[Oxygen in medicine - basics, applications and risks]

Oxygen is a central component in the treatment of acute and chronic diseases associated with hypoxemia. Nevertheless, in everyday clinical practice it is often administered reflexively, even when documented or clearly suspected hypoxemia - the most important prerequisite for appropriate oxygen therapy - is absent. Dyspnea alone is not an indication, as patients with breathlessness but without hypoxaemia ge-nerally do not benefit from oxygen administration. Controlled titration with clearly defined target ranges is essential in order to avoid risks such as hypercapnia, coronary and cerebral vasoconstriction, oxygen toxicity, absorption atelectasis, or even increased mortality. Long-term oxygen therapy remains a prognostically relevant intervention in patients with stable chronic hypoxaemia. This article summarizes the physiological principles, indications, risks, technical delivery systems, and reimbursement considerations relevant to primary care practice.