Hemodynamic effects of conventional and high frequency oscillatory ventilation in normal and septic piglets

The cardiovascular effects of high frequency oscillation (HFO) and conventional ventilation (CMV) were evaluated in 10 piglets prior to and during an infusion of group B streptococci (GBS). Animals were randomized to begin ventilation with either HFO or CMV. Arterial blood gases, cardiac output (CO), and pulmonary artery (Ppa), pulmonary wedge (Ppw) and arterial blood pressures were measured. These values were recorded at a mean airway pressure (MAP) of 2 cm H₂O for both modes of ventilation after which a continuous infusion of GBS (4 x 10⁷ CFU/kg/min) was begun. MAP was increased in both ventilators in the following sequence. 4, 8 and 12 cm H₂O. Prior to GBS infusion, HFO was associated with small but significant changes in hemodynamic parameters when compared to CMV for the following: Ppa (15 ± 4 vs. 13 ± 4.0 mm Hg; p < 0.03), Ppw (3 ± 1 vs. 2 ± 1 mm Hg; p < 0.02), and CO (0.24 ± 0.08 vs. 0.25 ± 0.09 l/min/kg; p < 0.05). Similar statistically significant increases in Ppa (p < 0.005) and Ppw (p < 0.0001), and decrease in CO (p < 0.007) were present during GBS infusion when animals were ventilated with HFO, irrespective of the MAP used. Our results suggest that the use of HFO in both normal piglets and those receiving an infusion of GBS results in mild but consistent impairment in cardiovascular function compared to CMV. In summary, these data demonstrate that HFO has no beneficial effect compared to CMV at similar MAP in the management of the septic piglet model and may in fact further compromise the animal's hemodynamic status.