Oxygen therapy can be a life saving treatment for patients with hypoxia and several other conditions.

In most countries, the law states that oxygen should never be withheld from a patient. However, in some clinical scenarios, the administration of oxygen therapy can do more harm than good.

Oxygen is a blood vessel constrictor or vasoconstrictor. As blood vessels are constricted, circulation in the peripheral blood vessels is significantly reduced, an effect that was previously thought to increase the risk of stroke. However, according to “Henry’s law,” the additional oxygen is dissolved in the blood plasma, which enables a compensating change to occur where oxygen supports neurons that may be starved of oxygen, as well as reducing inflammation and post-stroke edema in the brain.Some of the adverse side effects of oxygen therapy are described below:

• A form of oxygen therapy called hyperbaric oxygen therapy has been widely used in the treatment of stroke since 1990. The therapy has occasionally caused seizures but due to the effect of dissolved oxygen on neurons, the seizure is not usually followed by any further negative effect. Such seizures usually occur as a result of oxygen toxicity. Hypoglycemia can also contribute to the risk but careful monitoring of the patient’s food intake can usually prevent this being a factor.
• In infants, the administration of high levels of oxygen can induce overgrowth of the blood vessels in the eye and lead to blindness. This condition is referred to as retinopathy of prematurity (ROP).
• Patients with chronic obstructive pulmonary disease are at a particular risk of accumulating carbon dioxide if they are administered supplemental oxygen and these patients needs to be carefully monitored to prevent supplemental oxygen becoming dangerous rather than beneficial.