Oxygen toxicity: Difference between revisions
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==Background== | ==Background== | ||
* | *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 at sea level, breathing unpressurized air) can be tolerated indefinitely<ref name="Hedley">Hedley-Whyte J. Pulmonary Oxygen Toxicity: Investigation and Mentoring. The Ulster Medical Journal. 2008;77(1):39-42.</ref> | |||
**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<ref name="Hedley" />, however there is no predictable pattern or sequence of symptoms for CNS toxicity (initial symptom may be seizure/coma)<ref name="Bitterman" /> | |||
{{Diving Physiology}} | |||
==Clinical Features== | ==Clinical Features== | ||
=== Central nervous system === | ===Pulmonary=== | ||
*Tunnel vision | *Tracheobronchial irritation (initial manifestation) → pleuritic [[chest pain]], [[dyspnea]] and [[cough]]ing<ref name="Thomson">Thomson L, Paton J. Oxygen toxicity. Paediatr Respir Rev. 2014 Jun;15(2):120-3.</ref><ref name="Bitterman">Bitterman H. Bench-to-bedside review: Oxygen as a drug. Critical Care. 2009;13(1):205. doi:10.1186/cc7151.</ref> | ||
*Tinnitus | *Atelectasis | ||
*Diffuse alveolar damage → [[Pulmonary edema]]/[[ARDS]] | |||
===Central nervous system=== | |||
*[[visual disturbances|Tunnel vision]] | |||
*[[Tinnitus]] | |||
*[[Nausea]] | *[[Nausea]] | ||
* | *Facial twitching | ||
*Irritability (personality changes, [[ | *Irritability (personality changes, anxiety, [[confusion]], etc.) | ||
*[[ | *[[Seizure]] | ||
=== Ocular | ===Ocular=== | ||
*Retinopathy of prematurity | *Retinopathy of prematurity (retrolental fibroplasia) - seen in premature infants | ||
*Hyperoxic myopia - seen in adults exposed to repeated toxic levels of oxygen<ref>Anderson B, Farmer JC. Hyperoxic myopia. Transactions of the American Ophthalmological Society. 1978;76:116-124.</ref> | |||
**Resolves spontaneously over several weeks | |||
==Differential Diagnosis== | ==Differential Diagnosis== | ||
{{Scuba diving DDX}} | {{Scuba diving DDX}} | ||
== | ==Evaluation== | ||
*Generally clinical | |||
==Management== | ==Management== | ||
* | *Lower inhaled partial pressure of oxygen to as low as tolerated while maintaining tissue perfusion<ref name="Deutschman">Deutschman, C. S., & Neligan, P. J. (2010). Evidence-based practice of critical care. Philadelphia, PA: Saunders/Elsevier.</ref> | ||
==Disposition== | ==Disposition== | ||
*Admit | |||
==See Also== | ==See Also== | ||
*[[Oxygen therapy]] | |||
==External Links== | ==External Links== | ||
== | |||
==References== | |||
<references/> | <references/> | ||
[[Category: | [[Category:Environmental]] | ||
Latest revision as of 16:41, 31 October 2025
Background
- 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 at sea level, breathing unpressurized air) 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.
- Dalton's Law applies to the total pressure of an ideal gas mixture being the sum of the partial pressures of each individual gas.
- Divers may used Enriched Air NITROX mixtures to proportionally increase partial pressures of oxygen and reduce partial pressures of nitrogen while diving.
- At extremes of depth, additional inert gasses such as helium in TRIMIX are used to further reduce partial pressures of both oxygen and nitrogen below toxic levels.
- Henry's Law applies to the dissolvability of gasses into fluids, including body tissues, being proportional to the partial pressure of the gas.
- The increased pressure at depth causes divers to breath their gas mix at increased pressure to defeat the external water pressure.
- Increased inhaled partial pressures of nitrogen increase risk of nitrogen narcosis, and dissolved nitrogen in tissues re-expanding in micro-bubbles on ascent is the essential cause of decompression sickness. This can affect divers at any depth, including commonly-seen recreational diving depths of 20m/60ft or less.
- Increased inhaled partial pressures of oxygen, generally beyond 1.4-1.6atm, increases risk of oxygen toxicity. This is typically not a substantial risk in common depths of recreational divers at 20m/60ft of depth or less, but can be for more advanced divers at deeper depths.
- The increased pressure at depth causes divers to breath their gas mix at increased pressure to defeat the external water pressure.
Clinical Features
Pulmonary
- Tracheobronchial irritation (initial manifestation) → pleuritic chest pain, dyspnea and coughing[3][2]
- Atelectasis
- Diffuse alveolar damage → Pulmonary edema/ARDS
Central nervous system
- Tunnel vision
- Tinnitus
- Nausea
- Facial twitching
- Irritability (personality changes, anxiety, confusion, etc.)
- Seizure
Ocular
- 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
- Barotrauma of descent
- Otic barotrauma
- Pulmonary barotrauma
- Sinus barotrauma
- Mask squeeze
- Barodentalgia (trapped dental air causing squeeze)
- Barotrauma of ascent
- Pulmonary barotrauma (pulmonary overpressurization syndrome)
- Decompression sickness (DCS)
- Arterial gas embolism
- Alternobaric vertigo
- Facial baroparesis (Bells Palsy)
- At depth injuries
- Oxygen toxicity
- Nitrogen narcosis
- Hypothermia
- Contaminated gas mixture (e.g. CO toxicity)
- Caustic cocktail from rebreathing circuit
Evaluation
- Generally clinical
Management
- Lower inhaled partial pressure of oxygen to as low as tolerated while maintaining tissue perfusion[5]
Disposition
- Admit
See Also
External Links
References
- ↑ 1.0 1.1 Hedley-Whyte J. Pulmonary Oxygen Toxicity: Investigation and Mentoring. The Ulster Medical Journal. 2008;77(1):39-42.
- ↑ 2.0 2.1 Bitterman H. Bench-to-bedside review: Oxygen as a drug. Critical Care. 2009;13(1):205. doi:10.1186/cc7151.
- ↑ Thomson L, Paton J. Oxygen toxicity. Paediatr Respir Rev. 2014 Jun;15(2):120-3.
- ↑ Anderson B, Farmer JC. Hyperoxic myopia. Transactions of the American Ophthalmological Society. 1978;76:116-124.
- ↑ Deutschman, C. S., & Neligan, P. J. (2010). Evidence-based practice of critical care. Philadelphia, PA: Saunders/Elsevier.