Patric Gonçalves’ MSc Thesis Defence

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

Thesis Supervisor: Dr. Michael Koehle
Committee members: Dr. Nadine Borduas-Dedekind, Dr. Bill Sheel
Defence Chair: Dr. Karim Khan

Abstract:
Introduction: Individuals with exercise-induced bronchoconstriction (EIB) are at greater risk when exposed to ozone (O3) air pollution, but whether impairments in pulmonary or cardiovascular functions are adaptable to repeated exposures to O3 has yet not been investigated. This study aimed to examine whether repeated exposures to a controlled level of O3 can mitigate the impairments on pulmonary and cardiovascular functions in individuals with EIB. Methods: A double-blinded, cross-over, randomized trial of 11 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 parts per billion 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 baseline and post-pre.

Results: Thirteen individuals 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/s 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 impaired on Days 1 and 2 of O3 exposure but not on days 3,4 and 5. On Day 2, cardiovascular function also seemed impaired, despite the decline not being statistically significant.