EP0102816A2
Expired / Lapsed
EP
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Pulse oximeter
Assignee: Nellcor Inc
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Filing: 1983-08-25
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Granted: —
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Expires: 2003-08-25
Abstract
Abstract @ A pulse oximeter is disclosed of the type wherein light of two different wavelengths is passed through human or animal body tissue, such as a finger, an ear, the nasal septum or the scalp, so as to be modulated by the pulsatile component of arterial blood therein, and thereby allowing indication of oxygen saturation. The level of incident light is continually adjusted for optimal detection of the pulsatile component, while permitting accommodation to variable attenuations due to skin color, flesh thickness and other invariants. At significant slope reversal of the pulsatile component to negative (indicating a wave maximum), wave form analysis of blood flow occurs. A quotient of the pulsatile component of light transmission over the constant component of light transmission is measured for each of two wave lengths by direct digital tracking. The respective quotients are thereafter converted to a ratio, which ratio may be thereafter fitted to a curve of independently derived of oxygen saturation. Calibration is disclosed by solving four unknowns at at least four differing saturations. An output of pulse rate, pulse flow and oxygen saturation is given. An incident light source duty cycle is chosen to be at least 1 in 4 so that noise, inevitably present in the signal, may be substantially eliminated and filtered. Provision is made for a local battery-driven low power consumption instrument capable of being substantially independent of ambient light noise.
Inventors
- 👤 William New, Jr.
- 👤 James E. Corenman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 02:13
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/145; A61B5/1455; A61B5/14551; A61B5/02; A61B5/024; A61B5/02416; G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/314; G01N21/3151
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
204 words
A pulse oximeter including a light emitting means for directing light into the flesh of a patient characterised in that the means includes first and second sources for emitting sequential light pulses in the red and infrared ranges; at least one sensor sensitive to each of said light sources arranged in use to have a light path through the flesh of the patient from the first and second sources; each light source having duty cycle of or less than one part in two with respect to time, the sensor in use viewing light transmission from each light source during a first part of the duty cycle of each light source and viewing ambient light during a second part of the duty cycle of each light source; the sensor outputting signals in use to an amplifier, the amplifier through putting the signal from the sensor during the first part of the duty cycle and through putting a signal corresponding to ambient light during a second part of said duty cycle; and means for subtracting one of the amplified signals from the other of the amplified signals so that a signal or signals due to ambient light is or are substracted from the sensed light signal.
Claim 2
Dependent Claim
204 words
A pulse oximeter including a light emitting means for directing light into the flesh of a patient characterised in that the means includes first and second sources for emitting sequential light pulses in the red and infrared ranges; at least one sensor sensitive to each of said light sources arranged in use to have a light path through the flesh of the patient from the first and second sources; each light source having duty cycle of or less than one part in two with respect to time, the sensor in use viewing light transmission from each light source during a first part of the duty cycle of each light source and viewing ambient light during a second part of the duty cycle of each light source; the sensor outputting signals in use to an amplifier, the amplifier through putting the signal from the sensor during the first part of the duty cycle and through putting a signal corresponding to ambient light during a second part of said duty cycle; and means for subtracting one of the amplified signals from the other of the amplified signals so that a signal or signals due to ambient light is or are substracted from the sensed light signal.
Claim 3
Dependent Claim
62 words
An oximeter according to Claim 1 and wherein the amplifier includes a positive input and a negative input and further including means for switching the first part of the duty cycle of each light source to one of said amplifier inputs and the second part of said duty cycle of each light source to the input of opposite sign of said amplifier.
Claim 4
Dependent Claim
150 words
A pulse oximeter comprising at least one light source for outputting light of a preselected wavelength into the flesh of a patient; at least one light sensor addressed to the flesh of said human adjacent the input of said light source having an indirect path through the flesh of said human from said light source characterised by;means for continually monitoring intensity of light received by said light sensor to detect increasing absorption of light in a first time period due to the arterial inflow of blood to said flesh and decreasing absorption of light in a second time period due the the arterial outflow of blood; and means for adjusting the light intensity output of said light source during one of said light periods only to maintain a predetermined range of light intensity at said light sensor during said arterial flow only, whereby optimum tuning of said monitoring means occurs.
Claim 5
Dependent Claim
150 words
A pulse oximeter comprising at least one light source for outputting light of a preselected wavelength into the flesh of a patient; at least one light sensor addressed to the flesh of said human adjacent the input of said light source having an indirect path through the flesh of said human from said light source characterised by;means for continually monitoring intensity of light received by said light sensor to detect increasing absorption of light in a first time period due to the arterial inflow of blood to said flesh and decreasing absorption of light in a second time period due the the arterial outflow of blood; and means for adjusting the light intensity output of said light source during one of said light periods only to maintain a predetermined range of light intensity at said light sensor during said arterial flow only, whereby optimum tuning of said monitoring means occurs.
Claim 6
Dependent Claim
48 words
An oximeter according to Claim 3 wherein said means for adjusting the light level of said light source during one of said light periods is synchronized to the second time period, so that adjustment of the level of the light source occurs during the arterial outflow of blood.
Claim 7
Dependent Claim
47 words
An oximeter according to claim 3 or 4 including two light sources for outputting light of differing preselected wavelengths into the flesh of a patient and wherein the intensities of both the light sources are adjusted in the second time period during the arterial outflow of blood.
