Effect of ramp bicycle exercise on exhaled carbon monoxide in humans

The effect of exercise on the increase of exhaled CO in smokers compared to non-smokers has not been clarified yet. In this study we compared the dynamics of exhaled CO before, during and after exercise between smokers and non-smokers. A group of 8 smokers and a group of 8 non-smokers underwent a bicycle exercise in a ramp fashion to near maximum intensity. Ventilation and gas exchange, and CO exhalation were continuously measured every 30-s before, during and after the exercise. The fraction of CO (F-CO) in the exhaled air decreased gradually, but the total amount of exhaled CO ((V) over dot(CO)) increased in a linear manner during the ramp exercise, and FCO and (V) over dot(CO) returned to the pre-exercise level within several minutes after exercise in all subjects. A linear relationship was observed between (V) over dot(O2) and (V) over dot(CO); and between (V) over dot(E) and (V) over dot(CO) in both the whole period of measurement and during the ramp exercise period in all subjects. However, the (V) over dot(CO) at 0 W, the peak (V) over dot(CO) and the slope coefficients in the regression equation between (V) over dot(CO) and (V) over dot(O2); and between (V) over dot(CO) and (V) over dot(E) in the ramp exercise as well as the entire periods of measurement were significantly higher in smokers compared with those in non-smokers, and these were correlated with the number of cigarettes smoked per day. It was concluded that CO exhalation increases linearly with the increase of (V) ovet dot(O2) and (V) over dot(E) during exercise, and habitual smoking shifts these relationships upward depending on the number of cigarettes smoked daily.