WO2015175360A1 - Dispositif pour oxymétrie en l'absence de pouls destiné à estimer la saturation artérielle en oxygène de manière non invasive chez des patients présentant un pouls faible ou absent - Google Patents

Dispositif pour oxymétrie en l'absence de pouls destiné à estimer la saturation artérielle en oxygène de manière non invasive chez des patients présentant un pouls faible ou absent Download PDF

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Publication number
WO2015175360A1
WO2015175360A1 PCT/US2015/030057 US2015030057W WO2015175360A1 WO 2015175360 A1 WO2015175360 A1 WO 2015175360A1 US 2015030057 W US2015030057 W US 2015030057W WO 2015175360 A1 WO2015175360 A1 WO 2015175360A1
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WIPO (PCT)
Prior art keywords
arterial blood
light
attenuance
tissue
wavelengths
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PCT/US2015/030057
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English (en)
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Thomas K. Aldrich
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Montefiore Medical Center
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Publication of WO2015175360A1 publication Critical patent/WO2015175360A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers

Definitions

  • Arterial oxygen saturation refers to the concentration of oxygen in arterial blood.
  • Arterial oxygen saturation (Sa0 2 ) estimated by pulse oximetry is referred to as Sp02.
  • Pulse oximetry estimates arterial oxygen saturation by taking a ratio of pulsatile changes in attenuance (absorbance plus scatter) of a fingertip at two wavelengths of light, typically 660nm (red) and 905nm (infrared), selected for their differing absorption characteristics by oxy- and reduced hemoglobins (Weiben, 1997; Zjilstra, 1991).
  • attenuance attenuance plus scatter
  • changing attenuance is determined by (1) pulsatile changes in the volume of blood in the light path, (2) hemoglobin concentration, (3) relative concentrations of oxy- and reduced hemoglobins, and (4) the attenuation coefficients of oxy- and reduced hemoglobins at the relevant wavelength.
  • the pulse volume, and hemoglobin concentration terms cancel out, allowing saturation to be estimated by comparison of the ratio with empirically-derived standard data (Weiben, 1997).
  • Pulse oximetry fails when the pulse volume is too small to achieve acceptable signal to noise ratios.
  • Common clinical scenarios of pulse oximetry failure include patients with peripheral vascular disease, patients in circulatory shock, and patients on continuous flow left ventricular assist devices (LVADs).
  • LVADs left ventricular assist devices
  • the present invention addresses the need for improved methods and apparatus for measuring arterial saturation noninvasively in patients in whom pulsatile blood flow is reduced or absent.
  • the invention provides apparatus and techniques of estimating arterial blood oxygenation (percentage of oxyhemoglobin or saturation of arterial blood hemoglobin with oxyhemoglobin) in persons, in particular in persons with insufficient pulse volume for standard pulse oximetry.
  • the invention also provides systems for estimating arterial oxygen saturation (Sa0 2 ) in a patient in whom pulsatile blood flow is reduced or absent, comprising: one or more devices for emitting two or more wavelengths of light; one or more light detecting devices; and one or more computing devices comprising one or more processors, a memory unit, a display device, and a computer-readable storage medium including computer- readable code that is read by the one or more processors to perform a method comprising the steps of: alternately transilluminating a tissue of the patient with two or more wavelengths of light; measuring change in transmission separately for each of the two or more wavelengths of light across the tissue during occlusion of arterial blood flow to the tissue and after release of occlusion of arterial blood flow to the tissue, where light levels at each wavelength at points of time after release of occlusion are expressed as a fraction of the maximum light level that occurs during occlusion, yielding a relative transmittance (T) level for each wavelength of light; calculating arterial blood attenuance (T) level
  • Figure 1 Example of manual occlusion of radial and ulnar arteries.
  • Figure 2 Raw photoplethysmograms. Red and infrared photoplethysmograms collected from one normal subject, during quiet breathing on room air, followed by a 5 second occlusion of radial and ulnar arteries, during which light transmission increases, because venous blood drains, while there is no arterial inflow. At the 17 second time point, the occlusion was released, causing decrease in transmitted light due to arterial blood inflow. The data identified by the oval are selected for further analysis.
