EP0807402A1
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EP
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Photoplethysmographic perfusion index monitoring
Assignee: Datex Ohmeda Inc
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Filing: 1997-03-24
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Granted: —
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Expires: 2017-03-24
Abstract
Abstract A 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 received 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.
Inventors
- 👤 Jonas A. Pologe
- 👤 Robert M. Tobin Jr.
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 08:22
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/68; A61B5/6801; A61B5/6813; A61B5/6825; A61B5/6826; A61B5/02; A61B5/026; A61B5/0261; A61B5/145; A61B5/1455; A61B5/14551; A61B5/683; A61B5/6838; A61B5/14552
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
142 words
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 the optical path length change for each of a plurality of sampling time intervals; and, e. summing the plurality of optical path length changes over a predetermined total time interval.
Claim 2
Dependent Claim
23 words
A method as claimed in claim 1 wherein the predetermined total time interval is the time interval for a systolic to diastolic transition.
Claim 3
Dependent Claim
27 words
A method as claimed in claim 1 wherein the predetermined total time interval is the time interval for contiguous diastolic to systolic and systolic to diastolic transitions.
Claim 4
Dependent Claim
20 words
A method as claimed in claim 1 wherein the predetermined total time interval includes at least one complete half-cardiac cycle.
Claim 5
Dependent Claim
39 words
A method as claimed in claim 1 further comprising the steps of: selecting an extinction coefficient related to the spectral content of each of the emitters in use; and, calculating the perfusion index based on the selected extinction coefficients.
Claim 6
Dependent Claim
52 words
A method as claimed in claim 1, further comprising the steps of: (f) repeating steps (a) through (e) in claim 1 a plurality of times to obtain a sequence of perfusion index values; and (g) averaging the perfusion index values obtained in step (f) above to obtain an average perfusion index value.
Claim 7
Independent Claim
167 words
An apparatus for the generation of a perfusion index indicative of the perfusion of a portion of tissue of a patient by pulsating arterial blood comprising a probe (20) and a monitor (100); the probe (20) comprising: emitting means (24,25) for illuminating the tissue portion of the patient with one or more approximately monochromatic light signal each having a unique spectral content; means (28) 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 (60) for transmitting the received light intensity signals to the monitor (100); and, the monitor (100) comprising: calculating means (107) for determining, from the received light intensity signals generated for each of the approximately monochromatic received light signals, the optical path length change for each of a plurality of sampling time intervals; and, means for summing the plurality of optical path length changes over a predetermined total time interval.
Claim 8
Dependent Claim
38 words
An apparatus as claimed in claim 7 wherein the means for summing the plurality of optical length path changes sums the plurality of optical length path changes for a time interval equivalent to the systolic to diastolic transition.
Claim 9
Dependent Claim
38 words
An apparatus as claimed in claim 7 wherein the means for summing the plurality of optical length path changes sums the plurality of optical length path changes for a time interval containing at least one half cardiac cycle.
Claim 10
Dependent Claim
38 words
An apparatus as claimed in claim 9 wherein the means for summing the plurality of optical path length changes sums the plurality of optical length path changes from the peak to the valley of the half cardiac cycle.
References Cited (Backward Citations)
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