Vibratory ventilation decreases filtration of fluid in the lungs of newborn lambs.

To compare effects of vibratory and mechanical ventilation on fluid balance in the newborn lung, we measured pulmonary arterial and left atrial pressures, pleural and airway pressures, lung blood flow and lymph flow, and concentrations of protein in lymph and plasma of 19 healthy lambs, 2-4 weeks old, during a 2- to 4-hour period of spontaneous breathing, followed by 4-8 hours of mechanical ventilation at 30 breaths/min and 4-8 hours of vibratory ventilation, in which the lambs received 1650 whiffs of air/min. In 8 of 22 studies, we increased lung microvascular pressure by filling a balloon catheter in the left atrium with saline. There was no significant difference in mean airway pressure during the two types of ventilation. Despite higher lung vascular pressures, lymph flow was less and lymph protein concentration was greater during vibratory than during mechanical ventilation. These findings are consistent with reduced lung fluid filtration, possibly from reduced pulmonary blood flow and increased perimicrovascular pressure, during vibratory ventilation. In eight lambs killed after 8 hours of vibratory ventilation, extravascular lung water was normal and microscopy showed no edema. We conclude that vibratory ventilation has no adverse effect on lung fluid balance and may benefit lambs by decreasing net filtration of fluid into their lungs.