Medical FAQs

Here's a list compiled over the years of commonly asked questions. The list was created by DAN MDs and represent specific, evidence-based recommendations our member should take into consideration.


After a recent dive, I surfaced and noticed that my eyes were bloodshot and I had two black eyes. Have you ever heard of this?
Like the air spaces in our sinuses and ears, we must also equalise the air space in our masks as we descend. Failure to equalise the air space by exhaling through the nose can create a negative pressure within the mask.

The negative pressure, in effect, creates suction. This is referred to as “mask squeeze”, which can cause varying degrees of  barotrauma to the soft tissues of the face and eyes.
The soft tissue around the eyes swells (periorbital edema) and discolours, manifesting as redness or bruising (ecchymosis). The eyes themselves may appear bloodshot. Unless there is eye pain or visual problems present, there is no specific treatment for facial barotrauma.

The injuries from a mask squeeze can take up to two weeks or more to resolve. The body will eventually reabsorb the ecchymosis and edema. The individual’s appearance may worsen before improving.

A physician or an eye specialist should immediately address any eye pain or visual disturbances, such as blurred vision or partial loss of the visual field. These symptoms are rare with mask squeeze.
The best treatment for mask squeeze is prevention. Exhaling through the nose during descent (as done naturally, for example, with the Valsalva equalisation technique) will minimise the risk of facial barotrauma.

I made two dives about a month ago. The first was to 27 meters for 20 minutes, and the second was to 11 meters for 35 minutes. I was well within my computer guidelines, we did not do a safety stop, and I may have had one slightly fast ascent. I was OK until about four days after the dive, when I noticed a sharp pain in my elbow. If I'm not using my arm, I don' t notice any pain at all. But if I rotate my forearm or bend my elbow, I still get a dull ache. Is there any way this could be related to my dives?
If you were symptom-free for four full days, then it is unlikely that subsequent symptoms are related to decompression illness and your dive. The nitrogen you absorbed during your dives has to follow the physiology of basic gas laws - it cannot stay in the body tissues once the partial pressure of nitrogen in the ambient air we breathe drops down to sea-level pressures.

Although nitrogen leaves the body in a much slower fashion than we take it on, it still must leave. After diving, you should be equilibrated to ambient nitrogen in 24 hours.
If the pain can be produced with movement of the affected joint only, then it is more than likely a musculoskeletal strain or injury.

The pain generally associated with decompression illness is not affected by movement or lack of movement and usually remains fairly constant.
The ability to reproduce the symptom with movement indicates a stress or repetitive movement injury.
If you have not seen your personal physician it would be wise to do so.
Appropriate therapy is indicated to prevent permanent injuries.

Last week I got a saltwater aquarium with an anemone and a small lionfish. I saw the lionfish swimming through the anemone and thought it was going to hurt the anemone, so I reached in the tank and pushed the lionfish away. It nailed me on the fingers, and now they're all swollen and blistered. Is there anything I can do?
Lionfish (as well as scorpionfish and stonefish) possess dorsal, anal, and pelvic spines that transport venom from their venom glands into puncture wounds. Common reactions include redness or blanching, swelling and blistering (lionfish). The injuries can be extraordinarily painful and occasionally life-threatening (in the case of a stonefish).

The Treatment

Soaking the wound in non-scalding hot water to tolerance (43.3 to 45˚ C) may provide dramatic relief of pain from a lionfish sting; is less likely to be effective for a scorpionfish sting, and may have little or no effect on the pain from a stonefish sting, but it should be done nonetheless, because the heat may inactivate some of the harmful components of the venom.
If the injured person appears intoxicated or is weak, vomiting, short of breath or unconscious, seek immediate advanced medical care.
Wound care is standard, so – for the blistering wound – appropriate therapy would be a topical antiseptic (such as silver sulfadiazene cream or bacitracin ointment) and daily dressing changes. A scorpionfish sting frequently requires weeks or months to heal, and therefore requires the attention of a physician. There is an antivenin available to physicians to help manage the sting of the dreaded stonefish.

Is it safe to dive with a perforated tympanic membrane?
A perforated tympanic membrane (ear drum) can be caused by diving, or have other non-related causes. Most traumatic perforations heal spontaneously.

Following an appropriate time after they have healed, you can return to diving if your physician feels the healing is solid and there is no evidence of Eustachian tube problems.
This usually takes about two months after it is healed.
If the perforation does not heal, then an ear surgeon can repair the damage.
After healing has taken place, the same rules as above apply. It is important to check for chronic nose and sinus problems if there is no healing.

Chronic perforations that do not heal are a contraindication to diving. Some have advocated the use of ear plugs for these individuals, but if there is any water leakage, it could cause a severe infection.

