Flextube reflectometry for level diagnosis in patients with obstructive sleep apnoea and snoring

The aim of this study was to use sound reflections in a flexible tube (flextube reflectometry) for identifying the predominant obstructive level of the upper airway in a series of patients referred to a sleep clinic. We also wished to study the relationship between the number of flextube narrowings per hour recording and the RDI (respiratory disturbance index = apnoeas and hypopneas per hour recording) by ResMed AutoSet (AS), which is a device based on nasal pressure variations. We performed sleep studies on 54 patients referred for snoring or OSA; 1) at home with AS; 2) in hospital using flextube reflectometry and AS simultaneously. The predominant obstructive level of the upper airway was retropalatal in 15 of the patients and retrolingual in 25 of the patients determined by flextube reflectometry. In 14 there was no predominant level of narrowing. We found a statistically significant correlation between the number of flextube narrowings per hour recording and the RDIs by the AS (Spearman's correlation coefficient r = 0.62, p < 0.001, n = 54). Flextube reflectometry may provide useful information regarding the level of obstructive predominance during obstructive events. The method also determines the frequency of respiratory disturbances and records snoring sound.