What is Oxygen Toxicity?
Oxygen is vital for our survival. But, if we breathe in more oxygen than needed, we might suffer from a condition called hyperoxia, which can cause oxygen toxicity or oxygen poisoning. This usually happens in two scenarios: one where a person is exposed to extremely high oxygen concentrations for a short time, and the second where a person is exposed to less concentration but for a long time. Depending upon the exposure, it can cause either acute or chronic oxygen toxicity.
In simple words, acute toxicity causes effects on our central nervous system, the part of the body that includes our brain and spinal cord. On the other hand, chronic toxicity affects our lungs primarily. Severe cases of oxygen toxicity can be harmful, resulting in cell damage and even leading to death. Specific groups of individuals, such as those undergoing hyperbaric oxygen therapy, those exposed to high oxygen levels for a long time, premature infants, and divers, are more likely to face the risk of oxygen toxicity.
What Causes Oxygen Toxicity?
Breathing in too much oxygen over a long period of time or breathing in a very high amount of oxygen in a short period can damage the cells lining the lungs. This harm can lead to the air sacs, or alveoli, in your lungs collapsing. The effects on the lungs can start as early as within 24 hours of breathing in pure oxygen. You might experience symptoms like chest pain, heaviness in the chest, coughing, and difficulty breathing due to inflammation in the windpipe and bronchial tubes and the collapse of some parts of the lung, which can lead to fluid filling up in the lungs. Luckily, these lung symptoms tend to get better around 4 hours after you stop being exposed to too much oxygen.
Your nervous system can also be affected, leading to a variety of possible symptoms. Early symptoms can vary a lot from person to person, but twitching around the mouth and in the small muscles of the hand is a relatively common feature. If you’re exposed to high oxygen pressures for a long time, you might experience ringing in your ears, feeling upset or uneasy, nausea, and seizures. Certain conditions can make the effects on the nervous system occur faster, such as high levels of carbon dioxide, stress, fatigue, and cold temperatures.
Risk Factors and Frequency for Oxygen Toxicity
The Bert effect refers to the impact on the central nervous system (CNS) due to too much oxygen, commonly seen with oxygen therapy. This usually occurs with a higher dose of oxygen, and the risk can vary. Generally, the risk can be as common as 1 in 2000 to 3000 treatments. However, this risk increases to 1 in 200 under higher pressure (2.8 to 3.0 times the normal atmospheric pressure). On the other hand, the risk lowers to 1 in 10,000 for treatments of 2 times the total atmospheric air pressure or less. About 2% of people show signs of CNS symptoms as a result of too much oxygen, with a 0.6% chance of experiencing seizures.
The Smith effect is another term for lung damage due to excessive oxygen and usually happens after exposure to over half the total atmospheric air pressure. The chance of showing signs of lung damage from too much oxygen is 5%. It’s important to note that preterm newborns are especially at risk for lung and eye damage with long-term exposure to high oxygen levels.
- The Bert effect explains the CNS symptoms due to excessive oxygen, with a risk variance based on treatment pressure.
- About 2% of people will demonstrate CNS symptoms, with a 0.6% risk of seizures.
- The Smith effect reflects lung damage from prolonged exposure to excess oxygen, occurring at more than half the total atmospheric air pressure.
- There’s a 5% chance of showing lung damage symptoms from excessive oxygen.
- Preterm newborn babies are notably exposed to the danger of lung and eye damage from long-term high oxygen levels.
- Certain chemicals, like the cancer treatment drug bleomycin, can increase the risk of oxygen toxicity.
Signs and Symptoms of Oxygen Toxicity
Some symptoms of this condition may include confusion, difficulty breathing, and changes in vision such as nearsightedness and development of cataracts. There are various symptoms that affect different systems in the body, which are as follows.
Central Nervous System symptoms:
- Headache
- Feeling irritable or anxious
- Dizziness
- Confusion
- Rapid breathing
- Hiccups
- Cold shivering
- Fatigue
- Tingling sensation in the limbs
- Changes in vision, such as blurry or tunnel vision
- Nausea
- Muscle twitching
- Convulsive seizures
Pulmonary (Lung) Toxicity symptoms:
- Mild tickle or mild burning sensation when breathing in
- Uncontrollable coughing
- Coughing up blood
- Difficulty breathing
- Abnormal lung sounds
- Fever
- Redness of the nasal lining
- X-rays show inflammation and fluid in the lungs
Eyes symptoms:
- In premature babies, eye problems such as premature retinopathy and excess tissue behind the lens
- Fluid buildup in the retina, the back part of the eye
- Cataract development (from long-term exposure)
Testing for Oxygen Toxicity
If you’re at risk for lung damage due to high levels of oxygen (known as pulmonary oxygen toxicity), your doctor will keep a close watch on your oxygen levels and look for signs of difficulty in breathing. They might conduct lung function tests and order a chest x-ray to spot early signs of the severe lung condition known as Acute Respiratory Distress Syndrome (ARDS).
Similarly, to check for early signs of eye damage due to high oxygen levels (ocular oxygen toxicity), your doctor might perform an eye exam, checking your visual sharpness and looking for changes in the lens of your eye, such as cloudiness (known as lens opacification).
Central Nervous System (CNS) oxygen toxicity affects the brain and can lead to the symptoms mentioned before, often accompanied by a fast heart rate (tachycardia) and excessive sweating (diaphoresis). If these signs show up during a hyperbaric oxygen therapy (a treatment that involves breathing pure oxygen in a pressurized room), the treatment will be stopped to prevent a seizure.
