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WO1996039927A1 - Procede pour la mesure non invasive, intermittente et/ou continue de l'hemoglobine, de la teneur en oxygene arteriel, et de l'hematocrite - Google Patents

Procede pour la mesure non invasive, intermittente et/ou continue de l'hemoglobine, de la teneur en oxygene arteriel, et de l'hematocrite Download PDF

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Publication number
WO1996039927A1
WO1996039927A1 PCT/US1996/009148 US9609148W WO9639927A1 WO 1996039927 A1 WO1996039927 A1 WO 1996039927A1 US 9609148 W US9609148 W US 9609148W WO 9639927 A1 WO9639927 A1 WO 9639927A1
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WO
WIPO (PCT)
Prior art keywords
blood
tissue compression
hemoglobin
measuring
volume
Prior art date
Application number
PCT/US1996/009148
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English (en)
Inventor
Dietrich Gravenstein
J. E. W. Beneken
Samsun Lampotang
Nikolaus Gravenstein
Michael A. Brooks
Gordon L. Gibby
Robert J. Atwater
Original Assignee
Blackbox, Inc.
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Publication date
Application filed by Blackbox, Inc. filed Critical Blackbox, Inc.
Priority to AU62561/96A priority Critical patent/AU6256196A/en
Publication of WO1996039927A1 publication Critical patent/WO1996039927A1/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
    • A61B5/145—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
    • A61B5/14532—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 for measuring glucose, e.g. by tissue impedance measurement
    • 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
    • A61B5/14535—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 for measuring haematocrit
    • 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
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
    • A61B5/414—Evaluating particular organs or parts of the immune or lymphatic systems
    • A61B5/417—Evaluating particular organs or parts of the immune or lymphatic systems the bone marrow
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6814—Head
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6814—Head
    • A61B5/6815—Ear
    • A61B5/6816—Ear lobe
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6814—Head
    • A61B5/682—Mouth, e.g., oral cavity; tongue; Lips; Teeth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6825—Hand
    • A61B5/6826—Finger
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/683—Means for maintaining contact with the body
    • A61B5/6838—Clamps or clips
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6824—Arm or wrist

Definitions

  • Partial pressure of oxygen (P0 2 ) in blood, percent hematocrit (Hct), percent arterial hemoglobin saturation (SaO j ), gram-percent total hemoglobin (THb), and arterial oxygen content (Ca0 2 ) are all readily available to the physician in modern hospitals. Unfortunately, however, measurement of these variables has until recently always required an invasive arterial puncture or phlebotomy. Once the whole blood sample is obtained, analysis is accomplished using spectrophotometric and chemical means.
  • Pulse oximeter design is well documented. It utilizes two light-emitting diodes (LED). Each LED is a light-emitting diode (LED).
  • LED emits a specific wavelength of light that is transmitted through the tissues to a photodetector.
  • An electrical signal consisting of two components is generated by the photodetector receiving the LED emission. There is an invariant direct current (DC) component to the signal which represents ambient background light and transmission of light through invariant, that is, nonpulsatile tissues such as skin, bone, and, to a certain extent, veins.
  • DC direct current
  • AC alternating current
  • THb, Ca0 2 continues to require arterial puncture or phlebotomy. Skin puncture procedures are painful to the patient, time consuming, and provide opportunities for infection. There is a great need for a rapid and accurate noninvasive means of assessing THb, Ca0 2 , and Hct. Such an assessment means would enable the health care provider to quickly evaluate and follow a patient's circulating blood status. Questions of hemodilution during volume expansion in the field, ER, ICU, and OR would be rapidly answered. Hemoconcentration after blood transfusion, hemodialysis or bone marrow transplantation could be followed without repeated venipuncture. Furthermore, many "routine" screening phlebotomies to assess THb and Hct such as for preoperative laboratory studies in children and adults could be eliminated.
