Effect of tidal volume and end tracheal tube leakage on end-tidal CO2 in very low birth weight infants.

Abstract

ObjectiveTo examine the extents to which low tidal volume (VT) and endotracheal tube (ETT) leakeage influence the accuracy of ETCO2 for estimating arterial PCO2 (PaCO2) in very low birth weight (VLBW) infants with mechanical ventilation.Study designAn observational study. We evaluated a total of 287 paired ETCO2 and PaCO2 values as well as VTs obtained from 22 VLBW infants with ventilation. Deming regression, quadratic discriminant analysis, and Bland–Altman analysis were performed.ResultETCO2 and PaCO2 were correlated (r2 = 0.5897, p < 0.0001). A quadratic discrimination analysis of the VT and the percentage of leak yielded 70.4% [95%CI, 65.1 to 75.7] discrimination for the agreement between ETCO2 and PaCO2. ETCO2 was strongly correlated with PaCO2 in the discriminant function Z > 0 group (r2 = 0.7234, p < 0.0001).ConclusionOur results indicate that ETCO2 is a good surrogate for PaCO2 when VT is high and ETT leak is low.