Sleep-related breathing disorders: definitions and measurements.

sleep medicine from around the world for the specific purpose of developing recommendations for the definition of clinical syndromes related to sleep-related breathing disorders in adults, and also to provide recommendations concerning the most appropriate measurement techniques to be used in the evaluation of these disorders. The work of the Task Force involved a number of meetings of the members, including working groups to evaluate particular aspects of the brief in detail. In addition, feedback was sought from members of the participating societies, usually by means of open discussion forums during annual meetings of the relevant societies. Finally, peer review of the draft report was obtained from a large number of outside experts. The final report was published in the journal Sleep in late 1999 [6], and has been described by many as a landmark in the evolution of the approach to the diagnosis and assessment of sleep-related breathing disorders. In addition to sleep apnoea syndrome, the report also addressed other sleep-related breathing disorders such as upper airway resistance syndrome, Cheyne‐Stokes respiration, and sleep hypoventilation syndrome. Standard approaches to the evaluation of levels of evidence were utilized in the evaluation of the scientific literature relevant to each aspect of the brief. In some instances, the scientific literature available allowed clear evidence-based recommendations to be provided in the report. In other instances, the scientific literature was regarded as sufficiently weak that no clear evidence-based recommendations could be provided. In these circumstances, recommendations were made by a consensus drawn from the task force membership as a whole. The Task Force considered the potential clinical significance of recurring episodes of increased upper airway resistance associated with arousal and sleep fragmentation, but not apnoea or hypopnoea, as originally described by GUILLEMINAULT et al. [7]. The Task Force agreed that these upper airway resistance episodes should be called respiratory effort-related arousals (RERA) and be considered part of obstructive sleep apnoea/hypopnoea syndrome (OSAHS). The definition of hypopnoea has been variable and unclear for many years. An important recommendation was that a hypoponea should be scored in the case of a reduction in flow of >50% measured by a validated means, or a reduction of 30‐50% associated with either an arousal or a desaturation of >3%. The definition of OSAHS severity in the report categorizes the syndrome into mild, moderate and severe categories, with mild OSAHS including a combined apnoea, hypopnoea and RERA frequency of as low as 5 events.h -1 , providing other symptoms such as daytime sleepiness are also present. This diagnostic threshold is lower than many