Low power monitoring systems and method

• US 9,351,688 B2
• Filed: 01/29/2013
• Issued: 05/31/2016
• Est. Priority Date: 01/29/2013
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Iyer, Darshan, Su, Mark
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US13/753,046
• Publication Number:
  US 20140214330A1
• Time in Patent Office: 1,218 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence

Abstract

The present disclosure relates to systems and methods for collecting patient data via a monitoring system, with reduced power consumption. In one embodiment, the monitoring system is configured to emit pulses of light, and detect the light after passing through patient tissue. The light data is emitted sporadically, and a waveform is reconstructed from the sporadically sampled light data. Physiological parameters from the patient may be calculated from the reconstructed waveform. The sporadic sampling may reduce the power consumption by the monitoring system.

Claims

1. A system comprising:

light drive circuitry configured to drive an emitter of a pulse oximetry sensor at an average frequency and an average pulse width to cause the emitter to emit light into a tissue of the patient at the average frequency and the average pulse width;

a processor configured to;

receive a set of data samples generated by a detector of the pulse oximetry sensor based on the light that passed through the tissue of the patient, wherein the set of data samples are indicative of a physiological signal of the patient, and the average frequency and the average pulse width cause the set of data samples to comprise an average sampling frequency less than twice the Nyquist frequency of the physiological signal;

construct a waveform representative of the physiological signal based on the set of data samples; and

calculate a physiological parameter based on the waveform.

2. The system of claim 1, comprising the pulse oximetry sensor, wherein the pulse oximetry sensor and the processor are coupled wirelessly.

3. The system of claim 1, further comprising a display coupled to the processor configured to display the waveform and/or the physiological parameter.

4. The system of claim 3, wherein the display is configured to display a portion of the waveform spanning a first time duration, and wherein the processor is configured to update the waveform based on an updated set of data samples spanning a second time duration shorter than the first time duration.

5. The system of claim 1, wherein the set of data samples comprise an average sampling frequency less than the Nyquist frequency of the physiological signal.

6. The system of claim 1, wherein the set of data samples comprise an average sampling frequency less than a fully sampled frequency of the physiological signal.

7. The system of claim 1, wherein the set of data samples comprise an average sampling frequency less than one quarter of a fully sampled frequency of the physiological signal.

8. The system of claim 1, wherein the processor is configured to construct the waveform by matching pursuit.

9. The system of claim 8, wherein the processor is configured to access a dictionary of components.

10. The system of claim 9, wherein the dictionary is customized based on the physiological signal.

11. The system of claim 1, comprising the pulse oximetry sensor, the emitter, and the detector, wherein the emitter comprises a first light emitting diode (LED) configured to emit red light and a second LED configured to emit infrared light, the detector is configured to generate the set of data samples corresponding to the red light and a second set of data samples corresponding to the infrared light, the processor is configured to construct the waveform by matching pursuit based on the set of data samples, and the processor is configured to construct a second waveform by shifting and/or scaling the waveform based on the second set of data samples.

12. The system of claim 11, wherein the processor is configured to calculate the physiological parameter based on the waveform and the second waveform.

13. The system of claim 12, wherein the physiological parameter is blood oxygenation.

14. The system of claim 1, comprising the pulse oximetry sensor, the emitter, and the detector.

15. The system of claim 1, wherein the processor is configured to:

select a function from a dictionary based on the set of data samples;

iteratively calculate a residual and an approximation based on the selected function; and

construct the waveform based on the approximation.

16. The system of claim 1, wherein the light drive circuitry is configured to drive the emitter at irregular intervals to cause the emitter to emit light into the tissue of the patient at irregular intervals comprising the average frequency and the average pulse width.

17. A method comprising:

emitting light sporadically over a period of time into a tissue of a patient via an emitter of a pulse oximetry sensor at a first average frequency corresponding to an average sampling frequency;

generating, via a detector of the pulse oximetry sensor, a set of sporadic data samples over the period of time and indicative of a physiological signal of the patient based on the light that passed through the tissue of the patient;

receiving the set of sporadic data samples at a processor;

using the processor to construct a waveform corresponding to the physiological signal based on the set of sporadic data samples; and

calculating a physiological parameter based on the waveform.

