The Effect of Breathing at the Resonant Frequency on the Nonlinear Dynamics of Heart Rate

Abstract

Investigation of the nonlinear dynamics of the heart rate is crucial for understanding the physiological mechanisms of various functional states and understanding the adaptation capacity of the human body. The purpose of this study was to evaluate some quantitative parameters of the nonlinear parameters of resonance in the heart rate variability. The study included 70 healthy students who underwent paced breath training. The heart rate was recorded during breathing at different respiratory rates (spontaneous breathing, 4.5, 5, 5.5, 6, and 6.5 breaths/min). The resonant frequency was determined using heart-rate spectral analysis. Nonlinear analysis of HRV was performed using entropy measures (ApEn, SampEn, and MSE), Correlation dimension, Detrended Fluctuation Analysis (DFA), Recurrence Plot (REC, DET, Lmean, Lmax, and ShanEn), the Poincaré plot (SD1 and SD2), and time asymmetry (GI and P). We observed a decrease in the level of complexity, an increase in the self-similarity of the RR intervals, a decrease in the chaotic component, and an increase in rhythm asymmetry during breathing at resonant frequency.