  • the subject invention concerns a novel means and device for noninvasive determination of total hemoglobin, arterial oxygen content, and hematocrit.
  • these determinations can be made intermittendy and/or continuously.
  • the novel procedure described here is painless and eliminates the need for skin punctures. It is cost effective because there is no need for needles, syringes, gloves, bandages, or skilled technicians.
  • critical data can be obtained in seconds rather than minutes or hours and continuously rather than episodically.
  • the determination of the blood parameters of interest is accomplished by measuring the change in the mass of hemoglobin (Hb0 2 , RHb, or THb) resulting from a measured or controlled change in volume of blood
  • Hb0 2 , RHb, or THb the change in the mass of hemoglobin
  • THb the change in the mass of hemoglobin
  • the change of mass of hemoglobin species associated with a controlled change in volume can be measured photometrically by passing light of appropriate wavelength(s) through a portion of the body.
  • the attenuation of the light which can be detected by a photometer is related to the amount of hemoglobin species in the blood being analyzed.
  • changes occur in the volume or hemoglobin species concentration of blood being analyzed corresponding changes in the mass of hemoglobin species can be measured.
  • Figure 1 is a schematic representation of one embodiment of the invention where Hb0 2 is measured directly and a pulse oximeter is utilized.
  • Figure 2 is a schematic representation of one embodiment of the invention where Hb0 2 is measured directly and a pulse oximeter is not explicitly incorporated.
  • FIG. 3 is a schematic representation of one embodiment of the invention where THb is measured directly and a pulse oximeter is not explicitly incorporated.
  • Figure 4 is a schematic representation of one embodiment of the invention where desired hemoglobin species is/are measured and a pulse oximeter is not explicitly incorporated.
  • Figure 5 is a diagram of the Caliper-mounted device for collection of dog data.
  • Figure 6 is dog data total hemoglobin (g/dL) versus ln(VJV])/Del-X (mm *1 ).
  • Figure 7 is a diagram of the device used for collecting human data.
  • Figure 8 is data of human population total hemoglobin (g/dL) versus lnCVJVJ/Del-X (mm '
  • Figure 9 is a data collection device.
  • Hb0 2 (g/dL) THb Sa0 2 .
  • oxygen content can be calculated if oxyhemoglobin is known. Therefore, if the mass of oxyhemoglobin molecules [mHb0 2 (g)] in a given volume [V(dL)] is known, the oxygen content of that volume can be determined. Stated another way, if a change in the mHb0 2 can be measured along with the corresponding change in volume, oxygen content can be measured. This relationship can be written
  • Hb0 2 (g/dL) [mHb0 2t2 _ mHbOai ]/[Vt2 - Vu], (4)
  • Hb0 2 ⁇ mHbO ⁇ V
  • ⁇ mHbO is the change in mass of the HbO, species and ⁇ V is the measured corresponding change in volume.
  • the value for ⁇ mHb0 2 if mHb0 2 is measured directly, can be calculated using a signal generated by a pulse oximeter, for example. mHb0 2 can also be determined indirectly. Indirect determination requires accurate Sp0 2 and either RHb or THb values. Sa0 2 and Sp0 2 are known to be close to each other. If RHb and Sp0 2 are known, then
  • Hb0 2 THb-RHb, (8)
  • Hb0 2 [(RHb x 100)/(100-Sp ⁇ 2 )]-RHb. (9)
  • Equation (2) can be utihzed for indirect mHb0 2 determination and equation (8) will then permit calculation of RHb.
  • Equations (4) and (5) The invention can be practiced utilizing Equations (4) and (5).
  • the same equations may be used for any hemoglobin species, e.g. for THb, using a wavelength of 810 nm. These equations are clinically useful approximations of the pertinent biological phenomena to be measured by the subject invention. Additional terms can be added to Equations (4) and (5). These additional terms reflect the relatively small effects which are attributable to respiration and other physiological activities.
