Altered surface tension of lung extracts and lung mechanics

Abstract

Reduction of the surface area of 24 extracts of rabbit lungs by four-fifths decreased the surface tension to a minimum value of 0–5 dynes/cm at 18–22 C. However, minimum surface tension was above 15 dynes/cm if 1) the temperature was raised to 42 C, 2) the extract was prepared with distilled water, 3) phospholipase C was incubated with the extract, and 4) cholesterol or oleic acid was added to the surface. If blood or serum was added during the extraction, minimum surface tension was usually (although not invariably) elevated. Rinsing diluted rat serum or chylomicrons through the airways increases elastic recoil of excised rat lungs. Other reports show that heating a lung above 42 C or rinsing a solution of phospholipase C through the airways also increases elastic recoil of excised rat lungs. Therefore, these conditions alter the surface tension of lung extracts and the pressure-volume characteristics of the lungs concordantly. In addition, we found that the surface tension of lung extracts was not stable below 24 dynes/cm. Similar instability of the surface within the lung should lead to gradual atelectasis if a low transpulmonary pressure is maintained. elastic recoil; atelectasis; compliance; lung surface Submitted on January 21, 1965