Diagnosis of Sleep-Disordered Breathing by Half-Night Polysomnography

Abstract

We hypothesized that sleep-disordered breathing (SDB), defined by the apnea index (AI), the apnea + hypopnea index (A+H/I), or the desaturation event frequency (number of desaturations > 5%/h slept) (DEF), could be diagnosed after less than full-night polysomnography (PSG). Forty-eight consecutive full-night PSG sessions were evaluated by separately analyzing the first half (PSG-½) and the total (PSG-T) sleep time: 134.42 ± 35.7 and 277.15 ± 56.5 min (mean ± SD), respectively.PSG-½ and PSG-T were not different with respect to AI. The DEF was statistically but not clinically higher during PSG-½ (41.72 ± 41 versus 37.95 ± 35.8, p = 0.04). Sensitivities, specificities, and predictive values of each PSG-½ parameter were determined by comparing the values with those measured during PSG-T, using cutoff frequencies of both 5 and 10 events/h slept to define SDB. At a cutoff frequency of 10, sensitivities and positive predictive values were high for all PSG-½ parameters (range, 94.6 to 96.9%). The specificities of the DEF and AI during PSG-½ were also high (93.75 and 95%, respectively), but the negative predictive value of the DEF was substantially better (93.75 versus 83.3%). With SDB defined by 5 events/h slept, there also were high sensitivities (87.9 to 93%), positive predictive values (93.6 to 100%), and specificities (86.7 to 100%) for all parameters. Negative predictive values, however, were substantially reduced (62.5 to 76.5%).We conclude that PSG during 2 h of sleep is an appropriate method for evaluating SDB. A positive finding is a reliable basis for diagnosis regardless of which parameter or frequency cutoff is used to define SDB. A negative finding is most reliable when the definition of SDB is based on a DEF of ⩾ 10, and it is not reliable for any parameter when a cutoff fequency of 5 is used.