30, etc. cm. water at time intervals between l and 3 minutes.
Inspiratory pressures, the integrated respiratory flow~ridal ~olume, and Borg CA 02238~30 1998-0~-2~
WO 98/14115 PCT/[rS96/15643 Dyspnea Units are stored in Cc)lllpuL~ memory, and are reported in graphic form7the Borg Dyspnea Units and Inspiratory Pressure plotted on the vertical "y" axiscoordinate against Time on the horizontal "x" axis coordinate. Optionally the rldal Volumes may be .simil~rly displayed on the vertical "~' axis coordinate. In 5 this manner the patient's level of dyspnea may be plotted against a standardized breathing pattern and inspiratory load stress, the normal subject indicating progressive dyspnea, and those subjects susceptible to asthmatic hazard and potential fatality indicating a minimal dyspnea response to progressive inspiratory muscle resistive stress, and with Hype~ventilation Syndrome patients0 and those subjects with Chronic Obstructive Pulmonary Diseases and/or other pulmonary pathological conditions indicating excessive dyspnea at inappropriately low inspiratory work loads.
In the ~lcrt:llcd embodiment the testing process is automated in the a~lu~liate time domain, by feedback computer control of inspiratory pressure 15 adjusting a variable inspiratory resistance device by means of a computer feedback controlled stepping motor. Inspiration Pressures, Tidal Volume, Borg Unit data and the minute by minute frequency of patient failure to achieve acceptable breathing performance is stored in computer memory for display and analysis. In an alternate mode of operation the operator may manually adjust the20 inspiratory pressure with reference to a separate mechanical pressure gauge.
This invention is general as to means and method to control breathing during breathing testing, and specific as to means and method to control breathing in a standardized manner while test;ng for dyspnea awareness with - increasing inspiratory resistance loading and stress of inspiratory musdes, to 25 thereby re~real patients with ina~n~liate and reduced breathing awareness that might subject them to asthma hazard and potential fatality, though the inventiveconcept would not be limited to specific testing for d~spnea awareness with inspiratory loading. This invention could also be used specifically to test patients for excessive dyspnea awareness as may be present in the condition of 5 Hyperventilation S~,rndrome and a variety of pulmonary pathologic conditions, including Chronic Obstructive Pulmonary Diseases and/or pulmonary Restrictive Diseases.
Referring to the simplified schematic diagram in Fig. l the Patient (l) inspires air through Inspiratory Resistance Device (2) via Directional Respiratory 0 Valve (3). Inspiratory and expiratory air is sensed by Plowrneter (4) and Mechanical Pressure Meter (5). The Patient (l) observes CRT (6) to visualize Prescribed Breathing Pattem (7) and by visual biofeedback means following Prompting Cursor (8) attempts to place their real time Breathing Signal (9) on the Prescribed Breathing Patten (7). At one minute intervals the patient is 15 prompted to indicate their perceived level of dyspnea on an electro-mechan;cal Linear Potentiometer ( l 0) calibrated in zero to ten Borg Dyspnea Units. Suitable differential pressure transducer and integrator means in conjunction with Flowmeter (4) senses respiratory flow which is integrated into Tidal Volume Signal (1l), and suitable pressure transducer means provides Respiratory 20 Pressure Signal (12) and Linear Potentiometer (l0) provides Borg Units Signal(13), all of which are input to Computer ~14) data storage and control means, to be output to Graphic Report (15) of Borg Dyspnea Display (16) and Inspiratory Pressure Display ( l 7) plotted against Time. Computer ( l 4) provides Inspiratory Resistance Feedbaclc Control Signal (l 8) to Inspiratory Resistive 25 Device (2).
CA 02238~30 1998-0~-2~
The schematic diagram in Fig. 2 is a more detailed overall description of the system design and the patient interactive devices. Patient ( 1 ) breaths through Flowmeter ~4) which provides a differential pressure due to Flowmeter Restrictions ( l 9). The flow generated differential pressure is sensed on each side 5 of Flowmeter Restrictions ( 19) and fletecte~l by Differential Pressure Transducer (20) with subsequent signal conditioning and analog to digital conversion by suitable hardware and/or software means for input of Tidal Volume Signal ( 1 1 )to Computer ( 14) . Optionally the differential pressure detection, signal conditioning and analog to digital conversion may be within Computer (14) or 10 by external devices. Respiratory pressure is sensed by Mechanical Pressure h~eter (S) and Pressure Transducer (21 )with subsequent signal conditioning and analog to digital conversion by suitable hardware andlor software means for input of Respiratory Pressure Signal (12) to Computer (14). Optionally the pressure detection, signal conditioning and analog to digital conversion may be within 5 Computer ( 14) or by external devices. Within Computer ( 14) all inspiratory and expiratory pressures at suitable sampling rates, for example 100 Hz., are storedbreath by breath in suitable computer memory array means, and pattern recognition algorithms detect and similarly store Peak Inspiratory Pressure and ~verage Inspiratory Pressure. Patient ( 1 ) in response to perceived dyspnea level 20 manipulates sliding scale Pointer (22) on Linear Potentiometer (10) to provide Borg Units Signal (13) to Computer (14). l~espiratory flow is directed by Directional Respiratory Valve (3) by Inspiration Valve (23) and ~xpiration Valve(24) which vents the patient's unobstructed exhaled breath to roorn air. Patient(1) inspires through Directional Respiratory Valve (3) which is attached to ~ Inspiratory Resistive Device (2). Variable inspiratory respiratory resistance is - provided by ~espiratory Resistance Plate (25) which exposes a variable sized orifice to Inspiration Chamber (27) b~r the operator rotating Respiratory Resistance Plate (25) manually by Handle (26) while observing Mechanical Pressure Meter (5). In the preferred embodiment Respiratory Pressure Signal (12) is compared to a pr~letf rrnined desired inspiratory pressure and Computer (14) generates an appropriate ~nspiratory E~esistance Feedbadc Control Signal (18) to Stepping Motor (28) and Reduction Gear (29) to turn Respiratory Resistance Plate (25) to achieve the desired inspiratory pressure. Patient (1) observes CRT (6) to visualize Prescribed 33reathing Pattern (7) and by visual biofeedback means following Prompting Cursor (8) attempts to place their real time Breathing Signal (9) on the Prescribed Breathing Patten (7). ~t one minute intervals the patient is prompted to indicate their perceived level of dyspnea by Pointer (22) on electro-mechanical Linear Potentiometer ( 10) calibrated in zeroto ten l~org Dyspnea Units. ~t the conclusion of the test, or optionally dynamically on a second CRT, data display and Graphics Report (15) are generated for direct ~riewing or hard copy report. The Borg Dyspnea Display ( 16) units and Pealc Inspiratory Pressure Display ( 17) units in cm. water, or optionally the A~verage In~ toly Pressure, is plotted on the vertical '~' axis ordinate versus Time on the horizontal "x" axis abscissa.
