Tidal Volumes Used to Initiate Ventilation Change Surfactant Treatment Responses in Preterm Lambs. † 1097

To evaluate the effect of tidal volumes (TV) used to initiate ventilation on the subsequent response to surfactant treatment (Rx), preterm lambs (129 d GA) were delivered by C-section and ventilated with TV 20 ml/kg (TV20), TV 10 ml/kg (TV10), or TV 5 ml/kg (TV5) for the first 30 min of life followed by surfactant treatment with Survanta® containing ¹⁴C-DPC dipalmitoylphosphatidylcholine. All groups then were ventilated similarly to maintain normal PCO² and PO² values to 6 hr of life. TV20 resulted in decreased lung function (Table). Total protein in alveolar wash was higher for TV20 (218±18 mg/kg) than for TV10 (137±12) and TV5 (104±20) (P<0.01).% recovery of¹⁴ C-DPC in lung was lower for TV20 (55±3.6%) than for TV5(77±6) (p<0.05).

Table 1

Blood flows to brain were measured with microspheres before and after Rx. Only flow to the brain before Rx: (TV5 (41±5% ml/kg·min), TV10(22±4), TV20(8±2) were different between 3 groups(P<0.05). High tidal volumes resulted in a decreased reponse to surfactant. The poor reponse to surfactant was associated with increased protein leak into the alveolar space and higher clearance of surfactant from the lung.