Despite its essential role in sustaining human life, oxygen can be highly toxic to humans under the circumstances of prolonged exposure to increased amounts of oxygen, which may be seen during hyperbaric oxygen therapy or in divers, who must inhale very large amounts of oxygen to sustain vital functions [1] [2] [3] [4]. Although many tissues have been reported as targets of oxygen toxicity, the two most important are the lungs and the central nervous system (CNS) [1] [4] [5]. The pathogenesis of tissue damage stems from accelerated formation of reactive oxygen species (ROS) in the presence of higher partial pressure of oxygen in the circulation. The CNS is particularly sensitive to these changes [1] [6]. Symptoms and signs of toxicity appear within few hours, most common being headaches, loss of consciousness, convulsions, and visual disturbances. The loss of peripheral vision and myopia are reversible, while cataracts are a delayed complication [1] [3]. On the other hand, respiratory manifestations such as carinal irritation, dyspnea, chest pain, an uncontrolled cough, tachypnea, and a sensation of choking are main indicators of lung-related oxygen poisoning [1] [3] [5]. Without cessation of exposure to high oxygen concentrations, pulmonary fibrosis, atelectasis, and acute respiratory distress syndrome (ARDS) may ensue [1] [5]. Neonates who suffered from oxygen poisoning could present with retinopathies, intraventricular hemorrhages, and chronic diseases of the lungs [1].

• Nausea

  Continuation of exposure can lead to vertigo and nausea followed by altered behaviour, clumsiness, and finally convulsions. The convulsions are usually tonic-clonic, and the patient has no memory of the crisis4,8. [inspectapedia.com]

  […] more adverse effect on subsequent excursions than will 20 fsw; a return to 20 fsw for periods of 95-110 min seems to provide an adequate recovery period from an earlier excursion and enables a second excursion to be taken without additional hazard; nausea [ncbi.nlm.nih.gov]

  Symptoms include nausea, headache, weakness, clumsiness, and confusion. Severe cases of carbon monoxide poisoning can cause seizures, loss of consciousness, or coma. Diagnosis is with a blood test. [merckmanuals.com]

• Loss of Appetite

  […] of appetite Experts also cite the obvious hazard of freezing-burns if someone comes in contact with liquid oxygen. [inspectapedia.com]

• Loss of Peripheral Vision

  The loss of peripheral vision and myopia are reversible, while cataracts are a delayed complication. [symptoma.com]

• Aphasia

  Definite: muscle twitching, tinnitus (ringing in the ears), blurred or tunnel vision, disorientation, aphasia (inability to express oneself by speaking), nystagmus (rapid side-to-side motions of the eye), or incoordination. [diversalertnetwork.org]

Timely cessation of exposure will result in complete resolution of symptoms [1] [5], but in the absence of an early diagnosis, consequences could be severe. For this reason, it is important to identify oxygen poisoning early on and establish the mode, as well as source of exposure in order to facilitate treatment. The physician must obtain a detailed patient history that will assess the presence of risk factors (eg. diving, hyperbaric oxygen therapy) and note the course and progression of symptoms, whereas physical examination, particularly lung auscultation, can detect crackles, rhonchi, or wheezing [5]. Laboratory investigation comprised of a complete blood count (CBC), serum electrolytes, but most importantly, arterial blood gas (ABG) analysis, should be performed as soon as possible, together with a chest X-ray that frequently shows findings consistent with bilateral pulmonary edema [5]. Spirometry is also a vital constituent of the diagnostic workup and many patients exhibit a reduction in the vital capacity (VC). The diffusing capacity for carbon monoxide and dynamic lung compliance are both reduced in certain cases [1].

• Pulmonary Infiltrate

  infiltrates and clinical deterioration; although the mechanism for development of the condition is obscure, a disruption of enzymatic activity is likely, perhaps as a result of free radical formation. [medical-dictionary.thefreedictionary.com]

• Candida

  View Article PubMed Google Scholar Cairney WJ: Effect of hyperbaric oxygen on certain growth features of Candida albicans. Aviat Space Environ Med. 1978, 49: 956-958. [doi.org]

1. Chawla A, Lavania A. Oxygen Toxicity. Med J Armed Forces India. 2001;57(2):131-133.
2. Fock A, Harris R, Slade M. Oxygen exposure and toxicity in recreational technical divers. Diving Hyperb Med. 2013;43(2):67-71.
3. Arieli R, Arieli Y, Daskalovic Y, Eynan M, Abramovich A. CNS oxygen toxicity in closed-circuit diving: signs and symptoms before loss of consciousness. Aviat Space Environ Med. 2006;77(11):1153-1157.
4. Hampson N, Atik D. Central nervous system oxygen toxicity during routine hyperbaric oxygen therapy. Undersea Hyperb Med. 2003;30(2):147-153.
5. Mach WJ, Thimmesch AR, Pierce JT, Pierce JD. Consequences of Hyperoxia and the Toxicity of Oxygen in the Lung. Nurs Res Pract. 2011;2011:260482.
6. van Ooij PA, Sterk PJ, van Hulst RA. Oxygen, the lung and the diver: friends and foes? Eur Respir Rev. 2016;25(142):496-505.