The importance of lung volumes in the investigation of heavy smokers

Introduction. - Lung hyperinflation (LH) has become a major concern in the management ofchronic obstructive pulmonary disease (COPD).Main aim. - To evaluate the role of lung volumes in the positive diagnosis of COPD and in theassessment of airway obstruction reversibility.Population and methods. - Three hundred and sixty-six male smokers over the age of 35with more than 40 pack-years exposure were included in the study. Plethysmographic datawere determined before/after taking a bronchodilator (BBD, ABD). Applied definitions: air-flow obstruction: BBD FEV1/FVC < 0.70. LH: BBD residual volume (RV) > upper limit of normal.Expressions of reversibility: -variable = (ABD - BBD) values; -init% = -variable/BBD value and-ref% = -variable/reference value. A 12%init and a 0.2 L increase in either FEV1or FVC or a10%ref or - 300 mL decrease in RV were considered as clinically significant.Results. - Over the 85 smokers without airflow obstruction, 68% had LH. In the hyperinflatedgroup (n = 314), and compared to changes in FEV1and FVC, these RV changes detected morerespondents (54% for FEV1and FVC vs. 65% for RV, P = 0.002). This was not the case for the groupfree from LH (n = 52) (23% for FEV1and FVC vs. 35% for RV, P = 0.09). In the 58 hyperinflatedgroups free from airflow obstruction, and compared to changes in FEV1and FVC, changes in RVdetected more respondents (24% for FEV1and FVC vs. 71% for RV, P = 0.0001).Conclusion. - In heavy smokers, it seems essential to include LH as a criterion for a positivediagnosis of COPD and of reversibility evaluation.