What is Pulmonary Barotrauma (Pressure Injury in the Lungs)?
Diving in open water is a favorite activity for both beginners and experienced divers. Many people choose to dive for fun, for competitive sports, for work, or for military training. The practice of diving as a profession goes back more than 5000 years, but it wasn’t until 1878 that Paul Bert started describing diving-related illnesses. This condition, recognized as caisson disease, was typically spotted in bridge workers after they came up from underwater. The workers often experienced symptoms like dizziness, difficulty breathing, and sharp abdominal or joint pain after their shifts. Interestingly, they felt fine while working, probably because they were rested at the start of their workday and grew tired towards the end. One common symptom was severe back pain that made them hunch over, giving caisson disease its nickname “the bends.”
One risk that divers face is an injury known as pulmonary barotrauma. This can occur during self-contained underwater breathing apparatus (SCUBA) diving or free diving. Pulmonary barotrauma can happen either when descending (negative pulmonary barotrauma or a lung squeeze) or ascending (positive pulmonary barotrauma or pulmonary overinflation syndrome). It most often happens during ascent due to the lungs expanding too much if a diver surfaces without exhaling or if air gets trapped in the lung. Barotrauma is an injury caused by a difference in pressure between a gas inside or outside the body and the surrounding gas or fluid. These types of injuries occur mainly due to the tension or expansion of the gas, or pressure passing through tissues. The complications could involve gas infiltrating the damaged tissue or local blood circulation, which might disrupt the function of organs or impact the blood circulation process.
What Causes Pulmonary Barotrauma (Pressure Injury in the Lungs)?
Boyle’s law explains that the volume of gas adjusts based on the pressure applied to it, assuming the temperature stays the same. In simple terms, as pressure increases when diving deeper underwater, the lung volume shrinks, and vice versa, the lung volume expands as one ascends to the surface due to decreasing pressure.
At sea level, where we experience no underwater pressure, air exerts a force of 14.7 lbs/in or 1 atmosphere absolute (1 ATA). When you dive 10 meters deep, the water pressure goes up by 1 ATA. Now, at 10 meters deep, the water pressure is 2 ATA, and the exerted air pressure doubles to 29.4 lbs/in, shrinking the lung capacity by half. The deeper you go, the more this trend continues. Your lung capacity decreases by 67%, 75%, and 80% on reaching 20 meters, 30 meters, and 40 meters deep respectively.
The steepest decline in lung capacity is seen in the initial 10 meters, where lung capacity drops by 50%. Lung injury, or pulmonary barotrauma, happens when pressures inside one’s lungs don’t match the outside environment pressures. This disparity crosses the lungs’ limit.
If transpulmonary pressures cross 60 to 70 mmHg, it can cause the lung’s air sacs to burst. Let’s say a diver’s lungs hold 6L of air at the surface. When they dive to 10 meters, that lung volume reduces to 3L. If this diver inhales a full capacity breath of 6L at this depth and then rushes to the surface without exhaling, this can cause a dangerous 50% expansion of the gas (from 6L to 9L). Experience and appropriate training can help divers avoid these injuries.
Henry’s law also plays a crucial role in diving. It states that the amount of gas that dissolves in a liquid is directly related to the pressure on the gas and liquid. Imagine when you open a soda bottle, the pressure is released, and fizz escapes. Similarly, when a diver descends, the nitrogen from the air tank can dissolve in their tissues or joint fluids. As the diver rises to the surface, where pressure is less, this nitrogen gradually moves out from their tissues, enters the bloodstream, and is then exhaled out. Rapid ascents, however, can cause the nitrogen to form bubbles too quickly that could harm tissues, cause clots, or trigger inflammation, leading to potential tissue damage.
Risk Factors and Frequency for Pulmonary Barotrauma (Pressure Injury in the Lungs)
There are about 9 million divers around the world, including three million in the United States. These divers tend to be around 30 years old, with the majority being men (60%). However, a significant portion (40%) are women. The most common injury among these divers is barotrauma, also known as pressure-related injuries.
- 80% of these injuries are related to barotrauma in the ear and sinuses.
- 15% are due to barotrauma in the lungs, which might result in arterial gas embolism (gas bubbles in the bloodstream).
- The remaining 5% of injuries are due to barotraumas affecting the stomach, teeth, or problems related to the diving mask or suit squeeze.
- When it comes to fatal incidents, the main causes are drowning, heart disease, and lung injuries leading to arterial gas embolism.
Many experts are asking for more detailed examinations and reporting to help gain a better understanding of the risk of these injuries.
Signs and Symptoms of Pulmonary Barotrauma (Pressure Injury in the Lungs)
Pulmonary barotrauma can occur during SCUBA diving and its symptoms can range from subtle to severe. The symptoms can show up immediately after surfacing or sometimes within ten minutes.
- Common symptoms include cough, shortness of breath, coughing up blood, chest pain, difficulty breathing, choking, voice changes, hoarseness, and trouble swallowing.
