Objective: To evaluate the mechanical load of retropalatal airway in obstructive sleep apnea patients, and to investigate the contributions of pharyngeal anatomy to upper airway collapsibility.
Methods: Static mechanical load of transpalatal pharynx was determined by opening pressure (Popen) of the segment during general anesthesia in 30 patients and 14 controls. Size of pharynx was measured while intraluminal pressure was controlled at 3-20 cm H2O (1 cm H2O = 0.09806 kPa) and the minimal intraluminal pressure that needed to compensate for the mechanical load of a retropalatal segment was determined.
Results: Pharyngeal cavity collapse at the level of the hard palate was observed in only one of the 30 subjects (3.3%), and in none of the 14 controls. At tongue base level, 23 subjects had a Popen > 0 cm H2O (76.7%) while in 7 of the controls (50.0%) had a Popen > 0 cm H2O. And at the level of the uvual and soft palate, pharyngeal collapses was observed in all subjects except in 9 of the controls (64.3%). The median of Popen was 8.3 [5.9;11.5] cm H2O in the patients group and was 2.7 [-3.9;6.0] cm H2O in the control group. Differences of Popen were significant between patients and controls (U = 58.500, P = 0.000). The correlation between Popen and AHI was also significant at 0.05 level (r = 0.377, P = 0.044).
Conclusions: Patients with sleep apnea have more collapsible passive upper airway than controls. Retropalatal and retroglossal airway are the most collapsible segments and positive pressures are needed to compensate for the mechanical loads.