18. The method of claim 17, wherein constructing the waveform comprises:

selecting from a dictionary a component, based on the set of sporadic data samples;

calculating a waveform approximation and a residual based on the selected dictionary component; and

repeating the selection until the residual falls below a threshold.

19. The method of claim 18, further comprising orthogonalizing the selected dictionary component.

20. The method of claim 18, wherein selecting the component comprises finding a function with the largest dot product between the function and the residual.

21. The method of claim 18, further comprising

generating, via the detector of the pulse oximetry sensor, a second set of sporadic data samples over the period of time and indicative of the physiological signal of the patient based on the light that passed through the tissue of the patient;

and

using the processor to construct a second waveform by shifting and/or scaling the waveform based on the second set of sporadic data samples.

22. The method of claim 21, comprising, using the processor, calculating the physiological parameter based on the waveform and the second waveform.

23. The method of claim 22, wherein the physiological parameter is blood oxygenation.

24. The method of claim 17, further comprising obtaining a first waveform, and wherein constructing the waveform comprises shifting and/or scaling the first waveform.

25. The method of claim 17, wherein the set of sporadic data samples comprises the average sampling frequency, and wherein the method further comprises calibrating the average sampling frequency.

26. The method of claim 25, wherein calibrating the average sampling frequency comprises:

emitting light at regular intervals over a second period of time into the tissue of the patient via the emitter of the pulse oximetry sensor at a second average frequency greater than the first average frequency;

generating, via the detector of the pulse oximetry sensor, a fully sampled dataset indicative of the physiological signal of the patient based on the light that passed through the tissue of the patient, the fully sampled dataset comprising a respective average sampling frequency of at least twice the Nyquist frequency of the physiological signal;

receiving the fully sampled dataset at the processor;

interpolating the fully sampled dataset to generate a first waveform;

sampling the first waveform at a first average sampling frequency to obtain calibration data samples;

constructing a calibration waveform based on the calibration data samples;

calculating an error between the calibration waveform and the first waveform; and

providing a light drive signal to the emitter to adjust the first average frequency at which the emitter emits light into the tissue of the patient to cause the detector to generate the set of sporadic data samples comprising the average sampling frequency based on the error.

27. The method of claim 25, wherein the calibrating is triggered based on a signal quality indication or a timer.

28. The method of claim 17, further comprising displaying the waveform or the physiological parameter.

29. The method of claim 17, further comprising displaying the waveform over a first time duration and updating the displayed waveform, wherein updating comprises obtaining a new set of sporadic data samples over a second time duration shorter than the first time duration, removing an initial portion of the displayed waveform that spans the second time duration to form a truncated waveform, adding the new set of sporadic data samples to the truncated waveform, generating a new waveform based on the new set of sporadic data samples and the truncated waveform, and displaying the new waveform.

30. A method comprising:

emitting light pulses into a tissue of a patient via an emitter of a pulse oximetry sensor at an average frequency and an average pulse width over a period of time;

generating, via a detector of the pulse oximetry sensor, a set of data samples indicative of a physiological signal of the patient based on the light pulses that passed through the tissue of the patient, wherein the average frequency and the average pulse width cause the detector to generate the set of data samples comprising an average sampling frequency less than twice the Nyquist frequency of the physiological signal over the period of time;

wirelessly transmitting the set of data samples from the pulse oximetry sensor to a processor;

selecting, using the processor, a function based on the set of data samples;

iteratively calculating a residual and an approximation based on the selected function;

generating a waveform, based on the approximation, that corresponds to the physiological signal; and

calculating, using the processor, a physiological parameter based on the waveform.

31. The method of claim 30, wherein the average frequency is between approximately 100 to 700 milliseconds and the average pulse width is between approximately 10 to 50 milliseconds.

32. The method of claim 30, comprising emitting the light pulses at irregular intervals over the period of time, thereby causing the set of data samples to include data samples spread at irregular intervals over the period of time.