Ask DAN: Commonly Asked Dive Medicine Questions | Scuba Diving

Ask DAN: Commonly Asked Dive Medicine Questions

Flying After Diving

January/February 2004

Q: How long should I wait to fly after I dive?

A: On May 2, 2002, Divers Alert Network hosted a one-day workshop to review the state of the knowledge about flying after diving and to discuss the need for new flying-after-diving guidelines for recreational divers. The workshop concluded that changes to the current flying-after-diving guidelines were justified. The new guidelines will be published in spring 2004 in the workshop proceedings.

The revised flying-after-diving guidelines apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet for divers who do not have symptoms of decompression sickness (DCS). The consensus recommendations should reduce DCS risk during flying after diving, but do not guarantee avoidance of DCS. Preflight surface intervals longer than the recommendations will reduce DCS risk further.

New Guidelines

> Flying after a single no-decompression dive: A minimum preflight surface interval of 12 hours is suggested.

> Flying after multiple no-decompression dives in a single day or multiple days of no-decompression diving: A minimum preflight surface interval of 18 hours is suggested.

> Flying after dives requiring decompression stops: There is little experimental or published evidence on which to base a recommendation for decompression dives. A preflight surface interval substantially longer than 18 hours appears prudent.

Migraine Headaches

March 2004

Q: During a recent open-water class I taught, a young woman developed a bad headache on the bottom at 20 feet. She went ashore with the assistant instructor and headed for migraine medication. Ten minutes later, she vomited. It turned out that she has a history of migraine headaches and takes medication to control them. As it turns out, she had a history of migraine headaches and took medication to control them. None of this was on her medical evaluation form. Later, she said her migraines are associated with exercise.

Can a migraine sufferer dive safely? Why would someone leave this information off their evaluation form?

A: Migraine headaches can be triggered by certain foods or smells, alcohol, stress, immersion in water or exertion. They can produce neurological symptoms such as visual loss and numbness, which may be indistinguishable from neurological decompression illness. Severity ranges from mild head pain to disabling discomfort with nausea and vomiting.

Some of the medicines used for migraine treatment and prevention can cause drowsiness, and could impair a diver's coordination and augment the effects of nitrogen narcosis. Each diver with migraine requires individual evaluation: While some migraine sufferers can dive safely, others may be advised against it.Divers omit medical information for a couple of reasons. Some simply don't understand the significance an illness may have during a dive and may not want to divulge a personal medical condition. Also, experienced divers sometimes advise beginners not to report all of their medical problems in order to prevent disqualification. A new diver may be told: "I dive with migraines, and I don't have any problems, so don't bother telling anyone."

Instructors should let students know that their information is confidential and make themselves available to speak in private with divers about medical issues. Remember, the DAN medical team is always available to speak with the student, the instructor or the student's physician. {mospagebreak}

Over-the-Counter Medications

April 2004

Q: Should I be concerned about using over-the-counter antihistamines and decongestants when diving?

A: No drug is completely safe. Drugs are chemicals and, by design, alter body functions through their therapeutic action. Moreover, they may have undesirable effects that vary by individual or environment. Most drugs have never been specifically tested in a diving or hyperbaric environment, but by understanding their usual actions and side effects it may be possible to predict what might happen when divers use them. So, research your medications. Learn their active ingredients. Warnings and directions provided by the manufacturer may alert you to the potential for a problem.Antihistamines are most often used to provide symptomatic relief of allergies, colds and motion sickness. They may have side effects including dryness of the mouth, nose and throat, and blurred vision. A side effect of many antihistamines is drowsiness, which could exacerbate nitrogen narcosis and impair a diver's ability to think clearly and react appropriately as needed. If an antihistamine is used by a diver, it should ideally be one of the less sedating type.

Decongestants cause narrowing of the blood vessels, which can relieve congestion by reducing swelling of the nasal mucosa. Decongestants may cause mild CNS stimulation and may have side effects such as nervousness, excitability, restlessness, dizziness, weakness, and a forceful or rapid heartbeat. These drugs can cause blood pressure to increase, particularly in people with hypertension. Medications known to stimulate the CNS may have a significant or undesirable effect on a diver. Package precautions or warnings may advise against use by individuals suffering from diabetes, asthma or cardiovascular disease.

Why You Have to Pee

May 2004

Q: No matter how many times I urinate prior to a dive, I always end a dive desperately having to go to the bathroom. I purposely don't drink before a dive, except two cups of morning coffee. I don't have a weak bladder or any form of incontinence. How can I control this?

A: The phenomenon you describe is known as immersion diuresis, and it occurs whenever the body is submerged in water. Immersion causes blood that is normally located in the leg veins to be sent to the large internal blood vessels and central organs such as the heart. In cold water the blood vessels in the extremities actually narrow. This is called vasoconstriction. This vasoconstriction occurs primarily in the skin and superficial tissues of the body, which increases the volume of blood sent to the heart.The increased blood volume in the major vessels is interpreted by your body as a fluid overload. This in turn forces the kidneys to produce urine to lower the central blood volume--the body's automatic response to preserve a balanced blood volume.

