Potential harms of oxygen therapy

It was previously common practice to use oxygen in the medical care of any patient who appeared breathless or acutely unwell. Evidence for improved clinical outcomes with routine use of oxygen in patients who are not hypoxaemic is lacking, and it may be harmful. Consequently, oxygen therapy is generally not indicated unless the patient is hypoxaemic—see Indications for acute oxygen therapy.

Possible harms of oxygen therapy include:

• hypercapnia, which can be fatal
• adverse consequences related to hyperoxaemia, including
  • absorption atelectasis
  • direct pulmonary toxicity
  • increased systemic vascular resistance and blood pressure
  • reduced coronary artery blood flow
  • reduced cardiac output
  • reduced cerebral blood flow
  • increased reperfusion injury.

Pulse oximetry does not detect hypercapnia and readings may be misleading in some clinical scenarios; see Pulse oximetry to monitor acute oxygen therapy.