The schematic diagram in Fig. 3 is a ~ore detailed overall description of the Inspiratory Resistive Device (2). Fig. 3a.) is a side view of Inspiratory 2 o Resistive De~rice (2) and Stepping Motor (28) with Reduction Gear (29) meshing wit~l Respiratory Resistance Plate (25). ~espiratory Resistance Plate (25) rotates about a central mount on Respiratory Resistance Device (2) and has a ~andle (26) to assist manual rotation to permit a variable sized orifice to be exposed to Inspiration Chamber (27). Fig 3~.) is a top view of Inspiratory l~esistive Device 2 5 (2) and Inspiration Chamber (27~ with centrally mounted Respiratory Resistance Plate (25) containing Variable Orifice (30). As Respiratory ~esistance Plate (25) CA 02238.730 1998 - 0.7 - 2.7 is rotated the opening of Inspiration Chamber (27) will be constricted to a greater or lesser degree, thereby producing a greater or lesser degree of inspiratory resistance. Fig 3c.) is a top view of Inspiratory ~esistive Device (2) and Stepping Motor (28) with Reduction Gear (29) meshing with ~espiratory ~esistance Plate 5 (25), thereby perrnitting motor adjustment of Variable Orifice (30) to automatically adjust airway resistance by computer controlled feedback means.
The schematic diagrams in Fig. 4 describes various visual biofeedback images seen on CRT (6). Fig. 4a.) shows Prescribed Breathing Pattern (7) displayed where Tidal Volume is depicted on the vertical "~' ordinate axis plotted 0 against Time on the horizontal "x" abscissa axis7 indicating Inspiration in anupward direction and Expiration in a downward direction. Fig. 4b.) indicates proper patient biofeedbaclc breathing performance with the patient Breathing Signal (9) superimposed on Prescribed Breathing Pattern (7) at Prompting Cursor (8). Fig. 4c.) indicates inadequate patient biofeedback breathing 15 performance with the patient Breathing Signal (9) falling below Prescribed Breathing Pattern (7) and Plu~ Ling Cursor (8). Fig. 4d.~ is identical to Fig. 4c.) and in addition shows plus and minus Phantom Line Error Lirnits (3 l ) above andbelow Prescribed Breathing Pattern (7) with a Negative Error Limit Detection (32) to trigger a~ iate audio and!or visual alarms. Not shovvn are multiple 20 Phantom Iine error detection limits, for example error limits of plus and minus 10% of Tidal Volume, plus and minus 20%, plus and minus 30%, etc. Fig. 4e.) is a display of patient pclro~lllance error detection without the display of thePhantom ~ines, wherein only Prescribed Breathing Pattern (7) and patient Breathing Signal (9) appear. In this option the patient Breathing Signal (9) 25 changes to different graphic characters andlor colors, depending on which zone of error detection the patient performance is operative. For example, perfect matching o~ the patient's breathing pclro~mance with Prescribed Breathing Program (7) might be indicated by a Small Closed Circle (3dr), acceptable breathing performance within plus and minus 10% indicated by a Small Open Cirde(35), and unacceptable patient performance in excess of plus and minus 5 25% indicated by Small Closed Squares (36). Fig.4 f.) is a display of patient exhaustion wherein the Patient Breathing Signal (9) is unable to follow Prescribed Breathing Program (7) and is unable to achieve a minimal Tidal Volume as depicted by Negative Error Limit (33) and thus indicating the need to terminate the testing procedure.
The schernatic diagrams in Fig. 5 describes various CRT graphic displays and/or hard copy printed reports of the deri~red data. Fig. 5a.) is the ~tiefe~ d embodiment wherein the testing procedure has been with constant prescribed inspiratory resistance load, as determined by a predetermined percentage of the Maximum Inspiratory Capacity. Graphics ~port (15) plots Borg Dyspnea ~Jnits and Pealc Inspiratory Pressure on the vertical r ordinate axis, against Time on the horizontal "x" abscissa axis. Optionally Average Inspiratory Pressure may besubstituted for Peak Inspiratory Pressure. Inspiratory Pressure Display ( I 7) in this mode of operation is a generally a straight line throughout most of the testing procedure, reflecting the ability of the patient to inspire the prescribed 20 Tidal Volume breath within the defined parameters of Prescribed Breathing Pattern (7). Near the end of the testing procedure the inspiratory pressure tends to diminish, reflecting patient exhaustion and the inability thelcfule to inspire the full prescribed Tidal Volume breath, though in some cases the patient may maintain their ability to breathe as prescribed despite fatigue and severe dyspnea.
25 Numeric Parameter Limit Failure (40) is accumulated and indicated at one minute intervals, and as indicated with increased failure of breathing control as WO 98/14115 PCT/US96/lS643 the patient becomes exhausted. ~ Normal Borg ~esponse (37) to progressive fatigue is indicated. Also shown is abnormal Diminished Borg Response (38) thereby indicating the patient to be susceptible of developing severe or potentiaUy fatal asthmatic exacerbations as such patients are relatively unaware5 of the severity of their condition and therefore may not p~omptly seek a~p~ ,iate urgent medical attention. ~lso shown is Excessive Borg Response (39~ as may be seen in subjects susceptible to the condition of HyperventilationSyndrome, or subjects with pulmoriary pathologic conditions such as Chronic Obstructive Pulmonary Disease. Fig. 5b.) is an alternate testing method wherein 10 the inspirato~y resistive load is applied in incremental steps at prescribed times, e.g. two minute intervals, and with prescribed resistive loads at each incremental step, e.g. zero, -2, -5, -10, -15, -20, -25, -30, etc. cm. of water pressure, with the patient breathing in a prescribed manner according to Prescribed Breathing Pattern (7). Displayed are examples of Normal Borg Response (37), Diminished 5 Borg Response (38) and Excessive Borg Response (39) and numeric Parameter Limit Failure (40) events.
