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. Author manuscript; available in PMC: 2015 Feb 6.
Published in final edited form as: Comput Cardiol (2010). 2014 Sep;41:781–784.

Figure 3. RSA and phase synchronization (CRPS) are distinct forms of cardio-respiratory coupling and their strength depend differently on breathing frequency.

Figure 3

(a) RSA nonlinearly increases (> 250%) with decreasing breathing frequency, and drops abruptly for very low breathing frequencies (Spearman’s rank order correlation: ρ = −0.42, p < 10−3). (b) In contrast to RSA, the strength of CRPS (length of CRPS episodes) is independent of the breathing frequency (Spearman ρ ≈ 0, p < 10−3). Error bars represent the standard error. Data are averaged over all subjects during the entire sleep period.