Nocturnal panic: response to hyperventilation and carbon dioxide challenges.

To examine the role of ventilatory response in nocturnal panic, subjects experiencing nocturnal panic were compared with those who experienced daytime panic attacks only. In particular, measures of chronic hyperventilation (baseline pCO2) and CO2 hypersensitivity (response to ventilatory challenges) were assessed. Subjective and psychophysiological measures were obtained during baseline, forced hyperventilation, and carbon dioxide inhalation phases of a standardized laboratory-based assessment. The groups did not differ with respect to subjective or physiological measures or to the frequency with which panic occurred during the assessment. The results do not lend support to models that emphasize central CO2 hypersensitivity and chronic hyperventilation as primary mechanisms underlying nocturnal panic.