Introduction: PLV has been reported to lessen airway and alveolar injury in animals and humans. Clinical benefit has been demonstrated with PLV therapy in MAS in animals. This prospective randomized non-blinded controlled laboratory study evaluated the effects of GV and PLV on lung histopathology in the newborn piglet MAS model.

Methods: Twenty-four piglets were anesthetized, ventilated and instrumented. Post meconium instillation, the hypoxic and acidotic piglets(1-4 days age; 1-2 kg wt) were randomly assigned to one of the two groups and were studied for 4 hours. 5 piglets each from GV and PLV groups were also randomized to receive 40ppm inhaled NO.

  • GV Conventional positive pressure gas ventilation with 100% O2

  • PLV FRC filled with perfluorodecalin and ventilated with 100% O2

At 4 hours, the animals were euthanised, lungs removed enbloc, inflated to 20cmH2O and then fixed in formalin. Each of the 5 lobes were scored for inflammation, lymphatic dilatation & mucus impaction, alveolar expansion, edema & hemorrhage and interlobar edema & hemorrhage. All scores were on a scale of 0-3 (3: greatest) by a pathologist* who was not aware of randomization.

Results: Median injury scores are shown in the attached table.

Table 1
Full size table

Conclusions: In this MAS experiment, PLV therapy for a duration of 4 hours did not result in changing the severity of lung injury that had been induced by the instilled meconium. In the PLV group, there seemed to be a trend in improved mean expansion and decreased lymphatic dilatation.