Method of Extracting the Instantaneous Phases and Frequencies of Respiration from the Signal of a Photoplethysmogram

Ekaterina I. Borovkova, Vladimir I. Ponomarenko, Anatoly S. Karavaev, Elizaveta S. Dubinkina and Mikhail D. Prokhorov ()
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Ekaterina I. Borovkova: Institute of Physics, Saratov State University, 83 Astrakhanskaya St., 410012 Saratov, Russia
Vladimir I. Ponomarenko: Institute of Physics, Saratov State University, 83 Astrakhanskaya St., 410012 Saratov, Russia
Anatoly S. Karavaev: Institute of Physics, Saratov State University, 83 Astrakhanskaya St., 410012 Saratov, Russia
Elizaveta S. Dubinkina: Institute of Physics, Saratov State University, 83 Astrakhanskaya St., 410012 Saratov, Russia
Mikhail D. Prokhorov: Institute of Physics, Saratov State University, 83 Astrakhanskaya St., 410012 Saratov, Russia

Mathematics, 2023, vol. 11, issue 24, 1-14

Abstract: We propose for the first time a method for extracting the instantaneous phases of respiration from the signal of a photoplethysmogram (PPG). In addition to the instantaneous phases of respiration, this method allows for more accurately extracting the instantaneous frequencies of respiration from a PPG than other methods. The proposed method is based on a calculation of the element-wise product of the wavelet spectrum of a PPG and the sequence of intervals between the heartbeats extracted from a PPG, and a calculation of the skeleton of the resulting spectrum in the respiratory frequency range. It is shown that such an element-wise product makes it possible to extract the instantaneous phases and instantaneous frequencies of respiration more accurately than using the wavelet transform of a PPG signal or the sequence of the heartbeat intervals. The proposed method was verified by analyzing the signals from healthy subjects recorded during stress-inducing cognitive tasks. This method can be used in wearable devices for signal processing.

Keywords: instantaneous phases; instantaneous frequencies; photoplethysmogram; electrocardiogram; respiration; RR intervals; wavelet transform; cardiorespiratory interaction; wearable devices (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2023
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