E3ACICGROUND OF THE~ INVENTION
This invention relates to improved methods and apparatus to detect patients with an abnormally altered perception of dyspnea. Of particular concern5 are asthma patients at risk for fatal asthmatic attaclcs. An unexpected risingincidence of fatal asthmatic attaclcs in recent years has been of concern to themedical profession.
The sensitivity of the testing procedure is enhanced by the test being performed under controlled conditions by having the patient breathe in a 0 precisely defined manner by visual biofeedback means, with the subject following a preclet.o~nined breathing pattern on a computer CRT or similar means. Hillsman incorporates by reference his U.S. Patent No. 3,991,304 which describes a sophisticated method to prompt patients to desired breathing patterns by visual biofeedback means.
Prior art has indicated patients who have survived a near fatal asthma attack have decreased dyspnea awareness to increased inspiratory resistance (See:
LOWERED CHEMOSENSITIVITY AND PERCEPTION OF DYSPNEA IN
PATIENTS WIT~I NEAR-F~TALASTHMA - Mlcuchi, ~. et all, Respiratory and Critical Care Medicine, Supplement, Volume l 49, Number 4, April 1994). The 20 cited investigators demonstrated decreased dyspnea awareness in near fatal asthma patients by imposing graded inspiratory respiratory resistance from zero to minus 30 cm. water/liter/second gauge pressure. But no attempt was made b~
these investigators to further control the experimental conditions by defining the testing tidal volume to the patient's available lung volume as reflected in the WO 98/1411~; PCT/US96/15643 patient's vital capacity, or the testing inspiratory resistance load to the patient's available maximum inspiratory pressure capability. Further, no attempt was made to otherwise precisely control the patient's breathing pattern or the precise timing of the breathing stages under the testing conditions, or to otherwise detect 5 whether or not the subjects were performing as required under the testing conditions. The~crol~, absent col~ chensive controlled breathing conditions the testing achieved was relatively crude and therefore less sensitive to defining and detecting dyspnea awareness as measured by the commonly used Borg scale of dyspnea, and likewise there was no assurance as to patient performance and 0 therefore data reliability.
~ n addition, there are many patients vvith Hyperventilation Syndrome, who perceive they ha~e dyspnea when in fact their respiratory function is normal, and definition and quantifying this abnormality and normalization with treatment is of value in the patient therapeutic program.
Further, many patients with dyspnea related to Chronic Obstructive Pulmonary Disease (Emphysema and Chronic Bronchitis) and other respiratory conditions undergo comprehensive Pulmonary Rehabilitation, including various measures to improve dyspnea distress. These measures include various medications, breathing exercises and breathing retraining in proper breathing 2 o patterns, respiratory muscle reconditioning and strengthening by various means, and general body reconditioning and strengthening. Present methodology to quantify dyspnea and measure improvement with the various treatment modalities has generally been controversial and unsa~isfactory. Therefore, thereis a need to properly define and quantify the dyspnea abnormality and an~
WO 98/1411~ PCTIUS96115643 normalization with the various treatments in the patient therapeutic program7 both to guide therapy and to document improvement for administrative needs.
The instant invention to comprehensively define the testing conditions relative to the patient's vital capacity and~or maximum inspiratory pressure 5 capability, and to further define the testing conditions by having the patientbreathe in a precisely controlled manner using predefined breathing patterns by visual biofee~1h~flc means, and to precisely control the sequence and timing of the testing events. Therefore, by establishing the breathing testing conditions the sensitivity, accuracy and reproducibility of the diagnostic methodology will be 0 enhanced. In addition, by placing definable plus and minus error limits abo~reand below the desired breathing analogs, with suitable audio and~or visual alarms to indicate if the patient breathing performance is outside acceptable limits, the diagnostician may determine whether or not the subject is performing in an acceptable manner to the testing methodology as defined by the operator Çor the 5 particular subject and thereby generating reliable testing data.
CA 02238~30 1998-0~-2~
WO 98/14115 PCT/US9611~i643 SUMMAR~ OF TH}~ INVENTION
It is therefore one object of the present invention to enhance the sensitivity of testing for dyspnea awareness by the testing procedures being precisely controlled as to breathing patterns with defined elements of respiratory 5 rate, inspiration to expiration time ratio, and inspiration and expiration breathing waveforrn analogs by visual biofeedback prompting means.
It is another object of the invention to enhance testing sensitivity in a first mode of operation by relating the testing tidal volume breath to a defined percentage of the patient's vital capacity capability, and to observe the patients 0 dyspnea awareness under controlled respiratory stress conditions to detect abnormal response.
It is yet another object of the invention to enhance testing sensitivity in a first mode of operation by relating the testing inspiratory restive load to a defined percentage of the patient's maximum inspiratory pressure capability. A
15 variable resistive load can be imposed by either a so-called non-linear adjustable "pinhole" orifice restrictive device or a so-called inspiratory "threshold" loading device, the non-linear resistive device being ~rcrcllcd in the present embodiment.
It is still another object of the invention to insure data integrity in all testing procedures by having the patient's breathing performance during testing 2 o tal~e place between definable percentage plus and minus tidal volume error limits, and to indicate on the patient's breathing signal what zone of reliabilit~ they are operating within, and to indicate with alarm means when breathing performance is unsatisfactory.
CA 02238530 l998-05-25 WO 98/14115 PCT/US96/Lr,643 It is a further object of the invention to have the patient indicate freely on a sliding electro-mecnanical device their Borg Unit level of dyspnea awareness, on a scale of zero to ten (0 to l0), with automatic input of same to computer J display and storage means.
It is an additional objective of the invention to perrnit testing other perceptual abnormality of patients for excessive dyspnea awareness, such as may occur in the Hyperventilation Syndrome.
