Cepstral domain pulse oximetry
First Claim
1. A method of processing at least first and second time domain plethysmographic signals obtained from a patient, said method comprising the steps of:
- selecting at least one desired portion of the first time domain plethysmographic signal;
selecting at least one desired portion of the second time domain plethysmographic signal;
transforming the selected desired portions of the first and second time domain plethysmographic signals into first and second frequency domain plethysmographic signal portions corresponding to the selected desired portions of the first and second time domain plethysmographic signals;
transforming the first and second frequency domain plethysmographic signal portions into first and second cepstral domain plethysmographic signal portions corresponding to the selected desired portions of the first and second time domain plethysmographic signals; and
examining at least one of the first and second cepstral domain plethysmographic signal portions to obtain information therefrom relating to a physiological condition of the patient.
1 Assignment
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Accused Products
Abstract
Processing of plethysmographic signals via the cepstral domain is provided. In one embodiment, a cepstral domain plethysmographic signal processing method (200) includes the steps of obtaining (210) time domain plethysmographic signals, smoothing (220) the time domain plethysmographic signals, performing (230) a first-stage Fourier transformation of the time domain plethysmographic signals to frequency domain plethysmographic signals, computing (240) power spectrums from the frequency domain plethysmographic signals, scaling (250) the power spectrums and performing (260) a second-stage Fourier transformation on the log-scaled spectrums to transform the power spectrums into cepstrums, and examining (270) the cepstrums to obtain information therefrom relating to a physiological condition of the patient such as the patient'"'"'s pulse rate or SPO2 level.
141 Citations
36 Claims
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1. A method of processing at least first and second time domain plethysmographic signals obtained from a patient, said method comprising the steps of:
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selecting at least one desired portion of the first time domain plethysmographic signal;
selecting at least one desired portion of the second time domain plethysmographic signal;
transforming the selected desired portions of the first and second time domain plethysmographic signals into first and second frequency domain plethysmographic signal portions corresponding to the selected desired portions of the first and second time domain plethysmographic signals;
transforming the first and second frequency domain plethysmographic signal portions into first and second cepstral domain plethysmographic signal portions corresponding to the selected desired portions of the first and second time domain plethysmographic signals; and
examining at least one of the first and second cepstral domain plethysmographic signal portions to obtain information therefrom relating to a physiological condition of the patient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of assessing the presence of motion artifacts in a time domain plethysmographic signal obtained from a patient, said method comprising the steps of:
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obtaining at least first and second instances of the time domain plethysmographic signal corresponding to at least first and second times;
transforming the first and second instances of the time domain plethysmographic signal to first and second instances of a spectral domain plethysmographic signal;
transforming the first and second instances of the spectral domain plethysmographic signal to first and second instances of a cepstral domain plethysmographic signal;
identifying corresponding peaks in the first and second instances of the cepstral domain plethysmographic signal; and
measuring a difference between Quefrencies associated with the identified corresponding peaks in the first and second instances of the cepstral domain plethysmographic signal. - View Dependent Claims (11, 12, 13, 15, 16, 17)
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14. The method of claim 14 further comprising:
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comparing the measured difference between frequencies associated with the identified corresponding peaks in the first and second instances of the spectral domain plethysmographic signal to at least one frequency difference threshold value; and
classifying motion present in the portion of the time domain plethysmographic signal between the first and second times based an outcome of said comparing step.
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18. A method of processing at least first and second time domain plethysmographic signals obtained from a patient, said method comprising the steps of:
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transforming the first and second time domain plethysmographic signals into first and second frequency domain plethysmographic signals;
transforming the first and second frequency domain plethysmographic signals into first and second cepstral domain plethysmographic signals;
obtaining a series of time domain estimates of an SPO2 level of the patient over a period of time using the first and second time domain plethysmographic signals;
obtaining a series of spectral domain estimates of the SPO2 level of the patient over the period of time using the first and second spectral domain plethysmographic signals;
obtaining a series of cepstral domain estimates of the SPO2 level of the patient over the period of time using the first and second cepstral domain plethysmographic signals;
comparing each of the series of time domain estimates of the SPO2 level of the patient, the series of spectral domain estimates of the SPO2 level of the patient, and the series of cepstral domain estimates of the SPO2 level of the patient obtained over the period of time with a series of DC tracking estimates of the SPO2 level of the patient obtained over the same period of time. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of processing first and second time domain plethysmographic signals obtained from a patient, said method comprising the steps of:
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transforming the first and second time domain plethysmographic signals into first and second frequency domain plethysmographic signals;
computing first and second energy spectrums from the first and second frequency domain plethysmographic signals;
transforming the first and second frequency domain plethysmographic signals into first and second cepstral domain plethysmographic signals;
using the first and second cepstral domain plethysmographic signals to identify spectral peaks in the first and second energy spectrums that are associated with a pulse rate of the patient;
computing normalized amplitudes of the identified spectral peaks;
utilizing the normalized amplitudes of the identified spectral peaks to obtain a perfusion index value for the patient. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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Specification