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.

Introduction: There 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 (DLCO) and using a DLCO-DLNO double diffusion test performed with a 5 s time of apnoea (DLCO).

Objectives: The primary objective was to compare DLCO and DLCO in healthy participants. The secondary objective was to evaluate the reproducibility of DLCO.

Material And Methods: We 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.

Results: Among the 153 study participants, there was no statistically significant difference between the mean values of DLCO (10.2 ± 2.2 mmol.min kPa) and DLCO (10.3 ± 2.2 mmol.min kPa; paired t-test p = 0.19). Corrected for the same FiO, DLCO was calculated at 10.5 ± 2.3 mmol.min kPa and was significantly different from DLCO (paired t-test p < 0.001). DLCO deviates from 1,6 mmol.min kPa (4,6 mL.min. mmHg) or 15 % of DLCO (17 % above and 13% below, for 95 % of the subjects). Forty-seven participants were included in the DLCO 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 kPa.

Conclusion: In 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.