It is a further additional objective of the invention to permit testing other perceptual abnormality of patients for excessive dyspnea awareness, such as may occur in Chronic Obstructive Pulmonary Disease7 such as Emphysema and/or Chronic Bronchitis, and/or other respiratory conditions.
It is a final object of the invention to enhance testing sensitivity in a second mode of operation b~ controlling the testing breathing pattern by visual biofrr-lh~rlc means while introducing progressive inspiratory loads precisely and automatically at prt .~et~rrnined time intervals.
These objectives are achieved by a computer based controlling system that displays the desired patient breathing patterns and real time patient pclr~lmance for patient biofeedback breathing control, and the patient indication of Borg defined units of dyspnea level. Inspiratory pressure is sensed7 input to the computer and automatically adjusted to prr-let-ormined levels. Data integrity isassured by automated detection of the patient's ~reathing pattern exceeding plusor minus tidal volume percentage error limits, with a~ riate indicating alarms.
CA 02238530 l998-05-25 In the first mode of operation the patient follows the prescribed breathing pattern and tidal volume based on a percentage of the patient's vital capacity at a constant inspirato~r pressure predetermined as a percentage of the patient's n~xim~l inspiratory pressure. The resultant data is plotted on a graph with the 5 ~3org IJnit dyspnea level plotted on the vertical "y" ordinate axis verslls Tirne on the horizontal "x" abscissa axis. Also numerically indicated at one minute intervals are the number of times the patient's breathing performance failed to remain within acceptable plus and minus defined parameter error limits.
In the second mode of operation the patient follows the prescribed 10 breathing pattern and tidal volume based on a percentage of the patient's vital capacity at progressively increasing inspiratol~ resistive loads, starting a zero load and then automatically increasing by suitable increments, e.g. minus 5 cm. waterpressure at suitable time intervals, e.g. every two mimltes. The resultant data is plotted on a graph with the Borg Unit dyspnea level on the vertical "y" ordinate5 axis versus Time on the Horizontal "~" abscissa axis, and in addition the inspiratory pressures are plotted on the vertical "y" axis. Also numerically indicated at one minute inter~rals are the number of times the patient's breathing performance failed to remain within acceptable plus and minus defined parameter error limits.
These and other objects of the invention will be seen in the following description and in the drawing.
WO 98/14115 PCT/US96/1~;643 T~IE D~WING
Fig. l is a simple schematic diagram of the overall system;
Fig. 2 is a schematic diagram of the system and patient interactive devices;
Fig. 3 is a schematic diagram of the Inspiratory Resistive Device, where 5 Fig. 3a is a side view of the Airway Resistor/Stepping Motor Assembly, and Fig. 3b is a top view of the ~irway Resistive Device, and Fig. 3c is a side view of the Airway Resistor/Stepping Motor Assembly;
Fig. 4 is a schematic diagram of the breathing Visual Biofeedbaclc Display, where Fig. 4a is a display of the patient ~ Ling program breathing analogs, and 10 Fig. 4b is a display of proper patient breathing performance matching the prompting analog display, and Fig. 4c is a display of inadeqllate patient breathing performance, not achievingthe cursor prompted analog display~ and Fig. 4d is a display of plus and minus Phantom Line error limits, and the 15 detection of inadequate patient performance, and Fig. 4e is a display of the prompting breathing analog and the patient real timebreathing performance, with changing symbols and!or color depending on which error limit the patient's breathing is operative, and Fig. 4f is display of an exhausted patient ~mable to maintain performance 2 o requirements and therefore termination of the test;
Fig. 5 is a display of the patient data, where Fig. 5a is a display of Constant Inspiratory Resistance plotting the Borg Dyspnea Scale and Inspiratory Pressure against time~ and Fig. 5b is a display of Incremental Inspiratory ~esistance plotting the Borg ~ 2~ Dyspnea Scale and Inspiratory Pressure against time.
CA 02238530 l998-05-25 WO 98/1411~; PCTIUS96/15643 DESC~IPTION OF P~EF~ED EMBODIMENTS
In the following description, metric units and standard respiratory terminology as defined by the American College of Chest Physicians are employed unless othervvise stated. Particular attention is directed toward the 5 testing of human subjects for susceptibility to fatal asthmatic attaclcs by detecting a decreased awareness of dyspnea distress during the imposition of an inspiratory resistance load. This has been found to be a valid method to test asthmatic patients in this regard, but the lcnown ~nethods have employed relatively simplemethodology that fails to standardize the testing conditions adequately. The 10 method and apparatus may alternatively be used to test subiects for e~cessive dyspnea awareness as may be present in the abnormal perception-related condition of Hyperventilation Syndrome, or to define and quantify the dyspnea of patients with Chronic Obstructive Pulmonary Disease and!or other respiratory conditions.
The underlying ob~ect of this invention is to define testing conditions for all a~ iate pulmonaIy function testing procedures in a more precise manner by visual biofeedbadc means, where the subject is encouraged to follow preciselydefined inspiration and expiration visual analogs and thereby malce the sensitivity, accuracy and reproducibility of the tested parameter optimally 2 o standardized. This is based on the general observation that the sophistication of modern pulmonary function testing equipment is usually more accurate than the methodology and the physiologic parameter being tested, due to the natural variability of native patient breathing pattems, and the alteration of these breathing patterns under testing conditions. Therefore, to improve the accuracy 2 5 of the relevant pulmonary function test, the variable patient breathing patterns must be standardized and quality controlled in order the measuring equipment CA 02238=730 lsss-o=7-2=7 and the measuring methodology produce more valid data on the tested patient functional parameter.
The underlying concept of the instant invention relates to precise breathing control using defined visual inspiration and expiration analogs for the 5 subject to follow7 with the subject's respiratory Tidal Volume defined as a pref~et~orrnined ~-elltage of their Vital Capacity, and the Inspiratory Resistance load a pr~let.orn~ined percentage of the subject's Maximum Inspiratory Pressure;or alternatively the Inspiratory Resistance being predetermined time incrementalsteps of predetermined resistance loads7 and to automate the procedure.
