Critical care medicine
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Six mongrel dogs, each serving as its own control, underwent ventilatory trials on high-frequency positive-pressure ventilation (HFPPV) and high-frequency oscillation (HFO), before and after oleic acid-induced lung injury. Central and distal airway pressures were compared to simultaneous measurements of oxygen transport and shunt fraction. Airway pressure differences were more pronounced with HFO. ⋯ Shunt fraction increased with decreased oxygen transport after lung injury in both models; however, the increase was less pronounced with HFO, which maintained a greater pressure gradient. The distal increase in airway pressures may be important in maintaining critical closing volumes in the diseased lung. By creating a pressure gradient, high-frequency ventilation by either jet or oscillator may improve functional residual capacity and oxygenation.