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Systematic review of studies of the effect of hyperoxia on coronary blood flow
Hamish Farquhar1, Mark Weatherall, Meme Wijesinghe
1Medical Research Institute of New Zealand, Wellington, New Zealand.
Insights
High-concentration oxygen therapy, recommended for heart attacks, may reduce coronary blood flow and oxygen consumption. This hyperoxia effect could potentially harm patients with cardiac conditions.
Area of Science:
- Cardiology
- Physiology
Background:
- International guidelines suggest routine oxygen for myocardial infarction.
- The physiological and clinical impact of this practice remains unclear.
Purpose of the Study:
- To systematically review human studies measuring coronary blood flow during oxygen breathing.
- To assess the effects of hyperoxia on coronary blood flow, vascular resistance, and myocardial oxygen consumption.
Main Methods:
- Systematic literature search of Medline, Cochrane, EMBASE, and CINHAL.
- Inclusion criteria focused on human studies measuring coronary blood flow while breathing oxygen versus room air.
- Primary outcome: coronary blood flow; Secondary outcomes: coronary vascular resistance, myocardial oxygen consumption.
Main Results:
- Six studies with 67 subjects (6 healthy, 61 cardiac disease) met criteria; meta-analysis was not feasible.
- High-concentration oxygen induced hyperoxia (mean Pao(2) 273–425 mm Hg).
- Hyperoxia significantly reduced coronary blood flow (-7.9% to -28.9%), increased coronary vascular resistance (21.5% to 40.9%), and decreased myocardial oxygen consumption (-15.3% to -26.9%).
Conclusions:
- Hyperoxia from high-concentration oxygen therapy markedly reduces coronary blood flow and myocardial oxygen consumption.
- These physiological changes suggest potential harm, impacting the use of high-concentration oxygen in cardiac and other disorders.
Background:
International guidelines recommend the routine use of oxygen in the initial treatment of myocardial infarction, yet it is uncertain what effect this might have on physiologic and clinical outcomes.
Methods:
We undertook a systematic search of Medline, Cochrane Database of Systematic Reviews, EMBASE, and CINHAL using the key words "oxygen," "coronary blood flow," "hyperoxia," and "coronary circulation" to identify human studies involving a measure of coronary blood flow while breathing oxygen and room air. The primary outcome measure was coronary blood flow; secondary outcomes included coronary vascular resistance and myocardial oxygen consumption.
Results:
From 2,072 potential publications, there were 6 studies from 4 publications that met the inclusion criteria, with 6 healthy subjects and 61 subjects with cardiac disease. It was not possible to undertake a meta-analysis due to methodological limitations. In the 6 studies, high-concentration oxygen therapy resulted in hyperoxia, with a range in mean Pao(2) of 273 to 425 mm Hg. Hyperoxia caused a significant reduction in coronary blood flow (mean change -7.9% to -28.9%, n = 6 studies). Hyperoxia caused a significant increase in coronary vascular resistance (mean change 21.5% to 40.9%, n = 4 studies) and a significant reduction in myocardial oxygen consumption (mean change -15.3% to -26.9%, n = 3 studies).
Conclusions:
Hyperoxia from high-concentration oxygen therapy causes a marked reduction in coronary blood flow and myocardial oxygen consumption. These physiologic effects may have the potential to cause harm and are relevant to the use of high-concentration oxygen therapy in the treatment of cardiac and other disorders.
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