School of Health Sciences, Locked Bag 1797 Penrith, Sydney, NSW 2751, Australia.
School of Medicine, Western Sydney University, Locked Bag 1797 Penrith, Sydney, NSW 2751, Australia.
Eur J Prev Cardiol. 2021 Mar 23;28(1):127-136. doi: 10.1093/eurjpc/zwaa001.
Oxygen is a pulmonary vasodilator. Although treatment of pulmonary arterial hypertension (PAH) is focused on pulmonary vasodilation, treatment guidelines do not recommend O2 therapy for patients unless they develop hypoxaemia. These guidelines point to a lack of evidence of benefit of O2 therapy from randomized controlled trials (RCTs) and to evidence of lack of benefit in a single RCT involving patients with Eisenmenger syndrome. These guidelines did not identify major limitations with the Eisenmenger study or consider other evidence of therapeutic benefit. Recent advances in mechanistic understanding of O2 effects on pulmonary vascular tone, along with substantial evidence of acute effects of O2 in PAH patients, challenge the view that benefits of O2 arise only through correction of hypoxaemia. Evidence presented in this review shows that O2 acts as a pulmonary vasodilator in patients who are normoxaemic; that this probably involves an alveolar mechanism in addition to a blood-borne (oxyhaemoglobin) mechanism; and that therapeutic benefit of O2 does not depend on arterial O2 levels. This suggests that O2 has potential therapeutic benefit for all patients with PAH. Clinical guidelines and practice related to O2 therapy need to be reassessed, and further research is needed.
氧气是一种肺血管扩张剂。虽然肺动脉高压（PAH）的治疗重点是肺血管扩张，但治疗指南并不建议对出现低氧血症的患者进行氧疗。这些指南指出，随机对照试验（RCT）缺乏氧疗获益的证据，而且一项涉及艾森曼格综合征患者的 RCT 也表明氧疗没有获益。这些指南没有发现艾森曼格研究的主要局限性，也没有考虑其他治疗获益的证据。最近在氧对肺血管张力的作用机制方面的研究进展，以及大量关于 PAH 患者氧的急性作用的证据，对氧的获益仅通过纠正低氧血症产生的观点提出了挑战。本综述中提出的证据表明，在氧合正常的患者中，氧作为一种肺血管扩张剂发挥作用；这可能除了血液源性（氧合血红蛋白）机制外，还涉及肺泡机制；而且氧的治疗获益并不依赖于动脉血氧水平。这表明，氧对所有 PAH 患者都具有潜在的治疗益处。与氧疗相关的临床指南和实践需要重新评估，还需要进一步的研究。
