Assessment of concordance between diffusion of carbon monoxide through the lung using the 10 s breath-hold method, and the simultaneous NO/CO technique, in healthy participants

Abstract

IntroductionThere is limited, large sample size, healthy control data comparing measurement of diffusing capacity of the lungs for carbon monoxide (DLCO) via the 10 s single-breath carbon monoxide uptake method (DLCO10) and using a DLCO-DLNO double diffusion test performed with a 5 s time of apnoea (DLCO5). ObjectivesThe primary objective was to compare DLCO5 and DLCO10 in healthy participants. The secondary objective was to evaluate the reproducibility of DLCO5. Material and methodsWe included medical students at Caen University Hospital, from 2008 to 2011. We performed a standard single-breath carbon monoxide uptake and combined DLCO and DLNO measurement for each participant. The combined test was repeated one week later. ResultsAmong the 153 study participants, there was no statistically significant difference between the mean values of DLCO10 (10.2 ± 2.2 mmol.min−1 kPa−1) and DLCO5 (10.3 ± 2.2 mmol.min−1 kPa−1; paired t-test p = 0.19). Corrected for the same FiO2, DLCO5 was calculated at 10.5 ± 2.3 mmol.min−1 kPa−1 and was significantly different from DLCO10 (paired t-test p < 0.001). DLCO5 deviates from 1,6 mmol.min−1 kPa−1 (4,6 mL.min−1. mmHg−1) or 15 % of DLCO10 (17 % above and 13% below, for 95 % of the subjects). Forty-seven participants were included in the DLCO5 reproducibility test. The 2 test sessions were carried out at 6 ± 2 day intervals. Reproducibilities for DLCO, DLNO, DmCO and Vc was respectively 1.2 (11 %), 6.8 (13%), 16.5 (32 %), 12.5 (17 %) mmol.min−1 kPa−1. ConclusionIn healthy participants, discrepancies between DLCO measured during the double diffusion and DLCO measured on an apnoea of 10 s are quite large. It may be an indication that the Roughton and Forster interpretation to describe this type of measurements is inadequate.