Cardiac and respiratory activity in panic disorder: effects of sleep and sleep lactate infusions.

Abstract

This study examined cardiac and respiratory activity in panic disorder patients and healthy comparison subjects during sleep, when the effects of anxious cognition and expectancy set are minimized. Heart rate, respiratory rate, end-tidal PCO2, and oxygen saturation were recorded for 11 panic disorder patients and 12 comparison subjects before and during sleep and before and after infusions of sodium lactate and a saline control. Panic disorder patients had higher oxygen saturations than comparison subjects before sleep onset and during sleep stages 0 and 2 before any infusions. The two groups did not differ on other respiratory variables and heart rate. Panic disorder patients responded to lactate infusions during stage 3-4 sleep with greater increases in heart rate and oxygen saturation, and possibly in respiratory rate and end-tidal PCO2, than comparison subjects. The saline control infusion had little effect. These findings suggest that panic disorder patients have greater cardiac and respiratory reactivity than healthy comparison subjects during sleep, when the influence of cognitive factors is minimal or absent.