Influence of cerebral activity in wakefulness on regulation of breathing

Thirteen healthy men, unaware of the objectives of this study, underwent passive or active overventilation lowering the end-expiration carbon dioxide tension to 25 mm. Hg or below. At the end of the period of hyperventilation, rhythmic respiration continued uninterrupted at approximately the control frequency. The volume of ventilation was above control during the first minute of recovery and then stabilized at about two-thirds of the control volume; it continued at this level for over 10 minutes during which time the end-expiration PCO2 gradually rose toward the control level. No instance of periodic breathing occurred. The absence of overventilatory apnea in the waking condition contrasts with its easy elicitation during general anesthesia. It is concluded that cerebral activity associated with wakefulness is a component of the normal respiratory drive, and that carbon dioxide acts by augmenting the effects of this component. Submitted on June 27, 1960