Conventional Oxygen Therapy: Technical and Physiological Issues

Dioxygen was discovered more than two centuries ago but the large-scale clinical utilization began during the twentieth century. The slowness of the introduction of oxygen as a therapy is explained by the initial caution linked to potential toxicity, technical administration problems and the first mixed results. Modern conventional oxygen therapy with continuous oxygen flow below 15 L/min is now one of the most used drugs in hospitals and in the prehospital setting. The first aim of oxygen therapy is to treat hypoxemia, and the second is to avoid hyperoxemia, a frequently overlooked complication. Hyperoxemia leads to induced hypercapnia in several clinical situations, especially in severe COPD patients; retinopathy in premature infants; arterial vasoconstriction; and cellular damage. The multi-organ and systemic toxicity of oxygen is responsible for increased mortality when this gas is administered liberally in acutely ill patients. The most recent recommendations favor a restrictive use of oxygen and oblige clinicians to consider hyperoxemia detrimental to patients such as hypoxemia. SpO2 between 88% and 92% should be targeted for patients at risk of hypercapnia (beyond COPD) and SpO2 between 90 and 94% should be targeted in other populations. New devices that accurately titrate O2 flow rate based on SpO2 target may help to achieve these goals.