  • THb(g/dL) Ca0 2 (mL 0 2 /dL)/[Sp0 2 x 1.39(mL 0 2 /g Hb0 2 )]. (10)
  • RBC red blood cell
  • the claimed device comprises a small appliance that is easily attached to the patient.
  • the device can be attached onto the finger, earlobe, wrist, lips, nares, tongue, cheek, or some other site.
  • the device further comprises a signal processing part that also displays the results.
  • the device displays Ca0 2 , THb, and an estimate of Hct continuously or intermittently.
  • MetHb, and Carboxy Hb (COHb), glucose, bilirubin, etc. can also be quantified.
  • the device does not necessarily require incorporation into a pulse oximeter, or similar device, to determine THb. Instead, an Sp0 2 value can be obtained via the digital output port of a pulse oximeter, or similar device, and input into the proposed device.
  • the device could be incorporated into a pulse oximeter (or similar device), as illustrated in Figure 1, or operate as a unit distinct from it as diagrammed in Figures 2, 3 and 4.
  • Example 17 provides in vivo results obtained using this embodiment of the invention.
  • the extension of this method to monitoring of other relevant blood constituents, besides hemoglobin, such as glucose, bilirubin or cholesterol is also described.
  • tissue compression method for deterniining THb and other blood constituents in vivo is similar to pulse oximetry theory.
  • the compression method differs from pulse oximetry in that actual concentrations of hemoglobin (or other light absorbing constituents such as glucose, bilirubin or cholesterol) may be determined.
  • the third compartment consists of immobile, sohd tissues.
  • the major light absorbers are species of hemoglobin: RHb, Hb0 2 , COHb and metHb.
  • COHb typically comprises 3% to 5% of all hemoglobin and as much as 10% to 15% in smokers.
  • MetHb is typically less than 1% of the total except in rare disease states.
  • the remaining hemoglobin is primarily split between RHb and Hb0 2 , depending on blood oxygen saturation. Not only are extinction coefficients different for each of these species, but the coefficients vary with wavelength of light.
  • K ⁇ ,, Km ⁇ and K ⁇ are extinction coefficients for RHb, Hb0 2 , and nonblood tissues and Cm,
  • 0 ⁇ 02 and C f are concentrations of RHb, Hb0 2 and the light absorbing substances in the nonblood tissues, respectively.
  • the subscript "1" indicates that measurements are made at a first point in time.
  • Optical path lengths are designated as L ⁇ , through blood and L-- through nonblood tissues.
  • Equation (13) may be duplicated for a second point in time, designated by the subscript "2", at which point the optical path length through the blood is different than at the first point in time:
  • equations (13) and (14) accomplishes three things. First, the light source intensity , is eliminated. Thus, lo need not be measured. Second, the last terms of equations (13) and (14) that account for nonblood tissues are also eliminated so that person-to-person differences need not be known. This second item is what makes it possible for our method and device to work on the general population without the need for individual calibration. Third, only the ratio of the variables I 2 and I, needs to be known and not their actual values. This means that measurement calibration for actual light intensity is not necessary. The equation that results from the subtraction is as follows:
  • a simplified model comprises hght passing from a source on one side of a volume of living tissue to a detector on the other side.
  • the blood and less mobile nonblood tissues occupy separate and distinct compartments.
  • the optical path length through blood decreases while the path length through nonblood tissues is unchanged.
  • the term ⁇ L ⁇ in equation (15) is due entirely to changes in the blood optical path length. If the actual value of ⁇ L B is known, then the only unknown values left in equation (15) are the concentrations of RHb and Hb0 2 (i.e., C ⁇ and Cm ⁇ , respectively).
  • K ⁇ is an empirically determined constant and ⁇ L ⁇ is measured or controlled by the device that compresses the tissue, THb may be calculated.
