State-dependent changes in the upper airway assessed by multidetector CT in healthy individuals and during obstructive events in patients with sleep apnea

Abstract

Objective: To determine whether airway narrowing during obstructive events occurs predominantly at the retropalatal level and results from dynamic changes in the lateral pharyngeal walls and in tongue position. Methods: We evaluated 11 patients with severe obstructive sleep apnea (OSA) and 7 healthy controls without OSA during wakefulness and during natural sleep (documented by full polysomnography). Using fast multidetector CT, we obtained images of the upper airway in the waking and sleep states. Results: Upper airway narrowing during sleep was significantly greater at the retropalatal level than at the retroglossal level in the OSA group (p < 0.001) and in the control group (p < 0.05). The retropalatal airway volume was smaller in the OSA group than in the control group during wakefulness (p < 0.05) and decreased significantly from wakefulness to sleep only among the OSA group subjects. Retropalatal pharyngeal narrowing was attributed to reductions in the anteroposterior diameter (p = 0.001) and lateral diameter (p = 0.006), which correlated with an increase in lateral pharyngeal wall volume (p = 0.001) and posterior displacement of the tongue (p = 0.001), respectively. Retroglossal pharyngeal narrowing during sleep did not occur in the OSA group subjects. Conclusions: In patients with OSA, upper airway narrowing during sleep occurs predominantly at the retropalatal level, affecting the anteroposterior and lateral dimensions, being associated with lateral pharyngeal wall enlargement and posterior tongue displacement.

Revaluing the role of the tongue in obstructive sleep apnea

“…In fact, the lateral pharyngeal wall is the site of insertion of the soft palate into the pharynx. Not surprisingly, Passos et al 3 found that, from wakefulness to sleep, lateral pharyngeal wall enlargement correlated significantly with retropositioning of the soft palate in all of the subjects studied.…”

“…In this issue of the JBP, Passos et al 3 present the results of multislice computed tomography of the airway in patients with OSA and healthy controls (mean apnea-hypopnea index of 57.1 events/h and 2.2 events/h, respectively) during wakefulness and monitored natural sleep. In the latter case, all control subjects maintained stable breathing during image acquisition, whereas the sleep-state images of the OSA group subjects were acquired during episodes of obstructive apnea or hypopnea, as confirmed by polysomnography.…”

“…To understand the dynamic changes in the airway that lead to obstructive events, Passos et al 3 evaluated the structures surrounding the pharynx. During sleep, the volume of the lateral pharyngeal wall increased significantly in OSA group subjects and did not change in control group subjects.…”

“…Studies involving imaging of the upper airway during sleep with concurrent polysomnography are still quite rare in the literature 4 . Therefore, Passos et al 3 are to be commended. The images in their study were obtained during natural sleep rather than by DISE.…”

“…Passos et al 3 speculated that, during sleep, the posterior displacement of the tongue would relax the palatoglossal arch and allow the folding and consequent increase in the volume of the lateral wall, as well as pushing the soft palate backwards, all of which, together, cause circumferential narrowing of the retropalatal airway. In that hypothesis, the tongue represents the leading mechanism of obstruction and causes the changes in the other pharyngeal structures.…”