Interaction in COPD experiment (ICE): A hazardous combination of cigarette smoking and bronchodilation in chronic obstructive pulmonary disease

Abstract

Chronic obstructive pulmonary disease (COPD) is a highly prevalent disease, characterised by poorly reversible, obstructive airflow limitation. Alongside other comorbidities, COPD is associated with increased morbidity and mortality resulting from cardiovascular disease - mainly heart failure and ischemic heart disease. Both diseases share an important risk factor, namely, smoking. About 50% of COPD patients are active cigarette smokers. Bronchodilation is the cornerstone of pharmaceutical treatment for COPD symptoms, and half of all COPD patients use long-acting bronchodilating agents. Discussion about these agents is currently focusing on the association with overall mortality and morbidity in COPD patients, of cardiovascular origin in particular. Bronchodilation diminishes the hyperinflated state of the lung and facilitates the pulmonary deposition of cigarette smoke by deeper inhalation into the smaller airways. Smaller particles, as in smoke, tend to penetrate and depose more in these small airways. In addition, bronchodilation indeed increases carbon monoxide uptake in the lungs, an important gaseous compound of cigarette smoke. Since the number of cigarettes smoked is positively correlated to mortality from cardiac events, we therefore hypothesise that chronic bronchodilation increases cardiovascular disease and mortality in COPD patients who continue smoking by increasing pulmonary retention of pathogenic smoke constituents. Indeed, a recent meta-analysis is suggestive that long-acting anticholinergics might increase cardiovascular disease if patients exceed a certain number of cigarettes smoked. To demonstrate the fundamental mechanism of this pathogenic interaction we will perform a randomised placebo-controlled cross-over trial to investigate the effect of maximum bronchodilation on the retention of cigarette smoke constituents. In 40 moderate to severe COPD patients we measure the inhaled and exhaled amount of tar and nicotine, as well during maximum bronchodilation as during administration of placebo. The fraction of retention of tar and nicotine is subsequently calculated for both circumstances and analysed for association with bronchodilation. Further observational cohort studies or randomised clinical trials designed to monitor cardiovascular events may well evaluate the interaction. Since many patients are at risk for this possibly hazardous interaction, its relevance to our society and healthcare is potentially great. The implication will be that the urgency to quit smoking is intensified. Besides, chronic bronchodilation - specifically long-acting bronchodilators - needs to be discouraged in smoking COPD patients that refuse to quit.