A79-11 Characterization of Palatal Prolapse During Polysomnography and Its Anatomical Correlations Using Upper Airway Computed Tomography

Rationale Obstructive sleep apnea (OSA) is characterized by recurrent episodes of upper airway obstruction during sleep. Expiratory flow limitation is common among OSA patients and is caused by palatal prolapse (PP). Expiratory cephalad movement of the soft palate leading to palatal prolapse causes nasopharyngeal obstruction and can be recognized as an abrupt reduction in nasal expiratory airflow. The frequency, mechanisms and anatomical determinants of PP have not been systematically examined. Understanding the relationship between PP, OSA severity, and upper airway anatomy could provide new insights into the pathophysiology of expiratory obstruction in OSA. We hypothesized that PP is common and associated with OSA severity and pharyngeal morphology. Methods Data from a previous study that assessed upper airway anatomy using computed tomography (CT) of men with and without OSA was analyzed. All subjects underwent in-lab polysomnography (PSG). Anthropometric data included age, weight, body-mass-index (BMI) and neck circumference. Expiratory flow limitation (EFL) was defined by the abrupt reduction of expiratory flow in nasal pressure cannula signal during at least three consecutive breaths. EFL index (EFLI) was calculated as the ratio between number of EFL events and total sleep time. OSA was defined by an apnea-hypopnea index (AHI) > 15 events/h. Anatomical structures involved in PP were analyzed through upper airway CT: retropalatal and retroglossal dimensions, soft palate length, presence of air between tongue and the soft palate and tongue volume. Anthropometric data, OSA severity and tomographic variables were compared between two groups according to the median EFLI. Partial correlation analysis controlled for AHI was used to test the association between EFLI, anthropometric variables, OSA severity and tomographic variables. Results The sample was composed of overweight middle-aged men with moderate OSA. PP was observed in 45 out of 46 OSA patients and in 16 out of 18 subjects without OSA. and anthropometric, respiratory and anatomical variables are displayed in Table 1. EFLI was associated with AHI (R = 0.329;P=0.008), retroglossal area (R=-0.258;P=0.043) and with lateral retroglossal dimension (R=-0.266; P = 0.037). EFLI and AHI were higher in the supine than in the lateral position (P < 0.001). Conclusions PP occurred in subjects with and without OSA and was associated with OSA severity. A smaller retroglossal airway may facilitate the decoupling between the tongue and the soft palate during expiration. The predominance in supine position highlights the contribution of gravitational and anatomical factors in the genesis of PP. This abstract is funded by: None