Effects of a synthetic lung surfactant on pharyngeal patency in awake human subjects.

We examined the effects of separate applications of saline and a synthetic lung surfactant preparation (Surf; Exosurf Neonatal) into the supraglottic airway (SA) on the anteroposterior pharyngeal diameter (Dap) and the airway pressures required to close (Pcl) and reopen (Pop) the SA in five awake normal supine subjects. Dap, Pcl, and P(op) were determined during lateral X-ray fluoroscopy and voluntary glottic closure when pressure applied to the SA lumen was decreased from 0 to -20 cmH2O and then increased to +20 cmH2O. After Surf application and relative to control, Dap was larger for most of the applied pressures, Pcl decreased (-12.3 +/- 1.9 to -18.7 +/- 0.9 cmH2O; P < 0.01), P(op) decreased (13.4 +/- 1.9 to -6.0 +/- 3.4 cmH2O; P < 0.01), and genioglossus electromyographic activity did not change (P > 0.05). Saline had no effect. These observations suggest that pharyngeal intraluminal surface properties are important in maintaining pharyngeal patency. We propose that surfactants enhance pharyngeal patency by reducing surface tension and adhesive forces acting on intraluminal SA surfaces.