Plethysmographic respiration rate detection

• US 10,098,550 B2
• Filed: 04/11/2016
• Issued: 10/16/2018
• Est. Priority Date: 03/30/2010
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Al-Ali, Ammar, Majmudar, Anmol
• Primary Examiner(s): Mallari, Patricia
• Assistant Examiner(s): TOTH, KAREN E
• Application Number:
  US15/095,912
• Publication Number:
  US 20160287090A1
• Time in Patent Office: 918 Days
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/0806 by whole-body plethysmography measuring blood flow using plethysmography A61B5/0295; impedance plethysmography A61B5/053; measuring volume of the body or parts thereof A61B5/1073
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• 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 5/7405 using sound
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/746 : Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61B 5/7475 : User input or interface means, e.g. keyboard, pointing device, joystick
• CPC Class Codes: G16H 15/00 : ICT specially adapted for medical reports, e.g. generation or transmission thereof
• CPC Class Codes: G16H 50/00 : ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics
• CPC Class Codes: G16H 50/30 : for calculating health indices; for individual health risk assessment

Abstract

A plethysmographic respiration processor is responsive to respiratory effects appearing on a blood volume waveform and the corresponding detected intensity waveform measured with an optical sensor at a blood perfused peripheral tissue site so as to provide a measurement of respiration rate. A preprocessor identifies a windowed pleth corresponding to a physiologically acceptable series of plethysmograph waveform pulses. Multiple processors derive different parameters responsive to particular respiratory effects on the windowed pleth. Decision logic determines a respiration rate based upon at least a portion of these parameters.

Claims

1. A respiration rate detection method comprising:

identifying a portion of a plethysmograph waveform which includes a physiologically acceptable series of plethysmograph waveform pulses;

deriving, using one or more processors, a plurality of different frequency spectrums from the portion of the plethysmograph waveform using a plurality of different techniques, each of the plurality of different frequency spectrums responsive to at least one respiratory effect on the portion of the plethysmograph waveform and including a plurality of local maximums, the plurality of different frequency spectrums comprising a first frequency spectrum and a second frequency spectrum,

wherein the first frequency spectrum is one of;

a baseline frequency spectrum responsive to a respiratory-induced baseline shift of the portion of the plethysmograph waveform,

an amplitude modulation (AM) frequency spectrum responsive to a respiratory-induced amplitude modulation of the portion of the plethysmograph waveform, and

a shape modulation (SM) frequency spectrum responsive to a respiratory-induced shape modulation of the portion of the plethysmograph waveform,

wherein second frequency spectrum is different from the first frequency spectrum and is one of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum;

determining whether the local maximums of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within a tolerance; and

generating a respiration rate from determining that at least one local maximum of each of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within the tolerance.

2. The respiration rate detection method of claim 1, further comprising:

generating a plurality of respiration rates from portions of the plethysmograph waveform; and

deriving a smoothed respiration rate from the plurality of respiration rates and the respiration rate.

3. The respiration rate detection method of claim 2, further comprising rejecting an additional respiration rate in response to determining that the additional respiration rate differs from the smoothed respiration rate by more than an amount.

4. The respiration rate detection method of claim 1, wherein the respiration rate is a frequency of one of the local maximums of the first frequency spectrum.

5. The respiration rate detection method of claim 1, further comprising identifying frequencies of the local maximums of the first frequency spectrum relative to a frequency corresponding to a pulse rate, wherein said determining whether the local maximums of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within the tolerance comprises comparing individual local maximums of the first frequency spectrum and individual local maximums of the second frequency spectrum in an order based at least on the identified frequencies of the local maximums of the first frequency spectrum relative to the frequency corresponding to the pulse rate.

6. The respiration rate detection method of claim 1, wherein said determining whether the local maximums of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within the tolerance comprises comparing individual local maximums of the first frequency spectrum and individual local maximums of the second frequency spectrum in an order based at least on magnitudes of the local maximums of the first frequency spectrum.

7. The respiration rate detection method of claim 1, further comprising outputting the respiration rate for presentation on a display to a user.

8. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the baseline frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform; and

generating the baseline frequency spectrum from the first conditioned pleth.

9. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the AM frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform;

demodulating the conditioned pleth to generate a demodulated pleth; and

generating the AM frequency spectrum from the demodulated pleth.

10. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the SM frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform;

generating a modulated metric from the conditioned pleth; and

generating the SM frequency spectrum from the modulated metric.

