Patterns of Lung Disease in a “Normal” Smoking Population: Are Emphysema and Airflow Obstruction Found Together?

Study objectives: We determined whether emphysema demonstrated on high-resolution CT (HRCT) scanning in apparently well smokers is associated with airflow obstruction. Interventions: Lung function testing and limited HRCT scanning. Design: Lung function measurements and scans were analyzed independently of each other. We used analysis of covariance to compare FEV1 and maximum expiratory flow at 50% of vital capacity (MEF50) values after suitable corrections, between subjects with and without parenchymal damage (emphysema and/or reduced carbon monoxide transfer coefficient [KCO]), and to compare indexes of parenchymal damage between subjects with and without airflow obstruction. Setting: Radiology and lung function departments of a district general hospital. Participants: Eighty current cigarette smokers and 20 lifetime nonsmoking control subjects (aged 35 to 65 years) who volunteered following publicity in local media. In all subjects, FEV1 was > 1.5 L; no subjects were known to have lung disease. Measurements and results: FEV1 and MEF50 were measured spirometrically; static lung volumes were measured by helium dilution and body plethysmography; KCO was measured by a single-breath technique. HRCT scans were analyzed for emphysema by two radiologists. Of smokers, 25% had HRCT emphysema, generally mild; 16.3% and 25% had reduced FEV1 and MEF50, respectively; 12.5% had reduced KCO. Smokers with airflow obstruction were not more likely to have parenchymal damage. Smokers with parenchymal damage did not have reduced airway function. Nonsmokers generally had normal airways and parenchyma. Conclusions: “Normal” smokers with lung damage had either airflow obstruction or parenchymal damage, but not generally both. (CHEST 2001; 120:743–747) Abbreviations: ANCOVA analysis of covariance; FRC functional residual capacity; HRCT high-resolution CT; Kco carbon monoxide transfer coefficient; MEF50 maximum expiratory flow at 50% of vital capacity; RV residual volume; SR standardized residual; TLC total lung capacity; Tlco carbon monoxide transfer factor; Va alveolar volume