Introduction In-laboratory Full Polysomnography (psg) with Manual Analysis Is Considered to Be the Gold Standard for the Diagnosis of Sleep

IN-LABORATORY FULL POLYSOMNOGRAPHY (PSG) WITH MANUAL ANALYSIS IS CONSIDERED TO BE THE GOLD STANDARD FOR THE DIAGNOSIS OF SLEEP APNEA-HYPOPNEA SYNDROME (SAHS).1 However the procedure is labor intensive and time consuming, and the capacity for PSG is limited considering the high prevalence of SAHS.2 Many portable recording devices intended to assess SAHS have been developed. The American Sleep Disorders Association has classified the recording devices into 4 categories of level 1 (standard polysomnography) to level 4 (singleor dual-bioparameter recording).3 There is a trade-off relationship between accuracy and convenience. Tracheal sound analysis has been used in some level 3 or level 4 devices. These devices detect periods of low tracheal sound intensity below an arbitrary threshold 4,5,6,8 or quiet periods that separate 2 snores defined by a high-intensity sound above an arbitrary threshold.7-9 The diagnostic accuracy of such a device has been reported to be relatively low when only 1 parameter from the tracheal sound analysis was employed.9 Therefore, most of these devices utilize not only parameters from tracheal sound analysis, but also those from other cardiorespiratory signals to detect abnormal breathing events.6-9 Tracheal sound analysis is also useful for the quantification of snoring.10 Moreover, Meslier et al11 have demonstrated that tracheal sound analysis can be used to identify respiratory efforts. Therefore, tracheal sound analysis is considered to have excellent potential in the evaluation of sleep-disordered breathing. We have developed a new system of tracheal sound analysis to detect sleep-disordered breathing,12 which seems to be relatively accurate but has yet to be fully validated. The algorithm used in this system is unique in that rather than detecting periods of low sound intensity below a fixed threshold, it detects fluctuations in the power of the tracheal sound. The aim of this study is to validate the system in a large number of consecutive subjects with suspected OSAHS.