Exertional-induced bronchoconstriction: Comparison between cardiopulmonary exercise test and methacholine challenging test

INTRODUCTION: Exertional-induced bronchoconstriction is a condition in which the physical activity causes constriction of airways in patients with airway hyper- responsiveness. In this study, we tried to study and evaluate any relationship between the findings of cardiopulmonary exercise testing (CPET) and the response to methacholine challenge test (MCT) in patients with dyspnea after activity. MATERIALS AND METHODS: Thirty patients with complaints of dyspnea following activity referred to “Lung Clinic” of Baqiyatallah Hospital but not suffering from asthma were entered into the study. The subjects were excluded from the study if: Suffering from any other pulmonary diseases, smoking more than 1 cigarette a week in the last year, having a history of smoking more than 10 packets of cigarettes/year, having respiratory infection in the past 4 weeks, having abnormal chest X-ray or electrocardiogram, and cannot discontinue the use of medicines interfering with bronchial provocation. Baseline spirometry was performed for all the patients, and the values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV/FVC were recorded. The MCT and then the CPET were performed on all patients. RESULTS: The mean VO(2) (volume oxygen) in patients with positive methacholine test (20.45 mL/kg/min) was significantly lower than patients with negative MCT (28.69 mL/kg/min) (P = 0.000). Respiratory rates per minute (RR) and minute ventilation in the group with positive MCT (38.85 and 1.636 L) were significantly lower than the group with negative methacholine test (46.78 and 2.114 L) (P < 0.05). Also, the O(2) pulse rate in the group with negative methacholine test (116.27 mL/beat) was significantly higher than the group with positive methacholine test (84.26 mL/beat) (P < 0.001). CONCLUSION: Pulmonary response to exercise in patients with positive methacholine test is insufficient. The dead space ventilation in these patients has increased. Also, dynamic hyperinflation in patients with positive methacholine test causes the reduced stroke volume and O(2) pulse in these patients.