- Symptoms can also include bluish skin or lips (cyanosis), respiratory failure, fainting, cardiac arrest, and even death.
Sometimes there may be no noticeable symptoms at all. Other times, there may be subtle signs like a crackling sound heard with a stethoscope over the heart due to air in the space between the lungs and chest wall, known as pneumomediastinum.
Subcutaneous emphysema, where air gets into the tissues under the skin, can cause symptoms like voice changes or a choking sensation, especially in the neck area. This condition can also make the skin feel crackly to the touch. The presence of air in the abdomen or pneumoperitoneum can also occur with this condition.
Pneumothorax, where air enters the space around the lungs and can cause a lung to collapse, is another possible outcome but is generally less common. When this happens, symptoms like chest pain, shortness of breath, rapid and shallow breathing, a faster heart rate, and unequal chest size can occur.
If a severe form of pneumothorax called tension pneumothorax develops, the pressure buildup can affect the heart and blood vessels, leading to circulatory failure, cardiac arrest, and death.
Air emboli, where air bubbles form and enter the bloodstream, can also occur. Mostly, these clumps of air end up in the heart or brain and block blood flow. This blockage can cause symptoms like loss of consciousness, seizures, cardiac arrest, headaches, confusion, numbness, tingling, paralysis, speech problems, or even stroke symptoms.
It’s also important to note that people with certain predispositions, such as those with previous decompression injuries, lung diseases like asthma and chronic obstructive pulmonary disease (COPD), pregnancy, those with genetic conditions like Marfan Syndrome, or any prior lung injuries or surgeries, are at higher risk of developing these complications.
Testing for Pulmonary Barotrauma (Pressure Injury in the Lungs)
If someone is thought to have a lung injury from diving (known as pulmonary barotrauma), it is crucial to get them medical help quickly. Once at the hospital, the doctor will take a medical history, do a physical exam, and carry out basic blood tests. They will also take an electrocardiogram, which measures the heart’s electrical activity, and an X-ray of the chest.
The chest X-ray will usually show air trapped in the central part of the chest (pneumomediastinum), but it could also show a collapsed lung (pneumothorax). There might also be signs of fluid or other substances within the lungs. If a person has serious symptoms after their dive, such as a severe headache, back pain, shortness of breath, changes in consciousness, or unexplained chest pain, there might be a need for more detailed imaging using a computed tomography (CT) scan or magnetic resonance imaging (MRI).
A spiral CT is best for looking out for a pneumothorax. If a person is suspected of having a collapsed lung but their chest X-ray is normal, a CT scan should be done. In fact, if a CT scan is done within six hours of the injury, it can indicate air in either the arterial or venous systems, which has implications for both the prognosis and the nature of the pathology. Ultrasound and echocardiography can also be useful for detecting air bubbles in the heart, skin tissue air, possible abscesses in facial swelling, as well as air in the abdominal cavity.
A blood test can help identify if there is an infection present, and if the proportion of red blood cells to blood volume (hematocrit) is more than 48%, there is a higher chance of nervous system sequelae (secondary result) one month after the injury. If the levels of a particular enzyme in the blood called creatine phosphokinase (CPK) are increasing, this indicates tissue damage due to tiny blockages in the blood vessels (microemboli). The EKG may notice a faster than normal heart rate (tachycardia), abnormal heart rhythms (arrhythmias), or a heart attack. The oxygen level in the blood can be tested using pulse oximetry or an arterial blood gas test to assess if there is low oxygen (hypoxia). After all these tests, the need for pressure equalisation (recompression) and therapy using a high concentration of oxygen at a higher than normal atmospheric pressure (hyperbaric oxygen therapy) should be evaluated promptly and accurately.
Treatment Options for Pulmonary Barotrauma (Pressure Injury in the Lungs)
If a diver is having a cardiac emergency, they need immediate medical help. This includes giving them emergency treatments for heart failure and making sure they have a secure intravenous line for delivering medications. They should also get extra oxygen and fluids to keep them hydrated. If they’re finding it hard to breathe or they’re not getting enough oxygen, despite breathing in pure oxygen, they may need a medical procedure called intubation to help them breathe.
Mild cases of pneumomediastinum, or air trapped in the middle of the chest, usually need no specific treatment as the body can absorb the air on its own. Providing extra oxygen can help those having low oxygen levels in their blood. The extra oxygen can also help the body absorb the trapped air faster. A pneumothorax, or collapsed lung, might resolve on its own, or it may require a chest tube thoracostomy, a procedure where a tube is inserted into the chest to remove air and allow the lung to re-expand. An emergency type of pneumothorax, called tension pneumothorax, always requires a chest tube thoracostomy to remove air, relieve pressure, and restore proper blood flow.