  • FIG. 4 Calculating Red/Infrared changing attenuance ratio (R/IR). Red attenuance is plotted against infrared attenuance for the data from nadir to peak attenuance. The slope of the resulting line represents average R/IR ratio, in this case 0.566.
  • R/IR red/infrared
  • the present invention provides a method of estimating arterial oxygen saturation (Sa0 2 ) in a patient in whom pulsatile blood flow is reduced or absent, comprising:
  • estimating arterial oxygen saturation (Sa0 2 ) in the patient by comparing the average arterial blood attenuance ratio with data from subjects with known Sa0 2 or with data from calibrating devices.
  • the invention also provides a system for estimating arterial oxygen saturation (Sa0 2 ) in a patient in whom pulsatile blood flow is reduced or absent, comprising:
  • one or more computing devices comprising one or more processors, a memory unit, a display device, and a computer-readable storage medium including computer-readable code that is read by the one or more processors to perform a method comprising the steps of: alternately transilluminating a tissue of the patient with two or more wavelengths of light,
  • estimating arterial oxygen saturation (Sa02) in the patient by comparing the average arterial blood attenuance ratio with data from subjects with known SaC>2 or with data from calibrating devices.
  • the patient can, for example, have a peripheral vascular disease (PVD), circulatory shock, and/or be on a continuous flow left ventricular assist device (LVAD) or extracorporeal membrane oxygenator (ECMO).
  • PVD peripheral vascular disease
  • LVAD left ventricular assist device
  • ECMO extracorporeal membrane oxygenator
  • the patient can also have any other disease or condition, or be undergoing any procedure, where pulsatile blood flow is reduced or absent.
  • Suitable tissues for use in these procedures include, for example, fingers (e.g., fingertip), toes, ears (e.g., earlobe), and hands, although other tissues could also be used.
  • the arterial blood flow to the tissue can be occluded, e.g., for approximately 5- 10 seconds. Shorter or longer periods of occlusion are also suitable.
  • venous blood flow from the tissue is also occluded during and for, e.g., approximately 2-5 seconds after arterial occlusion to the tissue.
  • Venous occlusion can be applied, e.g., by a 20-30 mmHg cuff.
  • the two or more wavelengths of light used to transilluminate the tissue can include any suitable pair of wavelengths.
  • Preferred examples include, but are not limited to, 660nm and 905nm, and 660 nm and 940 nm.
  • any two wavelengths would be suitable, for which the relative absorption by oxy- and reduced hemoglobins differs substantially.
  • the tissue is alternately transilluminated by the two or more wavelengths of light at 100-700 Hz, for example at 480 Hz or 600 Hz.
  • the change in light transmission of each wavelength is measured before, during, and for at least 1-3 seconds after release of arterial occlusion. Shorter or longer periods of light transmission measurement are also suitable.
  • the transilluminated light is measured by a light-detecting device, such as a photodiode.
  • a light-detecting device such as a photodiode.
  • the output of the photodiode or other light measuring device is amplified and digitized at a resolution of 14 bit or higher.
  • the average arterial blood attenuance ratio for two wavelengths is calculated by plotting arterial blood attenuance for one wavelength as a function of arterial blood attenuance for a second wavelength, where the slope of the plot represents the average arterial blood attenuance ratio for the two wavelengths. For example, a regression of arterial blood attenuance of 660nm wavelength (Red (R)) against arterial blood attenuance of 905nm wavelength (infrared (IR)) yields a slope estimate, equivalent to average R/IR ratio.
  • the measured R/IR ratio can be compared with a calibration equation or look-up table to yield an estimate of arterial oxygen saturation.
  • Calibrations for arterial oxygen saturation could also be obtained using measurements of R/IR ratios in subjects with known Sa0 2 , at various levels of Sa0 2 , achieved naturally or by exposing the subjects to hypoxic, normoxic, and hyperoxic gases.
  • calibration could be achieved using a non-living calibrating device, such as an artificial finger.
  • ratios of changing transmission rather than changing attenuance, compared with standards derived from subjects or nonliving calibrating devices with known Sa0 2 , could be used to generate estimates of Sa0 2 .
  • preferred devices for emitting light include, for example, two or more light emiting diodes (LEDs).
  • LEDs light emiting diodes
