Abstract: Objective To determine the sites of upper airway collapse by upper airway pressure measurements in subjects demonstrated to have obstructive sleep apnea (OSA) after uvulopalatopharyngoplasty (UPPP). Methods Nocturnal polysomnography and continuous upper airway pressure measurements with ApneaGraph were performed on 10 subjects with subjective snoring or excessive daytime sleepiness after UPPP. The ApneaGraph transducer catheter contained two pressure sensors and two temperature sensors used for determination of the obstruction sites and the apnoeic events during sleep. The obstructive sites were in the upper (retropalatal oropharynx) or lower levels( the retroglossal region). The lower limit of the upper airway obstruction was determined by the pressure patterns. The constituent ratio was used to reflect the obstructive proportion of different levels. The effects of posture on apnea hypopnea index(AHI) were also analyzed. Results 3 patients had moderate OSA and 7 patients had severe OSA. 6(60%) cases had predominant sites of obstructions in the upper level(the constituent ratio of the retropalatal obstruction ＞50%), and 4 patients(40%) in the lower level(the constituent ratio of the retroglossal obstruction＞50%). The supine AHI(66.52±22.51) was higher than the lateral AHI(47.82±21.82) and the difference between them was significant(P=0.017). Conclusion Upper airway pressure measurements can accurately identify the level of upper airway obstruction. Most patients with OSA following UPPP have the predominant obstructive sites at the retropalatal oropharynx and they tend to have more AHI in the supine position than in the lateral position.

Key words: Sleep apnea, obstructive, Uvulopalatopharyngoplasty, Manometry, Airway collapse