Characteristics of healthy subjects with positive bronchodilator response

Bronchodilator response (BDR) testing is commonly used to assess any improvement of spirometric measurements after beta agonist inhalation. The recent definition by the ATS/ERS defines a positive BDR as the improvement of FEV1 or FVC>10% compared to the predicted value as positive. While some studies demonstrated a lower mortality in individuals with a positive BDR, much about the significance is still unknown. We analysed the prevalence and characteristics of healthy participants with positive BDR using the Austrian general population LEAD cohort. All healthy 18-82 yeo subjects with complete pre- and post-BD lung function testing were included. Health was defined as neversmoking, no history of respiratory disease and absence of respiratory symptoms. Out of 3183 participants, 91 (2.4%, 62.6% females) demonstrated a positive BDR. Subjects with positive BDR had significantly lower FEV1, FVC (3.6l vs 4.1l males; 2.6l vs 3.0l females and 4.6l vs 5.1l males, 3.3l vs 3.7l females, respectively) and ratio. Interestingly, we also found a lower TLC (5.4l vs 5.6l) in females, but not in males with BDR. Furthermore, while a higher RV/TLC ratio (34.1% vs 30% males; 37% vs 34.1% females) was observed in both sexes, in males it remained significantly higher after bronchodilation. Specific conductance (sGaw) also was lower in participants with positive BDR (1.2 vs 1.4 males; 1.2 vs 1.5 females). Healthy subjects with positive BDR demonstrate significantly reduced airflow and lower lung volumes. The low FEV1/FVC ratio and sGaw in this group is suggestive of central large airway process. Longitudinal data are needed, to evaluate if BDR is caused by early pulmonary disease or just physiological variation.