Effect of intra-alveolar fluid on pulmonary surface tension properties

In 17 anesthetized dogs, 50–150 ml of isotonic saline or human amniotic fluid were instilled into a degassed lobe and after 2–6 hr of spontaneous or artificial ventilation, the lungs were excised. Static pressure-volume and extract surface tension values were then determined on a fluid- and a nonfluid-instilled lobe from each animal. When compared with nonfluid-instilled lobes the fluid-instilled lobes were found to have proportionately smaller volumes at maximum inflation ( P < .02) and during deflation ( P < .001) as well as regional areas with higher surface tension properties ( P < .001). It is proposed that the pressure-volume studies may furnish a useful means of assessing the anatomical extent of alterations in lung surface tension. There was a significant negative correlation between maximum inflation volumes and maximum surface tensions ( P < .001) as well as between the volumes during deflation and the minimum surface tensions ( P < .001). It is concluded that intra-alveolar fluid may inactivate or displace the surface-active material from the alveolar lining membrane. amniotic fluid; lung pressure-volume studies; lung surfactant Submitted on April 11, 1963