What is Inner Ear Decompression Sickness?

Scuba diving for fun is becoming more and more popular around the world, with about 1.2 million people taking part. While it used to mostly happen in warmer coastal waters, it’s now being done in various types of environments, including colder oceans, lakes, and manmade sites. This means that anyone who works in an emergency or urgent care setting, whether near the coast or not, could end up treating diving-related conditions. It’s vital for them to know the signs and symptoms of decompression sickness, a common condition related to diving.

Your inner ear plays a crucial role in your hearing and balance. It’s composed of an organ that’s shaped like a spiral and encased in bone, containing a fluid called endolymph. This fluid is involved in transmitting sounds and sensing changes in position. One part of the inner ear, the cochlea, is responsible for turning sound waves into signals the auditory nerve can understand, while other parts (the utricle, saccule, and semicircular canals) help regulate your sense of balance and position.

Inner ear decompression sickness (IEDCS) is a condition seen in scuba divers that’s not entirely understood yet. Its likely cause is the formation of gas bubbles in the fluid-filled spaces in the inner ear if a diver ascends too quickly. Another theory suggests that some patients might also have an abnormal connection that allows gas to cross from one side of the heart to the other, and this could contribute to the condition if gas gets into the artery that supplies the inner ear. The most common symptom of inner ear decompression sickness is sudden dizziness, but it can also cause ringing in the ears or sudden hearing loss, either on their own or in any combination.

What Causes Inner Ear Decompression Sickness?

Decompression sickness (DCS), also known as “the bends”, typically occurs when gas bubbles form in a diver’s blood vessels and body tissues. This happens when a diver breathes in gas under pressure while diving, causing the blood to absorb an excess amount of nitrogen. As the diver rises closer to the surface and the surrounding pressure decreases, the excess nitrogen is usually released out through the lungs in a process likened to letting the air out of a tire. This process needs to happen slowly. However, if the pressure changes too quickly (for instance, during a fast ascent), the dissolved gas can form bubbles in the blood and tissues, potentially leading to blockages and swelling.

In deep-sea diving, especially when helium-oxygen mixtures are used, a special form of DCS can occur. It is commonly observed in professional divers but could also affect recreational divers diving at great depths. The exact reason behind this isn’t fully understood, but it’s thought that helium- a gas that spreads faster than nitrogen- may enter tissues that are already saturated with gas, creating bubbles even if the diver is at a depth where pressure is consistent. This is known as isobaric counter diffusion.

Therefore, it’s crucial for divers to plan their gas mixtures and swimming depth very carefully to avoid this situation, especially when the body is nearing gas saturation. Making sure to include appropriate decompression stops during the dive can greatly help minimize these risks.

Risk Factors and Frequency for Inner Ear Decompression Sickness

Inner ear decompression sickness (IEDCS), which affects divers, is an extremely rare condition. It’s hard to determine the exact number of cases, but one source mentions that the chance of it happening is between 0.2 to 0.3% for each recreational dive. However, other sources suggest this percentage is overestimated. There’s a wider agreement that the general risk of getting any type of decompression sickness is between 0.01 to 0.095%, depending on the group of divers.

About 25% of recreational divers who experience neurologic decompression sickness also have problems with their vestibular-cochlear system, which affects balance and hearing.
In a study, venous-arterial shunts, which are abnormal passageways between arteries and veins, were found in 81% of patients diagnosed with inner ear DCS. This is a lot more compared to the 25% found in patients who never developed decompression illness (DCI).
This finding suggests that people with these shunts might be at a higher risk of developing inner ear DCS.

Signs and Symptoms of Inner Ear Decompression Sickness

Decompression sickness, also known as DCS, isn’t only seen in divers. Instances have been reported in pilots, astronauts, and compressed air workers like caisson workers, especially in situations involving high altitudes or pressures. Although DCS is less common in dives less than ten meters deep, longer and deeper recreational dives may increase the risk.

If a person’s experiencing the symptoms, they usually show up within two hours of surfacing, in some rare instances even while the patient is still under pressure. On average, symptoms typically begin around 36 minutes after decompression. The common signs of Inner Ear Decompression Sickness (IEDCS) include dizziness or vertigo, difficulty with coordination, nausea, and vomiting. Rings in the ears (tinnitus) and hearing loss are also seen in about a quarter of cases.

Dizziness/vertigo
Difficulty with coordination
Nausea and/or vomiting
Ringing in the ears or tinnitus
Hearing loss

It’s important to remember that IEDCS can sometimes be seen on its own, but if a patient is experiencing dizziness, balance troubles, or hearing loss after a dive, they should be examined for other possible diving-related injuries or signs of decompression sickness. It’s also important to rule out any causes that aren’t related to diving.

All patients should be given a full neurological examination including tests for balance, gait, spatial awareness, eye movements, and hearing in both ears. They should also be checked for pain and numbness, skin rash, pain in their muscles or skeleton, and how well their lungs are working.

Testing for Inner Ear Decompression Sickness

Barotrauma of the inner ear in divers can be hard to tell apart from decompression sickness of the inner ear. This requires carefully considering diving risks, and asking detailed questions about any ear-related incidents during diving. The HOOYAH criteria can be useful to help figure out the cause of inner ear symptoms, using thoughtfully collected patient history and physical checks.