  • the tissue compression method described here may be used to determine actual blood constituent concentrations instead of just ratios of concentrations like the pulse oximeter does. Since the method involves compressing tissues to change the optical path length through blood, the optical path length change is controlled and not dependent on the variability of natural pulsations, as in pulse oximetry. Thus, large signals on the order to 10% to 40% of the DC value are possible on demand with consequent improvements in signal to noise ratio and accuracy of blood parameter determination. Because of the increased signal strength, the tissue compression method is useful in quantitating other blood constituents that do not absorb light as strongly as or are present in more dilute concentrations than the various species of hemoglobin. The tissue compression method may also be adapted to the use of more than one wavelength of light to quantitate more than one blood constituent.
  • blood glucose may be measured according to the above described theoretical considerations using at least one wavelength, for example, 9,700 nm. Since measuring blood glucose is difficult due to its weak light absorption characteristics and its dilute concentration in the blood, glucose determination may require one or more reference wavelengths for its measurement. Matrix algebra derivations solving for glucose imply that the additional wavelength needed for glucose concentration determination may be any wavelength that accurately measures some other blood constituent - hemoglobin, for instance. What this means is simply that once hemoglobin concentration has been determined from a system using one wavelength, the addition of a second, glucose-sensitive or other blood constituent-sensitive, wavelength allows accurate measurement of glucose or other constituent where it could not do so by itself.
  • Photometric Unit - comprising a laser diode or other hght emitting source (810 nm, 9700 nm, etc.), for example, filtered, collimated, ultra bright white light sources, and control circuitry, photodiode and signal conditioning circuitry and mounting hardware.
  • Tissue Compression Unit - comprising a mechanical linkage for effecting appropriate tissue compression kinematics, stepper motor and drive circuitry, linear actuator and associated hardware.
  • C. Precision Distance Measuring Unit - comprising, for example, linear variable differential transformer (LVDT), driving circuitry and mounting hardware.
  • LVDT linear variable differential transformer
  • Data Collection and Conditioning Unit - comprising, for example, a personal computer with multichannel analog to digital board for data filtering, amplification, conditioning for display, and storage.
  • a Force Measurement Unit strain gauges and bridge circuitry mounted to mechanical linkages for measuring tissue compressive forces and mechanical linkage deformations.
  • the noninvasive device to determine THb and Hct values based on the photometric methods explained above comprises five subunits with an optical sixth subunit.
  • the first is the photometric subunit comprised of, for example, a near isobestic point (810 nm) communications type laser diode (LT010MF, Sharp Corp., Osaka, Japan) with control circuitry (IR3C01 Sharp Corp., Osaka, Japan), or like light source capable of emitting light of the desired wavelength for a given chromophore to be measured, an integrated photodiode and amplifier circuit chip with signal conditioning circuitry
  • Light sources capable of creating a radiant energy source of wavelengths up to 11,000 nm are known in the art.
  • the tissue compression subunit comprises a four bar mechanical linkage for effecting tissue compression kinematics.
  • the opposing arms of this subunit move together along nearly parallel paths.
  • This linkage may be driven manually or by stepper motor with linear actuator (e.g., motor model P310.158 and linear gear box model LIO.100.01, Portescap US, Inc., 36 Central Ave., Hauppauge, NY) hardware and control circuitry.
  • linear actuator e.g., motor model P310.158 and linear gear box model LIO.100.01, Portescap US, Inc., 36 Central Ave., Hauppauge, NY
  • the precision distance measurement subunit comprises, for example, a linear differential variable transformer (LVDT) (model S300, Columbia Research Labs, Inc., 1925 MacDade Blvd.,
  • LVDT linear differential variable transformer
  • Woodlyn, PA 19094 with the core mounted to one arm of the tissue compression subunit and the transformer primary and secondary windings to the other arm and control circuitry.
  • any means for precisely measuring the comparison distance would be acceptable.