0 In the ~lere~led embodiment the patient sees a visual analog of inspiration and expiration on a computer CRT or TV display7 and with a simultaneous display also visualizes their real time breathing performance analog7 with the Tidal Volume breath indicated on the vertical ~lly~l ordinate axis plotted against Time on the horizontal ~Ixll abscissa axis. The patient is instructed to match their real time breathing performance to the desired performance analog as indicated by flashing cursor means in the a~ropfiate time domain using so-called visual biofeedback means; thereby conforming the patientls breathing to a defined standard breathing pattern. The Tidal Volume breath is determined as a defined standard percentage7 generally between 25% and 50% of an independently 2 o measured Vital Capacity breath. The Inspiratory Resistive negative pressure load is determined as a defined standard percentage7 generally between 25% and 75%
of an independently measured Maximum Inspiratory Pressure. I'he ~espiratory Rate is defined generally between 5 and l 5 breaths per minute. The Inspiration to Expiration Time Ratio is defined generally between 1: l and l :3. The Inspiratory Pause Time is defined as a percentage of the Inspiratory Time WO 9811411S PCT/US96tl5643 generally between zero and l 0%, and the Expiratory Pause Time is defined as a percentage of the Expiratory Time generally between zero and 25%. The Inspiration and ~ild~ion waveforms are defined as linear or various curvilinear forms. Thus all the components of the breathing cycle may be defined precisel~
5 and displayed as a visual analog of breath volume plotted against time, and with the patient following the breathing analog at the flashing cursor the method therefore becomes an instantaneous breath flow controller as dictated by the fundamental ec~uation Volume = Flow X Time. In another mode of operation multiple plus and minus analog error limits as a percentage of the Tidal Volume 10 may be defined and optionally displayed, to detect patient performance falling outside defined limits, with suitable auditory and/or visual alarms to indicate deficient performance. Optionall~ the error limit analogs ma~ be hidden from display, with the displayed patient breathing signal changing shape andlor colordepending on wnich error limit the patient's breathing performance is operative.
In the ~refc~l~cd embodiment the Inspiratory ~esistive Load remains constant, with the patient attempting to maintain the desired breathing pattern until unable to maintain said standardized breathing pattern due to fatigue or excessive r~spir~tory distress. At one minute intervals the patient is prompted to indicate their perceived dyspnea level in standard Borg numeric units on a scale2 o of zero to ten (0 to 10), zero indicative of no perceived dyspnea and ten being indicative of maximal perceived dyspnea, by sliding a pointer along a linear potentiometer or similar device for data input. In an alternate mode of operation the Inspiratory Resistive Load is progressively incremented in predetermined negative pressure loads ~ressed as cm. water, for example zero, -2, -S, -10, -15, -20, -25, -30, etc. cm. water at time intervals between l and 3 minutes.
Inspiratory pressures, the integrated respiratory flow~ridal ~olume, and Borg CA 02238~30 1998-0~-2~
WO 98/14115 PCT/[rS96/15643 Dyspnea Units are stored in Cc)lllpuL~ memory, and are reported in graphic form7the Borg Dyspnea Units and Inspiratory Pressure plotted on the vertical "y" axiscoordinate against Time on the horizontal "x" axis coordinate. Optionally the rldal Volumes may be .simil~rly displayed on the vertical "~' axis coordinate. In 5 this manner the patient's level of dyspnea may be plotted against a standardized breathing pattern and inspiratory load stress, the normal subject indicating progressive dyspnea, and those subjects susceptible to asthmatic hazard and potential fatality indicating a minimal dyspnea response to progressive inspiratory muscle resistive stress, and with Hype~ventilation Syndrome patients0 and those subjects with Chronic Obstructive Pulmonary Diseases and/or other pulmonary pathological conditions indicating excessive dyspnea at inappropriately low inspiratory work loads.
In the ~lcrt:llcd embodiment the testing process is automated in the a~lu~liate time domain, by feedback computer control of inspiratory pressure 15 adjusting a variable inspiratory resistance device by means of a computer feedback controlled stepping motor. Inspiration Pressures, Tidal Volume, Borg Unit data and the minute by minute frequency of patient failure to achieve acceptable breathing performance is stored in computer memory for display and analysis. In an alternate mode of operation the operator may manually adjust the20 inspiratory pressure with reference to a separate mechanical pressure gauge.
This invention is general as to means and method to control breathing during breathing testing, and specific as to means and method to control breathing in a standardized manner while test;ng for dyspnea awareness with - increasing inspiratory resistance loading and stress of inspiratory musdes, to 25 thereby re~real patients with ina~n~liate and reduced breathing awareness that might subject them to asthma hazard and potential fatality, though the inventiveconcept would not be limited to specific testing for d~spnea awareness with inspiratory loading. This invention could also be used specifically to test patients for excessive dyspnea awareness as may be present in the condition of 5 Hyperventilation S~,rndrome and a variety of pulmonary pathologic conditions, including Chronic Obstructive Pulmonary Diseases and/or pulmonary Restrictive Diseases.
Referring to the simplified schematic diagram in Fig. l the Patient (l) inspires air through Inspiratory Resistance Device (2) via Directional Respiratory 0 Valve (3). Inspiratory and expiratory air is sensed by Plowrneter (4) and Mechanical Pressure Meter (5). The Patient (l) observes CRT (6) to visualize Prescribed Breathing Pattem (7) and by visual biofeedback means following Prompting Cursor (8) attempts to place their real time Breathing Signal (9) on the Prescribed Breathing Patten (7). At one minute intervals the patient is 15 prompted to indicate their perceived level of dyspnea on an electro-mechan;cal Linear Potentiometer ( l 0) calibrated in zero to ten Borg Dyspnea Units. Suitable differential pressure transducer and integrator means in conjunction with Flowmeter (4) senses respiratory flow which is integrated into Tidal Volume Signal (1l), and suitable pressure transducer means provides Respiratory 20 Pressure Signal (12) and Linear Potentiometer (l0) provides Borg Units Signal(13), all of which are input to Computer ~14) data storage and control means, to be output to Graphic Report (15) of Borg Dyspnea Display (16) and Inspiratory Pressure Display ( l 7) plotted against Time. Computer ( l 4) provides Inspiratory Resistance Feedbaclc Control Signal (l 8) to Inspiratory Resistive 25 Device (2).
