Can eucapnic hyperventilation prolong a subsequent breath-hold?

ABSTRACT

Previous studies have shown that, upon breaking a maximal breath-hold (BH), reinhalation of the expired gas allows an additional period of breath-holding. This indicates that mere ventilatory movements can diminish the urge to breathe. We sought to determine if vigorous ventilations, performed immediately prior to a maximal BH and in such a way that CO2 stores are not changed, can prolong a subsequent BH. Maximal BHs were accomplished with and without a preceding period of hyperventilation. The gas breathed during hyperventilation was air with 4.37% CO2, or oxygen containing either 0.04% CO2 (hypocapnic hyperventilation) or 4.37% CO2 (eucapnic hyperventilation). During hyperventilation, expired minute volume and frequency were clamped at 60 L/min and 30 breaths/min, respectively. End-tidal and transcutaneous CO2 tensions were monitored. Eucapnic hyperventilation did not prolong maximal BHs. Therefore, the ventilatory movements of hyperventilation do not appear to affect the duration of a subsequent maximal BH if these movements are not accompanied by changes in CO2 stores.