  • the data collection and conditioning unit Among the variables to be assimilated by the data collection and conditioning unit are the measurements of initial tissue thickness, tissue compression distance, photodiode signal strengths, tissue compression forces and time of compression. Time of compression is potentially important because non-blood tissue fluids are somewhat mobile, but not nearly so mobile as blood. In addition to measuring the necessary elements, it would also be desirable for the data collection unit for perform the necessary calculations as described above to provide a continuous readout of blood constituents.
  • a power supply subunit powers all the electronic signal conditioning circuits and drives the laser diode and the stepper motor.
  • the data collection subunit may comprise, for example, a Gateway2000 80486-based personal computer (Gateway2000, 610 Gateway drive, North Sioux City, SD) equipped with a 12 bit multichannel analog to digital converter board (model Dt2814, Data Translation, Inc., 100 Locke Drive, Marlborough, MA 01752) for acquiring signals.
  • a force measurement subunit may optionally be provided to measure compression forces and to allow monitoring at mechanical arm deformations upon actuation of the tissue compression unit.
  • the force measurement subunit can be incorporated so as to act as a safety interlock, interrupting power to the tissue compression unit as soon as a pre-set limit is exceeded.
  • the force measurement subunit also enables an operator of the device to enter calibration corrections to account for such known individual variable such as elevated blood pressure which may otherwise provide for an undesirable bias in the collected data.
  • the laser diode 1 and photodiode 2 forming the photometric unit are mounted behind glass, which may include polarizing filter, directly on the calipers of a micrometer.
  • the photometric unit is integral to the tissue compression unit, which in this case requires no stepper motor.
  • the precision distance measuring unit 3 is provided by the readout from the micrometer as the opposing jaws of the micrometer are used to compress an illuminated body part placed between the opposing jaws of the micrometer.
  • a data collection unit 4 comprising a signal conditioning (amplification and filtering) and a separate display unit, provides a readout of the hght intensity produced by the laser diode 1 and the amount of light received by the photodiode 2.
  • the power supply is shown as 5.
  • a source of radiant energy 1 a receiver of radiant energy 2, comprising the photometric unit.
  • the photometric unit is integral to the tissue compression unit, which further comprises a motorized pump platform 6 and a motor driven screw 7, for achieving precise compression of a tissue placed between the light source 1 and receiver 2.
  • the precise amount of compression produced by action of the motorized compression unit provided a precisely measured amount of linear distance change between the hght source 1 and detector 2, and this information is fed directly to a multi-channel data acquisition and controller system 4.
  • the tissue compression unit and precise distance measuring unit 3 of the invention are, in this embodiment of the invention, integral to each other.
  • a power source 5 is indicated, and the data collection unit 4 is exemplified as a two component unit comprising a multi-channel data acquisition and controller system and a personal computer which is capable of performing all the necessary calculations of light intensities detected and change in optical length to provide a continuous readout for any given wavelength/blood component.
  • force measurement unit 8 comprising a pressure transducer, is provided and can act as a power interrupt (interlock) to stop tissue compression if a pre-set pressure limit is exceeded.
  • Figure 9 exemplifies a preferred embodiment.
  • the radiant energy source (e.g., a laser diode) 1 and detector 2 are shown on opposing arms of the device, thereby forming an integral photometric unit/tissue compression unit.
  • the tissue compression unit is actuated by a stepper motor 9, which transmits tissue compression pressure to the photometric unit.
  • the amount of compression is measured by a linear variable differential transformer (LVDT) 3 which acts as the precision distance measuring unit.
  • LVDT linear variable differential transformer
  • the power supply which energizes the stepper motor, the LVDT, and the photometric unit, is not shown.
  • Strain gauges are provided as the force measurement unit with the previously described function of tissue compression interrupt.
  • the invention claimed here can be practiced with only one light source and a means of ⁇ V determinatioa Access to Sp0 2 output (obtained from any accurate source, such as a pulse oximeter) is required to calculate either THb and Hct, or Ca0 2 , depending upon the algorithm chosen.
