Effect of intra-alveolar meconium on pulmonary surface tension properties

To evaluate the effect of meconium on pulmonary surface tension properties, the mechanics of 30 excised, separated canine pulmonary lobes were studied. Meconia were blended in normal saline to produce solutions of 10% and 20%. Solutions were filtered to remove large particles and instilled endobronchially into the canine lobes. The static pressure-volume deflation curve of each lobe was determined before and 4 h after instillation of either normal saline or meconium solution. In the saline control group (eight lobes), the curve was essentially unchanged before and after instillation. In the 10% meconium group (14 lobes), the curve was significantly depressed after instillation, especially at a transpulmonary airway pressure of 10 cm H₁O )p < .05) and 5 cm H₂O (p < .005). In the 20% meconium group (eight lobes), the depression of the pressure-volume curve was essentially the same as that of the 10% solution group. It is concluded that meconium depresses the surface-active properties of the alveolar linings.