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. Author manuscript; available in PMC: 2012 Nov 14.
Published in final edited form as: Eur Respir J. 2009 Dec 23;36(3):569–576. doi: 10.1183/09031936.00153809

FIGURE 1.

FIGURE 1

Study protocol. Subjects were studied twice: during placebo and during pentobarbital treatment. Each study day, measurements were performed during wakefulness (before and after test-drug application) and sleep. During sleep, subjects were studied at atmospheric pressure first, to measure normal breathing and the respiratory response to inspiratory carbon dioxide insufflation. Subjects were then put on continuous positive airway pressure (CPAP) (3 mmHg) to avoid flow limitation, and negative-pressure ramps were performed until arousal. GG-EMG: genioglossus electromyography; Pcrit: critical closing pressure.