Correlation of exhaled carbon monoxide and nitric oxide with airflow obstruction in asthma and chronic obstructive pulmonary disease patients

The aim of this study was to quantify lung oxidative stress in patients with asthma and chronic obstructive pulmonary disease by measuring levels of exhaled carbon monoxide and nitric oxide. Levels of exhaled carbon monoxide, nitric oxide were evaluated in exhaled air of asthma and COPD patients. Moreover, correlation of CO and NO concentrations with degree of airflow obstruction (FEV1% predicted) were also measured. The mean exhaled CO level was significantly much higher among COPD (6.47 ± 0.44 ppm, p<0.01) and asthma patients (6.13 ± 0.42 ppm, p<0.05) as compared to controls (4.62 ± 0.41 ppm). There was no significant difference found in the levels of CO between asthma and COPD (p>0.05). %COHb levels were remarkably higher in COPD (p<0.01) and asthma patients (p<0.05). It was also found that the levels of exhaled NO remarkably increased in asthma (41.56 ± 3.22 ppb, p<0.001) and COPD patients (29.22 ± 2.43 ppb, p<0.01) as compared to control (17.42 ± 1.01 ppb). There was a significant negative correlation found between exhaled CO and NO with FEV1% predicted in asthma and COPD. Moreover, we have also found a remarkable positive relation between exhaled CO and NO. The present study demonstrated that the levels of CO, NO and %COHb in exhaled air might have played a significant role in lung oxidative stress and inflammation. Moreover, these biomarkers in exhaled air may provide a simple, noninvasive and sensitive approach with which to monitor airway inflammation and to assess the response to drug treatment.