• Pimon Ruttanaumpawan, Alexander G Logan, John S Floras, T Douglas Bradley, and CANPAP Investigators.
• University of Toronto, Toronto, ON, Canada.
• Sleep. 2009 Jan 1; 32 (1): 91-8.

Study ObjectivesAt termination of obstructive apneas, arousal is a protective mechanism that facilitates restoration of upper airway patency and airflow. Treating obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) reduces arousal frequency indicating that such arousals are caused by OSA. In heart failure (HF) patients with central sleep apnea (CSA), however, arousals frequently occur several breaths after apnea termination, and there is uncertainty as to whether arousals from sleep are a consequence of CSA. If so, they should diminish in frequency when CSA is attenuated. We therefore sought to determine whether attenuation of CSA by CPAP reduces arousal frequency.DesignRandomized controlled clinical trial.Patients And SettingWe examined data from 205 HF patients with CSA (apnea-hypopnea index [AHI] > or =15, > 50% were central) randomized to CPAP or control who had polysomnograms performed at baseline and 3 months later.Measurements And ResultsIn the control group, there was no change in AHI or frequency of arousals. In the CPAP-treated group, the AHI decreased significantly (from [mean +/- SD] 38.9 +/- 15.0 to 17.6 +/- 16.3, P < 0.001) but neither the frequency of arousals nor sleep structure changed significantly.ConclusionThese data suggest that attenuation of CSA by CPAP does not reduce arousal frequency in HF patients. We conclude that arousals were not mainly a consequence of CSA, and may not have been acting as a defense mechanism to terminate apneas in the same way they do in OSA.

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