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 (PetCO(2)) measurement in preterm infants. The aim of this study was to evaluate the effects of different dead space to tidal volume ratios (V(D)/V(T)) on the correlation between PetCO(2) and arterial carbon dioxide pressure (PaCO(2)) 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 PetCO(2) and PaCO(2) 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 PetCO(2) and PaCO(2) pairs from 34 neonates were analyzed. There was a moderate correlation between PetCO(2) and PaCO(2) 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 PaCO(2) and PetCO(2) 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 V(D)/V(T) in the post-surfactant treatment group when compared to the pre-surfactant treatment group (P = 0.003). CONCLUSIONS: V(D)/V(T) decreased significantly after surfactant therapy and the correlation between PetCO(2) and PaCO(2) was higher after surfactant therapy in preterm infants with RDS.