Oxygen: a new look at an old therapy

Oxygen is essential for aerobic respiration yet is potentially toxic. The capability to efficiently deliver sufficient oxygen for optimal cellular function, while minimising oxidant-induced tissue damage has been achieved through complex physiological processes which have developed through evolution. Until recently these physiological adaptations have been poorly appreciated in the practice of medicine, where high concentration oxygen therapy has been routinely administered to breathless patients, without consideration of the potential risks of oxygen toxicity. However, the recognition that both hypoxaemia and hyperoxaemia may cause harm has led to the recommendation that oxygen should only be prescribed if the patient is hypoxaemic and that its administration should be titrated to relieve hypoxaemia, and to avoid hyperoxaemia. It is also recommended that oxygen should be considered a drug which is prescribed for specific indications to achieve a specified arterial oxygen saturation range, and that the response is monitored to guide ongoing therapy.