Effect of ramp bicycle exercise on exhaled carbon monoxide in humans

Abstract

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 V̇ CO increased in a linear manner during the ramp exercise, and F CO and $$ V̇ CO returned to the pre-exercise level within several minutes after exercise in all subjects. A linear relationship was observed between $$ V̇ O2 and V̇ CO and between V̇ E and V̇ CO in both the whole period of measurement and during the ramp exercise period in all subjects. However, the V̇ CO at 0 W, the peak V̇ CO and the slope coefficients in the regression equation between V̇ CO and V̇ O2 and between V̇ CO and V̇ 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 V̇ O2 and V̇ E during exercise, and habitual smoking shifts these relationships upward depending on the number of cigarettes smoked daily. © 2011 The Physiological Society of Japan and Springer.