EFFECT OF SLOWED RESPIRATION ON CARDIAC PARASYMPATHETIC RESPONSE TO THREAT

The present study was designed to examine the effect of voluntarily sl owed respiration on the cardiac parasympathetic response to a threat: the anticipation of an electric shock. Thirty healthy college students were randomly assigned to the slow, fast, and nonpaced breathing grou ps (10 subjects each). Subjects in the slow and fast paced breathing g roups regulated their breathing rate to 8 and 30 cpm, respectively, an d those in the nonpaced breathing group breathed spontaneously. Immedi ately after the period of paced or nonpaced breathing for 5 minutes, t he subjects were exposed for 2 minutes to the anticipation of an elect ric shock during breathing paced at 15 cpm. The amplitude of the high frequency (HF) component of the heart rate variability, an index of ca rdiac parasympathetic tone, significantly decreased during the threat in the fast and nonpaced breathing groups, whereas it was unchanged in the slow paced breathing group. No significant difference was observe d among the three groups in the amplitude of respiration during the th reat. Results suggest that a slowed respiration decreases the cardiac parasympathetic withdrawal response to the threat. This study provides a rationale for the therapeutic uses of the slowed respiration maneuv er in attenuating the cardiac autonomic responses in patients with anx iety disorder.