1At a glance
- Primary Cause
- Trapped expanding air during ascent due to blocked passages
- Common Locations
- Middle ear (most common), sinuses, tooth cavities, dry suits
- Onset Depth
- Can occur at shallow depths, often 1-2 metres (3-6 feet) during initial ascent
- Symptoms
- Pain, pressure, fullness in ears/sinuses; rarely vertigo or bleeding
- Prevention
- Avoid diving with congestion, slow ascent, gentle equalisation on ascent
- First Aid
- Descend slightly until pain subsides, then ascend very slowly
- Recovery Time (Mild)
- Hours to a few days, depending on severity
- Maximum Pressure Differential
- Can reach 101 kPa (1 atmosphere) from surface to 10 metres (33 feet)
2Recognising and Preventing Reverse Blocks
Recognising the symptoms of a reverse block is the first step in managing it safely. Typically, divers will experience a feeling of increasing pressure or fullness in their ears or sinuses, followed by sharp pain during ascent. This pain may intensify rapidly if the ascent continues. In some cases, a diver might also experience mild vertigo, a popping sensation, or even a small amount of blood from the nose or ear canal, indicating more severe tissue damage.
Prevention is always better than treatment. The most effective way to prevent a reverse block is to avoid diving if you are congested due to a cold, allergies, or sinus infection. Decongestants can sometimes offer temporary relief but may wear off underwater, leading to issues. Ensure your Eustachian tubes and sinus passages are clear before diving. During ascent, maintain a slow, controlled rate, typically no faster than 9 metres (30 feet) per minute, and perform gentle, active equalisation techniques, such as swallowing or wiggling your jaw, to help open the passages. Do not force equalisation if you feel pain.
3Types of Reverse Blocks and Their Implications
| Location | Typical Symptoms | Severity | Prevention Strategy | Liveaboard Relevance |
|---|---|---|---|---|
| Middle Ear | Sharp ear pain, fullness, muffled hearing | Common, can lead to ear drum rupture | Gentle equalisation on ascent, avoid diving with congestion | Most frequent; multi-day diving increases risk of mild inflammation |
| Sinuses | Facial pain (forehead, cheekbones), headache, pressure | Less common than ear, can cause sinus bleeding | Ensure clear sinus passages, slow ascent | Congestion from AC or travel can exacerbate; watch for early signs |
| Tooth Cavities | Sharp tooth pain ('tooth squeeze') | Rare, indicates dental issue needing attention | Regular dental check-ups, avoid diving with unsealed dental work | Unlikely if dental health is good; can ruin a trip if it occurs |
| Dry Suit (trapped air) | Pinching or squeezing of skin under suit | Minor discomfort, easily resolved | Ensure proper venting of air from suit | Relevant for dry suit divers; proper technique prevents entirely |
4Managing a Reverse Block Underwater
Should you experience the symptoms of a reverse block during an ascent, the immediate and most crucial action is to stop ascending. Descend slightly by a metre or two (3-6 feet) until the pain subsides. This allows the surrounding water pressure to gently recompress the trapped air, reducing the pressure differential on your tissues. Once the discomfort eases, attempt a very slow, controlled ascent, perhaps even slower than your typical safety stop rate. Try gently wiggling your jaw or swallowing to facilitate air release. If the pain returns, descend again. Never force an ascent through pain.
If you repeatedly experience a reverse block, or if the pain is severe and persistent, it's safest to abort the dive and surface very carefully. After surfacing, avoid diving until the condition causing the block has resolved, and seek medical advice from a dive physician if symptoms persist or worsen. Ignoring a reverse block can lead to more serious injuries such as barotrauma to the middle ear or sinuses, which can require extended time out of the water.
5Reverse Blocks on Liveaboard Trips
Liveaboard diving often involves multiple dives a day over several consecutive days, which can increase the risk of developing conditions that predispose you to a reverse block. Constant exposure to air conditioning, varied climates, or simply increased diving activity can sometimes lead to mild congestion or inflammation in your ear and sinus passages. It's vital to stay well-hydrated, get adequate rest, and monitor your physical condition throughout your trip.
Before and between dives on a liveaboard, pay close attention to any signs of congestion or difficulty equalising. If you feel even slightly congested, consider sitting out a dive or at least taking extra precautions. Communicate any discomfort to your dive guide or boat crew. Carrying a nasal spray (only if approved by a dive doctor and used cautiously) for emergency congestion, and being proactive about hydration and rest, can help minimise the risk and ensure your liveaboard experience remains safe and enjoyable for its entire duration.
6Common misconceptions
Myth: Reverse blocks only happen at deep depths. Fact: Reverse blocks can occur at very shallow depths, often just 1-2 metres (3-6 feet) below the surface, as the relative change in pressure is greatest closer to the surface during ascent.
Myth: If you can equalise on descent, you won't get a reverse block. Fact: The mechanisms for equalising on descent (forcing air in) and ascent (allowing air out) are different. Congestion might not prevent air from entering during descent but can easily block its escape during ascent.
Myth: Taking a strong decongestant will prevent reverse blocks. Fact: While decongestants can clear passages, their effects can wear off underwater. Diving on decongestants is generally discouraged by dive professionals as it can mask underlying issues and lead to a block when the medication's effect diminishes.
FAQ
What is a reverse block in scuba diving?
A reverse block is a condition where expanding air, most commonly in the middle ear or sinuses, becomes trapped during ascent because it cannot escape through congested passages. This creates a pressure differential that causes pain and can lead to injury.
How does a reverse block happen?
As a diver ascends, ambient pressure decreases, causing trapped air within body cavities to expand. If the Eustachian tubes (for ears) or sinus ostia are blocked due to inflammation or mucus, this expanding air has no escape, leading to a reverse block.
What should you do if you get a reverse block while ascending?
Immediately stop your ascent and descend slightly by a metre or two until the pain subsides. Then, try ascending very slowly, attempting gentle equalisation techniques like wiggling your jaw. If pain returns, descend again.
Can a reverse block cause permanent damage?
While most reverse blocks are temporary and resolve without lasting issues, severe cases can lead to barotrauma, such as a ruptured eardrum, sinus haemorrhage, or fluid in the middle ear. These require medical attention and can result in temporary hearing loss or infection if not treated.
Can I dive again after experiencing a reverse block?
It's best to avoid diving until all symptoms have completely resolved and the underlying cause of congestion or inflammation has cleared. If you experienced significant pain or other symptoms, it is advisable to consult a dive physician before returning to diving.
Are reverse blocks common on liveaboard trips?
The risk of developing a reverse block can be slightly higher on liveaboards due to multiple consecutive dives, potential fatigue, and exposure to different environments like air conditioning, which can contribute to congestion. Staying hydrated and well-rested is key.