Photoplethysmograph signal-to-noise line enhancement
First Claim
1. In a photoplethysmograph for characterizing blood volume of the type having a light source and a detector disposed about a region of body tissue containing a specified blood vessel, an improvement comprising a pressure member for selectively pressurizing the specified blood vessel.
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Accused Products
Abstract
A ring plethysmograph having a pressure adjustment for locally pressurizing one side of a finger thereby biasing the pressure on an artery wall so that the plethysmograph is optimally sensitive without interfering with blood flow. An auxiliary photodetector, possibly with a second light source, is disposed on the low-pressure side of the finger for two purposes: providing a noise reference for canceling noise on the plethysmograph signal, and also for providing a separate motion signal for monitoring the activity level of a patient.
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Citations
11 Claims
- 1. In a photoplethysmograph for characterizing blood volume of the type having a light source and a detector disposed about a region of body tissue containing a specified blood vessel, an improvement comprising a pressure member for selectively pressurizing the specified blood vessel.
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6. A monitoring system for monitoring a physiological characteristic of a patient, the monitoring system comprising:
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a. a source of light disposed proximately to a region of body tissue of the patient;
b. at least one sensor for providing a signal based on detection of light through a specified blood vessel of the body tissue; and
c. a pressure member in contact with and not encircling the region of body tissue for applying pressure through the region of tissue to the specified blood vessel.
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7. In a photoplethysmograph for characterizing blood volume of the type having a first light source and a detector disposed about a region of body tissue containing a specified blood vessel, an improvement comprising a motion reference signal generator, the motion reference signal generator comprising:
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a. a second light source disposed substantially proximally to the body tissue; and
b. a second detector located at a position distinct from that of the first detector for generating a motion signal. - View Dependent Claims (8, 9, 10)
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11. A method for obtaining contemporaneous plethysmographic and motion data with respect to a body member, the method comprising;
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a. encircling the body member with a ring having at least one light source and at least two detectors;
b. deriving a plethysmographic signal from the first detector based on light transmission along a first path including a specified blood vessel; and
c. deriving a motion signal from the second detector based on light transmission along a second path.
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Specification