The Effect of Inhaled Nitric Oxide on Deadspace in COPD

Plain-language summary

Chronic obstructive pulmonary disease (COPD) is a progressive disease of the respiratory system that generally develops as a result of smoking. Most people with COPD are classified as having "mild" disease severity and may not have significantly impaired lung function (e.g. flow) as measured by traditional lung function tests. However, multiple studies have shown that patients with mild disease already have significant damage to the small airways and blood vessels of the pulmonary system. This results in a considerable portion of the lung that does not participate in gas exchange, a phenomenon called physiologic dead space. Mild COPD patients develop symptoms of intolerable breathlessness early in exercise compared with healthy individuals. Previous studies have shown that pulmonary vasodilators, which locally increase blood vessel radius, may improve gas exchange and reduce symptoms of breathlessness in patients with mild COPD. Therefore, the objective of this study is to determine the effect of reducing dead space with a pulmonary vasodilator on the intensity of breathlessness during exercise in patients with mild COPD. This five visit, double-blinded, placebo-controlled crossover study will test the impact of inhaled nitric oxide, a direct vasodilator, during cardiopulmonary exercise on dead space and breathlessness intensity. Use of an esophageal catheter during testing will additionally permit measurement of neural drive to breathe and pulmonary mechanics throughout the protocol. Though patients with mild COPD represent the majority of the COPD population, their symptoms remain poorly managed by current, inefficient standard of care. The proposed study will examine dead space reduction as a novel therapeutic target for improving breathlessness and exercise tolerance in patients with mild COPD.

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