Pulse oximeter using a virtual trigger for heart rate synchronization
First Claim
1. An apparatus comprising:
- means for generating a first signal from a periodic physical activity;
means for generating a second signal having a first frequency corresponding to said periodic physical activity;
means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and
means for processing said first signal in periods defined by said virtual trigger.
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Accused Products
Abstract
The present invention provides an improved method and apparatus for more accurately calculating and measuring vital information such as oxygen saturation and pulse rate when an ECG signal is not available. Instead of using an ECG R-wave as a trigger to overlay optical pulses, a virtual trigger is generated based on the heart rate and used to overlay optical pulse data. The optical information from a number of periods is added together, with the beginning of each period being determined by the issuance of the virtual trigger. In this way, the maximum and minimum of the optical signal should be lined up with each other in each period and added together to give a cumulative maximum and minimum. This enables precise identification of the maximum and minimum of the signal, and thus allows calculation of the oxygen saturation at that point.
251 Citations
28 Claims
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1. An apparatus comprising:
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means for generating a first signal from a periodic physical activity; means for generating a second signal having a first frequency corresponding to said periodic physical activity; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and means for processing said first signal in periods defined by said virtual trigger. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A pulse oximeter comprising:
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oximeter means for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; means for receiving a heart rate signal having a first frequency corresponding to a heart rate of said patient; means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said first frequency; and means for processing said oximeter signal in periods defined by said virtual trigger. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method comprising the steps of:
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generating a first signal from a periodic physical activity; receiving a second signal having a first frequency corresponding to said periodic physical activity; generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency; and processing said first signal in periods defined by said virtual trigger. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method of operating a pulse oximeter comprising the steps of:
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generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; receiving a heart rate signal having a frequency corresponding to the heart rate of said patient; generating a virtual trigger having said frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said frequency; and processing said oximeter signal in periods defined by said virtual trigger. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A pulse oximeter comprising:
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a photodetector for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient; a heart rate frequency generator providing a heart rate frequency; a sampling circuit producing digital samples of said oximeter signal for a plurality of periods; and a processing circuit for generating a virtual trigger having a frequency equal to said heart rate frequency, said virtual trigger being independent of any feature of a waveform corresponding to a heart rate other than a frequency of said heart rate, said virtual trigger defining said plurality of periods, said processing circuit including first means for averaging samples in said plurality of periods, second means for inhibiting generation of a virtual trigger based on heart rate frequencies greater than a first predetermined frequency and less than a second predetermined frequency, third means for inhibiting generation of said virtual trigger based on a heart rate frequency that varies at more than a predetermined rate, and fourth means for determining a maximum and a minimum value of said oximeter signal in said periods, including examining all samples in each period. - View Dependent Claims (28)
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Specification