[Rebreathing method for measuring CO transfer factor in children]

The reference technique to measure the diffusing capacity of the lung for carbon monoxide (DLco) is the single-breath method (sb). For patients unable to perform this method, the rebreathing method (rb) can be used. However, the clinical relevance of DLCOrb has not been evaluated. The aim of this study was to assess the feasibility of the rb method in children seen in a clinical setting and its relationships with sb method.

We prospectively included children referred for 1) a suspected or confirmed interstitial lung disease (ILD group) (DLCOsb and DLCOrb measurements) ; 2) controlled asthma with normal lung function (DLCOrb measurements to derive DLCOrb/KCOrb expected values). DLCOrb was computed from the decrease in CO and Helium concentrations during tidal breathing in a rebreathing bag.

Data on DLCOrb measurements were available for 53 (91%) children in the ILD group and 48 (91%) control children (mean (range) 11.5 (4.3-18.2) and 9.5 (4-17) years ; respectively). In the ILD group, high or moderate correlations were found between raw DLCOrb and DLCOsb values (rhô=0.82 ; P<0.0001) and between KCOrb and KCOsb (rhô=0.62 ; P<0.0001), respectively. Results expressed as percentage predicted were moderately correlated (rhô=0.55 ; P=0.0003 for DLCO ; rhô=0.51 ; P=0.001 for KCO).

DLCOrb is easy to perform in children and gives values that are highly correlated to DCLOsb. Our preliminary results are in favour of a possible clinical use after further validation.