Dietary Nitrate Supplementation in Stable Chronic Obstructive Pulmonary Disease (COPD): A Randomised Controlled Trial

None listed

Dietary nitrate is known to protect against adverse cardiovascular events by reducing blood pressure and via effects on the vascular endothelium. Several studies have also shown that dietary nitrate supplementation (in the form in beetroot juice) leads to improvements in exercise performance in healthy subjects and elite athletes. No such investigation has been undertaken in patients with chronic obstructive pulmonary disease. Improving exercise tolerance and performance in this group of patients may significantly enhance the benefits derived from pulmonary rehabilitation in a sustainable fashion. The aims of this project are to establish whether beetroot juice supplementation is safe and effective in improving exercise performance in patients with stable chronic obstructive pulmonary disease (COPD) who attend an outpatient exercise program. It is a randomised placebo-controlled double-blinded crossover trial. Subjects with stable mild-moderate COPD are recruited and randomised to receive beetroot juice, BJ (in a commercially available form) or placebo, PL (an alternative juice). The placebo will either be beetroot juice which has been nitrate-depleted or apple & blackcurrent juice (depending on availability). There will be 3 phases to the study. Phase 1 is designed to assess safety. 10 of the subjects are randomly selected to take part in this phase. Subjects ingest a small dose of beetroot juice, and blood pressure and heart rate are observed over several hours. Phases 2 and 3 are designed to assess changes in exercise performance. All subjects take part in these phases. Baseline exercise tests are performed during the first session of testing. These comprise 2 incremental shuttle walk tests followed by an endurance shuttle walk test (ESWT). The following data is collected: distance walked, heart rate, blood pressure, oxygen saturation, symptom scores (Borg scale), all according to standardised procedures. There is then a 3-day wash-in period during which subjects drink beetroot juice or placebo twice daily. On day 4 the subjects attend for the 2nd testing session during which they perform a repeat ESWT four hours after the morning treatment dose with the same data collected. This is followed by a 4-day washout period. Phase 3 involves the crossing-over of subjects from each treatment group to the alternative treatment and repeating the testing as per phase 2. The data is then analysed to determine the magnitude of any decrease in blood pressure, improvement in exercise performance and change in symptom scores.