Effects of Traffic-Related Air Pollution on Exercise Endurance, Dyspnea, and Cardiorespiratory Responses in Health and COPD
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BACKGROUND: Individuals with COPD have increased sensitivity to traffic-related air pollution (TRAP) such as diesel exhaust (DE), but little is known about the acute effects of TRAP on exercise responses in COPD. RESEARCH QUESTION: Does exposure before exercise to TRAP (DE titrated to 300 μg/m3 particulate matter < 2.5 μm in diameter [DE300]) show greater adverse effects on exercise endurance, exertional dyspnea, and cardiorespiratory responses to exercise in participants with mild to moderate COPD compared with former smokers with normal spirometry and healthy control participants? STUDY DESIGN AND METHODS: In this double-blind, randomized, placebo-controlled, crossover study, 11 healthy control participants, nine former smokers without COPD, and nine former smokers with COPD were separately exposed to filtered air (FA) and DE300 for 2 h separated by a minimum of 4 weeks. Participants performed symptom-limited constant load cycling tests within 2.5 h of exposure with detailed cardiorespiratory and exertional symptom measurements. RESULTS: A significant negative effect of TRAP on exercise endurance time was found in healthy control participants (DE300 vs FA, 10.2 ± 8.2 min vs 12.9 ± 9.5 min, respectively; P = .03), but not in former smokers without COPD (10.1 ± 6.9 min vs 12.2 ± 8.0 min, respectively; P = .57) or former smokers with COPD (9.8 ± 6.4 min vs 8.4 ± 6.6 min, respectively; P = .31). Furthermore, significant increases in inspiratory duty cycle and absolute end-expiratory and end-inspiratory lung volumes were observed, and dyspnea ratings were elevated at select submaximal measurement times only in healthy control participants. INTERPRETATION: Contrary to our hypothesis, it was the healthy control participants, rather than the former smokers with and without COPD, who were negatively impacted by TRAP during exercise. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT02236039; URL: www. CLINICALTRIALS: gov.
