Respiratory calorimeter

• US 6,572,561 B2
• Filed: 03/12/2002
• Issued: 06/03/2003
• Est. Priority Date: 01/16/1998
• Status: Expired due to Term

• Current Assignee: Microlife Medical Home Solutions Inc.
• Original Assignee: HealtheTech, Inc.
• Inventors: Mault, James R.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US10/096,202
• Publication Number:
  US 20020173728A1
• Time in Patent Office: 448 Days
• Field of Search: 600/529, 600/531, 600/532, 600/538, 128/200.24
• US Class Current: 600/532
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• 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 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/087 Measuring breath flow

Abstract

An indirect calorimeter operative to measure the respiratory oxygen consumption per unit time of a subject includes a respiratory connector operative to be supported in contact with a subject, so as to pass respiratory gases as the subject breathes into the respiratory connector, and a bi-directional flow meter having an ultrasonic flow transducer that bi-directionally transmits and receives ultrasonic signals to the transducer to generate a signal as a function of the volume of gases passing through the flow meter. The indirect calorimeter also includes a gas concentration sensor operative to generate a signal as a function of an instantaneous carbon dioxide content of gases passing by the gas concentration sensor. The indirect calorimeter further includes a computing device operative to receive signals from the flow meter and the gas concentration sensor, and conduits interconnecting the respiratory connector, the flow meter and the gas concentration sensor, so that the subject'"'"'s inhalations and exhalations pass through the flow meter and the subject'"'"'s exhalations pass over the gas concentration sensor and the computer is operative to receive the signals from the gas concentration sensor and the flow meter to calculate the subject'"'"'s oxygen consumption.

Claims

1. An indirect calorimeter operative to measure the respiratory oxygen consumption per unit time of a subject, comprising:

a respiratory connector operative to be supported in contact with a subject so as to pass respiratory gases as the subject breathes into said respiratory connector;

a bi-directional flow meter having an ultrasonic flow transducer that bi-directionally transmits and receives ultrasonic signals to said transducer to generate a signal as a function of the volume of gases passing through said flow meter;

a gas concentration sensor operative to generate a signal as a function of an instantaneous carbon dioxide content of gases passing by said gas concentration sensor;

a computing device operative to receive signals from said flow meter and said gas concentration sensor; and

conduits interconnecting said respiratory connector, said flow meter and said gas concentration sensor, so that the subject'"'"'s inhalations and exhalations pass through the flow meter and the subject'"'"'s exhalations pass over the gas concentration sensor;

the computer being operative to receive the signals from said gas concentration sensor and said flow meter to calculate the subject'"'"'s oxygen consumption.

2. An indirect calorimeter as set forth in claim 1 wherein one ultrasonic transducer is positioned on an upper wall of the bi-directional flow meter, and another ultrasonic transducer is positioned on a lower wall of the bi-directional flow meter.

3. An indirect calorimeter as set forth in claim 1 wherein said flow meter includes an ultrasonic transducer positioned on a side wall of said flow meter at an angle and another ultrasonic transducer positioned on the side wall opposing said first transducer at an angle, so that ultrasonic pulses from said transducers are transmitted at an angle to the gas flow direction.

4. An indirect calorimeter as set forth in claim 1 wherein said ultrasonic transducer includes a plurality of microscopic transducers arranged in an array.

5. An indirect calorimeter as set forth in claim 4 wherein said microscopic transducers measure temperature, pressure and humidity, for correcting the gas flow rate due to the effects of temperature, pressure or humidity.

6. An indirect calorimeter as set forth in claim 1 wherein said gas concentration sensor is an infrared absorption sensor.

7. An indirect calorimeter as set forth in claim 1 wherein said gas concentration sensor is a capnometer.

8. An indirect calorimeter as in claim 1 wherein said gas concentration sensor is a fluorescence based oxygen sensor.

9. An indirect calorimeter as in claim 1 wherein said gas concentration sensor is a combined infrared absorption sensor for measuring the concentration of carbon dioxide and a fluorescent quenching sensor for measuring the concentration of oxygen.

