What is Aerospace Decompression Illness?
Aerospace decompression illness (ADI) happens when the human body experiences low air pressure, like when we ascend in diving or reach high altitudes. These changes cause the nitrogen gas, usually dissolved in our body fluids and tissues, to be quickly released, form bubbles in our bloodstream, and affect different parts of our body, like the joints, brain, skin, and lungs. This happens during activities like aircraft flights without pressurization, flights with fluctuating cabin pressure, flying shortly after diving, and using altitude chambers. Common symptoms are joint pain, headaches, numbness, and vision changes, with severe cases leading to paralysis, seizures, unconsciousness, or even death.
The reason decompression sickness happens during diving is due to the nitrogen buildup in the body, which forms bubbles when we come back to areas with less pressure. On the other hand, high-altitude decompression sickness is because the nitrogen already in our bodies at the ground level starts forming bubbles when we go to places with lower air pressure.
Decompression sickness is divided into two types. Type I mainly impacts the skin, joints, and lymphatic vessels. In contrast, Type II affects the central nervous system and is considered more severe. We normally classify them based on which parts of the body are affected:
– ‘Cutaneous’ refers to the skin and is also known as ‘the Creeps.’
– ‘Arthropathy’ means it affects the joints and is also often called ‘the Bends.’
– ‘Cardiopulmonary’ indicates it affects the heart and lungs and is also called ‘the Chokes.’
– ‘Neurology’ means it impacts the brain, spinal cord, and nerves and is known as ‘the Staggers.’
Decompression sickness is often tricky as it can present with a wide range of symptoms. Between 44% and 67% of people with the sickness experience symptoms within 2 hours of coming back to ground level, while the rest may show symptoms 20 hours or more later. The primary treatment involves hydrating and giving high-concentration oxygen, with the method depending on how severe the symptoms are. In cases involving pressure changes, such as scuba diving and flights, medical professionals should always consider the possibility of decompression sickness due to its varied symptoms.
What Causes Aerospace Decompression Illness?
- Altitude Decompression Illness (ADI) can happen in various circumstances, such as using high-altitude military chambers or due to incorrect pressurization in aircraft or flight suits.
- The condition often arises when one is exposed to altitudes above 25,000 feet.
- Commercial planes usually have a pressurized cabin to prevent ADI, but failure of this system or traveling on noncommercial aircraft can still lead to decompression sickness.
- People who go scuba diving and then take a flight soon after are more prone to ADI.
- A general advice is to wait 12 hours after a single dive before flying.
- For those involved in multiple dives or those requiring decompression stops, it’s recommended to wait up to 48 hours before flying.
- However, even with these precautions, some people may still experience decompression sickness.
Risk Factors and Frequency for Aerospace Decompression Illness
High altitudes can cause Altitude Decompression Illness (ADI) through various ways. This can include scenarios such as the military using high-altitude chambers, aircraft not being pressurized correctly, or issues with flight suits. There isn’t a specific altitude where we can say with certainty that decompression sickness won’t happen. Even though commercial flight companies often have pressurized cabins, the systems can fail or may not be present in non-commercial flights. This can potentially lead to decompression sickness. Most cases of ADI happen when people are more than 25,000 feet above sea level.
If you go SCUBA diving before a flight, you have higher chances of developing ADI during the flight. At the moment, there aren’t fixed guidelines, but general advice suggests one should wait for 12 hours before flying if they made only one dive in a day. If you make multiple dives in a day, or if you have to take decompression stops during your dive, you should consider a waiting period of up to 48 hours before flying. However, it’s important to remember that even if you follow these recommendations, you might still get decompression sickness.
Signs and Symptoms of Aerospace Decompression Illness
Decompression illness is a condition that can occur following activities like diving, flying, or being in an air pressure chamber. It can cause a wide range of symptoms, based on the part of the body that’s affected. People with this condition may not recognize its significance and may neglect to mention relevant activities while reporting their medical history.
Here is a breakdown of potential symptoms based on the body system affected:
- Musculoskeletal: Bubbles of nitrogen can build up in the joints, particularly in the elbows, shoulders, hips, wrists, knees, and ankles. This can cause deep pain of varying intensity, which is often worsened by movement.
