High-frequency ventilation at rates of 375 to 1800 cycles per minute in four neonates with congenital diaphragmatic hernia.

Neonates with congenital diaphragmatic hernias (CDH) often die because of pulmonary hypoplasia and high pulmonary vascular resistance (PVR). Pulmonary hypertension and right-to-left shunting precedes progressive hypoxia and death. PVR is increased by acidosis and by high airway pressures. High-frequency oscillation (HFO) is a new technique which may improve the outcome for such infants. Gas exchange in HFO is achieved by directing rapid pulsations of small volumes of gas down the trachea, typically at rates greater than 200 cycles per minute, volumes less than 25% of dead space, and low airway pressures. Gas transport results from augmented diffusion, not from bulk flow. Four neonates with CDH deteriorated on conventional mechanical ventilation and required hand ventilation at rates above 200 per minute. HFO at frequencies from 375 to 1800 cycles per minute was then initiated using a flow-interrupter type of oscillator. A marked fall in PaCO2 and a rise in pH resulted. The elimination of CO2 was very efficient with low mean airway pressures (less than 15 mm Hg). The initial improvement during HFO probably resulted from a decrease in PVR due to reversal of the acidosis. However, all four babies died after 13 to 80 hours of HFO. Neonates with CDH who remain hypercapneic despite conventional mechanical ventilation can be successfully ventilated by HFO. Use of HFO produces respiratory alkalosis which may stabilize PVR in the normal range and improve survival rate.