  • one or more of the light emitting devices could be laser diodes, or incandescent or other light sources, modified by optical filters.
  • Preferred light detecting devices include, e.g., at least one photodiode.
  • a broad-band light source could be used, and optical filters could be interposed between the transilluminated finger or tissue and one or more light-detecting devices.
  • the system can include a device for occluding arterial blood flow to the tissue of the patient and/or a device for occluding venuous blood flow from the tissue of the patient.
  • Apparatus and technique to transiently occlude and release the arteries supplying the relevant body part examples include occluding the radial and ulnar arteries, but other arteries could be used. Occlusion could be accomplished, e.g., by manual compression of the arteries; by automated compression, using a firm occluder device incorporated into a wristband or other device; by inflated cuff around the forearm, base of the fingertip, or other body part, or by other means. A second cuff inflated to a lower pressure might be used to prevent venous outflow upon release of occlusion.
  • Apparatus and technique to identify the adequacy of arterial occlusion during the occlusion/release maneuver are accomplished in one embodiment by monitoring the rate of rise in light level of one or more wavelengths, relative to baseline light level, and alerting the operator (or the software) if the rise or the rate of rise falls below a predetermined threshold.
  • Apparatus and technique to identify the adequacy of venous outflow during arterial occlusion to determine the optimal release point This can be accomplished by monitoring the rate of rise in light level of one or more wavelengths and automating the release of occlusion when the rate of rise declines to a predetermined rate.
  • Examples of the apparatus include a pulse oximeter probe, containing two or more LEDs or other light-emitting devices, and at least one photodiode or other light- detecting device, interfaced with a microprocessor and a display.
  • An occluder device can be incorporated, e.g., into a wrist-band, capable of applying momentary firm pressure to the ventral aspect of the wrist, specifically over the course of the radial and ulnar arteries, without impeding venous outflow from the hand.
  • the device can be adjustable in position, to allow for varying patient wrist size and conformation.
  • the microprocessor can be programmed to detect the adequacy of pulsatile changes in light attenuance, and, if such changes were adequate, the device would function as a standard pulse oximeter, reporting pulse rate and pulse oximetric estimate of SaC>2 (Sp0 2 ).
  • the microprocessor If the microprocessor detects inadequate pulsations, it would activate an indicator on the display. When the operator desires an estimate of Sa0 2 , the operator would provide input to the microprocessor, which would then initiate a series of several, e.g., 5 to 10 second occlusions of, e.g., the radial and ulnar arteries, monitored by the microprocessor as magnitude and rate of increase in light transmission at one or more wavelengths. When a predetermined increase in transmission has occurred, accompanied by a predetermined rate of decrease in transmission, or a predetermined time has passed, the arterial occlusion would be abruptly released.
  • the microprocessor would perform the calculations illustrated in Figure 4 to determine, e.g., a R/IR ratio, and refer to a lookup table or regression equation to compute an estimate of SaC>2.
  • a median result from, e.g., at least 3 occlusions could be reported as an estimate of Sa02, perhaps best abbreviated as SplC ⁇ (for estimate of SaC>2 from pulseless oximetry).
  • An enhancement to the device would be the addition of estimates of carboxy- and met-hemoglobin levels, both during standard pulse oximetry and during the pulseless operation of the device.
  • Carboxyhemoglobin and methemoglobin percentages would be calculated using multiple-regression-derived formulae including at least three variables: a ratio of changing attenuance of 630nm to changing attenuance at 905nm, a ratio of changing attenuance of 660nm to changing attenuance at 905nm, and a ratio of changing attenuance of 730nm to changing attenuance at 905nm, as previously described (Aldrich 2005). Many other pairs of wavelengths would be potentially suitable to make these calculations.
  • This device would be particularly useful in vascular disease practices and heart failure programs, where pulselessness is not uncommon, and would be an important addition to operating rooms, endoscopy suites, emergency rooms, and general medical and surgical wards, which have to deal with pulseless patients.
