Central Sleep Apnea and Acetazolamide Therapy-Reply

In Reply. —Shore and Millman, together with Sharp et al, 1 have observed three patients with central sleep apnea that converted to obstructive apnea with acetazolamide administration. This phenomenon has several possible explanations. First, as suggested by Sharp et al, 1 the subclassification of apneas into obstructive and central may be inappropriate, as a patient's condition may convert from one form of apnea to another with changes in central respiratory drive. This, however, is not always the case, as our six patients demonstrated. A second explanation might be that the three patients of Shore and Millman and Sharp et al had a predisposition to obstructive apnea, with decreased upper-airway caliber. 2 As a result, with the increased respiratory drive produced by acetazolamide, greater inspiratory pressure developed, causing upper-airway collapse and obstruction. Finally, these three patients may originally have had obstructive sleep apnea. Over time, the recurrent hypoxia and hypercapnia resulting