Measurements of end-tidal carbon monoxide (ETCO) have been shown to reflect blood carboxyhemoglobin level and, when corrected for inspired air (ETCOc), can be used as a non-invasive index of heme degradation and total bilirubin production. However, the sampling of breath from neonates usually involved the insertion of a 5-French catheter into the nares. It can be argued that this is an invasive procedure. We studied term (≥ 37 wk) and preterm neonates with the Baby's Breath CO analyzer (Natus Medical, Inc., San Carlos, CA). This fully automated instrument for ETCOc determination requires that a 5-French, three-port (one end and two side) catheters be inserted 14 mm into the nares(Vreman et al, Clin Chem 1996;42:50-6). In addition, we made duplicate measurements of ETCOc and ETCO2 with an end-port only catheter placed at the nares. Data are given as mean and (range). No statistically significant difference (p<0.05) between the two catheter positions was found by analysis of variance using the Scheffé F-test.Table

Table 1
Full size table

We conclude, on the basis of both ETCOc and ETCO2 measurements, that truly non-invasive catheter placement at the entry of the nares is equally effective to insertion at 14 mm and might be preferred over the intranasal position.