Effect of different breathing patterns on nonlinearity of heart rate variability.

We studied the effects of different respiratory patterns, namely, spontaneous breathing, paced breathing (at a rate of 10 breaths/min and at their mean spontaneous breathing frequency) and breath holding, on the nonlinear characteristics of heart rate variability (HRV). The results showed that paced breathing at both rates significantly diminished the nonlinearity of HRV detected by the Volterra-Wiener series method in comparison with spontaneous breathing, while breath holding increased it. These findings indicate spontaneous breathing rate is probably optimum to maintain cardiopulmonary coupling nonlinearly, and thus to minimize the influence on cardiovascular variabilities.