10. An indirect calorimeter operative to measure the respiratory oxygen consumption per unit time of a subject, comprising:

a source of respiratory gases;

a respiratory connector operative to be supported in contact with the subject so as to pass respiratory gases as the subject breathes into said respiratory connector;

a bi-directional flow meter having ultrasonic transducers, wherein said transducers generate a signal as a function of the volume of the gases passing through the flow meter during inhalation and exhalation;

an infrared (IR) absorption sensor, wherein said IR sensor operatively generates a signal as a function of the instantaneous CO₂ content of the gases passing over said IR sensor;

a florescence quench sensor, wherein said quench sensor operatively generates a signal as a function of the instantaneous O₂ content of the gases passed over said quench sensor;

conduits interconnecting said source of respiratory gases, said respiratory connector, said flow meter, said IR sensor, and said quench sensor, upon the subject inhaling, to cause respiratory gas from said source to pass through said flow meter to the respiratory connection, and upon the subject exhaling to pass the exhaled gas by the IR sensor, the quench sensor and through the flow meter; and

a means for receiving the resultant signals from said flow meter, said IR sensor and said quench sensor for determining a volume of CO₂ exhaled by the subject over a period of time.

11. An indirect calorimeter as set forth in claim 10, wherein the volume of CO₂ exhaled is determined from the integral of the product of the instantaneous flow meter signal by the IR sensor signal over the period.

12. An indirect calorimeter as set forth in claim 11, wherein the oxygen consumption is determined from the integral volume of gases inhaled over the period less the volume gases exhaled over the period multiplied by the quench sensor signals.

13. An indirect calorimeter as set forth in claim 10 wherein one ultrasonic transducer is positioned on an upper wall of the bi-directional flow meter, and another ultrasonic transducer is positioned on a lower wall of the bi-directional flow meter.

14. An indirect calorimeter as set forth in claim 10 wherein said flow meter includes an ultrasonic transducer positioned on a side wall of said flow meter at an angle and another ultrasonic transducer positioned on the side wall opposing said first transducer at an angle, so that ultrasonic pulses from said transducers are transmitted at an angle to the gas flow direction.

15. An indirect calorimeter operative to measure the respiratory oxygen consumption per unit time of a subject, comprising:

a respiratory connector operative to be supported in contact with a subject so as to pass respiratory gases as the subject breathes into said respiratory connector;

a bi-directional flow meter having an ultrasonic flow transducer positioned on an upper wall of the bi-directional flow meter, and another ultrasonic flow transducer is positioned on a lower wall of the bi-directional flow meter, that bi-directionally transmit and receive ultrasonic signals between said ultrasonic flow transducer to generate a signal as a function of the volume of gases passing through said flow meter;

a gas concentration sensor operative to generate a signal as a function of an instantaneous carbon dioxide content of gases passing by said gas concentration sensor;

a computing device operative to receive signals from said flow meter and said gas concentration sensor; and

conduits interconnecting said respiratory connector, said flow meter and said gas concentration sensor, so that the subject'"'"'s inhalations and exhalations pass through the flow meter and the subject'"'"'s exhalations pass over the gas concentration sensor;

the computer being operative to receive the signals from said gas concentration sensor and said flow meter to calculate the subject'"'"'s oxygen consumption.

16. An indirect calorimeter as set forth in claim 15 wherein said flow meter includes an ultrasonic transducer positioned on a side wall of said flow meter at an angle and another ultrasonic transducer positioned on the side wall opposing said first transducer at an angle, so that ultrasonic pulses from said transducers are transmitted at an angle to the gas flow direction.

17. An indirect calorimeter as set forth in claim 15 wherein said ultrasonic transducer includes a plurality of microscopic transducers arranged in an array.

18. An indirect calorimeter as set forth in claim 17 wherein said microscopic transducers measure temperature, pressure and humidity, for correcting the gas flow rate due to the effects of temperature, pressure or humidity.

19. An indirect calorimeter as set forth in claim 15 wherein said gas concentration sensor is an infrared absorption sensor.

20. An indirect calorimeter as set forth in claim 15 wherein said gas concentration sensor is a capnometer.

21. An indirect calorimeter as in claim 15 wherein said gas concentration sensor is a fluorescence based oxygen sensor.

22. An indirect calorimeter as in claim 15 wherein said gas concentration sensor is a combined infrared absorption sensor for measuring the concentration of carbon dioxide and a fluorescent quenching sensor for measuring the concentration of oxygen.