Leong Paul, Basham Jane E, Yong Theresa, Chazan Adrian, Finlay Paul, Barnes Sara, Bardin Phillip G, Campbell Donald
Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia.
Department of General Medicine, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia.
BMC Pulm Med. 2015 May 2;15:52. doi: 10.1186/s12890-015-0057-4.
Dietary nitrate supplementation has been shown to decrease the oxygen cost of exercise and prolong exercise tolerance, as measured by sub-maximal exercise endurance distance and time at 85% V̇O2max, in both elite athletes and normal healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) have reduced quality of life and ability to perform activities of daily living attributable to diminished exercise tolerance, and dietary nitrate may be able to ameliorate this.
We performed a double-blind, computer-randomized placebo control crossover trial at a tertiary Australian hospital to investigate whether dietary nitrate supplementation as beetroot juice (BR) would augment submaximal exercise endurance in individuals with spirometrically confirmed stable moderate COPD. Volunteers underwent an incremental shuttle walk test to determine V̇O2max followed by a test dose of BR to establish safety in the study population. Participants performed an endurance shuttle walk test (ESWT) at 85% V̇O2max after randomization to either a 3 day wash-in of BR (4.8 mmol twice a day) or placebo (nitrate deplete BR), with a final dose on the morning of testing. They then crossed over after 4 day washout. Repeated measures two sided paired t-tests were employed.
35 participants were recruited with 19 completing the trial. In the initial safety phase, we measured systolic blood pressure over four hours post first dose of BR, and found a mean 10 mmHg decrement maximal at 1 hour. One individual developed symptomatic postural hypotension and was excluded. The primary outcomes of ESWT distance and time to fatigue improved by 11% and 6% respectively; however these differences did not achieve statistical significance (p = 0.494 and 0.693 respectively).
Our study does not support a role for routine dietary nitrate supplementation for enhancement of exercise endurance in COPD.
Australia and New Zealand Clinical Trial Register: ACTRN12611001088932.
膳食硝酸盐补充剂已被证明可降低运动的氧气消耗并延长运动耐力，这在精英运动员和正常健康受试者中均通过次最大运动耐力距离以及在85%最大摄氧量（V̇O2max）时的运动时间来衡量。慢性阻塞性肺疾病（COPD）患者由于运动耐力下降，生活质量降低且日常生活活动能力受限，而膳食硝酸盐或许能够改善这一状况。
我们在一家澳大利亚三级医院进行了一项双盲、计算机随机、安慰剂对照交叉试验，以研究作为甜菜根汁（BR）的膳食硝酸盐补充剂是否会增强肺功能测定确诊为稳定中度COPD个体的次最大运动耐力。志愿者接受递增穿梭步行试验以确定V̇O2max，随后进行BR试验剂量以确定研究人群的安全性。参与者在随机分为BR（每天两次，每次4.8 mmol）或安慰剂（硝酸盐耗尽的BR）进行3天导入期后，于测试当天早晨服用最后一剂，然后在85% V̇O2max下进行耐力穿梭步行试验（ESWT）。4天洗脱期后他们进行交叉。采用重复测量双侧配对t检验。
招募了35名参与者，19名完成试验。在初始安全阶段，我们在首次服用BR后4小时测量收缩压，发现平均下降10 mmHg，在1小时时最大。1名个体出现症状性体位性低血压并被排除。ESWT距离和疲劳时间的主要结局分别改善了11%和6%；然而这些差异未达到统计学显著性（分别为p = 0.494和0.693）。
我们的研究不支持常规膳食硝酸盐补充剂在增强COPD患者运动耐力方面的作用。
澳大利亚和新西兰临床试验注册中心：ACTRN12611001088932。