The criteria include:
“H” stands for if it’s hard to clear your ears,
“O” stands for when the symptoms started showing up,
the second “O” is for examining the ear with an otoscope (an instrument used to look into the ears),
“Y” for understanding your specific dive profile or dive history,
“A” for any other additional symptoms,
and finally, “H” for any changes in hearing.

To figure this out, your doctor will take a detailed history, as well as a clinical assessment. This might include pure tone audiometry (a test used to identify hearing sensitivities), serial audiometry (a series of these tests), a fistula test (tests to detect abnormal openings), and electronystagmography (a test to examine uncontrolled eye movements). This way, they can reach the most accurate conclusion about your symptoms and health.

Treatment Options for Inner Ear Decompression Sickness

Hyperbaric oxygen therapy, also known as recompression therapy, is the main treatment for decompression sickness (DCS) and inner-ear decompression sickness (IEDCS). This therapy involves increasing the surrounding air pressure to help any gases trapped in your body return to their normal state. It also increases oxygen delivery to affected tissues.

The process continues with controlled decompression which allows gases to gently leave the body, preventing any problematic gas bubbles from re-forming. Over time, the pressure is reduced until it’s back to normal atmospheric levels, like the surface of Earth. Some patients might need more than one session of this therapy, especially if symptoms come back.

If this therapy is not immediately available, giving the patient oxygen at 100% concentration is important. This helps to get rid of any excessive gases in the body quickly, even after any symptoms have subsided.

Another part of initial treatment for IEDCS entails giving the patient enough fluids, usually crystalloid solutions, which are water-based and easily absorbed by the body. There could be a risk of clot formation due to free gas in the blood activating platelets – the cells that help blood to clot. To counter this, it may be necessary to give the patient antiplatelet drugs, like aspirin, which reduce the ability of platelets to form clots.

In suspected cases of IEDCS, inner ear injury due to pressure changes, or barotrauma, cannot be ruled out easily. Because of this, clinicians might consider a bilateral myringotomy. This is a procedure where a small hole is made on both eardrums to relieve pressure or drain fluid. However, if it’s uncertain whether the problem is due to either barotrauma or IEDCS, the doctors may still proceed with the hyperbaric oxygen therapy, as it is not expected to cause harm.

When trying to figure out if someone has decompression sickness in the inner ear, doctors need to consider similar conditions. These include:

Inner ear barotrauma (damage from changes in air pressure)
Arterial gas embolism (plugging of an artery by an air bubble)
Oxygen toxicity (poisoning from too much oxygen)
Persistent alternobaric vertigo (dizziness due to unequal pressure in the ears).

If the patient only presents with symptoms related to hearing or balance, doctors should also consider more common issues like earwax blockage and benign paroxysmal positional vertigo, a common but harmless cause of dizziness. Other central nervous system disorders such as strokes or mini-strokes could also mimic the symptoms of inner ear decompression sickness. This highlights the need for a thorough history, including diving activities, and a detailed physical exam.

It can be tough to tell the difference between decompression sickness in the inner ear and inner ear barotrauma, as they share many of the same symptoms. This makes the patient’s history and the specific signs of their condition all the more important to look at. Swift treatment is crucial for patients with decompression sickness—they need to undergo rapid re-pressurisation. On the other hand, patients with barotrauma don’t need immediate re-pressurisation. Their management can start with medication and proceed to surgery if necessary.

What to expect with Inner Ear Decompression Sickness

Generally, most people fully recover from Decompression Sickness (DCS), especially when they receive proper treatment. DCS is a condition that can occur in divers if they ascend too quickly, resulting in symptoms like joint pain, dizziness, and fatigue. However, full recovery from Inner Ear Decompression Sickness (IEDCS), a specific type of DCS that affects the inner ear, appears to be less frequent. Studies have found that between 32% and 91% of patients experience ongoing issues even after treatment, with most studies indicating that over 85% of patients still have residual problems.

Issues affecting balance, known as vestibular deficits, are found to be more common than hearing issues, or cochlear deficits. This corresponds with the fact that patients tend to experience balance issues more frequently at the onset of the condition.

According to one source, even when patients receive appropriate recompression therapy, which is a type of treatment that involves increasing the ambient pressure to relieve symptoms, it is common for them to continue experiencing balance and hearing-related issues, indicating a challenge in completely overcoming the effects of this condition.

Possible Complications When Diagnosed with Inner Ear Decompression Sickness

While they are infrequent, there can be complications from hyperbaric oxygen therapy. These adverse reactions might include barotrauma (harm caused by increased air or water pressure) affecting the ears, sinuses, and lungs. Other complications could be pneumothorax (a collapsed lung), pulmonary edema (fluid in the lungs), myopia (short-sightedness), and oxygen toxicity.

Potential Risks:

Barotrauma affecting the ears, sinuses, and lungs
Pneumothorax or collapsed lung
Pulmonary edema or fluid in the lungs
Myopia or short-sightedness
Oxygen toxicity

Preventing Inner Ear Decompression Sickness

Thanks to advancements in technology and the implementation of safety measures, decompression sickness (DCS) has become quite rare. Divers, aviators, and those who work in high-pressure environments should be well-versed in and adhere to safety procedures relevant to their field. This is especially crucial for divers who need to follow decompression schedules strictly. Decompression sickness, also known as ‘the bends’, often happens when divers ascend too quickly, causing nitrogen bubbles to form in the body. Most cases of Inner Ear Decompression Sickness (IEDCS), a specific type of DCS affecting the inner ear, occur when these decompression schedules are not followed carefully.