Although HBO produces some vasoconstriction, it has been found that any potential vasoconstriction is outweighed by the tremendous increase in tissue oxygen levels during treatment. Foremost contraindications are acute lung infection, history of acute asthma, untreated pneumothorax and presence of air containing cavities such as pneumoencephalus. Chronic pulmonary disease or history of spontaneous pneumothorax must always be identified before HBO therapy. Other conditions that give rise to concern are the presence of or repeated episodes of middle ear infection. In those who cannot equalize pressures, myringotomy may be required, but will not be done without the agreement of the referring physician and the otolaryngologist who is requested to perform the procedure.
Seizures are a rare complication of exposure to high levels of oxygen.
Patients with seizure disorders must have their seizures adequately controlled before HBO treatment. The risk of an oxygen seizure is increased by heavy ethanol intake which must be avoided. The very rare occurrence of a seizure can be controlled by decreasing the inspired oxygen concentration. It is worth recalling that a seizure in an hyper-oxygenated state is different than a convulsion breathing room air. The use of anticonfulsants is not needed for most HBO induced seizures.