The effect of smoking on the severity of mechanisms of acute exacerbations of COPD

COPD (Chronic Obstructive Pulmonary Disease) worldwide has a prevalence of 10% in men and 8.5% in women. Exacerbations of COPD account for approximately 10% of all acute medical admissions. Projected prevalence figures suggest that by 2020 COPD will be the third leading cause of mortality worldwide thus imposing a significant burden on healthcare resources in the future. Acute exacerbations are not only responsible for a decline in the patient’s quality of life, but have a major socioeconomic impact. Following a pilot study that showed current smokers recover lung function much more slowly from their exacerbation than ex smokers, I initiated a properly powered prospective study to investigate the difference between the two groups.A total of 58 patients admitted with acute infectious exacerbations of COPD were recruited to the study to determine the effect of smoking status on their exacerbation. Throughout the admission lung function was measured. Sputum was cultured for bacteria, and PCR used to detect viral infection. Blood and sputum cells were analyzed by flow cytometry. Serum was collected for CRP levels.Ex-smokers recovered significantly more quickly than current smokers in all spirometric parameters (P<0.01), and were discharged sooner (mean 3.08 vs 5.59 days, P<0.001). Sputum culture was positive for more pathogenic bacteria in current smokers, especially H. influenzae, which was associated with a significantly higher CRP rise (p<0.05) than any other organism. CD8+ T cells predominated in the sputum of ex-smokers while CD4+ T cells were the dominant cell type in current smokers (p<0.01).Current smoking is a risk factor for more severe exacerbations, delayed recovery and prolonged hospitalization. This may result from a variety of factors including bacterial, immune mediated responses and systemic inflammation