  • the device could take the place of a standard pulse oximeter in many settings, functioning as a standard pulse oximeter, without intermittent arterial occlusion, and, because it could also measure methemoglobin (which can be seen in pulseless patients, e.g., vascular and heart failure patients, because of their exposure to nitrates) and carboxyhemoglobin, it would do a better job of screening and monitoring than a standard 2- wavelength pulse oximeter.
  • the device would function as a standard pulse oximeter unless it detects pulselessness, in which case it would signal that fact and either automatically or when activated, shift to the pulseless mode and make its measurements.
  • This invention provides an approach to measuring arterial saturation noninvasively by comparing the change in transmittance (relative transmission) of two (or more) wavelengths observed across tissue (e.g., a finger, toe or hand) when arterial supply to the tissue is momentarily occluded or upon release of such occlusion.
  • tissue e.g., a finger, toe or hand
  • the only change in transmittance observed upon release of occlusion is due to inflow of arterial blood, so comparison of pre- to post release attenuance (the logarithm of the reciprocal of transmittance) is proportional to arterial saturation.
  • Arterial blood attenuance of 660nm was then plotted against arterial blood attenuance of 905nm, yielding a straight line ( Figure 4), the slope of which represents the average red/infrared arterial blood attenuance ratio (R/IR).
  • Figure 5 shows the calibration curve results. Medians of at least 2 (usually 3 to 5) replicate measurements are shown. The data follow an inverse relationship between SpC>2 and R/IR ratio. Data for the normal subjects (NS #1 through 5) defined a clear calibration curve. Data for the nine measurements in seven LVAD patients fell slightly above the calibration curve calculated for the normal subjects, underestimating SaC>2 by an average of 1.1 percentage points (maximum 3.4 percentage points), acceptable for clinical determinations of the adequacy of oxygenation.
  • LVAD left ventricular assist devices
  • PVD peripheral vascular disease
  • Arterial occlusion allows venous blood to drain from the tissue of interest.
  • the subsequent release of occlusion allows arterial blood to flow into the tissue, making, for practical purposes, arterial blood the only contributor to changing light transmission and attenuanee.
  • the technique described in this application measures oxygenation of arterial blood, not venous blood or a mixture of arterial and venous blood. It is possible that continuing small changes in venous blood content of, e.g., the fingertip during occlusion and after release may contribute slightly to the observed changes in light transmission. For that reason, venous occlusion can be applied by, e.g., 20-30 mmHg cuff on, e.g., the forearm, during and for a few seconds after release of arterial occlusion.
  • Cuff-occlusion above arterial systolic blood pressure may be a suitable means of arterial occlusion, potentially simpler to automate than is manual occlusion.
  • cuff occlusion would prevent venous outflow during the occlusion, preventing the rise in transmission that occurs during manual arterial occlusion, and may lead to more "contamination" of subsequent transmission measurements by changing venous blood content. That problem could be addressed by continuing post-release venous occlusion. So, for example, two cuffs could be applied to the forearm, one inflated to 30 mmHg and the other to ISOmmHg, both for 5 seconds. The 150mmHg cuff would be abruptly deflated to provide arterial blood flow to the tissue, and the 30 mmHg cuff would remain inflated for a further 2-5 seconds to maintain venous occlusion.
  • the present invention provides a new approach to measure arterial oxygenation noninvasiveiy in patients in whom pulse oximetry fails: for example, those with poor peripheral pulses because of PVD or because they are on continuous flow left ventricular assist devices (LVADs).
  • the technique involves a 5-second occlusion of, e.g., radial and ulnar arteries, followed by an abrupt release.
  • a fingertip on the same hand is alternately transilluminated by two (or more) wavelengths of light, e.g. 660nm (red) and 905nm (infrared) at a rapid rate ( ⁇ 60()hz).
  • Attenuance of each of the wavelengths is recorded during the 1-2 seconds after release of occlusion, and a ratio of changing attenuance of red to changing attenuance of infrared light (R/IR.) is calculated.
  • R/IR can be converted to an estimate of arterial oxygen saturation (Sa0 2 ) by comparison with data from subjects with known SaO? or from data from a non-living calibrating device.
  • the device could be used for standard pulse oximetry and shift to the pulseless mode only when the pulse is inadequate for reliable pulse oximetry readings.

