Synchronization of respiration.

In order to study synchronization of respiration, three different videofragments were presented to 21 normal subjects. Each fragment showed a 'therapeutic interview' specially performed for this purpose, with a 'patient' breathing in a particular way. The respiration of model 1 was deep, slow and clearly audible, the pattern of model 2 was rapid, superficial and slightly audible and that of model 3 was normal and hardly perceptible. The fragments were presented in three different sequences and each sequence was followed by seven subjects. Respiration amplitude (Vt), respiration irregularity (SD of Vt), respiration frequency (RF) and frequency of skin conductance responses (SCRF) were measured. Changes in mean values of these variables were demonstrated during the fragments; an increase in RF was the most pronounced and reliable change. These 'overall' physiological changes did not support the synchronization hypothesis, nor were they at variance with it: they seemed to be effects of attention. A detailed (cycle by cycle) analysis did reveal a synchronization effect in fragment 1. The number of cycles in the subject which were in rhythm with the model's respiration was significantly larger than could have been expected by chance. The effect of synchronization, however, was small and transient as it did not affect the mean RF and Vt of fragment 1.