  • the novel device can be built into a pulse oximeter; no additional hght source is required.
  • the component that determines ⁇ V is also supphed. The measurement of changes in mHb0 2 is then correlated to volume changes that are either passively measured or actively produced.
  • Example 2 Changes in the mass of oxyhemoglobin, total hemoglobin, and reduced hemoglobin molecules can be measured via absorption photometry using hght having a wavelength from between about 400 nm and about 1100 nm. Other blood components may be measured using wavelengths up to and including 11,000 nm. For example, a wavelength of about 660 nm can be used for direct Hb0 2 measurement ( Figure 2). Other wavelengths which can be utilized include 810 nm (direct THb determination, see Figure 3) and 940 nm (direct RHb measurement). These wavelengths of hght are sensitive to changes in mHb0 2 , mTHb, and mRHb, respectively.
  • the corrected AC signal can be extracted from a standard pulse oximeter. Alternatively, such a corrected AC signal could be readily obtained by a person skilled in the art utilizing standard equipment and photometric procedures. However, correction of the AC signal is not necessary in all applications.
  • the AC or DC signal can be used in the algorithm where THb is measured directly
  • the desired DC or AC signal is then used to calculate ⁇ mHb0 2 .
  • mHb0 2 is measured directly, for example, this can be done by generating a calibration curve which relates change of mHb0 2 to changes in 660 nm corrected AC signal amplitude.
  • ⁇ mHb0 2 can be determined indirectly with the DC signal from an 810 nm hght source.
  • THb is measured directly and with Sp0 2 , ⁇ mHb0 2 is then calculated using equation (2).
  • Ohmeda 3700 (Ohmeda, Boulder, CO) pulse oximeters are accurate to within 7% of their displayed saturations (Cecil, W.T., K.J. Thorpe, E.E. Fibuch, and G.F. Tuohy [1988] J. Clin. Monit. 4(1):31- 36).
  • hght source Although only a single hght source is needed in most adult patients, more than a single light source can also be employed. Indeed, additional light sources may be useful in determining Ca0 2 in circumstances where other hght-absorbing hemoglobin species are present.
  • Measurement of other hght-absorbing blood constituents may also require additional hght sources to optimize the measurement accuracy. Determination of the proper wavelength to be used for measuring various blood constituents is within the skill of those trained in this field.
  • any type of energy which can be measured and used to quantitate blood constituents may be used to practice the subject invention.
  • any form of electromagnetic radiation, sound wave, or magnetic property which can be used to trans-irradiate a body part can be utilized so long as the characteristics of the energy are altered by the relevant blood constituents and so long as these changes can be measured and correlated with changes in blood volume.
  • NIBP noninvasive blood pressure
  • This commercially available device rapidly pressurizes and depressurizes the bladder to maintain the finger surrounded by the bladder at nearly constant volume during the pulse.
  • the pressure changes in the bladder can be correlated to volume changes in the finger utilizing standard gas law calculations. These calculations take into account original bladder volume, gas temperature, change in bladder volume and compliance of the bladder.
  • a second approach for determining volume changes is to measure changes in the length of the light path between the light source and photodetector. Then the volume is approximated by modelling the hght path.
  • this model can be a cylinder between emitter and detector with a cross-sectional area equal to the receptive field of the photodetector.
  • Measurements or changes in volume can be made passively or actively. Passive measurement would involve, for example, measuring the actual finger expansion and contraction with each pulse. We have been able to show that finger volume does change with each pulse.
  • the finger was placed into a closed rigid chamber (syringe plunger port) filled with an incompressible fluid (water).
  • a pressure transducer (Datascope P3 Module interfaced with a Datascope 870 Monitor, Datascope Corp., Paramus, NJ) was primed with water and connected to the syringe tip. A pulsatile pressure wave form was obtained and reproduced. This provides evidence that the finger does indeed experience volume changes with blood pulsation.
