The increasing awareness of sleep-disordered breathing (i.e obstructive sleep apnea) has created a growing demand for polysomnography (sleep study), resulting in excessive waiting times in many laboratories. Sleep centers have therefore needed to develop methods to improve their efficiency. Unfortunately many patients find it difficult to fall asleep in the unfamiliar environment of a laboratory setting (the "first-night effect"), circumstances that may prolong falling alseep and staying sleep. Likewise, intolerance of continuous positive airway pressure (CPAP) may also reduce the quality of the sleep study. Poor quality studies may lead to an inability to make a diagnosis or adequately titrate CPAP therapy. Unsatisfactory studies may need to be repeated.