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Plethysmographic respiration processor

  • US 9,307,928 B1
  • Filed: 03/30/2011
  • Issued: 04/12/2016
  • Est. Priority Date: 03/30/2010
  • Status: Active Grant
First Claim
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1. A plethysmographic respiration detector responsive to respiratory effects appearing on a detected intensity waveform measured with an optical sensor at a blood perfused peripheral tissue site so as to provide a measurement of respiration rate, the plethysmographic respiration detector comprising:

  • a preprocessor configured to identify a portion of a plethysmograph waveform which includes a physiologically acceptable series of plethysmograph waveform pulses;

    one or more processors configured to use a plurality of different techniques to derive a plurality of different frequency spectrums using the portion of the plethysmograph waveform, each of the plurality of different frequency spectrums responsive to at least one respiratory effect on the portion of the plethysmograph waveform and including a plurality of local maximums, the one or more processors comprising at least two of;

    a baseline processor configured to receive the portion of the plethysmograph waveform and output a baseline frequency spectrum responsive to a respiratory-induced baseline shift of the portion of the plethysmograph waveform,an amplitude modulation (AM) processor configured to receive the portion of the plethysmograph waveform and output an AM frequency spectrum responsive to a respiratory-induced amplitude modulation of the portion of the plethysmograph waveform, anda shape modulation (SM) processor configured to receive the portion of the plethysmograph waveform and output a SM frequency spectrum responsive to a respiratory-induced shape modulation of the portion of the plethysmograph waveform,wherein a first frequency spectrum of the plurality of different frequency spectrums is one of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum, and a second frequency spectrum of the plurality of different frequency spectrums is different from the first frequency spectrum and is one of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum; and

    a decision logic configured to determine a respiration rate based at least on a comparison of one or more local maximums of the first frequency spectrum and one or more local maximums of the second frequency spectrum, the decision logic comprising;

    a peak detector configured to operate on at least two of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum so as to determine the local maximums of the at least two of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum, anda comparator configured to determine if the local maximums of the at least two of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum occur at matching frequencies within a first tolerance,wherein the decision logic is configured to generate a respiration rate output if the comparator finds at least one local maximum of each of the at least two of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum occur at matching frequencies within the first tolerance.

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