Pulmonary function and exercise challenge test in Thai children: 10 years post respiratory syncytial virus infection.

OBJECTIVE: To report the occurrence of asthma, pulmonary function and exercise challenge test abnormalities found in Thai children, who 10 years earlier had lower respiratory tract infection caused by respiratory syncytial virus (RSV-LRI). PATIENTS AND METHODS: 37 children, with RSV-LRI admitted at Ramathibodi Hospital during January 1986 through December 1987, were contacted, of whom 13 patients responded and completed history-review-questionnaires. Pulmonary function measurements at pre- and post-exercise and testing for bronchodilator response were performed. RESULTS: The occurrence of physician-diagnosed asthma in the patients with and without family history of allergic diseases was 75 per cent and 40 per cent, respectively. Of 11 patients who performed spirometry, 45 per cent had concave flow-volume curves, 36 per cent showed decreased ratio of forced expiratory flow in the first second (FEV1) to forced vital capacity (FVC) and 27 per cent showed either decreased forced expiratory flow between 25-75 per cent of FVC (FEF25-75%) or peak expiratory flow rate (PEFR). Of 8 patients who completed exercise challenge tests, 87.5 per cent showed markedly decreased PEFR at post exercise challenge tests and 37.5 per cent had markedly decreased FEV1. 62.5 per cent and 25 per cent showed markedly increased PEFR and FEV, respectively, after inhalation of bronchodilators. CONCLUSION: This study suggests that the occurrence of asthma in children, who had previous RSV-LRI, is relatively high compared with that reported in general Thai children. Baseline pulmonary function tests showed evidence of airway obstruction as demonstrated by concave-shaped flow-volume curves, decreased FEV1/FVC ratio, FEF25-75% and PEFR. The presence of bronchial hyperreactivity to exercise challenge test and positive response to bronchodilators confirms the evidence of exercise-induced bronchospasm in children with history of RSV-LRI.