Claim 8
Dependent Claim
218 words
A pulse oximeter comprising a light emitting means for directing light into the flesh of a patient characterised in that the means includes first and second light sources respectively in the red and infrared ranges; and by at least one light sensor addressed to the flesh of said patient adjacent said light sources to receive light passing through the flesh from said light sources; the light sensor for sensing light from the light sources and outputting sequentially a first signal from the first light source and a second signal from the second light source, each light source having alternate sequential duty cycles of less than one part in two parts of time, so that said light sensor first samples the light from the first light source passing through the flesh of said human, thereafter the light sensor secondly samples ambient light passing through the flesh, thirdly samples the light from the second light source passing through the flesh and fourthly samples ambient light passing through the flesh; a comparison circuit connected to the output of the sensor, this comparison circuit comparing the output of a digital to analog converter to the light received from the light source, means for producing a ratio of the varient portions of the light signals to the non-varient portions of the light signal.
Claim 9
Dependent Claim
218 words
A pulse oximeter comprising a light emitting means for directing light into the flesh of a patient characterised in that the means includes first and second light sources respectively in the red and infrared ranges; and by at least one light sensor addressed to the flesh of said patient adjacent said light sources to receive light passing through the flesh from said light sources; the light sensor for sensing light from the light sources and outputting sequentially a first signal from the first light source and a second signal from the second light source, each light source having alternate sequential duty cycles of less than one part in two parts of time, so that said light sensor first samples the light from the first light source passing through the flesh of said human, thereafter the light sensor secondly samples ambient light passing through the flesh, thirdly samples the light from the second light source passing through the flesh and fourthly samples ambient light passing through the flesh; a comparison circuit connected to the output of the sensor, this comparison circuit comparing the output of a digital to analog converter to the light received from the light source, means for producing a ratio of the varient portions of the light signals to the non-varient portions of the light signal.
Claim 10
Dependent Claim
91 words
An oximeter according to claim 6 further including first and second amplifiers connected to the output of said comparison circuit, the amplifiers receiving an offset signal which constitutes an invarient portion of the output of the comparison circuit and negatively amplifying the offset signal and the first and second amplifiers receiving the first and second light signals respectively, so that the outputs of said first and second amplifiers constitute the varient portions of light signals, the outputs of the first and second amplifiers omitting a substantial portion of the invarient portions.
Claim 11
Dependent Claim
179 words
A pulse oximeter for determining arterial oxygen saturation and indication volume of blood flow in a patient, said oximeter including light emitting means characterised by the means,comprisin g first and 'second light emitting sources for emitting sequential light pulses in the red and infrared into the flesh of a patient; and by a sensor sensitive to each of the light sources having an indirect light path through the flesh of said human from said first and second light sources; said sensor sequentially outputting signals to an amplifier from each of said light sources; means for digitally tracking the light absorption; means for dividing the change of light transmission due to the pulsatile component of blood flow with respect to the total light transmission to determine a quotient of light absorption for each optical wavelength to determine blood flow; means for making a ratio related directly to the respective quotients of light transmission at each said frequency and means for fitting the ratios of light transmission to experimentally determined saturations at said ratio to enable the optical determination of saturation.
Claim 12
Dependent Claim
179 words
A pulse oximeter for determining arterial oxygen saturation and indication volume of blood flow in a patient, said oximeter including light emitting means characterised by the means,comprisin g first and 'second light emitting sources for emitting sequential light pulses in the red and infrared into the flesh of a patient; and by a sensor sensitive to each of the light sources having an indirect light path through the flesh of said human from said first and second light sources; said sensor sequentially outputting signals to an amplifier from each of said light sources; means for digitally tracking the light absorption; means for dividing the change of light transmission due to the pulsatile component of blood flow with respect to the total light transmission to determine a quotient of light absorption for each optical wavelength to determine blood flow; means for making a ratio related directly to the respective quotients of light transmission at each said frequency and means for fitting the ratios of light transmission to experimentally determined saturations at said ratio to enable the optical determination of saturation.
Claim 13
Dependent Claim
22 words
An oximeter according to claim 2 or 8 and wherein the light sources have a duty cycle of one part in four.
Claim 14
Dependent Claim
59 words
lO. An oximeter according to claim 8 or 9, wherein the means for digitally tracking the light transmission includes for each said frequency a first positive input including the transmitted light signal and a second time input subtracting out ambient lighting from the transmitted light signal preferably substantially only the variant portion of the light transmission pulse being amplified.
Claim 15
Dependent Claim
9 words
The oximeter of claim 1 including a calibrating instrument.
Claim 16
Dependent Claim
86 words
A calibrating instrument for an oximeter comprising at least one light path arranged to communicate at a light receiving end with the light sources of the oximeter and a light emitting end to a spacial interval overlying the path of said filter; at least a second light path communicated from the outlet of said first light pipe to transmit light to the photosensor of said oximeter; means for passing a filter having a absorption component through said interval between said light pipes to emulate the pulse.
Claim 17
Dependent Claim
86 words
A calibrating instrument for an oximeter comprising at least one light path arranged to communicate at a light receiving end with the light sources of the oximeter and a light emitting end to a spacial interval overlying the path of said filter; at least a second light path communicated from the outlet of said first light pipe to transmit light to the photosensor of said oximeter; means for passing a filter having a absorption component through said interval between said light pipes to emulate the pulse.
References Cited (Backward Citations)
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