Air pollution affects regional lung structure and function, according to Jiwoong Choi, PhD.
Choi
During his presentation on Monday, Dr. Choi, research assistant professor in the Division of Pulmonary, Critical Care, and Sleep Medicine in the Department of Internal Medicine at the University of Kansas School of Medicine in Kansas City, presented the results from a prospective quantitative CT (QCT) imaging and computational fluid dynamics (CFD) study. The CT imaging-based study was one of four sub-projects included in a four-year joint project conducted by a multicenter, multidisciplinary international collaborative research team, supported by a Korean Environmental & Industrial Technology Institute grant.
The impetus for this research was the urgent need to better understand the impact of air pollution on lung health and lung diseases.
"Although previous studies have shown the impact of air pollution on lung health and disease, air pollution-associated alteration in regional lung structure and function has not been specifically shown enough," Dr. Choi said.
Analyzing the Effects of Air Pollution
"To maximize the capability of imaging, we conducted QCT analysis with inspiratory and expiratory thin-section chest CT scans and computational fluid dynamics (CFD) simulations of tidal breathing," he explained.
CFD-simulated regional pressure distribution through the entire conducting airways in COPD (upper) and IPF (lower) patients with excessive air pressure drop associated with high air pollution exposure. Image courtesy of Jiwoong Choi, PhD
The researchers prospectively collected inspiratory and expiratory CT scans, direct and address-based pollution measurements and pulmonary function test (PFT) results from 270 participants who were enrolled in five different institutions in South Korea. Patients were divided into the following categories: those with healthy lungs (age = 68 ± 10 years, 15 men and 51 women), those with asthma (age = 60 ± 12 years, 39 men and 56 women), those with chronic obstructive pulmonary disease (COPD) (age = 69 ±7 years, 66 men and 10 women) and those with idiopathic pulmonary fibrosis (IPF) (age = 72 ±7 years, 43 men and 10 women).
The investigators derived three clusters from machine learning of air pollution measurement data and computed 185 regional lung structural and functional features—including 72 air flow features of tidal breathing—from in-house one-dimensional (1D) computational fluid dynamics (CFD) simulations. They also used ANOVA, post-hoc tests and Pearson's correlation to analyze data. "The methods were sensitive enough to detect and characterize subclinical changes in structural and functional features in the regional lung and provide new information that may provide visualized and quantitative evidence of what happens in the lung when various types and levels of air pollution exposure occur," Dr. Choi noted.
Drawing Conclusions
The study's results suggest that small airway disease is more commonly associated with particulate matter (PM) exposure across disease states. Specifically, the researchers found a correlation between PM1, PM2 and PM4 exposures and CFD-derived airway resistance (R) of the whole lung (r=0.416, 0.485 and 0.436). They also found that normalized airway diameters (Dh*) at the right lower lobe segmental branches (sRLL) were significantly smaller (-8.2%, p=0.017) in the high PM exposure group compared with the low exposure group.
"Although we may need fuller investigation to confirm, air pollution exposure was associated with reduced air pressure-derived work rate of the lung in asthma but with increased work rate of the lung in COPD and IPF," Dr. Choi said. "This might be attributable to large airway remodeling in asthma and parenchymal damage in COPD and IPF."
Being aware of air pollution-associated pathophysiological changes and the risk of adverse respiratory outcomes in patients with chronic lung disease may help physicians better understand the causes of certain features that are not very common across the disease, Dr. Choi added.
Access the presentation, "Quantitative CT and Computational Fluid Dynamics Analysis of Air Pollution Impacts on Tidal Breathing in Asthma, COPD, and IPF Lungs," (M3-SSCH03-3) on demand at Meeting.RSNA.org.
