Physiologic analyzer

• US 4,368,740 A
• Filed: 11/03/1980
• Issued: 01/18/1983
• Est. Priority Date: 11/03/1980
• Status: Expired due to Term

• Current Assignee: Sensormedics Corporation (Becton, Dickinson & Co)
• Original Assignee: Cybermedic Incorporated 1341 Cannon Louisville Company 80027
• Inventors: Binder, Andy S.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/203,355
• Time in Patent Office: 806 Days
• Field of Search: 128/716, 128/718, 128/719, 128/725
• US Class Current: 600/531
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production

Abstract

A physiologic analyzer is disclosed for continuous measurement of a subject'"'"'s metabolic functions in which signals from ventilatory flow rate sensors and gas analyzers are processed to provide continuous measurement of the subject'"'"'s ventilatory volume, carbon dioxide production, oxygen consumption, respiratory exchange ratio, and other metabolic functions of interest. An expiratory oxygen concentration sampler is enabled only when oxygen concentration deviates from the inspired value. When enabled, the sampler provides at its output a series of discrete signals proportional to successive instantaneous values of oxygen concentration in expired breath. A similar sampler is used in the processing of the carbon dioxide concentration signals. A respiratory cycle timer measures elapsed time between successive inspirations and provides a breath duration signal which is used for rate computations. Interpretation and analysis of test results is greatly facilitated by displaying all metabolic measurements as a function of oxygen consumption.

Claims

1. A physiologic analyzer comprising:

means continuously sensing the flow rate of expired breath and providing an expired flow signal proportional thereto;

means continuously sensing the proportion of oxygen in inspired and expired breath and providing an oxygen concentration signal proportional thereto;

means continuously sensing the proportion of carbon dioxide in inspired and expired breath and providing a carbon dioxide concentration signal proportional thereto;

an expiratory flow integrator enabled only during expiratory breath and having its input connected to said expiratory flow signal and which samples and integrates said expiratory flow signal at intervals of t seconds and provides at its output a series of signals V₀ through V_n where V_n is proportional to the volume expired during the time elapsed between t_n-1 and t_n ;

an expiratory oxygen concentration sampler which is enabled only when oxygen concentration deviates from the inspired value and which samples oxygen concentration every t seconds and provides at its output a series of signals X₀ through X_n proportional to successive instantaneous values of said oxygen concentration;

an expiratory carbon dioxide concentration sampler which is enabled only when carbon dioxide concentration deviates from the inspired value and which samples carbon dioxide concentration every t seconds and provides at its output a series of signals Z_O through Z_n proportional to successive instantaneous values of said carbon dioxide concentrations.

2. The device of claim 1 further comprising:

means continuously sensing the flow rate of inspired breath and providing an inspired flow signal proportional thereto;

a respiratory cycle timer having its input connected to said inspiratory flow signal, said timer measuring the time elapsed between successive inspirations and providing at its output a breath duration signal proportional thereto;

an oxygen volume multiplier having two multiplying inputs, one of said inputs connected to the output of said expiratory flow integrator and the other of said inputs connected to the output of said oxygen concentration sampler, said oxygen volume multiplier multiplying V_n ·

X_n to provide at its output a series of signals V₀·

X₀, . . . , V_n ·

X_n proportional to the successive incremental values of oxygen uptake within a breath;

a carbon dioxide volume multiplier having two multiplying inputs, one of said inputs connected to the output of said expiratory flow integrator and the other of said inputs connected to the output of said carbon dioxide concentration sampler, said carbon dioxide volume multiplier multiplying V_n ·

Z_n to provide at its output a series of signals V₀ ·

Z₀, . . . , V_n ·

Z_n proportional to successive incremental values of carbon dioxide production within a breath.

3. The device of claim 2 further comprising:

an oxygen consumption totalizer having its input connected to the output of said oxygen volume multiplier and providing at its output a totalized oxygen volume signal proportional to the sum V₀ ·

X₀ +. . . +V_n ·

X_n ;

an oxygen consumption divider having a divident input connected to said totalized oxygen volume signal and a divisor input connected to said breath duration signal and providing at its output a quotient signal proportional to the rate of oxygen uptake;

a carbon dioxide production totalizer having its input connected to the output of said carbon dioxide volume multiplier and providing at its output a totalized carbon dioxide production signal proportional to the sum V₀ ·

Z₀ +. . . +V_n ·

Z_n;

a carbon dioxide production divider having a dividend input connected to said carbon dioxide totalizer and a divisor input connected to said breath duration signal and providing at its output a quotient signal proportional to the rate of carbon dioxide production.

