Late Breaking Abstract - Dietary nitrate supplementation increases exercise endurance time in COPD patients using ambulatory oxygen

Abstract

Background: Dietary nitrate supplementation reduces the oxygen cost of exercise in COPD but not endurance time (Curtis et al. 2015). Individuals using ambulatory oxygen may show a greater response. Nitric oxide (NO) regulates blood flow, mitochondrial respiration and improves pulmonary vascular resistance. Under the hypoxic conditions found in skeletal muscle of COPD patients, NO can be generated via the nitrate-nitrite-NO pathway, suggesting hypoxic patients may benefit from nitrate supplementation. Aim: To assess if dietary nitrate supplementation improves exercise endurance in COPD patients who use ambulatory oxygen. Hypothesis: Dietary nitrate supplementation will improve endurance walking time in COPD patients who need supplemental oxygen. Methods: A double blind, placebo-controlled, cross-over study comparing the effect of 140ml nitrate-rich beetroot juice (BR) with a matched placebo (PL), nitrate-depleted beetroot juice, in patients with COPD. Primary outcome measure was exercise endurance time, via the endurance shuttle walk test, assessed 3 hours after ingesting BR or PL. Results: n=20 (female 40%, age 67.6±8.5years, BMI 25.2±4.7kgm-2, FEV1 %predicted 27±8.1%). Nitrate supplementation significantly increased exercise endurance time: BR 194.6sec (89.1 – 1200.0) vs PL 159.1sec (78.6 – 785.0). Estimated treatment effect of BR vs PL 62sec (95%CI 33, 106) p Conclusion: Administration of dietary nitrate increases exercise endurance time in COPD patients who require ambulatory oxygen.