Abstract 157

Aim: To compare efficacy of high frequency ventilation (HFV) and conventional mechanical ventilation (CMV) during inhalation of nitric oxide (iNO) in experimental meconium aspiration syndrome. Materials: Adult rabbits subjected to anaesthesia, intratracheal intubation and conventional mechanical ventilation (CMV). Intervention: Induction of respiratory failure with intratracheal instillation of 10% human meconium. Measurements and Results: Respiratory failure was evidenced by PaO2 <10 kPa (FiO2 1.0) and a reduction of dynamic compliance (Cdyn) of respiratory system>30% from baseline. The animals were then divided into two groups either as a control or as treated with iNO at 20 ppm (NO). In each group the animals were initially ventilated with either CMV or HFV for 3 h and crossed over to receive HFV or CMV for another 3 h (CMV-HFV, HFV-CMV), respectively. In the initial 3 h treatment, the animals subjected to HFV-CMV in the Control, and those with both HFV-CMV and CMV-HFV in the NO group had significantly reduced values of oxygenation index (OI, 7±4, 6±3, 7±, respectively, p<0.05) compared to those with CMV-HFV in the Control group(17±8). In the latter 3 h for the Control group, the animals with CMV-HFV didn't have any improvement of OI (18±7) and those with HFV-CMV became deteriorated significantly (17±9), whereas those in both CMV-HFV and HFV-CMV of the NO group still had moderate improvement of OI(11±4, 11±2, respectively). Neither HFV nor iNO had any effects in improvement of Cdyn. Conclusions: Both HFV alone and a combined treatment of iNO with CMV or HFV are more effective in improvement of oxygenation than that with CMV only in this animal model.