Effect of chronic pulmonary artery ligation on pulmonary mechanics and surfactant.

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Abstract
The left main pulmonary artery of 17 dogs was ligated for periods of 2-98 days. In vitro static air pressure-volume studies showed that total lung volume was reduced by 40-50% of control lungs for the 1st 35 days following ligation. Two ligated lobes studied at 50 and 98 days following ligation had normal total lung volumes. The inflation characteristics of the ligated and control lungs were similar when the volumes were related as a proportion of total lung volume. Lobes ligated from 2 to 14 days had a significant decrease in proportional volume on deflation (P < . 01), indicating increased retractive forces of inflatable alveoli. Minimum surface tension ([gamma] min.) was significantly elevated for this group (P< . 01). By 25-35 days both [gamma] min. and increased retractive forces had returned to normal values. Saline inflation demonstrated the presence of noninflatable areas in ligated lobes, but no increase in tissue elastic recon was found. It is concluded that chronic pulmonary artery ligation results in an increase in surface-tension forces of inflatable alveoli for the 1st 2 wks. as well as mechanical obstruction of the airways for the 1st mon. These changes reverted to normal after 50 days of pulmonary artery ligation.