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Emphysema on Thoracic CT and Exercise Ventilatory Inefficiency in Mild-to-Moderate COPD.
- Source :
- COPD: Journal of Chronic Obstructive Pulmonary Disease; Apr2017, Vol. 14 Issue 2, p210-218, 9p
- Publication Year :
- 2017
-
Abstract
- There is growing evidence that emphysema on thoracic computed tomography (CT) is associated with poor exercise tolerance in COPD patients with only mild-to-moderate airflow obstruction. We hypothesized that an excessive ventilatory response to exercise (ventilatory inefficiency) would underlie these abnormalities. In a prospective study, 19 patients (FEV<subscript>1</subscript> = 82 ± 13%, 12 Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 1) and 26 controls underwent an incremental exercise test. Ventilatory inefficiency was assessed by the ventilation (E)/CO<subscript>2</subscript> output (CO<subscript>2</subscript>) nadir. Pulmonary blood flow (PBF) in a submaximal test was calculated by inert gas rebreathing. Emphysema was quantified as % of attenuation areas below 950 HU. Patients typically presented with centrilobular emphysema (76.8 ± 10.1% of total emphysema) in the upper lobes (upper/total lung ratio = 0.82 ± 0.04). They had lower peak oxygen uptake (O<subscript>2</subscript>), higher E/ CO<subscript>2</subscript> nadir, and greater dyspnea scores than controls (p < 0.05). Lower peak O<subscript>2</subscript> and worse dyspnea were found in patients with higher E/ CO<subscript>2</subscript> nadirs (≥30). Patients had blunted increases in PBF from rest to iso- O<subscript>2</subscript> exercise (p < 0.05). Higher E/ CO<subscript>2</subscript> nadir in COPD was associated with emphysema severity (r = 0.63) which, in turn, was related to reduced lung diffusing capacity (r = −0.72) and blunted changes in PBF from rest to exercise (r = −0.69) (p < 0.01). Ventilation "wasted" in emphysematous areas is associated with impaired exercise ventilatory efficiency in mild-to-moderate COPD. Exercise ventilatory inefficiency links structure (emphysema) and function (D<subscript>L</subscript>CO) to a key clinical outcome (poor exercise tolerance) in COPD patients with only modest spirometric abnormalities. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15412555
- Volume :
- 14
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- COPD: Journal of Chronic Obstructive Pulmonary Disease
- Publication Type :
- Academic Journal
- Accession number :
- 121994396
- Full Text :
- https://doi.org/10.1080/15412555.2016.1253670