Oxygen therapy in acute coronary syndrome: current NICE recommendations

Editor–I read with great interest the concise guidance by O'Driscoll and colleague (Clin Med August 2011, pp 372–5) on emergency oxygen use in adult patients. Oxygen therapy is widely used in both acute and chronic cardiac care. Traditionally for decades, any patient presenting with chest pain is instantaneously administered high flow oxygen. This concept originally started as we realised oxygen could ease angina pain.¹ It was subsequently believed that this would ease myocardial ischaemia in patient's presenting with acute coronary syndrome (ACS). It quickly became norm to administer high-flow oxygen therapy to patients presenting with acute chest pain.

However, more recently, there have been many reports of harmful effects of high-flow oxygen in ACS patients where the patient might not be hypoxic. High flow oxygen has been shown previously to reduce cardiac output,² attribute to arterial vasoconstriction^3–5 and also to increase systemic vascular resistance.⁶ More recently, two systematic reviews suggest that the routine use of high-flow oxygen in uncomplicated myocardial infarction may result in a greater infarct size and possibly increase the risk of mortality.^7,8

The Resuscitation Council UK, the National Institute for Health and Clinical Excellence and the British Thoracic Society have recently appreciated this concern of oxygen therapy in ACS patients and have changed their guidance accordingly. They all now suggest that oxygen therapy should be reserved for ACS patients with hypoxia (O₂ saturation below 94%).

From my current clinical experience, oxygen is still widely administered to ACS patients without hypoxia. This practice needs to change across the NHS and it will only happen with constant multidisciplinary education and the introduction of local oxygen prescription guidance in ACS patients.