Signal quality determination and signal correction system and methods

• US 8,357,099 B2
• Filed: 12/17/2007
• Issued: 01/22/2013
• Est. Priority Date: 12/21/2006
• Status: Active Grant

• Current Assignee: Philips RS North America LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Inventors: Gunneson, Paul B., Pierry, Anthony T.
• Primary Examiner(s): Foley, Shanon A
• Application Number:
  US11/957,995
• Publication Number:
  US 20080161710A1
• Time in Patent Office: 1,863 Days
• Field of Search: None
• 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 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61M 16/021 operated by electrical means A61M16/202 – A61M16/205 take precedence
• CPC Class Codes: A61M 16/0816 Joints or connectors
• CPC Class Codes: A61M 16/0833 T- or Y-type connectors, e.g. Y-piece
• CPC Class Codes: A61M 16/0858 Pressure sampling ports
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2016/103 the CO2 concentration
• CPC Class Codes: A61M 2230/432 partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 partial O2 pressure (P-O2)

Abstract

A mainstream gas monitoring system and method that includes using a mainstream airway adapter and a gas sensing assembly associated with the airway adapter to measure an analyte of a gas flow through the adapter. A gas sensing portion outputs a signal indicative of the analyte in a gas flow in the mainstream airway adapter. A processing portion receives the signal from the gas sensing portion and determines an amount of the analyte in the gas flow based on the signal from the gas sensing portion. The processing portion determines whether the oxygen measurements are of sufficient quality for their intended use, such as for measuring oxygen consumption or metabolic estimations. Quality measurements may be used to improve accuracy of derived metabolic estimations. Methods are provided by which carbon dioxide measurements can be processed and substituted for direct oxygen measurement for all or part of a respiratory cycle.

Claims

1. A system for measuring respiratory gases, comprising:

a first sensor for generating a first signal as a measure of an amount of a first gas;

a second sensor for generating a second signal as a measure an amount of a second gas; and

a processor operatively connected with the first gas sensor and the second gas sensor for

receiving the first and second signals;

calculating a measure of quality of the first signal based on a comparison with the second signal;

substituting a portion of a reference signal for the first signal when the measure of quality falls below a predetermined threshold; and

adjusting the measured amount of the first gas based upon the measured amount of the second gas.

2. The system of claim 1, wherein the adjusting is based on one of an inverted representation of the second signal, scaled versions of the first and second signals, and a scaled representation of the second signal.

3. The system of claim 1, wherein the measure of quality is calculated using curve-fitting of the first signal to the second signal.

4. The system of claim 1, wherein the first gas sensor measures at least one of oxygen and carbon dioxide.

5. The system of claim 4, wherein the first gas sensor is a luminescent quenching sensor.

6. The system of claim 1, wherein the first gas sensor measures inspired oxygen and expired oxygen, and the processor outputs a waveform representative of the adjusted measured amount of at least one of the inspired oxygen and the expired oxygen.

7. The system of claim 1, wherein the second gas sensor measures CO₂.

8. The system of claim 7, wherein the second gas sensor is an infrared sensor.

9. The system of claim 1, wherein the second gas sensor measures an amount of expired second gas only, and does not measure the amount of inspired second gas.

10. The system of claim 9, wherein the second gas is CO₂ and the amount of inspired CO₂ is assumed to be zero.

11. The system of claim 1, wherein the second gas sensor measures both the amount of expired second gas and the amount of inspired second gas.

12. The system of claim 1, wherein the amount of the first respired gas and the amount of the second respired gas are measured as one of partial pressures of gas, and percentages of gas.

13. The system of claim 1, wherein the reference signal is derived from the second signal.

14. The system of claim 13, wherein the reference signal is a scaled inverted version of the second signal.

15. The system of claim 1, wherein the first signal is scaled to compensate for a change in the measure of quality.