Pulmonary and cardiovascular responses to a repeated exposure exercise protocol in ozone air pollution in adults with exercise-induced bronchoconstriction

Introduction: Individuals with exercise-induced bronchoconstriction (EIB) are at greater risk when exposed to air pollution, but whether impairments in pulmonary or cardiovascular functions are mitigated with repeated exposures to ozone (O₃) has yet not been investigated. This study aimed to examine whether repeated exposures to a controlled level of O₃ can induce adaptation to the impairments on pulmonary and cardiovascular functions in individuals with EIB. Methods: A double-blinded, cross-over, randomized trial of 10 study visits was performed. Subjects went through an EIB provocative test and a graded maximal exercise test for exercise intensity prescription. Participants cycled for 30 min at 60% of their maximal power output. They were randomized to start the first five study exposure visits on either room air (RA) or 170 ppb O₃. Spirometry and pulse wave velocity (PWV) measurements were performed at baseline and after exercise while blood pressure and dyspnea were assessed at end-exercise. A linear mixed effects model was used for differences across study visits, and t-tests for post-pre. Results: Thirteen individuals with mild to moderate EIB completed ten study visits, 53.8% were women, 61.5% had asthma. The decrease in mean forced expiratory volume in one second (FEV₁) in the provocative test was 17.2%. On Day 1 of O₃, FEV₁ decreased 0.2L compared to baseline, p= 0.03. FEV₁ on Day 1 of O₃ was lower than on Day 4 of RA, p= 0.04, and on Day 2 of O₃ it was lower than Day 5 of RA, p= 0.03. Forced expiratory flow in the middle portion of a maximal expiratory effort (FEF₂₅₋₇₅) was also lower on Day 2 of O₃ than Day 4 of RA, p= 0.02. FEF₂₅₋₇₅ was lower on Day 2 of O₃ than Days 4 and 5 of RA, p= 0.02 and p=0.04. Conclusion: Pulmonary function was significantly impaired on Days 1 and 2 of O₃ exposure but not on days 3,4 and 5. On Day 2, cardiovascular function showed a trend towards being impaired, which was not statistically significant.Education, Faculty ofKinesiology, School ofGraduat