This is NOT an emergency. I have a question: I’m a musician (saxophone, flute, and clarinet) and would like to know how long I should wait with playing an instrument after diving without increasing the risk of a decompression accident. After a dive it is not advisable to do any physical exertion. I always wait until my dive computer Galileo Sol doesn’t show any desaturation time anymore. Are there any guidelines?
Being this the case of wind instruments, the risk relates to the possible increase in intra-thoracic pressure that can facilitate the arterialisation of potential circulating venous bubbles, both having a cardiac or pulmonary right to left shunt, but also with ideal anatomical conditions.

This is because of significant quantities of VGE (venous gas emboli) which increase the right ventricular pressure and force the filter of the lung.

Waiting for the total desaturation time, shown on the Galileo diving computer, is not wrong but very precautionary.
The problem lies on VGE presence which cannot be detected after 3 hours from surfacing, in case of recreational dives. Time should be extended with advanced/tech dives but also in this case, VGE are rarely observed after 4-6 hours.

Can people with cochlear implants scuba dive?
Diving is a sport with some inherent risk and people with deafness or ear surgery may be at increased risk with scuba diving.

Regarding return to diving after implantation, a recipient should wait a minimum of 3 months after implantation, be able to autoinflate (equalize) the operated ear, be completely healed, free of symptoms such as vertigo, imbalance and pain and have complete resolution of the post-operative hemotympanum (blood behind the ear drum).
On examination with a microscope, the fistula test should be negative and the TM should not contact the electrode on maximum medial excursion.
(Your doctor will gently puff air into your ear canal to see if it makes you dizzy or if the eardrum touches the CI electrode).

Your neurological examination should be normal. Make sure to discuss these recommendations with your otologist and be sure to follow his/her recommendations.

I have a question about the degassing of my body. I am a technical diver and I'm always pretty tired after deep dives. I've played around with my gradient factors, but the problem persists. I have my whole body tattooed, with exception of head and feet. My question is: does degassing takes longer because of the ink in my body, or is that a myth?
This has no effect on the rate of degassing. The desaturation rate differs for everybody, even depending from day to day.

So the only logical approach is to reduce the saturation – This can be calculated using the depth, dive time and Nitrogen concentration (inert gas) in the breathing mix.

In the absence of a recompression chamber, does DAN recommend treating a "bent" diver with in-water recompression?
DAN does not recommend that symptomatic divers be recompressed while breathing standard air in the water. In some areas of the world, divers are treated with in-water recompression because of a lack of chamber facilities. At one time, divers were treated in recompression chambers using the U.S. Navy treatment tables and breathing air instead of oxygen.

The failure rate was high. It is unlikely that in-water recompression using air is more effective than those old treatment tables. In-water recompression with the diver breathing oxygen instead of standard air has been used successfully in some areas.
However, in-water recompression has its own dangers and should not be attempted without the necessary training and equipment, or in the absence of someone who can assess the diver medically.
The resources required for in-water recompression usually exceed the ability of those at the scene to properly assist the injured diver.

In-water recompression of any type is not currently recommended by DAN.

I was diving over the weekend, doing three dives each day, finishing about noon on Sunday. I had some trouble clearing on both days, and on the last dive I had a reverse block. I can hear just fine and I don't have any pain, but on the side of my neck I have several little bubbles that I can press on but which are not painful. Have you ever heard of this?
Air bubbles don't normally exist under the skin in the neck, or anywhere else in the body. Although it may seem as though this trapped air must have come from the middle ear, this would be a bit unusual, since you have no ear pain or other symptoms, such as a ringing or roaring sound, or even loss of hearing.

Middle ear barotrauma can easily damage the tympanic membrane or one of the more delicate internal membranes associated with sound transmission inside of the ear.
Although no one can say for sure, it is more likely that this trapped air - or subcutaneous emphysema - originated from pulmonary barotrauma.

Sometimes the lungs are over-pressurized, for instance, when we have difficulty clearing. This can happen when we attempt to put air into the sinuses and middle ear with more force than is necessary.
This can actually increase the amount of pressure in the air spaces of the lung, which then allows air to escape through lung tissue, where it can travel up to the shoulder, neck or even the face. Subcutaneous emphysema does not require recompression treatment.

However, it is a good idea to be evaluated by your physician to determine the underlying cause of the air bubbles.

It takes most tourists 24 hours to get to our resorts here in Thailand. I notice that many tourists begin diving immediately when they arrive and often start drinking quite a bit of alcohol. Aren't they at greater risk for decompression sickness after their long flight if they begin diving right after they arrive? Shouldn't they wait one day before they begin diving?
Mild dehydration can occur on long flights, especially when travellers cross several time zones; alcohol consumption can also contribute to dehydration. Generally speaking, dehydration is thought to predispose a diver to decompression illness because the washout of inert gas (nitrogen, in diving) is less effective in a dehydrated individual.

