DETECTION OF APNEAS, HYPOPNEAS AND AROUSALS BY THE AUTOSET IN THE SLEEP APNOEA HYPOPNOEA SYNDROME/

Limited sleep study systems are increasingly being used to diagnose th e sleep apnoea/hypopnoea syndrome, but validation is essential and det ection of arousal's desirable. One such system (AutoSet) was validated on an event-by-event basis, and the hypothesis that sudden large brea ths detected by this system mark arousal from sleep was also examined. Twenty consecutive patients (apnoea/hypopnoea index (AHI) 39+/-6 (SEM )) underwent polysomnography (PSG), which included real-time signals o f AutoSet (Version 3.03) scored events. PSG respiratory events were de fined using airflow and thoracoabdominal movement and AutoSet events u sing nasal pressure. All apnoeas were scored by both systems, but 41% mote hypopnoeas were scored on PSG and these were clinically significa nt, with 78% ending in cortical arousal. Twenty per cent of apnoeas an d hypopnoeas scored by the AutoSet occurred during wakefulness. Large breaths, defined as a two-thirds increase in ventilation, marked 77% o f respiratory-associated but only 9% of spontaneous arousals. Large br eaths also marked 48% of ''autonomic'' arousals following respiratory events without visible electroencephalographic changes. Twenty-seven p er cent of large breath's occurred during wakefulness. This study show s that the AutoSet and the standard polysomnographic approach differ i n their detection of hypopnoeas. The AutoSet underdetected hypopnoeas during sleep, but also included some hypopnoeas occurring during wakef ulness. Detection of large breaths may potentially be useful for ident ifying respiratory arousals. Detection of periods of wakefulness may i mprove the accuracy of the system.