Nocturnal Oxygen Desaturation in Sickle Cell Anemia-Reply

In Reply.—  We agree with Dr Walsh et al that the relationship between sleep-related oxygen desaturation and sickle cell disease warrants further study. Our findings do not presume that the nocturnal desaturation is necessarily a primary abnormality of sickle cell disease but rather that it is related to some degree of secondary chronic pulmonary dysfunction, which commonly occurs in these patients. In either case, however, we maintain that sleep-related desaturation may increase the vulnerability of such patients by initiating further sickling and vaso-occlusion.It is true that the enlarged tonsils in patient 1 might lead one to propose that the desaturation was caused by an insidious obstructive apnea. However, we did restudy patient 1 after tonsillectomy and adenoidectomy using a transcutaneous partial oxygen pressure monitor. We also found that Po₂ levels fell during sleep from a baseline of 67 mm Hg to a level of 30 to 40 mm