The evidence of an increased incidence of DCI on the first day of a dive trip is not sufficient to recommend a 24-hour waiting period before diving after flying.

However, it does indeed support the advice of starting off much more gradually with fewer, shallower, more conservative dives right in the beginning, especially whenever there has been significant travel; the potential for more dehydration; a delay since diving previously; where the use of unfamiliar, rented gear is involved; if there is a lack of familiarity with the dive-site; etc.

Taking it slow also gives divers an opportunity to rest and rehydrate, adjust to a new climate and time zone, and acquaint themselves with the new / rented dive equipment.

I’m going to climb Rinjani mountain outside of Bali next month and I’m planning to do some dives as well, before the climb. After booking I noticed that the schedule was steeper than I thought so I am looking for information regarding safety after diving. The plan is to make two morning (tank) dives at max 18 m, then chill out for the rest of the day. The day after will focus on the mountain climbing and it seems like we are reaching 2700 m. We are staying at +2500 m for the next 3 days. I am trying to collect information about this, but since flying is so much higher but at a shorter time, I’m slightly confused about it. Could you please advise me about the safety of this schedule?
When carrying out any ascent exceeding approximately 700 meters the recommendations of flying after diving apply.

Therefore, in your case, the DAN recommendation is to leave a surface interval of at least 18 hours and if any decompression is involved then it will be wise to extend the surface interval to some hours."

How long should I avoid diving after experiencing a perforated ear drum followed by an ear infection? I experienced the injury 3 weeks ago and I wondered if it's a case of weeks or months before I can get back in the water again.
It is difficult to say how long you need to stay out of the water following an ear perforation as it depends on how much damage the infection caused and how quickly you heal. What is certain is that it will be several weeks before the ear drum is fully healed and able to withstand the pressure differentials inevitable in diving.

You will need to interact with your ENT specialist and, when he/she reports it fully closed, you need to ask how long it will then take for full strength to occur based on the examinations undergone.
Unfortunately, after serious infection damage, the eardrum may not close spontaneously within the expected 6 weeks and some surgery will be required to close it.
After surgery an appropriate healing time must be factored in, till the ear drum can withstand pressure changes.

I read on the Internet that coral can continue to grow under my skin. Is that true?
No. Coral cannot live in human bodies. Coral are marine animals and are unable to grow outside of the marine environment. Some bacteria, parasites and other foreign organisms evolved to live and replicate within human tissues, but coral did not.

Although both humans and coral are members of the kingdom Animalia, their tissues and body systems are incompatible.

When you are injured, your body activates, recruits and increases production of leukocytes (white blood cells). This leukocyte production contributes to the pus that can accumulate at wound sites and promotes the elimination of foreign material.

If the body is unable to eliminate foreign material (such as coral), it will wall off the substance with immune cells, forming a granuloma. If this occurs, you may be able to feel a lump under the skin where the granuloma formed.
Keep an eye out for infection (manifesting as redness, swelling, warmth and pain) with such injuries, but rest assured that coral is not growing under your skin.

Why do the effects of decompression sickness (DCS) last longer than the 12 to 18 hours it takes to off-gas? Do the bubbles that cause DCS lead to other problems in the body that last longer? If that is the case, why are chamber dives effective in easing the symptoms of DCS even after a day or more has passed and the level of inert gas in the body is no longer elevated?
DCS can manifest in many ways and the signs and symptoms depend on the body system or systems being affected. DCS usually involves large numbers of small bubbles and their effects include mechanical tissue damage and the interruption of blood flow to some areas of the body.

Irritation can occur in the endothelium (the cells lining the blood vessels) which leads to inflammatory responses that may cause platelets to initiate clotting and white blood cells to accumulate. The inflammation and tissue damage take a while to heal, which is why DCS lasts longer than the time it takes to eliminate inert gas.

Hyperbaric oxygen therapy (HBOT) can be effective for days or even a week or more following a dive, because HBOT has significant anti-inflammatory properties and oxygenates injured tissues, thereby promoting healing. HBOT is frequently administered after tissue damage, inflammation and other injuries have occurred and no inert gas remains.

In these cases, its purpose is only to promote healing. However, HBOT administered very soon after the injury also promotes the washout of inert gas.

I recently had a stapedectomy. Can I dive and what are the risks involved?
Ear, nose and Throat (ENT) surgeons trained in diving medicine differ in their opinions regarding the wisdom of diving after a stapedectomy, which is a surgery to treat hearing loss by replacing the stapes bone in the middle ear with a prosthesis.

