Phase response curve analysis of heart rate variability with differing breathing rates

The phase response curve (PRC) method, which quantitatively and visually analyzes heart rate variability (HRV), is presented. This method tracks moment-to-moment interactions between heart rate and respiration as two coupled systems and quantifies the strength of this coupling. It also allows for the quantitation of stimulus amplitude or depth of respiration. The phase plane plot gives a visual idea of the time dynamics, and at fast breathing rates, the differences are quite noticeable. The differences in the PRC seen in three packed breathing rates are presented. Thirteen subjects performed the breathing protocol at 8, 12 and 18 breaths per minute (BPM) in the seated position