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.


Last year in October, I was hospitalized for acute coronary artery disease, treated with a coronary angioplasty and DES (Drug Eluting Stent) implant. The angiographic results were excellent, without any complications. My echocardiogram, which upon admission showed apical hypokinesia, upon dismissal showed normalization of all hypokinetic segments. I had my first routine check-up in the month of February with an ECG test, and a second check-up in May with CPET. The results were the following: the test was negative, and maximal exercise testing, after suspension of Metoprolol, was also negative for inducible myocardial ischemia. Are there any contraindications for diving activities?
The missing step to the clinical tests and check-ups that you have already performed, is an appointment for a medical with a hyperbaric trained physician, who can assess your fitness to dive.

In addition, concerning the type of dives that you will be able to perform from now on, you will surely have to avoid strong currents and cold water dives, and should limit yourself to purely recreational diving, which means a maximum depth of 30 m, and No-Deco.

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 have breast implants. I would like to learn to dive but am afraid of what the pressure will do to the implants. Are there any studies on this?
Three types were tested: silicone-, saline-, and silicone-saline-filled. In this experiment, the researchers simulated various depth/time profiles of recreational scuba diving. There was an insignificant increase in bubble size (one to four percent) in both saline and silicone gel implants, depending on the depth and duration of the dive.

The silicone-saline-filled type showed the greatest volume change.

Bubble formation in implants led to a small volume increase, which is not likely to damage the implants or surrounding tissue. If gas bubbles do form in the implant, they resolve over time.

Once sufficient time has passed after surgery, when the diver has resumed normal activities and there is no danger of infection, she may begin scuba diving.

Breast implants do not pose a problem to diving from the standpoint of gas absorption or changes in size and are not a contraindication for participation in recreational scuba diving. Avoid buoyancy compensators with constrictive chest straps, which can put undue pressure on the seams and contribute to risk of rupture.

I would like to know if deep stops are always recommended for recreational dives, if the depth of the deep stop must be half of the maximum depth reached or half of the maximum pressure reached, and if, for multi-day dives, it is always recommended to do this deep stop
The introduction of a deep stop at half of the maximum depth reached during recreational dives during the ascent phase seems to:
  • significantly decrease inert gas bubbles detected by a Doppler scan after a dive
  • reduce tension of inert gas in ‘fast’ tissues, which is an important fact to correlate with gas exchange happening in the spinal chord. 

Authors of scientific publications regarding this topic concluded that a deep stop can decrease the likelihood of suffering from decompression sickness.

I love to dive, but was recently diagnosed with Multiple Sclerosis. Can I continue?
This immunologic disease occurring in both young and middle-aged people is characterised by episodes of neurologic dysfunction, often separated by remission. He extent of disability is quite variable. Treatment has improved in recent years.

Fitness & Diving

  1. There is no evidence that diving in itself has an effect on the disease. About 20 years ago an unsuccessful effort was made to treat MS with hyperbaric oxygen. Patients neither suffered nor benefited from this treatment.
  2. Persons with MS are advised not to exercise to the point of exhaustion and to avoid becoming chilled or overheated. Diving candidates with MS should respect that advice.
  3. In each individual case, consider whether the candidate can handle the physical load and master the water skills. Diving candidates should talk to their DMO and neurologist about diving.

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 have a question concerning breastfeeding and diving. My wife and I have just had a baby. She is still breastfeeding and if everything goes well, she would like to carry on for the next 4 months at least. On the other hand, she is eager to resume diving. And I wondered if the nitrogen that gradually saturates our tissues and which will necessarily go into the milk can have an impact on the baby. We dive at a maximum depth of 30 m and stay within the limits of no-decompression diving. Have any studies been done in this field? What could be the impact on the baby? I think my wife will express her milk before diving so that she can feed the baby with non-nitrogenated milk, but how long does it take for nitrogen to desaturate the breast tissue?
There is no accumulation of nitrogen in breast milk, and even if this were the case, drinking this milk would not cause any risk of decompression in the baby. Your wife can therefore resume diving a few weeks after giving birth (in general, it is recommended to wait at least 3 weeks to recover from the “trauma” of childbirth and hormonal changes).

In the first few months, we recommend to stay within the limits of “no-deco dives”, i.e. dives which don’t have mandatory decompression stops – after all, the bodily changes induced by these 9 months of pregnancy should not be underestimated.

Only one disadvantage may occur when your wife dives during the months she is still breastfeeding: the pressure exerted by the dive suit on the chest and on the breasts could (in some cases) reduce milk production (it is a known technique for woman who want to stop breastfeeding, to wear tight clothes or bandages around the chest).
But as your wife will not wear the dive suit all day, this risk isn’t very high.

I am writing to you to have some information about the compatibility of trombophilia and scuba diving. My partner, who is a diver like me, after running some routine tests, discovered that she has trombophilia (mutation C677T in the gene MTHFR in homozygosity). Provided that she is 41 years old, a non-smoker, leads a healthy life, practices sports, and has never had cardiovascular thrombotic events so far, I would like to know if she will be able to continue performing diving activities from now on.
In order to understand if there is an actual risk or only a potential risk of thromboembolic events connected to the mutation carried by your partner, we advise you to complete a thromboembolic risk evaluation carried out by an hematologist.

Theoretically, your partner may be more susceptible to decompression illness, and therefore, we advise you to reduce any risks by taking appropriate precautionary measures with regard to dive profiles.

