[Nap polysomnography: sufficient grounds for initiating CPAP treatment?]

Nap polysomnography (NPSG) is a technique for rapid diagnosis of sleep apnea-hypopnea syndrome (SAHS). Although an apnea-hypopnea index (AHI) over 10 indicates a diagnosis of SAHS, treatment with nasal continuous positive airway pressure (CPAP) starts when the AHI exceeds 30.

To determine the diagnostic yield of NPSG for initiating CPAP and to evaluate the different types of polysomnographic findings.

Two hundred ninety-six patients suspected of having SAHS underwent NPSG lasting three hours. NPSG findings were considered positive at AHI > 30; normal at AHI < 10 with non-REM and REM sleep (more than 10%); invalid if the patient slept less than 60 minutes; and inconclusive if AHI was between 10 and 30 with REM, if AHI was < 30 without REM, or if upper airway resistance syndrome (UAS) was suspected. Positive and normal polysomnographic findings were considered diagnostic and the invalid and inconclusive findings were considered non-diagnostic. We also observed whether SAHS was predominantly obstructive, predominantly hypopneic, central-mixed, central-obstructive or miscellaneous, based on the type of event detected mot often during NPSG.

Seventy percent of the NPSG were diagnostic (55% positive and 15% normal) and 30% were not (12% invalid and 18% inconclusive). Fifty-five percent of the positive NPSGs were predominantly obstructive, 29% were predominantly hypopneic, 8% were central-mixed, 4% were central-obstructive and 4% were miscellaneous.

The diagnostic value of NPSG for initiating CPAP treatment is high. Predominantly hypopneic forms are particularly common.