Sleep studies for sleep-related breathing disorders.

Our understanding of sleep-related breathing disorders is still in a period of rapid change. Considerable uncertainty exists in several major areas of patient assessment. Although early definitions of sleep apnoea enshrined the concept of rigid guidelines, such an approach is no longer helpful, and may constrain potential advances. The recognition of the basic pathophysiological events in obstructive sleep apnoea (OSA) has evolved from purely apnoeas, to include hypopnoeas, and now to increased upper airway resistance alone. Our view as to the significant consequences of such respiratory events has also evolved from alterations to the classic sleep architecture, to hypoxic events, and now to micro-arousals and cardio-vascular events. The exact nature of a significant arousal is also far from clear, with the suggestion that perhaps even EEG based approaches to their measurement may not be telling us the whole story. Finally, the frequency of such respiratory events and their consequences, that lead to significant symptoms and long-term damage, is not known either. Thus, given this situation, the best we can achieve is broad guidelines that stress the main important physiological events and their consequences that need to be assessed, and then interpreted in conjunction with the patient's symptoms. This will not necessarily be the same for all patients and this report offers some general guidance, based on the experience of several centres throughout Europe.