Association of air pollution exposure with exercise-induced oxygen desaturation in COPD

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 O₂ desaturation during exercise in COPD patients with emphysema is unclear. Our aims were to estimate the prevalence of O₂ 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).

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 (PM₁₀) or of < 2.5 µM (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃) in patients with emphysema in this retrospective cohort study. EID was defined as a nadir standard pulse oximetry (SpO₂) level of < 90% or a delta (△)SpO₂ level of ≥ 4%. Ambient air pollutant (PM_2.5, PM₁₀, O₃, and NO₂) data were obtained from Taiwan Environmental Protection Administration (EPA) air-monitoring stations, usually within 10 km to each participant's home address.

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 PM₁₀, PM_2.5, and NO₂ were significantly associated with EID, PM₁₀ 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.

Long-term exposure to ambient PM₁₀, PM_2.5 and NO₂, but not O₃, was associated with EID.