Sigh rate and respiratory variability during normal breathing and the role of negative affectivity.

Spontaneous breathing was measured in healthy persons scoring either high (N=45) or low (N=30) on trait negative affectivity (NA), during a 10 min period of quiet sitting using the LifeShirt System®. Sighing and respiratory variability before and after sighs were assessed. Total respiratory variability of minute ventilation was indexed by the coefficient of variation and structured (correlated) variability was quantified by the autocorrelation. Total variability was higher before a sigh than before a non-sigh, without concomitant differences in structured variability, suggesting more random variability before a sigh. After a sigh, correlated variability increased whereas it remained the same after a non-sigh. Thus sighing acted as a resetter of the respiratory system. However, when comparing the low and the high NA group, this pattern was specific for high NA individuals. We conclude that it is important to take into account individual difference variables when studying the psychophysiological functions of sighing.