Cigarette Smoking and the Disadvantages of Using a Fixed Ratio of FEV1/FVC to Diagnose Airway Obstruction

Cigarette smoking is the primary cause of world-wide premature death. Therefore, thoracic physicians should try to inform patients of the harm smoking causes to airways and blood vessels. Unfortunately, in pursuing the goal of reducing the impact of chronic obstructive pulmonary disease, simple “global” guidelines were established to identify airway obstruction, but only when the ratio of the one-second to forced vital capacity (FEV1/FVC) was less than 70%. The FEV1/FVC is the key identifier of airway obstruction and normally declines with age, approximately 1% every 4 years. At age 30, the mean FEV1/FVC for non-smokers is about 84%, minimally dependent on ethnicity, gender, or height. When a smoker’s FEV1/FVC is a few percentage points below the mean predicted for their age, airway obstruction is likely. At age 30, FEV1/FVC values of 75% (9% below mean predicted) are statistically abnormal. Calling such a smoker “normal” could be considered deceptive. I recommend that we: 1) identify airway obstruction early, especially in younger smokers; 2) counsel smokers and non-smokers regarding the damage smoking causes to airways and blood vessels; and 3) help our smokers with pharmacologic tools and single or group counseling to help them overcome their addiction. These practices should help reduce premature deaths.