The High-Frequency Pneumatic Flow Interrupter: Effects of Different Ventilatory Strategies

Abstract

We used a piglet model of respiratory failure to compare the physiologic and path- ologic effects of two different ventilatory strategies provided by a high-frequency, pneumatic, flow-interrupter ventilator (HFFI). The strategies employed were con- tinuous high frequency ventilation interrupted either by deflationary pauses or by pulsatile inflationary waves. Twelve piglets (mean age 4 days, mean birthweight 1.4 kg) randomly assigned to either the deflationary or the inflationary group received saline lung lavage and 6 hours of HFFI ventilation (10 Hz, 1.0 FIO2). Suc- cessful gas exchange was accomplished without cardiovascular compromise with both strategies. Mean airway pressures required by animals in the deflationary group were higher than those in the inflationary group. In the deflationary group, 5/6 piglets and in inflationary group 1/6 piglets presented with airway mucosal damage beyond the trachea. Significant pneumonitis was seen in all animals in the deflationary group but in only one of those in the inflationary group. In this model, the deflationary strategy led to airway and lung damage, whereas the inflationary strategy was associated with minimal airway and lung injury, perhaps due to the maintenance of high lung volume and enhanced alveolar recruitment.