Target saturations of 94 to 98 per cent, or 88 to 92 per cent if at risk of hypercapnia
Expansion
Target ranges
- 94 to 98 per cent for most acutely unwell patients
- 88 to 92 per cent for those at risk of hypercapnic respiratory failure: COPD, severe kyphoscoliosis, neuromuscular disease, obesity hypoventilation, cystic fibrosis
- In cardiac arrest and critical illness, give the highest concentration initially and titrate once stable
Why not more is better: hyperoxia causes absorption atelectasis, worsened ventilation-perfusion matching through release of hypoxic pulmonary vasoconstriction, the Haldane effect raising carbon dioxide, coronary and cerebral vasoconstriction, and free radical injury. Liberal oxygen has been associated with worse outcomes in myocardial infarction and stroke.
Devices should match the requirement: Venturi masks give a fixed concentration and are preferred where control matters; nasal cannulae and simple masks are variable performance.
Practical points: prescribe on the drug chart with a target range, record the delivery device and flow, monitor saturations and take a blood gas in anyone at risk of hypercapnia.
Never withhold oxygen from a hypoxic patient for fear of retention; give controlled oxygen and monitor the carbon dioxide instead.