The following are the characteristics of dive profiles with the lowest production of bubbles: 

  • do not plan dives with compulsory decompression stops
  • avoid, as much as possible, repetitive dives, or if you wish to dive repetitively, make sure your surface intervals are long enough (not less than 3 hours, and best if longer)
  • limit your bottom time to no more than 70% of the No-Deco time indicated by your computer upon reaching maximum depth, or as suggested by your dive tables
  • perform your dive by reaching maximum depth right at the start and then “ascending”, and avoid staying at shallow depths and then going deeper again
  • if your dive computer allows advanced settings, set the GF Low to less than 30 and the GF High to 70
  • if possible, use enriched air mixes and set your computer or use dive tables as if you were diving on air

I have recently had a defibrillator implanted by my doctor. After I recover, what are my chances of going back to diving? I am told that it works as a pacemaker too
These implantable devices have been found to benefit patients at a high risk of ventricular tachycardia, ventricular fibrillation, or other rhythm defects that can lead to sudden cardiac arrest. The pacemaker feature will increase the heart rate of the patient if it slows to an inefficient rate. With or without the pacemaker feature, these internal devices are used to treat potentially life-threatening rhythms.

It is the opinion of diving medicine professionals that due to this potential life threat, individuals with these implanted devices are disqualified from diving.

These devices are intended to prevent sudden cardiac arrest, but the heart itself may be in generally poor health which is not compatible with safe diving. As relaxing as diving is there is still an increased work-load placed on the heart.
The heart needs to be able to respond effectively to any increased exercise demand, especially in an emergency situation.

A heart that is prone to life-threatening rhythms has most likely sustained injury from coronary artery disease or other conditions that affect the muscle tissue of the heart, or its electrical pathways. Any exercise restrictions from the diver’s cardiologist would be a good indicator that diving would hardly be in their best interest.

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.

I recently returned from a dive vacation. I experienced trouble with a tooth about a week after my return, and three days later required a root canal. My dentist said he knew another diver who had required root canal work; my wife's friend, also a diver, required a root canal too. Is this a coincidence or is it a problem related to diving?
There has been no established cause-and-effect relationship between root canals and scuba diving. It is possible that the repetitive action of clenching a scuba regulator with your teeth may have exacerbated an underlying problem.

Root canal therapy is generally necessary after a tooth nerve has been damaged from a direct blow to the dental area or the result of decay, abscess, or infection.
Most root canals are done in patients who are over 50 years of age and who have had one of these events occur after a lifetime of using their teeth.
In the thousands of certified divers over age 50, root canals are rarely reported. In all likelihood, the problem was just coincidental and would most likely have occured even if you had not participated in scuba diving.
There is a small risk of infection immediately after a root canal, but once you are released by your dentist, you should have no problem when diving.

I’m 45 years old and a diver since 2012. I would like to know if I can dive with inflammatory bowel disease.
Inflammatory bowel disease (IBD) can result from ulcerative colitis or Crohn’s disease. The major symptoms are diarrhea, which can be bloody; abdominal pain; nausea; and vomiting, often with fever and weight loss.

Commonly, IBD usually occurs to divers aged 20 to 40 years and who experience the following: 

  • Intermittent disease with long periods of normal bowel functioning; and 
  • Complications including anemia, electrolyte disturbances, dehydration, poor absorption of fluids, liver disease and generalized fatigue. 

Drug treatment often involves corticosteroids, which can impair one’s ability to fight infections.

Fitness and diving
Someone with symptomatic IBD should not dive until treatment has caused remission and they do not need medication. A person experiencing no significant complication of IBD or its treatment and has adequate cardiovascular fitness could consider diving.

I had a spontaneous pneumothorax a few months ago. How long should I wait before diving again?
Unfortunately for you, nowadays a spontaneous pneumothorax is recognised as an absolute contraindication for diving.

This is because of two reasons:

  1. If it occurred without any injury (so the name “spontaneous”), it can happen again at any time. In fact, there are some statistics showing that half of those persons who had spontaneous pneumothorax in the past, will have it again in future.
  2. If pneumothorax occurs while diving, any decrease of pressure, for example during surfacing, will increase volume of air in the pleural cavity leading to a tension pneumothorax, when internal pressure will compress the lung and the heart.

This is a real life-threatening disorder, especially when occurring underwater, just after surfacing or even on the diving boat. All in all, the risk is too high for potentially fatal consequences, so you should understand that you should avoid diving. And this restriction expands also for any hyperbaric exposures, like for example hyperbaric chambers, even for training purposes.

Is it safe to breastfeed an infant after diving?
Yes, it is safe. A mother’s breast milk is not adversely affected by diving, and there is no risk of decompression sickness for the infant.

Although nitrogen accumulates in all of the tissues and fluids of the mother’s body, washout of inert gas occurs quickly after a safe dive.
Insignificant amounts of nitrogen may be present in the mother’s breast milk, but it is inert and poses no risk to the infant. However, because of the possible risk of bacterial growth on the skin under a suit, careful cleansing of the breast after diving and before feeding may help prevent systemic illness.

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.

I’m an instructor. Few day ago a guy came to me with a valid fit to dive certificate. He told me he suffers from epilepsy and he’s under treatment. I’m worried he can have a seizure when underwater, can you please give me some advice?
Regarding your student and in general any form of epilepsy, as long as the following three conditions are met, you can consider diving: - free of attacks for more than 5 years  - normal EEG  - medical therapy is no longer necessary

In this specific case the third condition is not satisfied, therefore I suggest you to recommend your student to be assessed by a specialist in diving and hyperbaric medicine in order to evaluate his fitness to dive in relation with his medical history

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.

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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