Pharyngeal size and shape during wakefulness and sleep in patients with obstructive sleep apnoea

Computed tomography has been used to study the pharyngeal airway during tidal breathing in wakefulness and during obstructive apnoeas in Non-REM sleep in patients with obstructive sleep apnoea. In supine subjects, contiguous transverse 10 mm sections were taken perpendicular to the posterior pharyngeal wall with a 2.1 s scan time. Studies during wakefulness showed that the narrowest section of the pharyngeal airspace was in the region posterior to the soft palate and that the minimal airway cross-sectional areas were significantly reduced in the group of patients with obstructive sleep apnoea compared to the group of control subjects without obstructive sleep apnoea. The studies during sleep showed that in all patients, the airspace posterior to the soft palate was a site of obstructive apnoeas. The length of the obstructed segment varied between patients, extending below the level of the soft palate in half the patient group. Airway narrowing and obstruction was due to posterior displacement of the soft palate and the tongue in the majority of patients, although lateral displacement of the pharyngeal walls was also observed. No occlusion was observed in the laryngopharynx although there was narrowing of oro- and laryngopharyngeal apertures below the site of obstruction during obstructive apnoeas. The size of the oropharyngeal airspace during wakefulness did not predict the presence of airway occlusion below the level of the soft palate when asleep. The variability between patients in the site(s) of upper airway obstruction during obstructive apnoeas have important implications for the choice of appropriate treatment in patients with obstructive sleep apnoea.