Abstract
Correlations between surface activities in vitro and lung pressure-volume characteristics in situ or in vivo were examined with modified lung surfactants. Correlations were found between the value of the minimum surface tension and lung pressure-volume characteristics in situ or in vivo. The surface tension in compression at 60% surface area was also correlated with the lung pressure-volume characteristics in situ and in vivo. Correlations between chemical components in the lung surfactant and its activities in vitro, in situ and in vivo were also examined. The content of disaturated phosphatidylcholine was correlated to the value of the minimum surface tension, the spreading rate and pressure-volume characteristics in situ and in vivo. These results showed that the following in vitro criteria are essential for a lung surfactant to give normal pressure-volume characteristics to the mammalian lung in situ and in vivo ; 1) a minimum surface tension of 10 dyn/cm or less, 2) a surface tension of 13 dyn/cm or less in compression at 60% surface area, 3) spontaneous spreading. Furthermore, we found that the content of disaturated phosphatidylcholine in the lung surfactant is an important determinant in relation to the above criteria.