11. The respiration rate detection method of claim 1, wherein the plurality of different frequency spectrums comprises a third frequency spectrum, and further comprising:

determining whether the local maximums of the first frequency spectrum, the second frequency spectrum, and the third frequency spectrum occur at matching frequencies within the tolerance; and

generating the respiration rate from determining that at least one local maximum of each of the first frequency spectrum, the second frequency spectrum, and the third frequency spectrum occur at matching frequencies within the tolerance,

wherein third frequency spectrum is different from the first frequency spectrum and the second frequency spectrum, and the third frequency spectrum is one of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum.

12. The respiration rate detection method of claim 11, further comprising:

generating a plurality of respiration rates from portions of the plethysmograph waveform; and

deriving a smoothed respiration rate from the plurality of respiration rates and the respiration rate.

13. The respiration rate detection method of claim 12, further comprising rejecting an additional respiration rate in response to determining that the additional respiration rate differs from the smoothed respiration rate by more than an amount.

14. The respiration rate detection method of claim 11, wherein the respiration rate is a frequency of one of the local maximums of the first frequency spectrum.

15. The respiration rate detection method of claim 11, further comprising outputting the respiration rate for presentation on a display to a user.

16. The respiration rate detection method of claim 11, wherein the first frequency spectrum is the baseline frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform; and

generating the baseline frequency spectrum from the first conditioned pleth.

17. The respiration rate detection method of claim 11, wherein the first frequency spectrum is the AM frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform;

demodulating the conditioned pleth to generate a demodulated pleth; and

generating the AM frequency spectrum from the demodulated pleth.

18. The respiration rate detection method of claim 11, wherein the first frequency spectrum is the SM frequency spectrum, and said deriving comprises:

generating a conditioned pleth from the portion of the plethysmograph waveform;

generating a modulated metric from the conditioned pleth; and

generating the SM frequency spectrum from the modulated metric.

19. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the baseline frequency spectrum, and the second frequency spectrum is the SM frequency spectrum.

20. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the AM frequency spectrum, and the second frequency spectrum is the SM frequency spectrum.

21. The respiration rate detection method of claim 1, wherein the first frequency spectrum is the baseline frequency spectrum, and the second frequency spectrum is the AM frequency spectrum.

22. The respiration rate detection method of claim 21, further comprising generating the respiration rate from determining that at least one local maximum of each of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within the tolerance and determining that an additional condition is met.

23. A respiration rate detection method comprising:

identifying a portion of a plethysmograph waveform which includes a physiologically acceptable series of plethysmograph waveform pulses;

deriving, using one or more processors, a plurality of different frequency spectrums from the portion of the plethysmograph waveform using a plurality of different techniques, each of the plurality of different frequency spectrums responsive to at least one respiratory effect on the portion of the plethysmograph waveform and including a plurality of local maximums, the plurality of different frequency spectrums comprising a first frequency spectrum and a second frequency spectrum,

wherein the first frequency spectrum is one of;

a baseline frequency spectrum responsive to a respiratory-induced baseline shift of the portion of the plethysmograph waveform,

an amplitude modulation (AM) frequency spectrum responsive to a respiratory-induced amplitude modulation of the portion of the plethysmograph waveform, and

a shape modulation (SM) frequency spectrum responsive to a respiratory-induced shape modulation of the portion of the plethysmograph waveform,

wherein second frequency spectrum is different from the first frequency spectrum and is one of the baseline frequency spectrum, the AM frequency spectrum, and the SM frequency spectrum;

determining whether the local maximums of the first frequency spectrum and the second frequency spectrum occur at matching frequencies within a tolerance by comparing the local maximums of the first frequency spectrum and the second frequency spectrum until;

(1) determining that one local maximum of the first frequency spectrum and one local maximum of the second frequency spectrum occur at matching frequencies within the tolerance;

or (2) determining that none of at least two of the local maximums of the first frequency spectrum and none of at least two of the local maximums of the second frequency spectrum occur at matching frequencies within the tolerance; and

generating a respiration rate in response to determining that one local maximum of the first frequency spectrum and one local maximum of the second frequency spectrum occur at matching frequencies within the tolerance.

24. The respiration rate detection method of claim 23, further comprising generating no respiration rate in response to determining that none of the at least two of the local maximums of the first frequency spectrum and none of the at least two of the local maximums of the second frequency spectrum occur at matching frequencies within the tolerance.