MANUAL VENTILATION WITH A FEW LARGE BREATHS AT BIRTH COMPROMISES THE THERAPEUTIC EFFECT OF SUBSEQUENT SURFACTANT REPLACEMENT IN IMMATURE LAMBS

The reason why some infants with respiratory distress syndrome fail to respond to surfactant, or respond only transiently, is incompletely u nderstood. We hypothesized that resuscitation with large breaths at bi rth might damage the lungs and blunt the effect of surfactant. Five pa irs of lamb siblings were delivered by cesarean section at 127-128 d o f gestation. One lamb in each pair was randomly selected to receive si x manual inflations of 35-40 mL/kg (''bagging'') before the start of m echanical ventilation, a volume roughly corresponding to the inspirato ry capacity of lamb lungs after prophylactic surfactant supplementatio n. Both siblings were given rescue porcine surfactant, 200 mg/kg, at 3 0 min of age. Blood gases and deflation pressure-volume (P-V) curves o f the respiratory system were recorded until the lambs were killed at 4 h. The P-V curves became steeper after surfactant in the control gro up, but no such effect was seen in those subjected to bagging. At 4 h, inspiratory capacity and maximal deflation compliance were almost thr ee times higher (p < 0.01) in the controls than in the bagged lambs. T he latter were also more difficult to ventilate and tended to have les s well expanded alveoli and more widespread lung injury in histologic sections. We conclude that a few inflations with volumes that are prob ably harmless in other circumstances might, when forced into the surfa ctant-deficient lung immediately at birth, compromise the effect of su bsequent surfactant rescue treatment. Our findings challenge current n eonatal resuscitation practice of rapidly establishing a normal lung v olume by vigorous manual ventilation.