This controversy extends to diving with any ear condition that increases the risk of permanent injury
All of us who dive place our hearing at risk and barotraumas (a pressure injury) of the middle and/or the inner ear increases the risk of hearing loss.
While some ENT experts absolutely recommend against diving for individuals with existing ear issues, other ENT experts are of the opinion that patients who understand and accept the potential risks may dive.

Limited studies have described small numbers of people diving after stapedectomies.
The results from these samples indicate that the subjects are not at an increased risk of injury when compared to the control groups of divers, provided they can safety equalize their ears and sinuses with the changes on ambient pressure.

With that said, the consequences of failure to equalise can be greater for those who have undergone stapedectomy procedures.
The inability to equalize the middle ear space effectively, or an attempt to do so too forcefully, may dislocate the prosthetic stapes.
Dislocation can be corrected only in surgery and may result in permanent hearing loss.

Diving after a stapedectomy also carries the risk that the desolation of the prosthesis may damage the round or oval window of the cochlea.

Such an injury can permanently affect both hearing and balance.

Again, it is not that the risk of injury is necessarily greater than that faced by other divers, but rather that there are greater consequences in the event of an injury.

Before deciding to pursue or return to diving, it is clearly in your best interest to candidly review your fitness to dive with a doctor and make a brutally honest risk versus benefit analysis based on the information available.

When I am not wearing a hood, I have no problems equalising my ears. On the other hand, when I wear it, I always have great difficulty. Why is there a difference?
When we pressurise the middle ear space using the Valsalva manoeuvre or another equalisation technique, the tympanic membrane (ear drum) bulges outward slightly.

If the ear canal is uncovered and can transmit that pressure, the water in the ear canal moves easily in response.

A hood that fits snugly against the outer ear can greatly restrict the movement of this water, hampering the diver’s ability to equalise.

An easy remedy to this is to insert a finger under the hood near the ear, which will allow the water to move more easily.

Another solution some divers choose to implement is to cut a hole from the inside of the hood, near the ear canal, through the inner lining and the neoprene but leaving the outer fabric or covering intact.
This hole allows the water to move with little restriction.

Can I dive with hypertension?
Basically, an increased blood pressure or hypertension is not a contraindication for recreational diving. However, it is important how pronounced the increased blood pressure is and whether there are already typical consequential damages as can be caused by longer existing hypertension.

Since in most cases an increased blood pressure requires treatment with medication with partly possible significant undesirable side effects, it first needs to be determined whether these medications are compatible with recreational diving.

I have been diagnosed with a 2nd Grade Patent Foramen Ovale (PFO). I know I can undergo surgery and have it closed with an umbrella device. Would the surgery be a resolution? Can I dive regularly after it?
In accordance with the Swiss Underwater and Hyperbaric Medical Society (SUHMS) guidelines, a diver with 2nd and 3rd Grade PFO can dive according to “low bubble diving recommendations”:
  1. Perform the deep phase of the dive first and avoid yo-yo dives (avoid repetitive entry into the 0-10 meter zone)
  2. Reduce surfacing speed to 5 meters per minute in the upper 10 meters
  3. Perform a safety stop at 3-5 meters depth for at least 5-10 minutes
  4. Don’t go to the limit of a no-decompression dive - Don’t perform dives with a decompression stop obligation
  5. Surface interval of at least 4 hours before the next dive
  6. Maximum of two dives a day
  7. Avoid intense skin warming after the dive (e.g.: sunbathing, hot shower, sauna)
  8. Diving with a Nitrox, using air decompression tables or computer setting, pay attention to oxygen toxicity
  9. Special underwater computers or software may reduce the risk


Moreover, to decrease the risk of bubbles transfer into the arterial blood stream: 

  • Avoid strenuous physical efforts during the last 10 metres of surfacing (fining or swimming against current at the end of the dive)
  • Avoid exhausting physical activity during two hours following the dive
  • It is absolutely prohibited to dive when having a cold. Coughing and forced Valsalva maneuver facilitate bubble transfer into the arterial blood stream.


Nonetheless, the surgery will be effective and after a complete healing you can go back to diving again. 

I’m a 76-year-old diver and, while undertaking an Exercise ECG, the doctors detected an Atrial Fibrillation. After urine and blood tests, the haematologist prescribed me Xarelto (Rivaroxaban). Can I still dive?
Atrial Fibrillation, not previously detected, was diagnosed through the Exercise ECG and this is why you are now under treatment with Xarelto (Rivaroxaban).

If this condition, although chronical, is characterized by a normal cardiac frequency with no symptoms during the physical exercise, as in your case, then safe diving is still possible.

I suffer from a low blood pressure. Is it safe for me to start diving?
Usually yes! If your low blood pressure does not impair your normal performance on land, there should be nothing to worry about while you are diving.

However I advise you to see a medical doctor before starting diving and to perform a clinical check, especially if you experience any signs or symptoms of low blood pressure (hypotension).

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