Pulse oximeter probe-off detector
First Claim
1. A detector for determining when a physiological sensor may not be properly positioned with respect to a measurement site, the detector comprising:
- a signal strength calculator which processes an input signal expected to be representative of at least one parameter measured by a physiological sensor to produce an output representative of a strength of the input signal; and
logic which indicates that the input signal may not represent the parameter when a predetermined portion of the output is below a threshold value, wherein the threshold value comprises a floor value below which a probe-off condition exists for all values of the output, and wherein the floor value comprises a ratio of a first value of a substantially alternating part of the output to a second value of a substantially non-alternating part of the output.
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Accused Products
Abstract
An intelligent, rule-based processor provides signal quality based limits to the signal strength operating region of a pulse oximeter. These limits are superimposed on the typical gain dependent signal strength limits. If a sensor signal appears physiologically generated, the pulse oximeter is allowed to operate with minimal signal strength, maximizing low perfusion performance. If a sensor signal is potentially due to a signal induced by a dislodged sensor, signal strength requirements are raised. Thus, signal quality limitations enhance probe off detection without significantly impacting low perfusion performance. One signal quality measure used is pulse rate density, which defines the percentage of time physiologically acceptable pulses are occurring. If the detected signal contains a significant percentage of unacceptable pulses, the minimum required signal strength is raised proportionately. Another signal quality measure used in conjunction with pulse rate density is energy ratio, computed as the percentage of total energy contained in the pulse rate fundamental and associated harmonics.
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Citations
33 Claims
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1. A detector for determining when a physiological sensor may not be properly positioned with respect to a measurement site, the detector comprising:
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a signal strength calculator which processes an input signal expected to be representative of at least one parameter measured by a physiological sensor to produce an output representative of a strength of the input signal; and
logic which indicates that the input signal may not represent the parameter when a predetermined portion of the output is below a threshold value, wherein the threshold value comprises a floor value below which a probe-off condition exists for all values of the output, and wherein the floor value comprises a ratio of a first value of a substantially alternating part of the output to a second value of a substantially non-alternating part of the output. - View Dependent Claims (2, 3, 4)
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5. A detector for determining when a physiological sensor may not be properly positioned with respect to a measurement site, the detector comprising:
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a signal strength calculator which processes an input signal expected to be representative of at least one parameter measured by a physiological sensor, to produce an output representative of a signal strength of the input signal; and
logic which indicates that a probe-off condition may exist when both a predetermined portion of the output is below a signal strength threshold and a signal quality of the input signal falls within a non-operative region. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A detector for determining when a physiological sensor may not be properly positioned with respect to a measurement site, the detector comprising:
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a limit selector outputting an energy ratio limit dependent upon a sensitivity mode of a physiological sensor; and
logic which indicates that a probe-off condition may exist when an energy ratio representative of an amount of energy in an input signal expected to be representative of at least one parameter measured by a physiological sensor, is below the energy ratio limit. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A pulse-off detector for determining when a physiological sensor may not be properly positioned on a measurement site by monitoring characteristics of a signal expected to be representative of at least one parameter measured by the physiological sensor, the pulse-off detector comprising:
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an energy ratio check which compares an energy ratio of a signal expected to be representative of at least one parameter measured by a physiological sensor, with an energy ratio limit;
a time fuse check which determines whether no acceptable values of the signal have been received;
a signal strength check which determines whether the physiological sensor is within operating limits defined by a relationship between a signal strength characteristic of the signal and a signal quality characteristic of the signal; and
logic which indicates that the physiological sensor may be in an off-probe condition based on at least one of the energy ratio check, the time fuse check and the signal strength check. - View Dependent Claims (28, 29, 30, 31, 32, 33)
wherein the logic indicates that the physiological sensor may be in the off-probe condition during a first signal condition or a second signal condition, wherein the first signal condition includes the signal strength check indicating that the signal strength characteristic is below a signal strength threshold, and wherein the second signal condition includes all of (a) the signal strength check indicating that the signal strength characteristic is outside the operating limits, (b) the energy ratio check indicating that the energy ratio of the signal is below the energy ratio limit, and (c) the time fuse check determining that no acceptable values of the signal have been received.
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Specification