Complications
Although uncommon, coma may result as a consequence of arterial gas embolism (AGE) causing local cerebral ischaemia, or severe nitrogen narcosis.
Initial first aid treatment should be given according to accepted principles of basic and advanced life support.
For patients with coma due to AGE, patients should be recompressed in a hyperbaric chamber as soon as is practically possible. Nitrogen narcosis is reversed by reduction of ambient pressure (i.e., ascent).
Occasionally middle-ear barotrauma predisposes to ear infection, suggested by the presence of pain a few days later. Broad-spectrum antibiotics are indicated.
May occur in severe decompression sickness, presenting with bradycardia, hypotension, and oliguria.
Initial first aid treatment should be given according to accepted principles of basic and advanced life support, with volume resuscitation, vasopressors for refractory hypotension, and prompt recompression.
Infection may occur in blood/mucus resulting from barotrauma to the mastoid air cells, or via extension from the middle ear.
Rarely, meningitis may develop as an extension of local infection (otitis media, sinusitis, etc.).
Expansion of gas in the sinuses or mastoid air cells may cause rupture of air or fluid into the cranial cavity, with sudden headache.
CT scan and/or MRI may be diagnostic.
Neurological toxicity may present initially with nausea, dysphoria, dizziness, tunnel vision, or paraesthesia. There is great inter- and intra-individual susceptibility.
Muscular twitching, especially of the face, can be a prelude to a generalised seizure. Immediate removal of the oxygen mask or hood is advisable. Oxygen seizures are generally brief. Anticonvulsants such as diazepam, lorazepam, levetiracetam, or phenytoin are rarely required. If anticonvulsants are required, the seizure, although triggered by the hyperbaric oxygen, more likely represents the underlying brain injury.[65]
Pulmonary toxicity is suggested by chest discomfort or tightness, cough, or dyspnoea and is common after typical treatment tables (e.g., United States Navy Treatment Table 6). With severe pulmonary oxygen toxicity, exudative and proliferative lung changes will eventually progress to fibrosis, but are generally reversible within a few days of stopping treatment. Intermittent exposure via the use of air breaks delays the onset of both forms of toxicity, such that they are rarely significant in practice.
Eye changes including reversible myopia and decreases in peripheral vision have been reported after weeks of treatment.
Incidence is variable, but seems to relate to longer diving experience, greater depth exposure, and previous history of decompression sickness. Dysbaric osteonecrosis is rare in recreational divers, but is seen in native diving fishermen, compressed air workers, and commercial divers. The pathogenesis is poorly understood, but it seems to be a delayed or long-term manifestation of decompression illness.
It may be asymptomatic, or present with limb pain or restricted joint movement, usually affecting the hip or shoulder.
Bone-imaging techniques (e.g., x-ray, bone scan, CT, and MRI) are useful for recognition, although their use in surveillance of divers at high risk is controversial.
The incidence of persistent neurological impairment after treatment for decompression illness varies widely between studies, seemingly dependent on the assay used and the population being assessed. In one study of recreational divers, psychometric and electronystagmographic abnormalities were seen in nearly 50% of subjects at 1 week, and <10% at 3 weeks, after decompression illness treatment.[61] Another study of commercial divers showed a threefold increase in self-reported 'forgetfulness or loss of concentration' when compared with non-diving offshore workers.[62] Hearing loss and musculoskeletal symptoms were also reported, although no long-term health effects were detected.
Testing and imaging correlate poorly with clinical condition.
Acute or chronic sinus infection may develop, and occasionally orbital cellulitis may occur. Broad-spectrum antibiotics are indicated.
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