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Respiratory exchange ratio sensor

  • US 7,390,304 B2
  • Filed: 03/31/2005
  • Issued: 06/24/2008
  • Est. Priority Date: 03/31/2005
  • Status: Active Grant
First Claim
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1. A device for directly measuring a person'"'"'s respiratory exchange ratio comprising, in combination:

  • (a) a housing having a lumen extending therethrough through which inspired and expired air is adapted to flow;

    (b) an oxygen fuel cell battery positioned in said lumen with an air inlet port of said battery facing a source of the expired air;

    (c) a constant current load circuit coupled to the oxygen fuel cell battery; and

    (d) a flowmeter circuit having a sensor element disposed at a location between the source of expired air and the air inlet port of said battery, said flowmeter circuit operative to produce an output signal proportional to a relative ratio of carbon dioxide to oxygen present in air expired by the person.

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