BREATH AND CARDIO RHYTHM

It is well-known that breathing has an impact on the modulation of the cardiac rhythm. Respiratory sinus arrhythmia (RSA) is heart rate variability in synchrony with respiration, by which the R-R interval on an ECG is shortened during inspiration and prolonged during expiration (fig. 5).

Fig. 5 : in a physiological breathing at rest, during the inspiration (downward curve), the cardiac rhythm increases;
it decreases during the expiration. The end of the inspiration seems to correspond at the highest cardiac rhythm
and the end of the expiration to the low cardiac rhythm.

When we recreate in real time the curve corresponding to the HF waveband, there is a perfect correlation with physiological breathing at rest (fig. 6.1).

Fig. 6.1 : the white curve corresponding to the HF waveband (in white) is in perfect phase with breathing. (in dark blue)

In this RSA, the size of the cardiac pulsations is inversely proportional to cardiac rhythm (HRV)

Fig. 6.2 : the red curve represents the size of the peaks of cardiac pulsations, the white one corresponding to the HF waveband,
the dark blue is breathing and the light blue HRV: the size of the pulsations increases with the inspiration.
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