COMPARISON OF PEDIATRIC END-TIDAL CO2 MEASURED WITH NASAL ORAL CANNULA CIRCUIT AND CAPILLARY PCO2

This study was designed to determine whether end-tidal carbon dioxide (ETCO2) values obtained by noninvasive oral/nasal cannula circuit with side-stream capnometry correlate reliably with capillary Pco2 (CapCO2 ) in a pediatric population without cardiopulmonary problems. Each pat ient was monitored until a reliable 5-minute ETCO2 waveform was obtain ed. A capillary blood gas sample was drawn while, simultaneously, ETCO 2 was recorded. The difference between CapCO2 and ETCO2 levels was tes ted with a paired t-test at P < .001. The limits of agreement were est ablished with a 95% confidence level. The stability of the measured di fference across the range of mean scores (CapCO2 + ETCO2/2), age, and respiratory rate was tested using simple linear regression. Fifty-eigh t children (23 girls and 35 boys) had mean ETCO2 readings of 33.96 mm Hg (SD 4.26), and mean CapCO2 readings of 35.93 (SD 4.04). A relative average bias of 1.96 with ETCO2 lower than CapCO2 was established with 95% limits of agreement of +/- 5.2 mm Hg (t = 5.71). Variability of d ifference scores was not related to range of mean scores (r = .08), ag e (r = .09), or respiratory rate (r = .25). End-tidal CO2 measured by an oral/nasal cannula capnometry circuit is a noninvasive method of as sessing indirect measurements of Pco2 in a normal pediatric population .