Treatment Options for Oxygen Toxicity
Exposure to high levels of oxygen can be harmful, and managing this so-called “oxygen toxicity” involves minimizing exposure to increased oxygen levels. This is particularly important in patients with severe lung conditions (such as ARDS) or in very young babies whose health is unstable, and who are at risk of a condition known as retrolental fibroplasia, which affects their eyes. If a person has an oxygen-induced seizure, it is typically a short-lived event that does not make them more prone to having epilepsy. Although there are concerns that such seizures could cause harm, they’re usually harmless and similar to the type of seizures some children get when they have a high temperature.
In scenarios where patients are undergoing hyperbaric oxygen treatments (therapy which involves breathing pure oxygen in a pressurized room), those at high risk may get better results from anti-seizure medications, longer air breaks, and limiting treatment pressure. There are also rules in place to avoid too much oxygen in jobs where people breathe in oxygen at higher-than-normal pressures, such as underwater divers, newborn care units, in hyperbaric medicine, and for astronauts. These rules have reduced the occurrence of seizures caused by oxygen toxicity, and any damage to the lungs and eyes is usually associated with complications involved with managing premature babies. Introducing “air breaks” (short periods of breathing regular air) during hyperbaric therapy, has also reduced the risk of such seizures.
Deep sea divers (who go below 185 feet) need to breathe mixtures that contain less than 21% oxygen to reduce the chance of oxygen toxicity. At these depths, they also have to change the gas they are breathing from nitrogen to helium. If a diver has a seizure underwater, they must come to the surface immediately. Even though they are at risk of lung injuries and decompression sickness (a risk associated with diving), the risk of drowning far outweighs these risks.
What else can Oxygen Toxicity be?
There are a number of health conditions that can sometimes be confused with oxygen toxicity. Usually, doctors can diagnose oxygen toxicity by referring to the symptoms and can confirm it through testing arterial oxygen levels. There are several conditions that a healthcare provider must also consider when trying to diagnose oxygen toxicity. These include:
- Carbon dioxide narcosis
- Carbon monoxide poisoning
- Hyperventilation
- Snake or other venomous bite or toxin intake
- Stroke
- Migraine
- Seizure disorder
- Infections
- Multiple sclerosis
- Low blood sugar (Hypoglycemia)
What to expect with Oxygen Toxicity
For adults, while high levels of oxygen in the nervous system can occasionally cause injury, research shows that any such damage is usually not long-lasting if the cause of the problem is removed. Similarly, any harm caused by excessive oxygen to the lungs can be reversed in most adults.
When it comes to infants, those who have experienced a type of lung damage known as bronchopulmonary dysplasia, and survived, usually regain close-to-normal lung function. This is because our lungs continue to grow for the first 5 to 7 years of our lives. However, these children may be more susceptible to respiratory infections throughout their lives, and these infections could be more severe than those experienced by their peers.
Retinopathy of prematurity (ROP), a disease affecting the eyes of premature babies, often reverses on its own, allowing for normal vision in later years. However, when ROP progresses to stages that require surgical treatment, the outcome can vary. Surgery often successfully restores the eye’s physical structure in stage 3 ROP, but the results are less favorable in more advanced stages. Even though the surgery can correct the eye’s structure, damage to the nervous system caused by the disease progression can lead to poorer vision. The presence of other diseases alongside ROP may also decrease the chances for a good outcome.
Possible Complications When Diagnosed with Oxygen Toxicity
Oxygen toxicity can result in a range of health issues that affect various critical body systems. It can lead to complications in the central nervous system, which include memory problems and episodes of convulsion. It can also inflict damage to the lungs, with symptoms varying from mild bronchitis and collapsing of lung tissue to severe lung damage identical to Acute Respiratory Distress Syndrome (ARDS).
Oxygen toxicity can also affect your eyes and ears. It can lead to temporary short sightedness, later development of cataracts, and in children, a vision problem called retrolental fibroplasia. Additionally, it can cause a fluid-filled swelling in the middle ear and degenerative bone disease.
People who have chronic obstructive pulmonary disease (COPD), severe asthma, weak respiratory muscles due to conditions like polyneuritis, poliomyelitis, or myasthenia gravis, or people suffering from decreased breathing due to drug overdose, head injury or increased brain pressure, are at risk of side effects from oxygen toxicity. It can cause a condition called carbon dioxide narcosis where the body’s drive to breathe decreases, leading to increased levels of carbon dioxide in the blood.
Side effects of Oxygen Toxicity:
- CNS Complications – Memory problems, Convulsions
- Lung damage – Varies from Mild bronchitis to severe lung damage
- Eye issues – Temporary short sightedness, cataract formation, retrolental fibroplasia in children
- Ear problems – Fluid-filled swelling, degenerative bone disease
- Respiratory issues in patients with COPD, severe asthma etc., leading to decreased breathing and increased carbon dioxide in blood
Preventing Oxygen Toxicity
The main challenge in using high levels of oxygen more frequently in medical treatments is the potential risk of harm and the narrow safety gap between the amount that helps and the amount that harms. However, being careful with the amount of oxygen used, how long it is used, and being aware of its possible harmful effects can make it safer to use. Additionally, the ability to control the dosage carefully allows us to widen the range of medical conditions in which it is beneficial to use this treatment. The harmful effects of too much oxygen are most noticeable in the respiratory system (our lungs and other parts involved in breathing) and central nervous system (our brain and spinal cord).