4. The device of claim 3 further comprising:

a respiratory exchange ratio divider having its dividend input connected to the output of said carbon dioxide production divider and a divisor input connected to the output of said oxygen consumption divider and providing at its output a signal proportional to the ratio of carbon dioxide produced to oxygen consumed.

5. The device of claim 4 further comprising:

an inspiratory flow integrator enabled only during inspiratory breath and having its input connected to said inspiratory flow signal and which samples and integrates said inspiratory flow signal at intervals of t seconds and provides at its output a series of signal I₀ . . . I_n where I_n is proportional to the volume inspired during the time elapsed between t_n-1 and t_n ;

an expiratory volume totalizer having its input connected to the output of said expiratory flow integrator and providing at its output a totalized expiratory breath volume signal proportional to the sum of V₀ +. . . +V_n;

an expiratory ventilation volume divider having a dividend input connected to said totalized expiratory volume signal and a divisor input connected to said breath duration signal and providing at its output a quotient signal proportional to the expired breath volume per unit of time;

an inspiratory volume totalizer having its input connected to the output of said inspiratory flow integrator and providing at its output a totalized inspiratory breath volume signal proportional to the sum I₀ +. . . I_n ;

an inspiratory ventilation volume divider having a divident input connected to said totalized inspiratory volume signal and a divisor input connected to said breath duration signal and providing at its output a quotient signal proportional to the inspiratory volume of breath per unit time;

an inspiratory-expiratory ventilation volume comparator having two comparing inputs, one connected to the output of said inspiratory breath volume divider and the other connected to the output of said expiratory breath volume divider and providing at its output an inspiratory-expiratory breath volume differential signal proportional to the difference between inspired and expired breath volume;

an exchange ratio adder having two adding inputs, one connected to the output of said inspiratory-expiratory ventilation volume comparator and the other input connected to the output of said carbon dioxide production divider providing at its output, during conditions of pure oxygen breathing, a signal proportional to the oxygen consumption per unit time.

6. The device of claim 3 further comprising:

a processor responsive to the output signals of said expiratory ventilation volume divider, said oxygen consumption divider, and said carbon dioxide production divider, said processor converting said output signals into actual values for the volume of expiratory ventilation, carbon dioxide production rate, and oxygen consumption rate.

7. The device of claim 6 further comprising:

display means connected to said processor and driven thereby for graphically displaying both expiratory flow rate and carbon dioxide production rate as a function of oxygen consumption rate.

8. The device of claim 7 further comprising:

a cardiotachometer having an output signal proportional to heart rate;

said processor further responsive to said cardiotachometer output signal and converting said output signal into actual values for heart rate;

said display means further graphically displaying heart rate as a function of oxygen consumption rate.

9. The device of claim 8 further comprising:

an oximeter having an output signal proportional to the oxygen content of arterial blood;

said processor further responsive to said oximeter output signal and converting said signal into actual values for arterial blood oxygen content;

said display means further graphically displaying arterial blood oxygen content as a function of oxygen consumption rate.

10. In a physiologic analyzer having means continuously sensing the flow rate of expired breath, means continuously sensing the concentration of oxygen in inspired and expired breath, and means continuously sensing the concentration of carbon dioxide in inspired and expired breath, the method comprising:

sampling and integrating the expiratory flow rate at intervals of t seconds to provide a series of values of expiratory volume V₀ through V_n where V_n is the volume expired during the time elapsed between t_n-1 and t_n ;

sampling, upon detecting oxygen concentration which deviates from the inspired value, the oxygen concentration every t seconds to provide a series of oxygen concentration values X₀ through X_n proportional to successive instantaneous values of expired oxygen concentration;

sampling, upon detecting carbon dioxide concentration which deviates from the inspired value, the carbon dioxide concentration every t seconds to provide a series of carbon dioxide concentration value Z₀ through Z_n proportional to successive instantaneous values of carbon dioxide concentration in expired breath.

11. The method of the previous claim further comprising multiplying V_n ·

X_n to provide a series V₀ ·

X₀, . . . , V_n ·

X_n proportional to the successive incremental values of oxygen consumption within a breath;

multiplying V_n ·

Z_n to provide a series of values V₀ ·

Z₀, . . . , V_n ·

Z_n proportional to successive incremental values of carbon dioxide production within a breath.