oxygen therapy

Ordinary air is only about one-fifth oxygen. Oxygen therapy is simply turning up that fraction of the air a patient breathes, so that more oxygen reaches the blood when the lungs cannot manage on room air alone. It is one of the oldest and most widely used treatments in medicine — and, like any drug, it has a right dose and a wrong dose.

Oxygen can be delivered along a spectrum of devices, from gentle to intensive: thin nasal prongs that add a little oxygen to each breath, simple or reservoir face masks that supply higher concentrations, and high-flow systems or ventilators for the sickest. The goal is to lift the blood oxygen into a safe target range — commonly an oxygen saturation around 94 to 98 percent for most patients, but deliberately lower (about 88 to 92 percent) for people at risk of carbon dioxide retention, such as those with advanced COPD.

Oxygen treats hypoxemia; it does not treat the disease causing it, so it is always paired with finding and fixing the underlying problem. An honest caveat: more is not always better. Too much oxygen can suppress the breathing drive in vulnerable patients and, at high concentrations over time, may itself injure the lungs, which is why oxygen is titrated to a target rather than given at maximum by default.