  • Measurement of actively produced volume changes can also be utilized. Active measurement results from compression and release of tissue at the measurement site by a known distance. If the hght source and the photodetector are brought closer together by an external force, e.g., a motor, which produces a volume change in the receptive field, the same data can be obtained.
  • an external force e.g., a motor
  • This method requires some amount of Hb0 2 to be displaced from the receptive field.
  • This procedure can result in the measurement of larger changes in volume compared to passive measurements of volume change during a pulse. Measuring larger volume changes can advantageously reduce experimental error during measurement.
  • the device and method of the subject invention can be utilized in conjunction with life support systems and other medical instrumentations.
  • the subject invention can be used as a sensor for a continuous automatic feedback loop that is designed to maintain Ca0 2 and/or THb or Hct.
  • An infusion pump, ventilator, and or anesthesia machine can be controlled by the sensor.
  • the sensor would enable the system to maintain levels of CaO, and/or THb/Hct at levels which are predetermined by the operator of the system.
  • Example 10 The wavelength and source of Hght employed in the design of the invention can be optimized by those skilled in the art, depending on the particular application. Thus, if direct mHb0 2 determination is desired, an approximately 660 nm light source can be utilized. If, however, direct mTHb determination is desired, a wavelength near the isobestic point of 805 nm (e.g., 810 nm) can be employed. If direct determination of RHb is sought, a light wavelength near 940 nm can be used. With any of these wavelengths, the remaining unknown parameters (THb and/or Hct and/or RHb and or Ca0 2 ) can be determined indirectly with the addition of an accurate Sp0 2 value using the various formulae discussed above.
  • THb and/or Hct and/or RHb and or Ca0 2 the remaining unknown parameters
  • the light can be from an LED and/or laser source, such as a laser diode.
  • the laser offers advantages over an LED because its emission spectra is much narrower, its power attenuation with increasing distance is small in comparison, its output is more directional and it is a more ideal beam Thus, reproducibihty and confidence are improved. These advantages allow for easier modeling and subsequent implementation of applications where the distance between hght source and receiver changes. If a laser or other hght emitting source is utilized, the use of fiber-optic technology may also be employed. Fiber-optic cables allow the somewhat motion-, temperature-, and current-sensitive laser or other hght emitting source and detector elements to remain protected and remote from the patient, and also provide an extremely high degree of electrical isolation between the patient and the device.
  • Noise consists of the background hght that enters the photovoltaic cell (PVC) and alters the signal output.
  • Polarizing films can be employed to reduce the effects of background scattered hght. This is achieved by placing a polarizing film in a known orientation between the emitter and tissue and another film in an identical orientation between the tissue and receiver. This configuration prevents randomly polarized hght from entering the PVC. As a consequence, scattered hght from the emitter, as well as ambient light that is rotated with respect to the orientation of the polarizing film, is filtered from the PVC input. All photoplethysmographic devices, including pulse oximeters, would benefit from this application.
  • polarizing films in this fashion has the added advantage of essentially defining a volume of tissues of similar cross-sectional area to the PVC.
  • the volume's length is the linear distance between emitter and detector. Hence, volume determination is simplified.
  • “Active" volume determination requires a physical displacement of the emitter relative to the PVC. This displacement can be mechanically limited to a known distance. It can also be limited by the tissue pressure upon one of the device elements (i.e., the PVC or light source), or by a combination of pressure and displacement.
  • the method of actively varying volume can be applied equally well to the new pulse oximeter technologies that employ reflectance or backscatter of hght for their signals. If one varied the slab length, width, or depth from which they receive their signals, essentially a volume change would have been made and similar algorithms to those described above would apply. Therefore, SpOj, THb, HbO,, RHb, Ca0 2 and local oxygen consumption could each be determined using these new technologies.
  • the claimed device can also be used to determine interstitial fluid content, or state of hydration.
  • Such a device would be beneficial in the clinical assessment of delirium, hypotension, tachycardia, and other medical conditions.
