Abstract
BACKGROUND: There is a link between exposure to air pollution and the increased prevalence of chronic obstructive pulmonary disease (COPD) and declining pulmonary function, but the association with O(2) desaturation during exercise in COPD patients with emphysema is unclear. Our aims were to estimate the prevalence of O(2) desaturation during exercise in patients with COPD, and determine the association of exposure to air pollution with exercise-induced desaturation (EID), the degree of emphysema, and dynamic hyperinflation (DH). METHODS: We assessed the effects of 10-year prior to the HRCT assessment and 7 days prior to the six-minute walking test exposure to particulate matter with an aerodynamic diameter of < 10 µm (PM(10)) or of < 2.5 µM (PM(2.5)), nitrogen dioxide (NO(2)), and ozone (O(3)) in patients with emphysema in this retrospective cohort study. EID was defined as a nadir standard pulse oximetry (SpO(2)) level of < 90% or a delta (△)SpO(2) level of ≥ 4%. Ambient air pollutant (PM(2.5), PM(10), O(3), and NO(2)) data were obtained from Taiwan Environmental Protection Administration (EPA) air-monitoring stations, usually within 10 km to each participant's home address. RESULTS: We recruited 141 subjects with emphysema. 41.1% of patients with emphysema exhibited EID, and patients with EID had more dyspnea, worse lung function, more severe emphysema, more frequent acute exacerbations, managed a shorter walking distance, had DH, and greater long-term exposure to air pollution than those without EID. We observed that levels of 10-year concentrations of PM(10), PM(2.5), and NO(2) were significantly associated with EID, PM(10) and PM(2.5) were associated with the severity of emphysema, and associated with DH in patients with emphysema. In contrast, short-term exposure did not have any effect on patients. CONCLUSION: Long-term exposure to ambient PM(10), PM(2.5) and NO(2), but not O(3), was associated with EID.