CA 02238~30 1998-0~-2~
The schematic diagram in Fig. 2 is a more detailed overall description of the system design and the patient interactive devices. Patient ( 1 ) breaths through Flowmeter ~4) which provides a differential pressure due to Flowmeter Restrictions ( l 9). The flow generated differential pressure is sensed on each side 5 of Flowmeter Restrictions ( 19) and fletecte~l by Differential Pressure Transducer (20) with subsequent signal conditioning and analog to digital conversion by suitable hardware and/or software means for input of Tidal Volume Signal ( 1 1 )to Computer ( 14) . Optionally the differential pressure detection, signal conditioning and analog to digital conversion may be within Computer (14) or 10 by external devices. Respiratory pressure is sensed by Mechanical Pressure h~eter (S) and Pressure Transducer (21 )with subsequent signal conditioning and analog to digital conversion by suitable hardware andlor software means for input of Respiratory Pressure Signal (12) to Computer (14). Optionally the pressure detection, signal conditioning and analog to digital conversion may be within 5 Computer ( 14) or by external devices. Within Computer ( 14) all inspiratory and expiratory pressures at suitable sampling rates, for example 100 Hz., are storedbreath by breath in suitable computer memory array means, and pattern recognition algorithms detect and similarly store Peak Inspiratory Pressure and ~verage Inspiratory Pressure. Patient ( 1 ) in response to perceived dyspnea level 20 manipulates sliding scale Pointer (22) on Linear Potentiometer (10) to provide Borg Units Signal (13) to Computer (14). l~espiratory flow is directed by Directional Respiratory Valve (3) by Inspiration Valve (23) and ~xpiration Valve(24) which vents the patient's unobstructed exhaled breath to roorn air. Patient(1) inspires through Directional Respiratory Valve (3) which is attached to ~ Inspiratory Resistive Device (2). Variable inspiratory respiratory resistance is - provided by ~espiratory Resistance Plate (25) which exposes a variable sized orifice to Inspiration Chamber (27) b~r the operator rotating Respiratory Resistance Plate (25) manually by Handle (26) while observing Mechanical Pressure Meter (5). In the preferred embodiment Respiratory Pressure Signal (12) is compared to a pr~letf rrnined desired inspiratory pressure and Computer (14) generates an appropriate ~nspiratory E~esistance Feedbadc Control Signal (18) to Stepping Motor (28) and Reduction Gear (29) to turn Respiratory Resistance Plate (25) to achieve the desired inspiratory pressure. Patient (1) observes CRT (6) to visualize Prescribed 33reathing Pattern (7) and by visual biofeedback means following Prompting Cursor (8) attempts to place their real time Breathing Signal (9) on the Prescribed Breathing Patten (7). ~t one minute intervals the patient is prompted to indicate their perceived level of dyspnea by Pointer (22) on electro-mechanical Linear Potentiometer ( 10) calibrated in zeroto ten l~org Dyspnea Units. ~t the conclusion of the test, or optionally dynamically on a second CRT, data display and Graphics Report (15) are generated for direct ~riewing or hard copy report. The Borg Dyspnea Display ( 16) units and Pealc Inspiratory Pressure Display ( 17) units in cm. water, or optionally the A~verage In~ toly Pressure, is plotted on the vertical '~' axis ordinate versus Time on the horizontal "x" axis abscissa.
The schematic diagram in Fig. 3 is a ~ore detailed overall description of the Inspiratory Resistive Device (2). Fig. 3a.) is a side view of Inspiratory 2 o Resistive De~rice (2) and Stepping Motor (28) with Reduction Gear (29) meshing wit~l Respiratory Resistance Plate (25). ~espiratory Resistance Plate (25) rotates about a central mount on Respiratory Resistance Device (2) and has a ~andle (26) to assist manual rotation to permit a variable sized orifice to be exposed to Inspiration Chamber (27). Fig 3~.) is a top view of Inspiratory l~esistive Device 2 5 (2) and Inspiration Chamber (27~ with centrally mounted Respiratory Resistance Plate (25) containing Variable Orifice (30). As Respiratory ~esistance Plate (25) CA 02238.730 1998 - 0.7 - 2.7 is rotated the opening of Inspiration Chamber (27) will be constricted to a greater or lesser degree, thereby producing a greater or lesser degree of inspiratory resistance. Fig 3c.) is a top view of Inspiratory ~esistive Device (2) and Stepping Motor (28) with Reduction Gear (29) meshing with ~espiratory ~esistance Plate 5 (25), thereby perrnitting motor adjustment of Variable Orifice (30) to automatically adjust airway resistance by computer controlled feedback means.
The schematic diagrams in Fig. 4 describes various visual biofeedback images seen on CRT (6). Fig. 4a.) shows Prescribed Breathing Pattern (7) displayed where Tidal Volume is depicted on the vertical "~' ordinate axis plotted 0 against Time on the horizontal "x" abscissa axis7 indicating Inspiration in anupward direction and Expiration in a downward direction. Fig. 4b.) indicates proper patient biofeedbaclc breathing performance with the patient Breathing Signal (9) superimposed on Prescribed Breathing Pattern (7) at Prompting Cursor (8). Fig. 4c.) indicates inadequate patient biofeedback breathing 15 performance with the patient Breathing Signal (9) falling below Prescribed Breathing Pattern (7) and Plu~ Ling Cursor (8). Fig. 4d.~ is identical to Fig. 4c.) and in addition shows plus and minus Phantom Line Error Lirnits (3 l ) above andbelow Prescribed Breathing Pattern (7) with a Negative Error Limit Detection (32) to trigger a~ iate audio and!or visual alarms. Not shovvn are multiple 20 Phantom Iine error detection limits, for example error limits of plus and minus 10% of Tidal Volume, plus and minus 20%, plus and minus 30%, etc. Fig. 4e.) is a display of patient pclro~lllance error detection without the display of thePhantom ~ines, wherein only Prescribed Breathing Pattern (7) and patient Breathing Signal (9) appear. In this option the patient Breathing Signal (9) 25 changes to different graphic characters andlor colors, depending on which zone of error detection the patient performance is operative. For example, perfect matching o~ the patient's breathing pclro~mance with Prescribed Breathing Program (7) might be indicated by a Small Closed Circle (3dr), acceptable breathing performance within plus and minus 10% indicated by a Small Open Cirde(35), and unacceptable patient performance in excess of plus and minus 5 25% indicated by Small Closed Squares (36). Fig.4 f.) is a display of patient exhaustion wherein the Patient Breathing Signal (9) is unable to follow Prescribed Breathing Program (7) and is unable to achieve a minimal Tidal Volume as depicted by Negative Error Limit (33) and thus indicating the need to terminate the testing procedure.
