The analysis, by Sakaguchi et al., of the role of high-flow nasal oxygen administered postoperatively in those diagnosed with obstructive sleep apnea (OSA) in lieu of conventional continuous positive airway pressure therapy is interesting.1  We would welcome further commentary from the authors on a few points, however.

First, although we agree that high-flow nasal oxygen improves sleep time and oxygenation compared with simple oxygen therapy and overcomes upper airway obstruction in OSA via a continuous positive airway pressure–like effect, the institution of 30-degree head-of-bed elevation can also increase pulmonary functional residual capacity and reduce pharyngeal critical closing pressure. These are known to improve oxygenation and relieve upper airway obstruction postoperatively.2,3  Surprisingly, this was not observed here. Conversely, oxygenation in the 30-degree head-of-bed elevation group was inferior to that in the supine position (table 21 ). Curiously, although the combination of high-flow nasal oxygen and...

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