Sustained preinspiratory cortical potentials during prolonged inspiratory threshold loading in humans

Abstract

Humans can program and control movements, including breathing-related movements. On the electroencephalogram (EEG), this preparation is accompanied by a low-amplitude negativity starting approximately 2.5 s before inspiration that is best known as a Bereitschaftspotential (BP). The presence of BPs has been described during the compensation of mechanical inspiratory loading, thus identifying a cortical involvement in the corresponding ventilatory behavior. The pathophysiological interpretation of this cortical involvement depends on its transient or enduring nature. This study addressed this issue by looking for BPs during sustained inspiratory loading (1 h). Nine healthy male volunteers were studied during unloaded quiet breathing and inspiratory threshold loading (with unloaded expiration). Analyses of EEG signal and ventilatory variables were used to compare beginning and end of sessions. Inspiratory threshold loading caused ventilatory modifications that persisted, unchanged, for an hour. The presence of a BP at the beginning and end of a session was the most frequent occurrence (6 of 9 cases with a 17-cmH2O threshold load; 8 of 9 cases with a 23-cmH2O load). These observations support the hypothesis that the cerebral cortex is involved in the compensation of sustained experimental inspiratory loading. How this translates to respiratory disease involving acute changes in respiratory mechanics remains to be determined.