The schernatic diagrams in Fig. 5 describes various CRT graphic displays and/or hard copy printed reports of the deri~red data. Fig. 5a.) is the ~tiefe~ d embodiment wherein the testing procedure has been with constant prescribed inspiratory resistance load, as determined by a predetermined percentage of the Maximum Inspiratory Capacity. Graphics ~port (15) plots Borg Dyspnea ~Jnits and Pealc Inspiratory Pressure on the vertical r ordinate axis, against Time on the horizontal "x" abscissa axis. Optionally Average Inspiratory Pressure may besubstituted for Peak Inspiratory Pressure. Inspiratory Pressure Display ( I 7) in this mode of operation is a generally a straight line throughout most of the testing procedure, reflecting the ability of the patient to inspire the prescribed 20 Tidal Volume breath within the defined parameters of Prescribed Breathing Pattern (7). Near the end of the testing procedure the inspiratory pressure tends to diminish, reflecting patient exhaustion and the inability thelcfule to inspire the full prescribed Tidal Volume breath, though in some cases the patient may maintain their ability to breathe as prescribed despite fatigue and severe dyspnea.
25 Numeric Parameter Limit Failure (40) is accumulated and indicated at one minute intervals, and as indicated with increased failure of breathing control as WO 98/14115 PCT/US96/lS643 the patient becomes exhausted. ~ Normal Borg ~esponse (37) to progressive fatigue is indicated. Also shown is abnormal Diminished Borg Response (38) thereby indicating the patient to be susceptible of developing severe or potentiaUy fatal asthmatic exacerbations as such patients are relatively unaware5 of the severity of their condition and therefore may not p~omptly seek a~p~ ,iate urgent medical attention. ~lso shown is Excessive Borg Response (39~ as may be seen in subjects susceptible to the condition of HyperventilationSyndrome, or subjects with pulmoriary pathologic conditions such as Chronic Obstructive Pulmonary Disease. Fig. 5b.) is an alternate testing method wherein 10 the inspirato~y resistive load is applied in incremental steps at prescribed times, e.g. two minute intervals, and with prescribed resistive loads at each incremental step, e.g. zero, -2, -5, -10, -15, -20, -25, -30, etc. cm. of water pressure, with the patient breathing in a prescribed manner according to Prescribed Breathing Pattern (7). Displayed are examples of Normal Borg Response (37), Diminished 5 Borg Response (38) and Excessive Borg Response (39) and numeric Parameter Limit Failure (40) events.
Claims (12)
1. A method for monitoring an asthma patient to determine decreased ability to perceive severe respiratory distress, comprising:
measuring the patient's respiration vital capacity for establishing controlled patient tidal volume;
measuring the patient's respiration maximal inspiratory pressure capacity for establishing controlled patient inspiratory resistive load;
establishing visual patient inspiration and expiration breathing pattern comprising determined tidal volume, respiratory rate, inspiration to expiration time ratio, and inspiration and expiration waveforms;
applying external inspiratory flow resistance determined from maximal inspiratory pressure while maintaining substantially controlled patient respiration; and evaluating patient dyspnea subjective perception response to said inspiratory flow resistance under conditions of controlled breathing to determine patient dyspnea perception to severe or potentially fatal asthma attack due to the patient's inability to perceive asthma severity.
measuring the patient's respiration vital capacity for establishing controlled patient tidal volume;
measuring the patient's respiration maximal inspiratory pressure capacity for establishing controlled patient inspiratory resistive load;
establishing visual patient inspiration and expiration breathing pattern comprising determined tidal volume, respiratory rate, inspiration to expiration time ratio, and inspiration and expiration waveforms;
applying external inspiratory flow resistance determined from maximal inspiratory pressure while maintaining substantially controlled patient respiration; and evaluating patient dyspnea subjective perception response to said inspiratory flow resistance under conditions of controlled breathing to determine patient dyspnea perception to severe or potentially fatal asthma attack due to the patient's inability to perceive asthma severity.
2. The method of Claim 1 wherein said measuring steps include the step of measuring patient's tidal volume, inspiration rate and expiration rate at ambient pressure in the absence of substantial external inspiratory resistance; and wherein stored normal respiration is retrievable for display and comparison.
3. A method for monitoring an asthma patient to determine susceptibility to severe respiratory disfunction, comprising:
measuring respiration and establishing patient respiration data, including normal inspiration and expiration patterns and vital capacity;
storing the measured respiration data for retrieval and display;
displaying a prescribed inspiration - expiration curve having a tidal volume substantially less than vital capacity for visual feedback and comparisonof patient performance under dynamic testing conditions;
applying variable external inspiratory flow resistance while maintaining patient respiration performance complying with the prescribed curve; and evaluating subjective patient response to said inspiratory flow resistance to determine the patient's relative ability to perceive respiratory distress.
measuring respiration and establishing patient respiration data, including normal inspiration and expiration patterns and vital capacity;
storing the measured respiration data for retrieval and display;
displaying a prescribed inspiration - expiration curve having a tidal volume substantially less than vital capacity for visual feedback and comparisonof patient performance under dynamic testing conditions;
applying variable external inspiratory flow resistance while maintaining patient respiration performance complying with the prescribed curve; and evaluating subjective patient response to said inspiratory flow resistance to determine the patient's relative ability to perceive respiratory distress.
4. The method of Claim 3 wherein said measuring step includes the step of measuring tidal volume, inspiration rate and expiration rate at ambient pressurein the absence of substantial external inspiratory resistance; and setting inspiration rate of the prescribed curve under dynamic testing conditions at about 50% of measured normal inspiratory maximum.
5. The method of Claim 3 including the step of increasing the external inspiratory flow resistance incrementally to about 60 cm water differential pressure.
