Comparison of bedside methods to assess lung mechanics in ventilated neonates: inflation pressure, amount of ventilation and optical compliance versus measured compliance.

Compliance of the respiratory system (CRS) is rarely measured in the critically ill neonate. Instead, inflation pressure (dP), amount of ventilation (dPxfr) and optical CRS are used as indirect parameters to characterize lung mechanics. In 30 randomly chosen newborns ventilated for various causes we investigated which of these bedside methods most accurately represents the compliance of the respiratory system. The correlation coefficient was much higher for the optically determined compliance (r = 0.91) than for the amount of ventilation (r = 0.67) or the inflation pressure alone (r = 0.46) versus the measured static compliance of the respiratory system.