High frequency positive pressure ventilation in experimental meconium aspiration syndrome

To compare high frequency positive pressure ventilation (HFV) to conventional ventilation (CV) in experimental meconium aspiration syndrome (MAS) adult rabbits were randomly assigned to one of four groups: sham (G1) n = 10, control (G2) n = 12, CV (G3) n = 6, and HFV (G4) n = 6. All animals were stabilized on an FI O2 of 0.70 after a tracheostomy and arterial line were placed. The alveolar-arterial oxygen difference (A-aDO2) was calculated for each blood gas measurement and mean airway pressure (MAP) measured in CV and HFV at the time of each blood gas. Human meconium (2 ml/kg of 25% solution) was instilled intratracheally (MI) in groups 2-4. Group 3 was then placed on conventional ventilation with a rate of 40 BPM while Group 4 with a rate of 400 BPM. Analysis of variance was used to compare A-aDO2 and MAP. There was no significant difference between group 4 and group 2, while there was a significant difference between group 3 and groups 2 and 4. Sustained inflation of 25 cm H2O as used for 20 seconds was used before HFV in a fifth group (n = 6) that was added to the study and was otherwise identical to HFV. There was no significant difference between the fifth group and group 2 or group 4. Our findings indicate HFV is not efficacious in experimental MAS whether or not sustained inflation is used.