Method and apparatus for improved photoplethysmographic perfusion-index monitoring
First Claim
1. A method for generating a perfusion index for a patient wherein a portion of tissue of the patient is perfused by pulsating arterial blood, the method comprising the steps of:
- a. generating from at least one emitter at least one approximately monochromatic light signal having a unique spectral content;
b. directing each of the, at least one, approximately monochromatic light signals into the portion of tissue;
c. detecting light transmitted through the portion of tissue to generate a received light intensity signal responsive to the detected light for each of the approximately monochromatic light signals;
d. determining from the received light intensity signals generated for each of the approximately monochromatic light signals an optical path length change for each of a plurality of sampling time intervals; and
,e. summing a plurality of the optical path length changes over a predetermined total time interval to generate the perfusion index value.
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Accused Products
Abstract
An improved method and apparatus for the monitoring perfusion of the tissue of a patient by arterial blood is provided. An optical path length change is calculated for a number of digitized samples of a received light intensity signal generated by a photo detector that receives light directed into a patient'"'"'s tissue by one or more light emitting diodes or laser diodes. The optical path length changes are summed over a predetermined time such as one half cardiac cycle or other set interval to generate a perfusion index. An average perfusion index value may also be generated. In calculating the perfusion index spectral content compensation may be employed to compensate for the variety of center wavelengths associated with the spectral contents of various emitters.
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Citations
23 Claims
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1. A method for generating a perfusion index for a patient wherein a portion of tissue of the patient is perfused by pulsating arterial blood, the method comprising the steps of:
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a. generating from at least one emitter at least one approximately monochromatic light signal having a unique spectral content; b. directing each of the, at least one, approximately monochromatic light signals into the portion of tissue; c. detecting light transmitted through the portion of tissue to generate a received light intensity signal responsive to the detected light for each of the approximately monochromatic light signals; d. determining from the received light intensity signals generated for each of the approximately monochromatic light signals an optical path length change for each of a plurality of sampling time intervals; and
,e. summing a plurality of the optical path length changes over a predetermined total time interval to generate the perfusion index value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An apparatus for generating a perfusion index indicative of the perfusion of a portion of tissue of a patient by pulsating arterial blood comprising a probe and a monitor;
the probe further comprising; emitting means for illuminating the tissue portion of the patient with one or more approximately monochromatic light signal each having a unique spectral content; means for detecting the light transmitted through the tissue portion; means for generating a received light intensity signal responsive to the detected light for each of the one or more approximately monochromatic light signals; means for transmitting the received light intensity signals to the monitor; and
,the monitor further comprising; calculating means for determining, from the received light intensity signals generated for each of the approximately monochromatic received light signals, an optical path length change for each of a plurality of sampling time intervals thereby generating a plurality of optical path length changes; and
,means for summing the plurality of optical path length changes over a predetermined total time interval to generate the perfusion index. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
Specification