Pulse oximeter
First Claim
1. A method for detecting the validity of measurement circumstances in connection with a monitoring device intended for determining the amount of at least one light absorbing substance in a subject, the monitoring device comprising emitters for emitting radiation at a minimum of two wavelengths, driving means for activating said emitters, and a detector for receiving said radiation at said wavelengths and for producing an electrical signal in response to the radiation, the method comprising the steps of:
- providing a drive signal to an emitter, the drive signal traveling in a direction to said emitter and having predetermined characteristics;
analyzing an electrical signal, traveling in a direction from a detector, in timed relation to said drive signal in order to detect whether a crosstalk component caused by electric power coupled directly from said drive signal is present in said electrical signal, said crosstalk component resulting from at least one of capacitive, inductive and resistive power coupling from said drive signal to said electrical signal; and
, taking predetermined measures when said crosstalk component is detected.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention relates to pulse oximeters used to measure blood oxygenation. The current trend towards lower power consumption has brought a problem of erroneous readings caused by intrachannel crosstalk, i.e. errors due to the coupling of undesired capacitive, inductive, or conductive (resistive) pulse power from the emitting side of the pulse oximeter directly to the detecting side of the oximeter. The pulse oximeter of the invention is therefore provided with means for detecting whether intrachannel crosstalk is present and whether it will cause erroneous results in the oxygenation measurements. The pulse oximeter is preferably further provided with means for eliminating intrachannel crosstalk which are adapted to control the measurement so that measurement signals can be obtained which are substantially void of crosstalk components.
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Citations
41 Claims
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1. A method for detecting the validity of measurement circumstances in connection with a monitoring device intended for determining the amount of at least one light absorbing substance in a subject, the monitoring device comprising emitters for emitting radiation at a minimum of two wavelengths, driving means for activating said emitters, and a detector for receiving said radiation at said wavelengths and for producing an electrical signal in response to the radiation, the method comprising the steps of:
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providing a drive signal to an emitter, the drive signal traveling in a direction to said emitter and having predetermined characteristics;
analyzing an electrical signal, traveling in a direction from a detector, in timed relation to said drive signal in order to detect whether a crosstalk component caused by electric power coupled directly from said drive signal is present in said electrical signal, said crosstalk component resulting from at least one of capacitive, inductive and resistive power coupling from said drive signal to said electrical signal; and
,taking predetermined measures when said crosstalk component is detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus for non-invasively determining the amount of at least one light absorbing substance in a subject, the apparatus comprising:
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emitters for emitting radiation at a minimum of two different wavelengths;
driving means for providing a drive signal to said emitters, the drive signal traveling in a direction to said emitters and having predetermined characteristics, wherein said emitters are activatable to emit said radiation, a detector for receiving said radiation at said wavelengths, wherein an electrical signal traveling in a direction from said detector includes at least a portion in response to the received radiation;
sampling means for sampling the electrical signal, whereby a sampled signal is obtained;
signal processing means for determining said amount by processing the sampled signal; and
crosstalk detection means for analyzing the electrical signal in timed relation to the drive signal in order to detect whether a crosstalk component being caused by electric power coupled directly from said drive signal is present in said electrical signal, said crosstalk component resulting from at least one of capacitive, inductive and resistive power coupling from the drive signal to the electrical signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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31. A method for detecting the validity of measurement circumstances in connection with a monitoring device intended for determining the amount of at least one light absorbing substance in a subject, the monitoring device comprising emitters for emitting radiation at a minimum of two wavelengths, driving means for activating said emitters, and a detector for receiving said radiation at said wavelengths and for producing an electrical signal in response to the radiation, the method comprising the steps of:
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driving an emitter by a drive signal traveling in a direction to the emitter and including one of the following pulses;
voltage pulses, the amplitude of which is insufficient to activate the emitter; and
,current pulses of different amplitudes;
analyzing an electrical signal traveling in a direction from the detector;
detecting a crosstalk component caused by electric power coupled directly from said drive signal, using at least one of the following checks;
checking whether the amplitude of the electrical signal exceeds a predetermined threshold during said voltage pulses; and
,checking whether the amplitude of the electrical signal exceeds another predetermined threshold during said current pulses when the amplitude of said current pulses is zero; and
,taking predetermined measures when said crosstalk component is detected. - View Dependent Claims (32, 33, 34, 35, 36)
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37. An apparatus for non-invasively determining the amount of at least one light absorbing substance in a subject, the apparatus comprising:
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emitters for emitting radiation at a minimum of two different wavelengths;
driving means for activating said emitters by a drive signal, said drive signal including one of the following pulses;
voltage pulses, the amplitude of which is insufficient to activate said emitters; and
,current pulses, the amplitude of which is zero at least once; and
,a detector for receiving said radiation at said wavelengths and producing an electrical signal in response to the radiation;
sampling means for sampling the electrical signal, whereby a sampled signal is obtained;
signal processing means for determining said amount by processing the sampled signal; and
crosstalk detection means for analyzing whether a direct electric crosstalk component is present in the electrical signal, the direct electric crosstalk component being caused by electric power coupled directly from said driving means to said electrical signal, said analysis including at least one of the following checks;
whether the amplitude of the electrical signal exceeds a predetermined threshold during said voltage pulses; and
,whether the amplitude of the electrical signal exceeds another predetermined threshold during said current pulses when the amplitude of said current pulses is zero. - View Dependent Claims (38, 39, 40, 41)
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Specification