Oxygen toxicity is a result of breathing molecular oxygen at elevated partial pressures. It is also known as oxygen poisoning or oxygen intoxication.
In normal conditions, we can never imagine oxygen being harmful for us. As the saying goes, however, too much of anything, and in its purest form, is probably not good for health. We are so accustomed to using adulterated things that, sometimes, we cannot accept or adapt to their purest forms.
If we do not get oxygen, even adulterated oxygen, we will probably die from lack of it. If, however, it is taken in its molecular form, elevated at partial pressures, and for a long period of time, it is harmful; especially for divers. This is known as oxygen toxicity.
This condition has a number of symptoms; it affects numerous body systems, from the central nervous system to the ocular system. It also leads to pulmonary problems.
The symptoms are:
- The trachea, bronchi, and lungs are affected, leading to a very prominent symptom of pain in the sternum, or breastbone. The passageway that carries air from the trachea to the lungs is also affected.
- In a few cases, inflammation and swelling of the lungs has been observed.
- Damage to the eyes has been seen in premature babies as a result of exposure to molecular oxygen, and also in those going through Hyperbaric Oxygen Therapy (HBOT).
- Confusion and anxiety
- Intense muscle contractions for several seconds
- Rapid spasms of alternate muscles
These are the symptoms of moderate oxygen toxicity. In extreme cases it can also lead to cell destruction, and eventually, death.
Toxicity of oxygen is a result of breathing it in at partial pressures, higher than those we are normally used to. This can happen in underwater diving, and also while using supplemental oxygen provision (specially for infants) or hyperbaric oxygen therapy.
For example, an exposure to oxygen at partial pressures above 1.6 bars (a unit of pressure), which is around 8 times the atmospheric concentration, can be connected with oxygen toxicity affecting the central nervous system. This is most commonly observed among divers and those undergoing Hyperbaric Oxygen Therapy (HBOT). This happens when the exposure to concentrations of oxygen is higher than 0.5 bar, which corresponds to an oxygen fraction of 50% at normal atmospheric pressure.
In case of ocular toxicity, the process differs for divers and infants. In infants, the retina is not in a fully vascularized state. On exposure to toxic forms of oxygen, the development of retinal vasculature is curbed, making it grow abnormally.
Exposure to Hyperbaric Oxygen Therapy for short periods of time and taking in 100% oxygen from a mask is one of the ways to deal with oxygen toxicity. If it is inside a hyperbaric chamber, it is air pressurized to about 2.8 bar. If the patient gets seizures during the therapy, they are managed by removal of the mask, which leads to a drop in the partial pressure of oxygen.
In cases where seizures happen to a diver underwater, the diver has to be brought to the surface as soon as possible. If there are signs of acute respiratory distress syndrome on account of toxicity, the fraction of oxygen which is administered is brought down.
When the scenario is that of infants who are administered supplemental oxygen for any disease, a ventilator may be required for the lung tissue to be inflated. Medicines like bronchodialators and pulmonary surfactants are used in tandem, with reductions in pressure of, and exposure to, oxygen. Further, laser surgery and cryosurgery have proven to reduce the risk of blindness as a result of damage to the retina, in case the toxicity goes beyond a specific limit.
It is actually a paradox that the substance which helps us live can lead to toxicity. The situation is not, however, hopeless as there are preventive techniques for this situation. To give you an example, divers are taught how to calculate the maximum operating depth for oxygen rich gases. Cylinders having such mixtures, if marked with that depth, can help too.