- Neurological: The brain, spinal cord, and other parts of the nervous system can be affected. Symptoms can include memory loss, headache, blurred vision, fatigue, seizures, dizziness, vomiting, numbness, weakness, and even paralysis.
- Respiratory: Nitrogen bubbles in the lungs can cause burning chest pain, coughing, and shortness of breath.
- Integumentary: This refers to the skin and can involve symptoms like swelling, itching, and mottled skin.
A rare complication of decompression illness is dysbaric osteonecrosis, which destroys bone tissue, particularly in the shoulder and hip. While often there are no symptoms, it can potentially lead to debilitating arthritis if left untreated.
Testing for Aerospace Decompression Illness
Diagnosing Acute Decompensation Into Infarction (ADI) is majorly based on a detailed physical check-up, which includes monitoring important health metrics like vital signs and the level of oxygen in the blood. In some situations, an electrocardiogram, which is a test that measures the electrical activity of the heart, might be suggested. At present, there are no exclusive diagnostic tests that can conclusively identify ADI.
However, one potentially helpful indicator is how a patient responds to hyperbaric oxygen therapy. This treatment involves breathing in pure oxygen in a pressurized room or tube. If a patient shows improvement after this therapy, it adds support to the diagnosis of ADI.
When a patient presents with an altered consciousness level, it becomes necessary to perform various health tests. These include checking blood sugar levels, complete blood count, electrolytes, oxygen saturation, ethanol (alcohol) level, presence of any drugs, carboxyhemoglobin (a compound in blood that forms in place of normal oxygen-carrying hemoglobin when someone inhales carbon monoxide), blood urea nitrogen (a waste product your body makes when it processes protein), and creatinine (a waste product your body makes as your muscles work).
If there’s no improvement in the patient’s mental state even after hyperbaric oxygen therapy, a computed tomography (CT) scan of the head may be considered. A CT scan can create detailed images of the brain and help detect any issues. In some cases, magnetic resonance imaging (MRI), which uses magnetic fields and radio waves to create images of the body, can be helpful, especially for patients with Central Nervous System (CNS) issues who don’t respond to oxygen therapy. However, it’s important to note that these imaging tests should not delay the patient’s immediate transfer for treatment. If symptoms persist, MRI can help guide further treatment and rule out other possible causes of the symptoms.
Treatment Options for Aerospace Decompression Illness
Decompression sickness can often occur during nonpressurized airplane flights, changes in cabin pressure, or flying shortly after diving. It can also come about with altitude chamber usage. If this condition develops while in the air, it’s crucial to administer 100% oxygen through a mask immediately. If the person is unconscious, they should be laid flat. It’s worth noting that the Trendelenburg position, earlier suggested for such cases, is no longer advised.
The airplane should immediately begin to descend with the aim of landing as soon as possible, regardless of whether the symptoms improve during the descent. If the person experiences joint pain, the joint should be kept still. It’s recommended to keep the person well hydrated with a balanced, sugar-free, isotonic solution. Non-caffeinated, non-alcoholic and non-fizzy drinks or even plain water are suitable for this. In severe cases, the person might need intravenous rehydration.
Once they land, individuals should seek care from a healthcare professional experienced in managing aviation- or hyperbaric-related health issues, even if symptoms seem to have disappeared.
It’s worth noting that decompression sickness – a relatively uncommon condition – is treated in a similar way to decompression sickness caused by scuba diving. It involves administering oxygen at ground level or in a hyperbaric (high-pressure) oxygen chamber. This helps to remove nitrogen from the body via the lungs. That’s why healthcare providers should be familiar with hyperbaric treatments and be able to contact hyperbaric specialists or chambers if needed.
The treatment could involve using 100% oxygen at ground level for two hours in less severe cases. If conditions are more severe, treatment might occur in a hyperbaric chamber.
The United States Navy has developed tables that provide guidelines for treating decompression sickness using recompression therapy. The sessions may be once or twice a day, lasting up to 300 minutes. They usually involve administering 100% oxygen at pressures between 2.5 and 3 atmospheres.
