A Randomized, Placebo-Controlled, Double-Blind, Crossover Trial of Inhaled Nitric Oxide in Patients With Mild-to-Severe COPD

BACKGROUND: Patients with advanced COPD have pulmonary vascular dysfunction and destruction; thus, it is unclear whether they are responsive to selective pulmonary vasodilators. RESEARCH QUESTION: What is the effect of inhaled nitric oxide (iNO) on exercise capacity in patients without hypoxemia with mild-to-severe COPD without pulmonary hypertension, and are there structural and/or functional predictors of response? STUDY DESIGN AND METHODS: peak]). RESULTS: peak were associated with improved ventilatory efficiency and reduced dyspnea (both P < .05). INTERPRETATION: peak with iNO were associated with improved ventilatory efficiency and reduced dyspnea. Our findings suggest a potential COPD pulmonary vascular endotype responsive to inhaled pulmonary vasodilators, characterized by greater small vessel perfusion or less vascular pruning, that is independent of severity of airflow obstruction, diffusing capacity, emphysema, or lung size. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT03679312; URL: www. CLINICALTRIALS: gov.