BACKGROUND Non-invasive assessment of inflammation is likely to be useful in the management of cystic fibrosis (CF). Exhaled carbon monoxide (CO) concentrations are increased in patients with clinically stable CF. A study was undertaken to determine whether this marker of oxidative damage is further increased during exacerbations of the disease.

RESULTS Twenty nine patients were in a stable condition while 15 had clinically defined respiratory exacerbations (increased cough and production of sputum, change in the quality of the sputum, shortness of breath, sensation of chest congestion, and deterioration of FEV₁) and represented the unstable group. Exhaled CO concentrations were 2.0 (0.15) ppm in the control group, were increased in the stable CF group to 2.7 (0.13) ppm (differences between means –0.67 (0.22), 95% confidence interval (CI) 0.22 to 1.12, p<0.01) and further increased in the unstable group to 4.8 (0.3) ppm (differences between means –2.15 (0.32), 95% CI 1.50 to 2.79, p<0.001). A significant correlation was found between the deterioration in FEV₁ and exhaled CO concentrations.

CONCLUSIONS This study shows that the measurement of exhaled CO is of potential value as an indicator of exacerbations in patients with CF and could be used as a simple method to monitor the course of the disease.