Optimal application of high-frequency ventilation in infants: a theoretical study

A recent study for preterm infants concluded that high-frequency ventilation (HFV) applied at 15 Hz, in comparison with conventional mechanical ventilation (CMV), did not lead to reduced incidence of barotrauma. The present theoretical study aimed to determine whether computed estimates of lung pressures during HFV and CMV are consistent with these findings. An existing theoretical model of lung mechanics and gas transport in HFV was modified for application to neonates, and new features were incorporated. Simulations were conducted assuming a constant level of eucapnia. It was found that peak alveolar pressures and the magnitude of alveolar pressure swings resulting from HFV at 15 Hz were in general comparable to those produced by CMV in healthy neonates and infants with bronchopulmonary dysplasia. For the latter group, peak alveolar pressures tended to be higher with HFV than in CMV, and application of HFV at 15 Hz was even less advantageous when pulmonary air leak was also present. However, the model predicted that at frequencies between 2 and 4 Hz, alveolar pressure swings and peak alveolar pressures could be minimized, and in some cases, reduced below the levels produced by CMV.