RESPIRATORY GAS ANALYZER FOR MEASURING AND DISPLAYING OXYGEN UPTAKE IN EXPIRED AIR

• US 3,834,375 A
• Filed: 07/20/1973
• Issued: 09/10/1974
• Est. Priority Date: 04/12/1972
• Status: Expired due to Term

• Current Assignee: Clifford Sanctuary, Donald C. Woods, John A. Bachman
• Original Assignee: Clifford Sanctuary, Donald C. Woods, John A. Bachman
• Inventors: Sanctuary, Clifford, Woods, Donald C., Bachman, John A.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/380,975
• Time in Patent Office: 417 Days
• Field of Search: 128/2.07,2.08 235/151.35 73/23R
• US Class Current: 600/532
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/093 the gases being exhaled into, or inhaled from, an expansible chamber, e.g. bellows or expansible bag
• CPC Class Codes: G01F 15/0755 involving digital counting

Abstract

A respiratory gas analyzer is provided in the form of a breath gas measuring instrument and system in which the oxygen uptake in the expired air of a subject, and the oxygen consumption per unit of weight of the subject, are periodically calculated and digitally displayed. A true sample of the expired air is accumulated by gradual extraction within the system of the invention on a periodic basis for gas analysis, and a computer included in the system calculates the oxygen depletion of each total sample to standard temperature and at ambient pressure and provides a digital display of oxygen uptake. An additional computer is included in the system which responds to the compensated oxygen depletion and to the subject'"'"''"'"'s weight to provide a digital display of the oxygen uptake per unit weight of the subject.

Claims

1. A respiratory gas analyzer for measuring and displaying oxygen uptake in the air expired by a subject for each of a succession of predetermined time intervals, said gas analyzer including:

positive displacement volume metering means for producing electric output pulses representative of the volume of air expired by the subject at standard temperature and ambient pressure;

a mouthpiece coupled to said volume metering means to enable the subject to introduce his expired air into the volume metering means;

volume computing means electrically coupled to said volume metering means and responsive to the electric output pulses therefrom for generating a series of electric pulses representative of the volume of air expired by the subject during each of the successive time intervals;

sampling means controlled by said volume metering means for deriving samples of the expired air from the input of the volume metering means with each sample being proportional to the total volume of the expired air passed through the volume metering means;

oxygen measuring means coupled to the sampling means for measuring the partial pressure of oxygen in each of the samples and for producing electric output pulses representative of such partial pressure;

oxYgen uptake computing means coupled to said volume computing means and to said oxygen measuring means and responsive to the electrical output pulses therefrom to calculate the oxygen uptake in the samples at standard temperature and ambient pressure during each of the successive time intervals; and

display means coupled to said uptake computing means for displaying the volume of oxygen uptake at the end of each of the time intervals under standard temperature and ambient pressure conditions.

2. The combination defined in claim 1, in which said oxygen uptake computing means implements the following equation:

V02 (Ve (K1+P'"'"''"'"'+K3P'"'"''"'"'m)/K2 where;

V02 normalized volume of oxygen uptake per unit time;

P'"'"''"'"' ambient pressure normalized;

P'"'"''"'"'m reduction in oxygen partial pressure normalized;

Ve number of volume samples of expired air passing through the measuring means for each time interval;

K1, K2 and K3 are constants.

3. The combination defined in claim 2, and which includes pressure normalizing circuit means included in said uptake computing means, and means coupled to said pressure normalizing circuit means for introducing electric pulses thereto representative of ambient pressure normalized (P'"'"''"'"').

4. The combination defined in claim 1, in which said measuring means includes an oxygen cell for measuring said partial pressure, and which includes oven means for said volume metering means and for said oxygen cell for maintaining said sample at a predetermined temperature above normal body temperature.

5. The combination defined in claim 4, and which includes drying means interposed between said sampling means and said oxygen cell for removing substantially all water vapor from the samples prior to their entry into the oxygen cell.

6. The combination defined in claim 1, and which includes manually operable digital switching means controllable to a setting representative of the weight of the subject, and further computing means coupled to said switching means and to said oxygen uptake computing means for computing the oxygen uptake for unit weight of the subject.