  • critical care settings e.g., emergency rooms
  • chronic care settings e.g., nursing homes.
  • the no ⁇ 'el device of the subject invention operates by measuring changes in signal strength that occur after a rapid compression (or decompression) of a tissue.
  • the tissue can be thought of as a two compartment system: the intravascular compartment that contains blood and the interstitial compartment that contains body water.
  • a hydrostatic pressure change is applied. Since the fluid cannot shift instantaneously between compartments, it shifts first within the compartment with the least resistance to flow.
  • the interstitial fluid is impeded from making rapid shifts because it is trapped in tissue planes and held within the interstitial compartment by hydrophihc molecules.
  • the blood within the intravascular compartment is capable of making rapid shifts.
  • the measured signal varies with the mass of absorber (i.e., mass of Hb0 2 , RHb, or THb, depending on the wavelength used) in the light path. As reasoned above, after rapid (de)compression, the signal can be expected to vary in a fashion that is related to hydration status.
  • a backscatter oximeter may be used to determine mixed venous O 2 content in the superficial jugular vein while Ca0 2 is determined at a peripheral site. Such a combination may provide a good solution to the Fick equation for cardiac output.
  • Another example of a new application is to combine the algorithms that directly determine mTHb and mHbO 2 by the new method and design an entirely new pulse oximeter based on measuring vascular volume changes.
  • LT010MF weU collimated laser diode
  • the laser diode module included a control chip (IR3C01 Sharp Corp., Osaka, Japan) to maintain stable power output.
  • the photodiode signal was transmitted by shielded cable to a signal conditioning unit for current to voltage conversion, amplification and filtering. The signal amplitude was then read off from a digital volt meter.
  • a mongrel dog was anesthetized with a barbiturate infusion. Data were collected by placing the dog's tongue between the glass slides of the caliper assembly and observing voltage readings with the tissue both uncompressed and compressed A block of material was mounted on the caliper slide to determine caliper excursions during compression. THb values were incrementally lowered by intravenous administration of a 0.9% saline solution. After each ad ⁇ nnistration of saline, blood was drawn and THb determined by CO-Oximeter (model IL-282, Instrument Laboratory, Lexington, MA). Photodiode signal measurements were taken with the tongue in uncompressed and compressed states.
  • the device shown in Figure 7 It was constructed from a motorized infusion pump. Again, the laser diode and the photodiode were mounted on opposing arms of the device, behind glass slides. The new device was used to compress finger tip tissue side- to-side and measure photodiode output. Data from five Caucasian and two African American volunteers were taken with tissue compression distances of 2.0 and 2.5 mm. THb values were determined from drawn blood samples by the CO-Oximeter as in the dog study.

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Abstract

L'invention concerne un nouveau moyen et un nouveau dispositif permettant la quantification non invasive de constituants sanguins importants. Il est ainsi possible de déterminer rapidement et aisément l'hémoglobine totale, la teneur en oxygène artériel, l'hématocrite et d'autres paramètres sans recourir à une ponction cutanée ou à une longue analyse de laboratoire. L'invention concerne la mesure ou le contrôle simultanés des variations volumiques et massiques de l'oxyhémoglobine, de l'hémoglobine totale, ou bien de l'hémoglobine réduite ou d'autres constituants sanguins tels que le glucose, la bilirubine ou le cholestérol. Les données obtenues grace à ces mesures servent à quantifier les paramètres étudiés.
PCT/US1996/009148 1995-06-07 1996-06-06 Procede pour la mesure non invasive, intermittente et/ou continue de l'hemoglobine, de la teneur en oxygene arteriel, et de l'hematocrite WO1996039927A1 (fr)

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AU62561/96A AU6256196A (en) 1995-06-07 1996-06-06 Method for noninvasive intermittent and/or continuous hemogl obin, arterial oxygen content, and hematocrit determination

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