Navigating complex scuba diving health risks requires a clear understanding of how underlying medical conditions and specialized breathing gases affect the body underwater. In this edition of Ask DAN, dive medicine experts tackle two crucial safety inquiries: how managing Mast Cell Activation Syndrome (MCAS) might influence your risk of decompression sickness (DCS), and what exactly causes the frustrating post-dive phenomenon known as “Oxygen Ear.”
Mast Cell Activation Syndrome and DCS
Q: I have been diagnosed with mast cell activation syndrome (MCAS). Will that increase my risk of decompression sickness (DCS) if I dive?
A: With MCAS, mast cells release excessive amounts of histamine and other chemicals, leading to symptoms such as inflammation, hives, and systemic allergic reactions. While there’s no direct evidence linking MCAS to an increased DCS risk, some associated factors could influence that risk.
MCAS triggers chronic inflammation, which is a suspected factor in DCS development. An existing inflammatory state might exacerbate the physiological impact of nitrogen bubbles, increasing the risk of DCS symptoms. To brush up on how to spot these warning signs early, explore our comprehensive guide on recognizing and responding to decompression sickness. Also consider how the side effects of medications used to treat MCAS might interfere with diving.
MCAS may also cause systemic allergic reactions triggered by common environmental factors such as cold, new foods, pressure, stress, vibration, sunlight, or exercise. These reactions could lead to dizziness, low blood pressure, cough, nausea, vomiting, eye redness, airway swelling, abdominal pain, syncope, wheezing, mild subjective mental status changes, congestion, gastrointestinal disturbance, rash, joint pain, and fatigue. Most of these reactions could mask or mimic DCS symptoms, making diagnosis and treatment more difficult.
Before diving, people with MCAS should consult with a doctor familiar with their condition and a dive medicine specialist, who can assess individual risks and recommend strategies to reduce DCS risk, such as avoiding known triggers, controlling inflammation, and adhering to conservative dive profiles. Proper management of both MCAS and dive risks is key to ensuring a safe experience.
Scuba diving health risks: Oxygen Ear
Q: What is Oxygen Ear?
A: Also known as middle-ear oxygen absorption syndrome, oxygen ear describes a gas volume imbalance in the middle ear after diving with breathing gas that has a higher oxygen fraction than air. The phenomenon is commonly associated with open-circuit diving using nitrox and closed-circuit rebreather diving. The high-oxygen-content gas fills the middle-ear space over the course of the dive. Post-dive, the tissues metabolise oxygen, reducing the total gas volume below what it would be if the space were filled with air. If this loss in gas volume is not equalised, relative negative pressure will develop. This is in effect a squeeze, which can present as ear fullness, mild discomfort and/or impaired hearing.
This problem can be avoided easily with occasional equalisation for several hours after diving. A person who is active, talking and/or laughing during this period may have no need to actively equalise. On the other hand, a person who goes to bed immediately after diving might wake up several hours later with mild discomfort. Full resolution is best achieved using gentle equalisation techniques. n
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FAQs
Can Mast Cell Activation Syndrome (MCAS) increase the risk of decompression sickness (DCS)?
While there is currently no direct clinical evidence linking MCAS to a higher incidence of DCS, the chronic inflammation caused by MCAS is a suspected contributing factor. An existing inflammatory state may worsen the physiological effects of nitrogen bubbles in the body.
What are the dangers of managing MCAS symptoms while scuba diving?
Environmental dive triggers like cold, pressure, and stress can cause systemic MCAS reactions (such as dizziness, airway swelling, and rapid heart rate). These reactions can dangerously mimic or mask actual DCS symptoms, making an accurate medical diagnosis much more difficult.
What is “Oxygen Ear” in scuba diving?
Oxygen Ear, medically known as middle-ear oxygen absorption syndrome, is a gas volume imbalance in the middle ear. It occurs after breathing gas with a higher oxygen fraction than regular air (like nitrox), leading to a negative pressure squeeze as tissues metabolize the trapped oxygen post-dive.
What are the symptoms of middle-ear oxygen absorption syndrome?
The most common symptoms of Oxygen Ear include a sensation of ear fullness, mild physical discomfort, and temporarily impaired hearing hours after completing a dive.
How can divers prevent and treat Oxygen Ear?
This condition can be easily prevented by occasionally equalizing your ears for several hours after a dive. If you go to sleep immediately after diving, you are more likely to wake up with discomfort, which can be resolved using gentle equalisation techniques.
This article was originally published in Scuba Diver Magazine
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Hey hi.
I’m wondering if you have any data to support your assertion of the cause of oxygen ear. I have doubts about the explanation. Let’s look at it logically:
So I’m suggesting that the common explanation for “oxygen ear” is a diving myth. The symptoms are real, but the causes are different than people think. This is supported by scientific evidence:
Shupak, A., Atttas, J., Aviv, S., & Melamed, Y. (1995). Oxygen Diving-induced Middle Ear Under-aeration. Acta Oto-Laryngologica, 115(3), 422–426. https://doi.org/10.3109/00016489509139341
Cheers!