Physiological significance of exhaled carbon monoxide in asthmatics

Abstract EN

Background : There were evidences that CO has the potential to contribute to the pathophysiology of asthma in pre-clinical asthma models.

Aim : This study was undertaken to investigate the relationship between exhaled CO concentrations and some pathophysiological components of asthma including airway obstruction, airway hyperresponsiveness and TGF-1, as an inflammatory marker, in asthmatic subjects.

Subjects and Methods : Ten normal subjects (5 female and 5 males) and fifteen asthmatic patients (7 females and 8 males) were included in this study.

Pulmonary function tests, exhaled CO monitoring, Methacholine inhalation challenge (MIC) and TGF-1measurements in induced sputum by ELISA were performed in all subjects.

Results : Asthmatics exhibited lower mean values of FEV1 (p < 0.001), FEV1 / FVC % (p < 0.01), FEF25-75 (p < 0.001), and higher mean exhaled CO concentration (p < 0.001), and sputum TGF-1 (p < 0.001) than controls.

Also, in MIC, asthmatics demonstrated airway hyperresponsiveness (PD20- FEV1 was 0.0711 ± 0.04 mg / ml) whereas controls showed no bronchoconstriction with provocation test.

Elevated exhaled CO values were significantly correlated with FEV1 (r = 0.838, p < 0.001), FEF25-75 % (r = 0.829, p < 0.001), FEV1 / FVC % (r = 0.903, p < 0.001), PD20-FEV1 (r = 0.855, p < 0.001) and TGF-1 (r = 0.939, p < 0.001).

Conclusion : The increased exhaled CO production is not only an indicator of inflammatory activity but also could be a causative link in the pathophysiology of asthma.

So, further elucidation of the potential role of CO may offer a therapeutic target for bronchial asthma.