We thank Roy et al.1  for their relevant comments on our article.2  As Roy et al. correctly pointed out, head-of-bed elevation by 30 degrees did not significantly improve oxygenation variables such as mean nadir oxygen saturation measured by pulse oximetry (Spo2), lowest Spo2, and percent time Spo2 < 90% in our study although, Souza’s previous study demonstrated improvement of both apnea hypopnea index (15.7 to 10.7 events/h) and lowest Spo2 (83.5 to 87%) in symptomatic obstructive sleep apnea (OSA) patients with only 7.5-degree head-of-bed elevation.3  It would be easy to comment that different patient populations and study design are the cause of the difference. However, we consider that Roy’s question has an important pathophysiologic background calling the readers’ attention. First, Souza’s patients are more obese than ours (body mass index: 29.6 ± 4.8 vs. 26.3 ± 4.5...

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