Property Action
Class Naturally occurring gas
Uses Improve FiO2, CO poisoning, hyperbaric O2 therapy
Pharmaceutics Clear, colourless, odourless gas at STP. Critical temperature -119°C, manufactured by fractional distillation. Highly flammable.
Route of Administration Inhaled
Dosing 0.21-1.0 FiO2
Absorption Diffusion across the alveolar capillary membrane in proportion to membrane area and partial pressure gradient, and inversely proportional to membrane thickness (Fick's Law)
Distribution Bound to plasma Hb, and dissolved in plasma
Metabolism Metabolised in mitochondria of cells during the citric acid cycle to produce ATP, creating CO2
Elimination Exhalation as CO2, or combined with H2O to produce HCO3- and eliminated in urine
Resp ↓ Respiratory drive in all individuals. May result in a fatal ↓ in those dependent on hypoxic drive. Pulmonary toxicity due to free radial formation when PiO2>0.6bar - pneumonitis/ARDS due to lipid peroxidation of the alveolar-capillary membrane. Absorption atelectasis.
CVS Improvement in all CVS parameters in the setting of hypoxia. However, hyperoxia ↓ CO, ↓PVR, ↓PAP, and causes coronary vasoconstriction with prolonged administration
CNS CNS O2 toxicity, typically at pressures >1.6 bar though this is variable. Presents with a variety of neurological symptoms, progressing to disorientation and seizure. Retrolental fibroplasia in neonates exposed to high FiO2.
Other Fire risk


  1. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
  2. RAH Advanced Diving Medicine Course Notes: Chapter 6 Oxygen and Carbon Dioxide Toxicity
Last updated 2020-09-02

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