[Brief polysomnographic studies in the diagnosis of the obstructive sleep apnea syndrome]

Firm diagnosis of obstructive sleep apnea syndrome (OSAS) is normally based on all-night-long polysomnograms, at considerable expenditure of time and money. Shorter studies have been proposed as an alternative. We have assessed the efficacy of polysomnograms recorded over the first three hours of nocturnal sleep (SN) for diagnosing OSAS and the results have been compared with those of polysomnograms recorded throughout the entire night (EN). Twenty-five male patients suspected of having OSAS were enrolled; 19 were diagnosed for OSAS by EN and 16 were diagnosed by SN, indicating 3 false negatives and a sensitivity of 84% for SS. No false positives were obtained by studying only the first three hours of sleep, indicating a specificity of 100%. Significant differences were found in minimum oxygen saturation (SatO2) and percent of total sleep time with intervals of SatO2 below 80%. We conclude that polysomnography during the first part of nocturnal sleep is a specific method for screening for OSAS and that, although this method's sensitivity is high, study should be continued throughout an entire night when results are negative. Desaturation levels may be underestimated in recordings lasting only the first half of the night.