Lung Trauma From Five Moderately Large Manual Inflations Immediately After Surfactant Instillation in Newborn Immature Lambs † 1678

The fluid-filled lung of the newly delivered preterm infant may be particularly sensitive to volutrauma. Thus, five moderately large lung inflations (8-16 mL/kg) given at birth to immature lambs significantly impaired the response to subsequent surfactant supplementation (Pediatr Res 1996;39:326A). We hypothesized that large inflations could be injurious also if given immediately after surfactant. Ten pairs of 127 days GA twin lambs were given porcine surfactant before the first breath, and were then mechanically ventilated with PEEP 4 cm H₂O, rate 50/min and FiO₂ 0.90 until the age of 4 h. One twin was given five sustained inflations of 16 mL/kg immediately after surfactant, while the other twin was given five inflations of the same size at 10-15 min of age. Significantly higher airway pressures were generated by inflations at birth than at 10-15 min (p < 0.01). The lambs given inflations at birth subsequently needed significantly higher peak inspiratory pressures (PIP) to achieve a normal PaCO₂. Two lung mechanical parameters, inspiratory capacity (IC) and maximal compliance(Crs), obtained from a standardized static pressure-volume diagram, were significantly lower in the lambs given inflations at birth. Furthermore, these lambs had IC and Crs in a range that we previously found to be associated with histologic signs of lung injury. We conclude that surfactant offers only partial protection against a very early volutrauma. Large breaths should not be forced into the lungs of premature infants directly after prophylactic surfactant treatment. Values in the table are means(SD) at 4 h.

Table 1 No caption available.