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Nocturnal Home Oximetry in Detecting the Sleep Apnea-Hypopnea Syndrome and in Working Up Hypersomnolence
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IN RESPONSE:
Both correspondents question the utility of nocturnal home oximetry in identifying the cause of excessive daytime sleepiness. We agree that diurnal hypersomnolence can be a major clinical manifestation of several diseases. Our study, however, was not designed to evaluate nocturnal oximetry in patients with hypersomnia but in patients suspected of having the sleep apnea-hypopnea syndrome. In our experience and that of others, no correlation exists between the respiratory disturbances index and daytime sleepiness [2], which is present in fewer than 30% of patients with mild to moderate sleep apnea-hypopnea syndrome [3]. In men 30 to 60 years of age, the estimated prevalence of sleep-related abnormal breathing is 24%; only 22.6% of these patients have hypersomnolence [4]. We agree that our results cannot be extended to the general evaluation of patients reporting excessive daytime sleepiness.
Concerning the utility of nocturnal oximetry in the presence of sleep fragmentation caused by other sleep-related breathing disorders (such as the upper airway resistance syndrome), we found that 76% of patients with this syndrome had an abnormal oximetry recording consisting of small and regular desaturations. This finding confirms previous results that showed small changes in oxyhemoglobin arterial saturation when upper airway resistance increases [5]. A polysomnographic study combined with a multiple sleep latency test represents the gold standard in the evaluation of the sleep apnea-hypopnea syndrome; however, because of the dramatic increase in the number of patients who are referred for sleep disturbances, it is the responsibility of sleep centers to develop and validate shorter diagnostic methods and pretest evaluations to select patients needing complete sleep studies. We strongly believe that nocturnal home oximetry can play an important part in such strategies. We agree that patients whose complaint is primary hypersomnolence require complete sleep studies.
Frederic Series, MD
Yvon Cormier, MD
Hopital Laval; Sainte Foy, Quebec, G1V 4G5 Canada
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
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