Quantifying cardio-respiratory phase synchronization - A comparison of five methods using ECGs of post-infarction patients

Anja Kuhnhold, Aicko Y. Schumann, Ronny P. Bartsch, Romy Ubrich, Petra Barthel, Georg Schmidt, Jan W. Kantelhardt

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Objective: Phase synchronization between two weakly coupled oscillators occurs in many natural systems. Since it is difficult to unambiguously detect such synchronization in experimental data, several methods have been proposed for this purpose. Five popular approaches are systematically optimized and compared here. Approach: We study and apply the automated synchrogram method, the reduced synchrogram method, two variants of a gradient method, and the Fourier mode method, analyzing 24h data records from 1455 post-infarction patients, the same data with artificial inaccuracies, and corresponding surrogate data generated by Fourier phase randomization. Main results: We find that the automated synchrogram method is the most robust of all studied approaches when applied to records with missing data or artifacts, whereas the gradient methods should be preferred for noisy data and low-accuracy R-peak positions. We also show that a strong circadian rhythm occurs with much more frequent phase synchronization episodes observed during night time than during day time by all five methods. Significance: In specific applications, the identified characteristic differences as well as strengths and weaknesses of each method in detecting episodes of cardio-respiratory phase synchronization will be useful for selecting an appropriate method with respect to the type of systematic and dynamical noise in the data.

Original languageEnglish
Pages (from-to)925-939
Number of pages15
JournalPhysiological Measurement
Issue number5
StatePublished - May 2017

Bibliographical note

Publisher Copyright:
© 2017 Institute of Physics and Engineering in Medicine.


  • cardio-respiratory coupling
  • circadian rhythm
  • phase synchronization


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