PERFLUOROCHEMICAL RESCUE AFTER SURFACTANT TREATMENT - EFFECT OF PERFLUBRON DOSE AND VENTILATORY FREQUENCY

To test the hypotheses that perfluorochemical (PFC) liquid rescue afte r natural surfactant (SF) treatment would improve pulmonary function a nd histology and that this profile would be influenced by PFC dose or ventilator strategy, anesthetized preterm lambs (n = 31) with respirat ory distress were studied using nonpreoxygenated perflubron. All anima ls received SF at Ih and were randomized at 2 h as follows and studied to 4 h postnatal age: 1) conventional mechanical gas ventilation (n = 8), 2) 30 ml/kg perflubron with gas ventilation [partial Liquid venti lation (PLV)] at 60 breaths/min(n = 8), 3) 10 ml/kg perflubron with PL V at 60 breaths/min (n = 7), and 4) 10 ml/kg perflubron with PLV at 30 breaths/min (n = 8). All animals tolerated instillation without addit ional cardiopulmonary instability. All perflubron-rescued groups demon strated sustained improvement in gas exchange, respiratory compliance, and reduction in pressure requirements relative to animals receiving SF alone. Improvement was directly related to perflubron dose and brea thing frequency; peak inspiratory pressure required to achieve physiol ogical gas exchange was lower in the higher-dose and -frequency groups , and mean airway pressure was lower in the lower-frequency group. Lun g expansion was greater and evidence of barotrauma was less in the hig her-dose and -frequency group; regional differences in expansion were not different as a function of dose but were greater in the lower-freq uency group. Regional differences in lung perflubron content were redu ced in the higher-dose and -frequency groups and greatest in the lower -dose and -frequency group. The results suggest that, whereas PLV of t he SF-treated lung improves gas exchange and lung mechanics, the prote ctive benefits of perflubron in the lung may depend on dose and ventil ator strategy to optimize PFC distribution and minimize exposure of th e alveolar-capillary membrane to a gas-liquid interface.