Objective
To examine the extents to which low tidal volume (VT) and endotracheal tube (ETT) leakeage influence the accuracy of ETCO
2
for estimating arterial PCO
2
(PaCO
2
) in very low birth weight (VLBW) infants with mechanical ventilation.
Study design
An observational study. We evaluated a total of 287 paired ETCO
2
and PaCO
2
values as well as VTs obtained from 22 VLBW infants with ventilation. Deming regression, quadratic discriminant analysis, and Bland–Altman analysis were performed.
Result
ETCO
2
and PaCO
2
were correlated (
r
2
= 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 ETCO
2
and PaCO
2
. ETCO
2
was strongly correlated with PaCO
2
in the discriminant function
Z
> 0 group (
r
2
= 0.7234,
p
< 0.0001).
Conclusion
Our results indicate that ETCO
2
is a good surrogate for PaCO
2
when VT is high and ETT leak is low.