When it comes to treating arterial gas embolism, a serious condition related to lung injury, time is of the essence. The best results occur when treatment starts within the first two hours. Delaying the treatment, like recompression and hyperbaric oxygen therapy (HBOT), for more than six hours can lead to worse outcomes. Recompression therapy involves pressurizing the patient in a dive chamber and should be performed by specially trained medical personnel. This therapy is mainly used for spinal cord injuries and neurological problems. Severely ill patients who don’t respond to initial therapy might need decompression at higher pressure levels and a special breathable gas mix of 50% helium and 50% oxygen, called heliox. As for the use of surfactants, substances that lower the tension within the lungs, it’s still being studied and is not yet a standard practice.
What else can Pulmonary Barotrauma (Pressure Injury in the Lungs) be?
When a SCUBA diver has lung injuries possibly caused by changes in pressure (known medically as “pulmonary barotrauma”), a doctor would need to consider many other conditions that might cause similar symptoms. These might include:
- Drowning or nearly drowning
- Heart attack (medically known as “myocardial infarction”)
- Blockage in the lungs’ blood vessels (medically known as “pulmonary embolism”)
- Stroke (medically known as “cerebral vascular accident”)
- Tearing of the large blood vessel in the neck (medically known as “carotid artery dissection”)
- Fluid accumulation in the lungs due to being submerged in water (medically known as “immersion pulmonary edema”)
- A severe worsening of asthma
- Spasms in the vocal cords that make it hard to breathe (medically known as “laryngospasm”)
- Stings or bites from sea creatures (medically known as “marine envenomation”)
- Toxic effects from using contaminated SCUBA gas
It’s important for the doctor to carefully consider these conditions and perform suitable tests to make an accurate diagnosis.
What to expect with Pulmonary Barotrauma (Pressure Injury in the Lungs)
The future health outcome for lung injuries related to SCUBA diving depends on how severe the injury is, and what type of lung injury occurred. Mild cases of a pneumomediastinum, where air collects around the lungs, or a pneumothorax, where air collects in the space between the lungs and chest wall, generally get better on their own without extensive treatment. Most people fully recover from these conditions.
However, a large pneumothorax or tension pneumothorax, where pressure builds up in the chest, requires a treatment where a tube is inserted to let the air out, but individuals should get better without continued issues.
Unfortunately, if an air or gas embolism occurs from a lung injury, which means air or gas enters the bloodstream and blocks a blood vessel, the outcome can be quite severe, with a 30% death rate. This is the second most common cause of death in divers, after drowning.
Possible Complications When Diagnosed with Pulmonary Barotrauma (Pressure Injury in the Lungs)
If you experience lung overexpansion while rising from SCUBA diving, you could possibly face a condition known as pulmonary barotrauma. This ailment can lead to a range of complications including:
- Pneumomediastinum: air leak into the middle of the chest
- Pneumopericardium: air leak around the heart
- Pneumoperitoneum: air leak into the abdominal cavity
- Subcutaneous emphysema: air leak under the skin
- Pneumothorax: collapse of a lung due to air in the chest cavity
- Tension pneumothorax: pressure on the lungs from trapped air in the chest
- Air gas embolism: air bubbles in the bloodstream
The most serious and feared outcome is cerebral air gas embolism, which can cause severe brain damage. Lung damage is commonly noticed on initial chest x-rays and CT scans in those who suffered from pulmonary barotrauma.
Other possible problems after a pulmonary barotrauma incident can include:
- Aspiration pneumonitis: inflammation of the lungs from inhaling something (like fluid or food) into the lungs
- Pneumonia: infection in the lungs
- Pleural effusions: build-up of extra fluid between the layers of the lung
- Empyema: collection of pus in the lungs
- Pyopneumothorax: presence of air and pus in the chest cavity
- Scarring & Fibrosis: hardening and scarring of lung tissue
- Decreased lung function
An air-gas embolism is an emergency situation. If not diagnosed and treated properly, it can cause intense neurological damage, leading to irreversible harm to the brain and spinal cord. Despite the potential dangers, most people with pulmonary barotrauma recover from minor injuries and complications without any long-term issues.
Preventing Pulmonary Barotrauma (Pressure Injury in the Lungs)
Divers who already have lung conditions, or who have had them in the past, have a higher risk of experiencing a traumatic injury to the lungs during diving. Anyone with a current or preexisting lung problem should have a medical check-up before they dive. People with conditions such as asthma, obstructive lung disease, emphysema, lung fibrosis, tuberculosis (whether active or in the past), sarcoidosis, and a history of spontaneous lung collapse are especially at risk of traumatic lung injury while diving. However, it’s worth noting that many diving injuries and fatalities can be avoided.
Before diving, it’s crucial to perform a thorough check of all equipment to ensure everything is functioning properly. Safe diving requires following good practices, the right training, and understanding the risks. Divers should also be reminded not to make multiple dives daily or to dive and fly in the same day, as these practices can alter their dive profile and increase risks. Recent research shows that cardio exercises before a dive, or during decompression stops, might actually lessen the formation of gas bubbles after a dive, which can be beneficial.
