How to interpret reduced forced expiratory volume in 1 s (FEV1)/vital capacity ratio with normal FEV1

The aim of the present study was to determine whether the combination of low forced expiratory volume in 1 s (FEV1)/vital capacity (VC) ratio with normal FEV1 represents a physiological variant or a sign of early airflow obstruction. We studied 40 subjects presenting with low FEV1/VC, but FEV1 within the range of normality predicted by European Respiratory Society reference equations, and 10 healthy controls. All subjects completed two questionnaires and underwent comprehensive pulmonary function testing, which included methacholine challenge and single-breath nitrogen wash-out. According to the questionnaires, the subjects were assigned to three groups, i.e. rhinitis (n=8), bronchial asthma (n=13) and chronic obstructive pulmonary disease (COPD; n=12). Subjects with negative responses to questionnaires were assigned to an asymptomatic group (n=7). Airway hyperresponsiveness was found in four subjects of the rhinitis group, all of the asthma group, and 10 of the COPD group; in the last two groups, it was associated with signs of increased airway closure and gas trapping. Bronchodilator response to salbutamol was positive in only a few individuals across groups. In the asymptomatic group, no significant functional changes were observed, possibly suggesting dysanaptic lung growth. In subjects with low FEV1/VC and normal FEV1, questionnaires on respiratory symptoms together with additional pulmonary function tests may help to clarify the nature of this pattern of lung function.