End-tidal carbon dioxide measurement in preterm infants with low birth weight

OBJECTIVE There are conflicting data regarding the use of end-tidal carbon dioxide (PetCO2) measurement in preterm infants. The aim of this study was to evaluate the effects of different dead space to tidal volume ratios (VD/VT) on the correlation between PetCO2 and arterial carbon dioxide pressure (PaCO2) in ventilated preterm infants with respiratory distress syndrome (RDS). METHODS We enrolled ventilated preterm infants (with assist control mode or synchronous intermittent mandatory mode) with RDS who were treated with surfactant in this prospective study. Simultaneous PetCO2 and PaCO2 data pairs were obtained from ventilated neonates monitored using mainstream capnography. Data obtained before and after surfactant treatment were also analyzed. RESULTS One-hundred and one PetCO2 and PaCO2 pairs from 34 neonates were analyzed. There was a moderate correlation between PetCO2 and PaCO2 values (r = 0.603, P < 0.01). The correlation was higher in the post-surfactant treatment group (r = 0.786, P < 0.01) than the pre-surfactant treatment group (r = 0.235). The values of PaCO2 and PetCO2 obtained based on the treatment stage of surfactant therapy were 42.4 ± 8.6 mmHg and 32.6 ± 7.2 mmHg, respectively, in pre-surfactant treatment group, and 37.8 ± 10.3 mmHg and 33.7 ± 9.3 mmHg, respectively, in the post-surfactant treatment group. Furthermore, we found a significant decrease in VD/VT in the post-surfactant treatment group when compared to the pre-surfactant treatment group (P = 0.003). CONCLUSIONS VD/VT decreased significantly after surfactant therapy and the correlation between PetCO2 and PaCO2 was higher after surfactant therapy in preterm infants with RDS.