Method and apparatus for measuring tissue perfusion
First Claim
1. A perfusion monitor for monitoring tissue perfusion in a body including:
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a probe, arranged to generate a pulsed source of light for irradiation onto a part of a body and a matched sensor, which transduces variations in the reflected light to an electric signal; and
, a signal processor, which receives the electric signal and compares the signal at a first time when the pulsed light source is on with a second time when the pulsed light is off, the first and second times being almost concurrent, and processes the signal to reduce or ameliorate the effect of ambient light in the signal.
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Accused Products
Abstract
Apparatus for measuring microcirculatory flow of a target tissue without the necessity for direct contact of a probe is disclosed. The apparatus includes a probe (10) arranged to generate a pulsed source of infrared light (16) and a matched infrared sensor (18) which transduces variations in the reflected light to an electric signal and a signal processor which compares the signal at a first time when the pulsed light source is on with a second time when the pulsed light is off. The signal is processed to reduce or ameliorate the effect of the ambient light in the signal and the Tissue Perfusion Index (TPI) is then calculated. Without the need to contact tissue, the apparatus can be used to measure the TPI for chronic ulcers on the extremities, the surface of the retina, the vascular pulp within a tooth or the surface of internal organs accessed by fiber optic or endoscopic means.
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Citations
13 Claims
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1. A perfusion monitor for monitoring tissue perfusion in a body including:
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a probe, arranged to generate a pulsed source of light for irradiation onto a part of a body and a matched sensor, which transduces variations in the reflected light to an electric signal; and
,a signal processor, which receives the electric signal and compares the signal at a first time when the pulsed light source is on with a second time when the pulsed light is off, the first and second times being almost concurrent, and processes the signal to reduce or ameliorate the effect of ambient light in the signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A perfusion monitor for monitoring tissue perfusion in a body including:
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a probe, arranged to generate a pulsed source of light for irradiation onto a part of a body and a matched sensor, which transduces variations in the reflected light to an electric signal; and
,a signal processor, which receives the electric signal and compares the electrical signal at a first time when the pulsed light source is on with a second time when the pulsed light is off, the first and second times being almost concurrent, the signal processor including means for processing the electrical signal to reduce or ameliorate the effect of ambient light in the signal;
means for generating a pulse curve from the signal means for calculating a heart rate (HR) from the pulse curve;
means for determining a running value A for the area under the pulse curve;
means for calculating a tissue perfusion index (TPI) from HR×
pulse curve area, where
TPI=A×
HR×
kwhere;
A=running value for area under signal curve HR=value for Heart Rate k=physiological constant for specific tissue. - View Dependent Claims (8)
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9. A method of measuring microcirculatory blood flow in a body comprising the steps of:
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using an emitter of pulsed light to irradiate an area of the body for measurement of microcirculatory changes;
receiving light reflected from the area at a distance from the area being irradiated by the incident light; and
determining from the reflected light a measure of the changes that correspond with the pulsatile filling and partial emptying of the microcirculation. - View Dependent Claims (10)
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11. A method of calculating the tissue perfusion index for an area or part of a body comprising the steps of:
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using an emitter of pulsed light to irradiate an area of the body part for measurement of microcirculatory changes;
receiving light reflected from the area at a distance from the area being irradiated by the incident light;
digitally sampling the signal;
generating a pulse curve from the signal calculating a heart rate (HR) from the pulse curve;
determining a running value A for the area under the pulse curve; and
calculating the Tissue Perfusion Index (TPI) defined by;
TPI=A×
HR×
kwhere;
A=running value for area under signal curve HR=value for Heart Rate k=physiological constant for specific tissue.
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12. (canceled)
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13. (canceled)
Specification