The Role of Surface Tension of Upper Airway Lining Liquid and Breathing Route in Sleep Disordered Breathing

This thesis examines the relationship between surface tension in the upper airway liquid, breathing route, and sleep disordered breathing. Upper airway surface tension values were examined in both healthy subjects and in those with obstructive sleep apnoea. To determine whether the enforced oral breathing route induced sleep disordered breathing via surface tension mediated mechanisms, healthy subjects were given exogenous surfactant with enforced oral route of breathing during sleep. The relationship between uncontrolled route of breathing and surface tension was then examined in subjects with severe obstructive sleep apnoea. Finally, exogenous surfactant and normal saline were administered to subjects to determine the presence of any therapeutic effect on obstructive sleep apnoea. The studies in this thesis i) described a range of surface tensions in healthy subjects, and in those with OSA, ii) investigated the role of breathing route on upper airway surface tension and OSA severity, and iii) investigated the role of exogenous surfactant as a therapeutic agent in both oral breathing induced sleep disordered breathing (in healthy subjects) and in subjects with mild to moderate obstructive sleep apnoea.