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Abstract

L'invention concerne des méthodes et des systèmes pour estimer la saturation artérielle en oxygène (SaO2) chez des patients présentant un flux sanguin pulsatile réduit ou absent.
PCT/US2015/030057 2014-05-13 2015-05-11 Dispositif pour oxymétrie en l'absence de pouls destiné à estimer la saturation artérielle en oxygène de manière non invasive chez des patients présentant un pouls faible ou absent WO2015175360A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022187101A1 (fr) * 2021-03-01 2022-09-09 Transonic Systems Inc. Procédé et appareil utilisant une caractéristique de débit sanguin de circuit d'oxygénation de sang extracorporel pour évaluation quantitative de paramètre physiologique de patient connecté

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4883055A (en) * 1988-03-11 1989-11-28 Puritan-Bennett Corporation Artificially induced blood pulse for use with a pulse oximeter
US5111817A (en) * 1988-12-29 1992-05-12 Medical Physics, Inc. Noninvasive system and method for enhanced arterial oxygen saturation determination and arterial blood pressure monitoring
US6615064B1 (en) * 1998-09-21 2003-09-02 Essential Medical Devices, Inc. Non-invasive blood component analyzer
US20050256386A1 (en) * 2002-01-31 2005-11-17 Chan Fang C D Venous pulse oximetry
US20060009685A1 (en) * 2004-07-08 2006-01-12 Orsense Ltd. Device and method for non-invasive optical measurements
US20070129614A1 (en) * 2001-03-16 2007-06-07 Nellcor Puritan Bennett Inc. Device and method for monitoring body fluid and electrolyte disorders
US20100240973A1 (en) * 2007-09-27 2010-09-23 Koninklijke Philips Electronics N.V. Blood oximeter

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4883055A (en) * 1988-03-11 1989-11-28 Puritan-Bennett Corporation Artificially induced blood pulse for use with a pulse oximeter
US5111817A (en) * 1988-12-29 1992-05-12 Medical Physics, Inc. Noninvasive system and method for enhanced arterial oxygen saturation determination and arterial blood pressure monitoring
US6615064B1 (en) * 1998-09-21 2003-09-02 Essential Medical Devices, Inc. Non-invasive blood component analyzer
US20070129614A1 (en) * 2001-03-16 2007-06-07 Nellcor Puritan Bennett Inc. Device and method for monitoring body fluid and electrolyte disorders
US20050256386A1 (en) * 2002-01-31 2005-11-17 Chan Fang C D Venous pulse oximetry
US20060009685A1 (en) * 2004-07-08 2006-01-12 Orsense Ltd. Device and method for non-invasive optical measurements
US20100240973A1 (en) * 2007-09-27 2010-09-23 Koninklijke Philips Electronics N.V. Blood oximeter

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022187101A1 (fr) * 2021-03-01 2022-09-09 Transonic Systems Inc. Procédé et appareil utilisant une caractéristique de débit sanguin de circuit d'oxygénation de sang extracorporel pour évaluation quantitative de paramètre physiologique de patient connecté

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