A new approach to detect early lung functional impairment in very light smokers

The aim of our study is to investigate if lung carbon monoxide diffusing capacity (DLCO) measured during effort is able to detect early respiratory functional impairment.

We enrolled 25 very light smokers and 20 healthy non smokers. Subjects underwent plethysmography, DLCO (single breath technique) and calculated effective pulmonary blood flow (Qc) by rebreathing method. During exercise by cycle ergometer (duration 10±2min; recovery 11±3min) DLCO and Qc were calculated at 25% and 50% of theoretical maximum workload.

At baseline lung function and Qc did not differ between groups. DLCO and DLCO/Qc measured during exercise were significantly greater in non smokers (p<0.001); Qc was not statistically different. In very light smokers, DLCO, DLCO/Qc measured during exercise significantly correlated with the number of pack years (r=-0.60 p<0.001; r=-0.58 p<0.05; r=-0.55 p<0.05, respectively).

In very light smokers there is lung function impairment and our data show that DLCO during exercise may reveal this underlying early damage.