6. A diagnostic method for determining a human patient's predisposition to abnormal dyspnea perception, comprising:
establishing the patient's respiratory performance parameters of tidal volume and air flow during at least one respiratory cycle;
imposing a physical resistance to normal respiration, while requiring the patient to perform respiratory functions to achieve a predetermined parameter;
and evaluating the patient's subjective response to respiratory stress in achieving said predetermined parameter.
establishing the patient's respiratory performance parameters of tidal volume and air flow during at least one respiratory cycle;
imposing a physical resistance to normal respiration, while requiring the patient to perform respiratory functions to achieve a predetermined parameter;
and evaluating the patient's subjective response to respiratory stress in achieving said predetermined parameter.
7. The diagnostic method of Claim 6 wherein the predetermined parameter is a fraction of maximum tidal volume; and wherein the physical resistance comprises inspiratory air flow resistance.
8. The diagnostic method of Claim 7 including the step of increasing inspiratory resistance incrementally in a series of respiratory cycles, while maintaining a prescribed respiratory flow pattern; and evaluating respiratory stress by subjective patient response.
9. The diagnostic method of Claim 8 wherein the patient achieves at least 50% of the patient's predetermined maximum tidal volume, as measured prior to imposing external air flow resistance at ambient pressure; and including the step of varying the inspiratory air flow resistance over a differential pressure range from ambient to at least 30 cm water pressure.
10. A diagnostic method for determining a human patient's perception of dyspnea, comprising:
establishing patient respiratory performance parameters of tidal volume and air flow during at least one respiratory cycle;
imposing a physical resistance to normal respiration, while requiring the patient to perform respiratory functions to achieve a predetermined parameter;
wherein the predetermined parameter is a fraction of maximum tidal volume;
and wherein the physical resistance comprises increasing incrementally inspiratory air flow resistance in a series of respiratory cycles, while maintaining a prescribed respiratory flow pattern; and evaluating respiratory stress by subjective patient response to perceived dyspnea, wherein the respiratory stress is expressed as inspiratory muscle discomfort and/or fatigue.
establishing patient respiratory performance parameters of tidal volume and air flow during at least one respiratory cycle;
imposing a physical resistance to normal respiration, while requiring the patient to perform respiratory functions to achieve a predetermined parameter;
wherein the predetermined parameter is a fraction of maximum tidal volume;
and wherein the physical resistance comprises increasing incrementally inspiratory air flow resistance in a series of respiratory cycles, while maintaining a prescribed respiratory flow pattern; and evaluating respiratory stress by subjective patient response to perceived dyspnea, wherein the respiratory stress is expressed as inspiratory muscle discomfort and/or fatigue.
11. The diagnostic method of Claim 10 wherein the patient achieves at least 50% of the patient's predetermined maximum tidal volume, as measured prior to imposing external air flow resistance at ambient pressure; and including the step of varying the inspiratory air flow resistance over a differential pressure range from ambient to at least 30 cm water pressure.
12. Evaluation apparatus for monitoring asthma patients to determine subjective perception of respiratory distress, comprising:
a pulmonary function device for measuring patient respiration vital capacity to establish controlled patient tidal volume;
a respiratory flow measurement and display device for measuring patient inspiration and expiration performance and displaying said performance concurrently with prescribed tidal volume, respiratory rate, inspiration: expiration time ratio, and inspiration and expiration waveforms, said measurement and display device employing a prescribed inspiration - expiration curve having a tidal volume substantially less than vital capacity for visual feedback and comparisonof patient performance under dynamic testing conditions;
means for setting variable external inspiratory flow resistance determined from maximal inspiratory pressure under controlled patient respiration conditions and incrementally variable over a differential pressure range from 0 to at least30 cm water pressure; and a comparison system for comparing patient dyspnea perception response to normal response to the inspiratory flow resistance under conditions of controlled breathing to determine patient dyspnea perception to severe asthma distress.
a pulmonary function device for measuring patient respiration vital capacity to establish controlled patient tidal volume;
a respiratory flow measurement and display device for measuring patient inspiration and expiration performance and displaying said performance concurrently with prescribed tidal volume, respiratory rate, inspiration: expiration time ratio, and inspiration and expiration waveforms, said measurement and display device employing a prescribed inspiration - expiration curve having a tidal volume substantially less than vital capacity for visual feedback and comparisonof patient performance under dynamic testing conditions;
means for setting variable external inspiratory flow resistance determined from maximal inspiratory pressure under controlled patient respiration conditions and incrementally variable over a differential pressure range from 0 to at least30 cm water pressure; and a comparison system for comparing patient dyspnea perception response to normal response to the inspiratory flow resistance under conditions of controlled breathing to determine patient dyspnea perception to severe asthma distress.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002238530A CA2238530A1 (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
| AU73804/96A AU7380496A (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
| PCT/US1996/015643 WO1998014115A1 (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002238530A CA2238530A1 (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
| PCT/US1996/015643 WO1998014115A1 (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2238530A1 true CA2238530A1 (en) | 1998-04-09 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002238530A Abandoned CA2238530A1 (en) | 1996-09-30 | 1996-09-30 | Abnormal dyspnea perception detection system |
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| Country | Link |
|---|---|
| CA (1) | CA2238530A1 (en) |
| WO (1) | WO1998014115A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0221044D0 (en) * | 2002-09-11 | 2002-10-23 | Micro Medical Ltd | Apparatus for measuring the strength of a person's respiratory muscles |
| GB0316349D0 (en) * | 2003-07-11 | 2003-08-13 | Micro Medical Ltd | Apparatus for determining respiratory muscle endurance of a person |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US3621833A (en) * | 1969-06-26 | 1971-11-23 | Robert Crane | Method and apparatus for automatically determining physiological parameters related to human breathing airway resistance and functional residual capacity |
| US3857385A (en) * | 1970-04-03 | 1974-12-31 | Jaeger E | Direct indicating devices for measuring respiratory resistance |
-
1996
- 1996-09-30 WO PCT/US1996/015643 patent/WO1998014115A1/en active Application Filing
- 1996-09-30 CA CA002238530A patent/CA2238530A1/en not_active Abandoned
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| WO1998014115A1 (en) | 1998-04-09 |
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