Because in many locations the demand for sleep studies exceeds resources, we evaluated the utility of split-day in-laboratory studies (SDS) in highly selected patients.

We studied 100 eligible cases: 68 males (age 48.6±1.3 [standard error, se] years, body mass index (BMI): 32.6±0.8kg/m²) and 32 females (age 50.9±2.4 years, BMI: 36.3±1.3kg/m²) with severe subjective sleepiness (Epworth sleepiness scale: ESS≥16) and suspected obstructive sleep apnea syndrome (OSAS).

There were 86 conclusive studies that yielded both a diagnosis and sufficient information for management (86.0%) and 14 inconclusive studies that did not yield sufficient information for management (14.0%). In six cases (6.0%) with an inconclusive study a diagnosis was made, however, no titration data was obtained. Thus a definitive diagnosis was obtained in 92.0% of all cases. Those with inconclusive studies had additional assessment, and eight of them ultimately had a final diagnosis of a sleep breathing disorder (SBD) and six had another sleep disorder: four had narcolepsy, one had a movement disorder, one had sleep deprivation. Thus there were six patients (6.0%) in whom SDS yielded only an SBD diagnosis but there was insufficient data for titration; two patients (2.0%) who ultimately had severe OSAS who were not diagnosed on SDS.

SDS was found to be useful in the evaluation and treatment of highly selected patients with severe daytime sleepiness (ESS≥16) and suspected OSAS.