Oxygen is often given by medical, nursing, and paramedical staff in community and hospital settings.1 2 However, this treatment is commonly neither prescribed nor targeted to a specific saturation. As with any treatment, indications and potential contraindications exist, and complications may occur. In acute emergencies high flow oxygen can save lives by preventing severe hypoxaemia. However, excessive oxygen can cause harm, and inadequate supervision of its use has been reported in both prehospital and hospital audits.3 4 To resolve some of these problems, the British Thoracic Society recently published guidelines on the use of emergency oxygen in adults.1

Despite the importance of oxygen uptake, transport, and delivery to the tissues, the physiology and pathophysiology of impaired oxygen delivery is surprisingly poorly understood by many emergency caregivers. Furthermore, the role of oxygen therapy is an area of medicine where strong opinions exist, despite there being relatively few randomised controlled trials. The resulting controversy has also led to different practices in different settings.

Conflicting advice is often given to health professionals during training, which can result in confusion. For example, many practitioners believe that oxygen alleviates breathlessness in non-hypoxaemic patients, and …