Abstract：
OBJECTIVE: This study aimed to systematically review the effect of nitrate supplementation on blood oxygen saturation.
METHODS: We searched PubMed, Scopus, and Cochrane Library databases from their inception up to October 2022. Two reviewers independently conducted two stages of the screening process to include a randomized controlled trial with nitrate supplementation versus placebo intervention assessing oxygen saturation among lowlanders going to either real or simulated high altitude environments. We used the Cochrane Risk of Bias 2.0 tool to assess the risk of bias in the included studies. Fixed-effect model meta-analyses were conducted for laboratory-based studies. Random-effect meta-analyses were conducted for real-world studies.
RESULTS: We found 7 trials that met the eligibility criteria. A meta-analysis of studies with some bias concerns showed an increase of 1.26 % in the SpO2 with 44 % I2 during submaximal exercise at simulated high altitudes (GRADE: low). On the contrary, a meta-analysis of studies without heterogeneity showed that nitrate supplementation aggravated oxygen saturation decline (-2.64 %, p = 0.03, GRADE: high) during rest in real high-altitude environments. A meta-analysis also showed that nitrate supplementation did not affect Acute Mountain Sickness (AMS) symptoms (GRADE: high).
CONCLUSIONS: Our results suggest that nitrate supplementation did not provide benefits for AMS prevention during rest at high altitudes. The low-quality evidence showing small beneficial effects of nitrate supplementation during exercise calls for further studies.
METHODS: We searched PubMed, Scopus, and Cochrane Library databases from their inception up to October 2022. Two reviewers independently conducted two stages of the screening process to include a randomized controlled trial with nitrate supplementation versus placebo intervention assessing oxygen saturation among lowlanders going to either real or simulated high altitude environments. We used the Cochrane Risk of Bias 2.0 tool to assess the risk of bias in the included studies. Fixed-effect model meta-analyses were conducted for laboratory-based studies. Random-effect meta-analyses were conducted for real-world studies.
RESULTS: We found 7 trials that met the eligibility criteria. A meta-analysis of studies with some bias concerns showed an increase of 1.26 % in the SpO2 with 44 % I2 during submaximal exercise at simulated high altitudes (GRADE: low). On the contrary, a meta-analysis of studies without heterogeneity showed that nitrate supplementation aggravated oxygen saturation decline (-2.64 %, p = 0.03, GRADE: high) during rest in real high-altitude environments. A meta-analysis also showed that nitrate supplementation did not affect Acute Mountain Sickness (AMS) symptoms (GRADE: high).
CONCLUSIONS: Our results suggest that nitrate supplementation did not provide benefits for AMS prevention during rest at high altitudes. The low-quality evidence showing small beneficial effects of nitrate supplementation during exercise calls for further studies.
摘要：
目的：本研究旨在系统评价补充硝酸盐对血氧饱和度的影响。
方法：我们搜索了PubMed，Scopus,和Cochrane图书馆数据库从成立到2022年10月。两名审查员独立进行了筛选过程的两个阶段，其中包括一项随机对照试验，其中包括补充硝酸盐与安慰剂干预，以评估进入真实或模拟高海拔环境的低地人群的氧饱和度。我们使用Cochrane偏差风险2.0工具评估纳入研究的偏差风险。对实验室研究进行固定效应模型荟萃分析。对真实世界的研究进行了随机效应荟萃分析。
结果：我们发现7项试验符合资格标准。对具有一些偏见的研究的荟萃分析显示，在模拟高海拔（等级：低）的次最大运动期间，SpO2增加了1.26％，I2增加了44％。相反,对没有异质性的研究的荟萃分析表明，补充硝酸盐会加重氧饱和度下降（-2.64％，p=0.03，等级：高）在真实的高海拔环境中休息时。荟萃分析还表明，补充硝酸盐不会影响急性山地疾病（AMS）症状（等级：高）。
结论：我们的结果表明，在高海拔地区休息期间补充硝酸盐对AMS预防没有好处。低质量的证据表明，在运动过程中补充硝酸盐的有益作用很小，需要进一步研究。
方法：我们搜索了PubMed，Scopus,和Cochrane图书馆数据库从成立到2022年10月。两名审查员独立进行了筛选过程的两个阶段，其中包括一项随机对照试验，其中包括补充硝酸盐与安慰剂干预，以评估进入真实或模拟高海拔环境的低地人群的氧饱和度。我们使用Cochrane偏差风险2.0工具评估纳入研究的偏差风险。对实验室研究进行固定效应模型荟萃分析。对真实世界的研究进行了随机效应荟萃分析。
结果：我们发现7项试验符合资格标准。对具有一些偏见的研究的荟萃分析显示，在模拟高海拔（等级：低）的次最大运动期间，SpO2增加了1.26％，I2增加了44％。相反,对没有异质性的研究的荟萃分析表明，补充硝酸盐会加重氧饱和度下降（-2.64％，p=0.03，等级：高）在真实的高海拔环境中休息时。荟萃分析还表明，补充硝酸盐不会影响急性山地疾病（AMS）症状（等级：高）。
结论：我们的结果表明，在高海拔地区休息期间补充硝酸盐对AMS预防没有好处。低质量的证据表明，在运动过程中补充硝酸盐的有益作用很小，需要进一步研究。
