A Randomized, Placebo-Controlled, Double-Blind, Crossover Trial of Inhaled Nitric Oxide in Patients With Mild-to-Severe COPD
Abstract
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: Sixty-one patients with mild-to-severe COPD (mean FEV1, 65% ± 18% predicted) were recruited to this randomized, placebo-controlled, double-anonymized, crossover trial. Assessments included pulmonary function, echocardiography, and quantitative CT scan. Small vessel volume fraction, defined as the vascular volume of blood vessels with a cross-sectional area 2 (BV5) divided by total vascular volume (TVV), was used as an index of small vessel perfusion or pulmonary vascular pruning. Participants received iNO or placebo (randomized) during 2 separate incremental exercise tests to determine exercise capacity (peak rate of oxygen consumption [Vo2peak]).
Results: The mean effect of iNO on Vo2peak was 0.36 mL/kg/min (95% CI, -0.18 to 0.89) in an unadjusted linear mixed effects model. In prespecified analyses, there was evidence of iNO effect modification by BV5/TVV, whereby higher BV5/TVV was associated with greater iNO-induced improvement in Vo2peak (adjusted mean change, 0.14 mL/kg/min; 95% CI, 0.02-0.26 per 1% increment in BV5/TVV),…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.
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