Spirometric indices of early airflow obstruction.

Thirty cigarette smokers and 25 non-smoking controls, all men were evaluated by history, physical examination and simple spirometry. The history and physical examination were not of much use in predicting airflow obstruction. Forced mid-expiratory flow (FEF 25-75%) was abnormally low in 23 of the 30 subjects, while forced expiratory volume in 1 second (FEV1) and FEV1/FVC (forced vital capacity) were less sensitive. Thus simple spirometry is a useful screening tool to detect early airflow obstruction even when it is clinically undetectable.