During PAV, the airway pressure increases in proportion to inspiratory flow and tidal volume throughout each spontaneous inspiration such that partial respiratory unloading of airway resistance and lung elastic recoil are induced. In contrast, fixed inflation pressure and timing profiles are imposed during Assist/Control (AC) and Conventional Mechanical Ventilation (CV). We compared PAV, AC, and CV in a randomized, three period crossover study.

Thirty infants in the recovery phase of RDS (age 2-10 d; mean birth weight, 839 g, range 615 - 1.175; Fi02 0.25, 0.21-0.4) were ventilated over consecutive 45 min periods with PA, A/C, and CV in random sequence and with a constant Fi02. PAV was adjusted to unload approximately the resistance of the endotracheal tube and the disease-related increase in lung elastic recoil. The mandatory rate during CV was matched to the rate observed during an A/C test period. Tidal volumes of 4-6 mL/kg were targeted during A/C and CV by adjusting the peak inspiratory pressure. During PAV, respiratory rate and tidal volume (VT) are determined by the infant.Table

Table 1
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Transpulmonary cycling pressures (Ptp) and mean airway pressures (MAP) were lower during PAV when compared to A/C and CV (**, p<0.001, ANOVA). The PaO2 was significantly higher during PAV compared to A/C (*, p=0.004).

We conclude that PAV decreases the transpulmonary pressure changes required to maintain normal ventilation and oxygenation during mechanical ventilation. We therefore speculate that PAV may reduce barotrauma and chronic lung disease in VLBW infants.