People can also reduce the chance of experiencing decompression sickness by breathing in 100% oxygen for 30 minutes before flying above 18,000 feet for 10 to 30 minutes. However, it’s crucial to keep taking the oxygen during the flight for it to work. Just having it during the flight alone doesn’t help avoid decompression sickness.
What else can Aerospace Decompression Illness be?
Determining if decompression illness is behind aviation-related issues can be quite difficult. Looking at 18 cases labeled as aviation decompression illness, it turns out more than half were probably misidentified.
The other illnesses it can often be mixed up with include:
- Dehydration
- Electrolyte imbalance
- Viral illnesses
- Mental health disorders
- Low oxygen levels (hypoxia)
- Eye migraines
- Brain lesions
- Ear drum rupture
- Ear infection
- Blockage of the ear canal
- Round window rupture
- Bronchial spasms
- Fluid around the heart
- Rapid heart rate
- Intestinal inflammation
- Motion sickness
- Food poisoning
- Urinary tract infections
- Prostate inflammation
- Drying effects of some medicines
- Nerve root diseases
- Nerve injuries
- Sprains
- Fractures
- Arthritis flare-ups
- Spinal disk herniation
- Skin inflammation
- Artery blockage
- Carbon monoxide poisoning
- Substance abuse
- Negative reactions to medications
- Heart attack
- Collapsed lung (pneumothorax)
Any tests necessary to reject other potential causes should be run because decompression illness can look like many other diseases. However, not having a clear diagnosis shouldn’t stop treatment. If decompression sickness is suspected, oxygen therapy should be started right away.
What to expect with Aerospace Decompression Illness
The protocol created by the United States Air Force, which involves breathing in 100% oxygen at ground level for type I altitude sickness, results in 94% of individuals not needing deeper treatment. It’s important to note that these results come from studies done in altitude chambers where altitude sickness occurs quickly.
For type II altitude sickness, the chances of getting better decrease as the time to treatment increases. Roughly 75% of patients completely get rid of their symptoms, while an additional 16% see their leftover symptoms disappear within the next 3 months. The chances of fully getting rid of the symptoms range from 57% to 75%, especially if treatment is delayed for more than 12 hours.
Possible Complications When Diagnosed with Aerospace Decompression Illness
Possible problems that can arise from arterial decompression illness (ADI) include things like paralysis, bone damage from bubbles (dysbaric osteonecrosis), arthritis, and permanent issues with the nervous system. In the most severe cases, it can even cause death.
Common Complications:
- Paralysis
- Bone damage due to bubbles, known as dysbaric osteonecrosis
- Arthritis
- Permanent issues with the nervous system
- Death in severe instances
Preventing Aerospace Decompression Illness
Decompression sickness, also known as altitude-related illness, happens when low air pressure triggers nitrogen, normally dissolved in the body, to form bubbles. Symptoms can include confusion, joint pain, shortness of breath, changes in vision, muscle weakness, headaches, and changes to the skin. It mainly happens in non-pressurized airplane flights, after problems with the pressure system, when flying soon after diving, or working in high altitude locations.
Those more likely to suffer from this illness are those who often fly above 18,000 feet within a short time, those who ascend rapidly, spend long periods at higher altitudes, older individuals, people with higher body fat percentages, those who are dehydrated, engage in physical activity during flights, or those who consume alcohol during flight.
If someone begins to show signs of decompression sickness while flying, the first steps should be to give them an oxygen mask with 100% oxygen and start descending immediately. It is crucial to land as soon as possible, even if their symptoms clear up during descent. It’s also important to provide the person with non-caffeinated and non-alcoholic drinks to rehydrate them. If the person becomes unconscious, the safest approach is to make them lie flat and provide them with intravenous fluids without glucose, if available.
Once safely on the ground, anyone affected by decompression sickness should seek medical evaluation, even if they feel better. The usual treatment involves receiving pure oxygen therapy for 2 hours. If symptoms persist or return, the patient may need to be treated with a higher level of oxygen in a hyperbaric chamber, and should continue to receive pure oxygen until they can be treated in one.
