A Novel Method of Distal End-Tidal CO2 Capnography in Intubated Infants: Comparison With Arterial CO2 and With Proximal Mainstream End-Tidal CO2

OBJECTIVE. The objective of this study was to evaluate a novel method of distal end-tidal CO(2) capnography by comparison with PaCO(2) and with the more standard method that measures mainstream proximal end-tidal CO(2) in intubated infants. METHODS. Included in the study were all infants who were ventilated with conventional mechanical ventilation and intubated with a double-lumen endotracheal tube in our NICU during the study period. Data were collected prospectively from 2 capnographs simultaneously and compared with PaCO(2). Sidestream distal end-tidal CO(2) was measured by a Microstream capnograph via the extra port of a double-lumen endotracheal tube. Mainstream proximal end-tidal CO(2) was measured via capnograph connected to the endotracheal tube. RESULTS. Twenty-seven infants (median [range] birth-weight: 1835 [490-4790] g; gestational age: 32.5 [24.8-40.8] weeks) participated in the study. We used for analysis 222 and 212 measurements of distal end-tidal CO(2) and proximal end-tidal CO(2), respectively. Distal compared with proximal end-tidal CO(2) had a better correlation with PaCO(2) and a better agreement with PaCO(2). The accuracy of distal end-tidal CO(2) decreased, but it remained a useful measure of PaCO(2) in the high range of PaCO(2) (>= 60 mm Hg) or in conditions of severe lung disease. A subanalysis for infants who weighed <1500 g (13 infants, 84 observations) revealed a good correlation and agreement between distal end-tidal CO(2) and PaCO(2) and poor correlation and agreement for proximal end-tidal CO(2). CONCLUSIONS. Distal end-tidal CO(2) measured via a double-lumen endotracheal tube was found to have good correlation and agreement with PaCO(2), remained reliable in conditions of severe lung disease, and was more accurate than the standard mainstream proximal end-tidal CO(2). Pediatrics 2008; 122: e1219-e1224