OBJECTIVETo study the characteristics and role of dynamic pressure-volume curve (P-V curve) in neonatal mechanical ventilation.

METHODSA dynamic P-V curve was automatically drawn by the Stephanie ventilator. The slope rate of dynamic P-V curve was measured in 25 neonates who received mechanical ventilation 1, 24, 48 and 72 hrs after ventilation and before weaning from ventilation. Minute-ventilation (MV), mean airway pressure (Pmean), and fraction of inspired oxygen (FiO2) were recorded. The patterns of dynamic P-V curve during abnormal ventilation (resistance to ventilator, part or complete airway obstruction, airway leaking and tracheal catheter exodus) were observed.

RESULTSWith the improvement of pulmonary disease, the slope rate of P-V curve and MV increased, Pmean and FiO2 decreased, and the P-V curve shifted to the volume axle. The slope rate of curve 48 and 72 hrs after ventilation and before weaning from ventilation (1.05+/-0.48, 1.10+/-0.42 and 1.13+/-0.37 mL/cmH2O respectively) increased significantly compared with that 1 hr after ventilation (0.76+/-0.53 mL/cmH2O) (p<0.05 or 0.01). Abnormal ventilation led to abnormal appearance of dynamic P-V curve.

CONCLUSIONSThe increasing slope rate of dynamic P-V curve and the curve shifting to volume axle in neonatal mechanical ventilation may be associated with the improvement of pulmonary disease. The appearance changes of the curve may be of value in the assessment of abnormal ventilation.