Pulmonary Arterial Pruning and Longitudinal Change in Percent Emphysema and Lung Function

Abstract

BACKGROUND: Pulmonary endothelial damage has been shown to precede the development of emphysema in animals, and vascular changes in humans have been observed in COPD and emphysema.RESEARCH QUESTION: Is intraparenchymal vascular pruning associated with longitudinal progression of emphysema on CT imaging or decline in lung function over 5 years?STUDY DESIGN AND METHODS: The Genetic Epidemiology of COPD Study enrolled ever smokers with and without COPD from 2008 through 2011. The percentage of emphysemalike lung, or "percent emphysema," was assessed at baseline and after 5 years on noncontrast CT imaging as the percentage of lung voxels < -950 Hounsfield units. An automated CT imaging-based tool assessed and classified intrapulmonary arteries and veins. Spirometry measures are postbronchodilator. Pulmonary arterial pruning was defined as a lower ratio of small artery volume (< 5 mm 2 cross-sectional area) to total lung artery volume. Mixed linear models included demographics, anthropomorphics, smoking, and COPD, with emphysema models also adjusting for CT imaging scanner and lung function models adjusting for clinical center and baseline percent emphysema.RESULTS: At baseline, the 4,227 participants were 60 AE 9 years of age, 50% were women, 28% were Black, 47% were current smokers, and 41% had COPD. Median percent emphysema was 2.1 (interquartile range, 0.6-6.3) and progressed 0.24 percentage points/y (95% CI, ABBREVIATIONS: BV5 = volume of pulmonary vessels less than 5 mm 2 in cross-sectional area; BV5a = volume of pulmonary arteries less than 5 mm 2 in cross-sectional area; COPDGene = Genetic Epidemiology of COPD; HU = Hounsfield units; PD15 = lung density at the 15th percentile; percent emphysema -950 = percentage of lung volume with attenuation < -950 Hounsfield units; TBVa = total arterial volume of interparenchymal vessels

Contributions of Emphysema and Functional Small Airway Disease on Intrapulmonary Vascular Volume in COPD

“…Most of the studies found that %CSA<5mm 2 or BV5 was positively correlated with FEV1 and FEV1/FVC, but negatively correlated with LAA%-950. 25–30 However, relevant studies on IPVV in smokers or patients with COPD found that the total IPVV was positively correlated with smoking severity and LAA%-950, which was consistent with the results of the correlation analysis on IPVV and emphysema in this study. 31–33 It suggested that small peripheral pulmonary vessels were susceptible to emphysema and hypoxia leading to loss, narrowing, or decreased filling.…”

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

“…Arteries and veins may be automatically mapped, peripherally matched, and classified ( 174 ). Loss of pulmonary vascular density or distal PA blood volume is associated with right heart failure indices in smokers ( 175 ), emphysema progression ( 176 ), and asthma severity ( 177 ).…”

Journal Club: Impaired Ventilatory Efficiency and Exercise Intolerance in Former/Current Smokers With Dyspnea Disproportionate to Their Lung Function: Pathophysiological Insights Gained Through Cardiopulmonary Exercise Testing

“…Other considerations suggested by the authors included occult cardiovascular disease and abnormal gas mixing with relatively preserved lung mechanics. The authors propose that the consistent association in the entire cohort between low KCO (and DLCO) and high nadir VE/VCO2 implicates pulmonary microvascular dysfunction 22,[24][25][26][47][48][49] as the primary pathogenic mechanism. The authors point out that past studies have shown that in GOLD stage 1 COPD, high nadir VE/VCO2 is primarily influenced by elevated physiologic dead space reflecting abnormally high ventilation/perfusion (V/Q) (presumably secondary to reduced perfusion secondary to microvascular dysfunction) and to a lesser extent a low regulated level of arterial CO2.…”

“…microvascular dysfunction. 12,14,17,[22][23][24][25][26] Other studies have examined the ventilatory efficiency--(minute ventilation [VE] to carbon dioxide production [VCO2]) VE/VCO2 nadir: the lowest ventilatory rate able to remove 1 liter of CO2 per minute during graded cardiopulmonary exercise testing (CPET). [27][28][29][30][31] While many clinicians are familiar with the concept of dynamic hyperinflation that can lead to breath stacking and dyspnea, fewer non-pulmonary physicians are familiar with the assessment of ventilatory efficiency.…”