Controlled study of respiratory responses during prolonged measurement in patients with chronic hyperventilation.

The respiratory responses of 17 patients with chronic hyperventilation but without demonstrable organic disease (group H) to various manoeuvres were compared with those of 21 healthy controls (group C). The responses were tested according to a 60 min protocol in which periods of rest were replaced by exercise, voluntary hyperventilation (VHV), reading, and CO2 inhalation. 5 patients with severe resting hypocapnia were investigated overnight during sleep. Chronic hyperventilation was of two types--persistent or provoked by exercise or VHV. It was due to modest increases in tidal volume and respiratory frequency but was generally not conspicuous. End-tidal PCO2 levels were gradually corrected to near normal during sleep but not by inhalation of CO2.