Role of exhaled carbon monoxide in assessment of chronic obstructive airway disease severity

Abstract

Chronic obstructive pulmonary disease (COPD) is a critical public health issue. Spirometric measurements are used to diagnose chronic obstructive lung disease, as per the guidelines of the GOLD initiative. Post-bronchodilator forced expiratory volume in 1 s (FEV1) is a predictor of mortality from COPD and helps to classify the disease’s severity. Smoking contributes to the high levels of exhaled CO. Evidence suggests that the exhaled CO level in COPD patients varies with degree of blockage and can be used to assess treatment response. Estimating the exhaled CO level can help assess airway inflammation and severity of airflow obstruction in individuals with COPD. Evaluate role of exhaled CO in assessment of severity of COPD. This cross-sectional study included 132 patients who visited the outpatient clinics or were admitted to the Chest Department, Kasr Alainy Hospital, Faculty of Medicine, Cairo University. The study participants were divided into three groups: group 1 nonsmoker healthy control, group 2 smoker non-COPD, and group 3 smoker COPD which further divided according to GOLD 2023 into mild, moderate, and severe COPD. The smoking status, exhaled CO, and spirometry test including FEV1/FVC and FEV1 were measured for each patient. Exhaled CO was significantly increased in the smoker group (mean 9.69, SD 3.11) compared to the nonsmoker group (mean 2.19, SD 0.98) with p-value < 0.001. Exhaled CO was also statistically significantly higher in the smoker COPD group (mean 10.45, SD 3.03) compared to the smoker non-COPD group (mean 7.05, SD 1.56) with p-value < 0.001. Although exhaled CO was increased in the severe COPD group compared to the mild and moderate group, there is no statistically significant difference between them. Exhaled CO is a fast, sensitive, noninvasive, and well-established method test that can be used to identify smokers from nonsmokers with 98.9% sensitivity at 4.5 cutoff value. Also, exhaled CO levels in COPD patients vary with different degrees of airway obstruction.