Maximum and minimum contact angles induced by pulmonary surfactants.

Abstract

Maximum and minimum contact angles have been determined by comparing the Wilhelmy method and the du Nouy method using a Langmuir trough. Under physiological conditions, including 100 per cent relative humidity at 37°C and compression to 75 per cent and 85 per cent of the initial surface area, application of a surfactant film increased both maximum and minimum contact angles in all cases. Maximum (advancing) contact angles, measured by raising the fluid level, gave mean values of up to 41·6° for DPPE and 34·5° for DPL, whereas minimum (receding) contact angles, measured by lowering the fluid level, gave mean values of up to 39·0° and 27·1° for DPPE and DPL, respectively. These results indicate that pulmonary surfactants have the capability of decreasing the hydrophilic nature of tracheal epithelium.