Method and apparatus for estimation of resting respiratory quotient

• US 6,884,222 B1
• Filed: 11/20/2003
• Issued: 04/26/2005
• Est. Priority Date: 11/20/2003
• Status: Expired due to Fees

• Current Assignee: James R. Braig
• Original Assignee: James R. Braig
• Inventors: Braig, James R.
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): Mallari, Patricia C.
• Application Number:
  US10/718,075
• Time in Patent Office: 523 Days
• Field of Search: 600/300, 600/301, 600529-543, 73/233
• US Class Current: 600/531
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption

Abstract

A method and apparatus for determining a user'"'"'s Respiratory Quotient (RQ) using just measured O₂ and CO₂ concentrations without use of a flow meter. The RQ is determined by measuring the user'"'"'s real-time inspired O₂ concentration (INS O2) and end tidal O₂ concentration (ETO2) and measuring the user'"'"'s real-time inspired CO₂ concentration (INS CO2) and end tidal CO₂ concentration (ETCO2), and then determining the user'"'"'s RQ from the measured INS O2, ETO2, INS CO2, and ETCO2 values in accordance with the following equation: RQ=(ETCO2−INS CO2)/(INS O2−ETO2). In order to avoid error introduced by the flow rate, the measurement steps are preferably performed while the user is in a resting condition. Also, ETCO2 is preferably measured as the maximum CO₂ value in a breath cycle of the user, while INS CO2 is preferably measured as the minimum CO₂ value in a breath cycle of the user. Similarly, ETO2 is preferably measured as the minimum O₂ value within a breath cycle of the user, while INS O2 is measured as the maximum O₂ value within a breath cycle of the user. On the other hand, the values of INS CO2 and ETCO2 also may be determined in accordance with the invention by analysis of a CO₂ waveform of a breath cycle of the user and the values of INS O2 and ETO2 determined by synchronizing timing of the O₂ waveform of a breath cycle of the user with the CO₂ waveform and sampling INS O2 and ETO2 values simultaneously with sampling of complementary CO₂ values determined by analysis of the CO₂ wavefomm. The RQ measuring device may include the oxygen and CO₂ sensors in a mainstream or sidestream configuration.

Claims

1. A method for determining a user'"'"'s Respiratory Quotient (RQ), comprising the steps of:

measuring the user'"'"'s real-time inspired O₂ concentration (INS O2) and end tidal O₂ concentration (ETO2);

measuring the user'"'"'s real-time inspired CO₂ concentration (INS CO2) and end tidal CO₂ concentration (ETCO2); and

determining the user'"'"'s RQ from the measured INS O2, ETO2, INS CO2, and ETCO2 values in accordance with the following equation;

RQ=(ETCO2−

INS CO2)/(INS O2−

ETO2).

2. The method of claim 1, wherein the measurement steps are performed while the user is in a resting condition.

3. The method of claim 2, wherein ETCO2 is measured as the maximum CO₂ value in a breath cycle of the user.

4. The method of claim 2, wherein INS CO2 is measured as the minimum CO₂ value in a breath cycle of the user.

5. The method of claim 2, wherein ETO2 is measured as the minimum O₂ value within a breath cycle of the user.

6. The method of claim 2, wherein INS O2 is measured as the maximum O₂ value with in a breath cycle of the user.

7. The method of claim 2, wherein values of INS CO2 and ETCO2 are determined by analysis of a CO₂ waveform of a breath cycle of the user.

8. The method of claim 7, wherein values of INS O2 and ETO2 are determined by synchronizing timing of an O₂ waveform of a breath cycle of the user with the CO₂ waveform and sampling INS O2 and ETO2 values simultaneously with sampling of complementary CO₂ values determined by maximum and minimum value analysis of the CO₂ waveform.

9. The method of claim 2, wherein the steps of measuring ETO2 and ETCO2 comprises the step of measuring ETO2 and ETCO2 in an exhaled breath of a patient, whereby the breath has been held for approximately 5-10 seconds prior to exhalation.

11. The device of claim 9, further comprising a facemask connected to a breathing adapter and adapted to sample the user'"'"'s inspired and expired respiratory gases.

10. A device for determining a user'"'"'s resting Respiratory Quotient (RQ), comprising:

a CO₂ sensor that measures the user'"'"'s real-time inspired CO₂ concentration (INS CO2) and end tidal CO₂ concentration (ETCO2);

an oxygen sensor that measures the user'"'"'s real-time inspired O₂ concentration (INS O2) and end tidal O₂ concentration (ETO2); and

a processor that determines the user'"'"'s RQ from the measured INS O2, ETO2, INS CO2, and ETCO2 values in accordance with the following equation;

RQ=(ETCO2−

INS CO2)/(INS O2−

ETO2).

12. The device of claim 10, wherein the CO₂ sensor and oxygen sensor are disposed on the breathing adapter in a mainstream system configuration.

13. The device of claim 10, further comprising a tube that carries gas samples from the facemask to the CO₂ sensor and the oxygen sensor configured in a sidestream system configuration.

14. A device for determining a user'"'"'s resting Respiratory Quotient (RQ), comprising:

a facemask adapted to receive gases inspired by a user and gases exhaled by the user;

a CO₂ sensor that measures the user'"'"'s real-time inspired CO₂ concentration (INS CO2) and end tidal CO₂ concentration (ETCO2);

an oxygen sensor that measures the user'"'"'s real-time inspired O₂ concentration (INS O2) and end tidal O₂ concentration (ETO2);

a processor that determines the user'"'"'s RQ from the measured INS O2, ETO2, INS CO2, and ETCO2 values in accordance with the following equation;

RQ=(ETCO2−

INS CO2)/(INS O2−

ETO2); and

an airway tube connected to the facemask so as to direct exhaled gases to said CO₂ sensor and said oxygen sensor for measurement.