Exhaled carbon monoxide concentration increases after exercise in children with cystic fibrosis

Oxidative stress and hypoxia, which may occur in cystic fibrosis patients (CF) at rest and may be worsened by exercise, induce the expression of heme oxygenase (HO)-1, resulting in increased carbon monoxide (CO) formation. We tested that exhaled CO level (eCO) was higher in CF patients than in healthy subjects, and that exercise increased CO production. Exhaled CO was measured electrochemically in 15 CF patients and 15 control subjects at rest (T0), immediately (T1) and 60 minutes after a symptom-limited incremental bicycle exercise test (T60). Arterial oxygen saturation (TcO2) was monitored transcutaneously. Data are given as mean+/-SEM. Baseline eCO was 1.90+/-0.26 ppm in the control and 1.93+/-0.27 ppm in the CF group. In both groups eCO was lower at T1 than at rest. In the control group eCO was also low at T60, but in the CF group it was increased compared to baseline level at this timepoint. Exercise caused oxyhemoglobin desaturation in CF patients which was related to the increase in eCO measured at T60 (r=0.67, p<0.01). Our findings suggest that exercise modulates the level of exhaled CO partly by worsening oxygenation in CF patients.