Oxygen Toxicity

In normal conditions, we would never ever imagine that oxygen can ever be harmful for us. But, as they say too much of anything and in its purest form is probably not good for health. We are so used to using adulterated things that sometimes we cannot accept and adapt to them in its purest form. Take for instance, oxygen. Usually, if we do not get oxygen even if it is adulterated, we would probably die of lack of oxygen. But oxygen if taken in molecular form, elevated at partial pressures, for a long period of time, is surprisingly harmful, especially for divers. This is called oxygen toxicity. More coming up on this issue.

Symptoms of Oxygen Toxicity

There are a number of symptoms, since it affects a number of body systems from central nervous system to ocular and pulmonary problems. Following are the symptoms:

• 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 lungs is also affected.
• In a few cases inflammation and swelling of lungs has been observed.
• Damage to the eyes has been observed in premature babies as a result of exposure to molecular oxygen and those going through Hyperbaric Oxygen Therapy (HBOT).
• Nausea
• Twitching
• Irritability
• Dizziness
• Confusion and Anxiety
• Intense muscle contraction for several seconds
• Rapid spasms of alternate muscle relaxation

These were the symptoms of moderate oxygen toxicity. In extreme cases it can also lead to cell destruction and eventually death. Now lets us see what causes these symptoms.

Causes of Oxygen Toxicity

As mentioned before, toxicity due to oxygen is a result of breathing oxygen at partial pressures, higher than those we are normally used to. This can happen while underwater diving, also using supplemental oxygen provision(specially for infants) and hyperbaric oxygen therapy. To give you an 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, most often than not, is observed amongst divers and those undergoing Hyperbaric Oxygen Therapy (HBOT). 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 is different from what happens in case of divers and infants. In infants, the retina is not in a fully vascularized state. Now, on exposure to toxic forms of oxygen, the development of retinal vasculature is curbed, and then it grows abnormally.

Treatment for Oxygen Toxicity

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 and the side effects of oxygen therapy. If it is inside a hyperbaric chamber, it is pressurized with air 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 the seizure happens to a diver underwater, the diver has to be bought to the surface, as soon as possible. Then, if there are signs of acute respiratory distress syndrome on account of toxicity, the fraction of oxygen which is administered is brought down. When it is the scenario that infants are administered supplemental oxygen for any disease, for the lung tissue to be inflated, a ventilator may be required. Medicines like bronchodialators and pulmonary surfactants are used in tandem with reductions in pressure and exposure of oxygen. Further, laser surgery and cryosurgery have been proved 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, isn't it? But the situation is not hopeless as there are preventive techniques to avoid 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, too, can help. Here is where I sign off. Take Care!