Oxygen toxicity


  • The harmful effects of breathing oxygen at higher partial pressures than normal
    • Partial pressure of O2 at sea level = 0.21 ATM
  • Toxicity based on both time of exposure and partial pressure of oxygen
    • Generally, FiO2 of 40% or less (0.40 ATM) can be tolerated indefinitely[1]
    • Most common in hyperbaric oxygen therapy, scuba divers and prolonged administration of normobaric supplemental oxygen
    • Pulmonary toxicity occurs sooner and at lower partial pressures than CNS toxicity[1], however there is no predictable pattern or sequence of symptoms for CNS toxicity (initial symptom may be seizure/coma)[2]

Diving Physiology

  • Pascals Law applies to the diving body (without air filled areas such as lungs) states that the pressure applied to any part of the enclosed liquid will be transmitted equally in all directions through the liquid.
  • Boyles Law applies to the diving body's air filled areas such as lungs, sinuses, middle ear, and states that the volume and pressure of a gas at a given temperature are inversely related.
    • At 2 ATA (10m/33ft) a given gas would be 1/2 it's volume, at 3 ATA (20m/66ft) it would be 1/3 it's volume and so on.
Boyle's Law

Clinical Features


Central nervous system


  • Retinopathy of prematurity (retrolental fibroplasia) - seen in premature infants
  • Hyperoxic myopia - seen in adults exposed to repeated toxic levels of oxygen[4]
    • Resolves spontaneously over several weeks

Differential Diagnosis

Diving Emergencies


  • Generally clinical


  • Lower inhaled partial pressure of oxygen to as low as tolerated while maintaining tissue perfusion[5]


  • Admit

See Also

External Links


  1. 1.0 1.1 Hedley-Whyte J. Pulmonary Oxygen Toxicity: Investigation and Mentoring. The Ulster Medical Journal. 2008;77(1):39-42.
  2. 2.0 2.1 Bitterman H. Bench-to-bedside review: Oxygen as a drug. Critical Care. 2009;13(1):205. doi:10.1186/cc7151.
  3. Thomson L, Paton J. Oxygen toxicity. Paediatr Respir Rev. 2014 Jun;15(2):120-3.
  4. Anderson B, Farmer JC. Hyperoxic myopia. Transactions of the American Ophthalmological Society. 1978;76:116-124.
  5. Deutschman, C. S., & Neligan, P. J. (2010). Evidence-based practice of critical care. Philadelphia, PA: Saunders/Elsevier.