Upper airway collapsibility and cephalometric variables in patients with obstructive sleep apnea

Increased pharyngeal collapsibility and abnormal anatomic structures have b een postulated to contribute to the pathophysiology of obstructive sleep ap nea (OSA) syndrome. It is unclear whether the abnormal craniofacial and sof t tissue features may affect the pharyngeal collapsibility and contribute t o the apnea density. In the present study we examine the relationship betwe en pharyngeal collapsibility and cephalometric variables in a group of 57 m ale OSA patients. Pharyngeal collapsibility was measured during the night o f nasal continuous positive airway pressure (nCPAP) titration by analyzing the pressure-flow relationship. Pharyngeal critical pressure (Pcrit) was ca lculated as the extrapolated pressure at zero flow. The patients, age 52.0 +/- 9.0 yr, had an average apnea-hypopnea index (AHI) of 72.6 +/- 31.8 and a mean Pcrit of 2.4 +/- 1.0 cm H2O. A significant correlation was found bet ween Pcrit and the soft palate length (SPI) (r = 0.27, p = 0.04), the dista nce from the hyoid bone to the posterior pharyngeal wall (H-Ph) (r = 0.29, p = 0.03), and the distance from the hyoid bone to posterior nasal space (H -Pns) (r = 0.32 p = 0.02). While in obese patients Pcrit was related to SPI and neck circumference, the distance of the hyoid bone to the mandibular p lane (H-MP) affected Pcrit in nonobese patients. Our results show that both pharyngeal soft tissue abnormalities and the lower position of the hyoid b one affect Pcrit in OSA patients, suggesting that an anatomic narrowing con tributes to the upper airway collapsibility.