Assessment of exhaled carbon monoxide in exacerbations of chronic obstructive pulmonary disease

Introduction Exhaled carbon monoxide (eCO) has been widely implicated as a pulmonary biomarker in respiratory diseases. The aim of this study was to investigate whether the treatment of patients with severe acute exacerbation of chronic obstructive pulmonary disease (AECOPD) could be aided by monitoring the changes in eCO. Methods The levels of eCO along with routine clinical parameters were analyzed in 29 current smoker and 33 ex-smoker COPD patients, first at the time of hospital admission, and again at discharge following the standard treatment. Patients with AECOPD were also stratified according to sputum bacteria. Results At exacerbation, the levels of eCO were increased in current smokers compared to ex-smokers (6.0 [2.0-9.5] versus 1.0 [1.0-2.0] ppm, p < 0.001). Similarly, eCO levels were higher in smokers after treatment (7.0 [2.0-12.5] versus 1.0 [1.0-2.0] ppm, p < 0.001). Treatment of AECOPD did not affect eCO concentrations. The levels of eCO were not statistically different between bacterial and non-bacterial AECOPD either. Investigating a subgroup of current smoker patients (n = 15), there was a significant correlation between the levels of eCO and blood carboxyhemoglobin concentrations both at exacerbation and discharge. No associations were found between eCO and lung function or blood gas parameters. Conclusion Our results suggest that monitoring eCO during the treatment of AECOPD is of limited clinical value.