Once you exit the water, circulating blood volume returns to near normal--less the fluid taken to produce urine, which is quickly replaced as the body draws fluid from body tissues, such as muscles. Unfortunately, you probably will also leave the water with a full bladder.

Since we are all subject to the same phenomenon under water, this is probably your normal response to immersion. Caffeine and alcohol are diuretics, and can increase urine flow further. Avoiding alcohol and caffeine before a dive will help reduce the problem. There is no way to avoid immersion diuresis. So, what to do? (a) suffer; (b) get a dry suit and wear a diaper; or (c) conquer squeamishness and urinate in your wetsuit--while you're still in the water.


June 2004

Q: I have hyperthyroidism. Is this a contraindication for diving?

A: It may not be in a person's best interests to scuba dive with untreated symptomatic hyperthyroidism (i.e., having an overactive thyroid gland). The thyroid is a vital gland that secretes the hormone thyroxine, which helps regulate body metabolism. In excess quantities, this hormone can increase the heart rate or produce cardiac problems, affect respiratory rate, decrease body weight and even interact with the central nervous system. Symptoms of hyperthyroidism can also include discomfort and anxiety.

Cardiac effects of hyperthyroidism include tachycardia (rapid heartbeat), serious dysrhythmias and heart failure. Hyperthyroidism can also cause muscular weakness and periodic paralysis.

The output of the thyroid gland can be controlled by medication, radiation, radioactive iodine or surgery. These procedures reduce the function of the thyroid and the amount of hormone released. Once the hormone level has been reduced to within the normal range (as assessed by blood tests), and the signs and symptoms of hyperthyroidism have resolved, a diver with a thyroid condition may resume diving, as long as he has no other major health problems and is physically fit.

Individuals who are treated for hyperthyroidism may in turn become hypothyroid (have reduced thyroid function) and may require supplemental thyroxine to raise their hormone levels back into the normal range. It is vital for all individuals with thyroid ailments to have their thyroid function measured regularly by blood tests. This can help diagnose hypo- and hyperthyroidism and can indicate the efficacy of treatment.

Participation in recreational scuba diving is usually considered safe for individuals with hyperthyroidism when they show no signs of the ailment and have normal thyroxine levels.

Sea Bather's Eruption

July 2004

Q: What should I do when I get a case of sea bather's eruption?

A: Sea bather's eruption, popularly but incorrectly known as "sea lice," can occur when the larvae of jellyfish come in contact with skin. Common signs include intensely itchy skin eruptions with small blisters and elevated areas of skin. Found primarily on body parts covered by swimwear, these lesions may also appear on the armpits, neck, arms and legs.

The primary offenders in Florida and Caribbean waters are the larvae of the thimble jellyfish, Linuche unguiculata. These larvae, generally half a millimeter long, can find their way into bathing suits and become trapped against the skin, where they sting. The larvae become nearly invisible in the water. The best method of identifying when the larvae are about is simply by the appearance of the rash on swimmers or divers.

The larvae are most prevalent in the months of April through July. Symptoms usually appear within 24 hours after exposure to the organism and persist for several days. Symptoms may include fever, chills, headaches, nausea and vomiting.

Often the symptoms are very mild, and other causes may be considered or diagnosed incorrectly at first. Many cases of sea bather's eruption clear spontaneously, but others require treatment.

You can prevent sea bather's eruption by wearing a full wetsuit or impermeable dive skin. Snorkelers wearing T-shirts and women wearing one-piece bathing suits are vulnerable because the fabric can trap the stinging larvae against the skin.

After diving or swimming in an area where jellyfish larvae are present, remove your wetsuit, dive skin or bathing suit before showering, because fresh water may discharge the nematocysts trapped in the fabric. There have been reports of the condition recurring when the same bathing suit is worn again, suggesting that the larvae may remain in clothing.

Diving After Bone Fractures

August 2004

Q: Six months ago, I sustained multiple fractures in my left leg. The fractures did not require surgery, but I was hospitalized for five days and I wore a full-leg cast. I did go to physical therapy. Two months ago, my doctor released me, allowing me to return to my regular activities. Can I safely return to diving?

A: Of course, you shouldn't dive with an acute fracture that hasn't fully healed. Because pain can limit the use of your fractured limb, it can impede your ability to dive safely. Also, swelling and changes in blood flow could impair the efficient release of nitrogen stored in the injured tissues, possibly increasing your risk of DCI. And symptoms caused by the injury, such as pain and numbness, burning, itching or tingling can add confusion to a diagnosis if DCI is being investigated.

However, after your fracture has healed, you've completed rehabilitation and gotten approval by an orthopedic surgeon, you can resume diving. There is little or no evidence to suggest you're at higher risk of DCI once you've healed completely.

If you experience persistent pain, numbness or weakness, a dive physician should evaluate your condition before you resume diving. If you return to diving, an orthopedic surgeon must carefully document your neurological, vascular and functional deficits. This documentation may prove useful for comparison by a physician who is trying to rule out possible decompression illness following a dive or series of dives.

In many patients with chronic pain, no further injury occurs through increased activity. In fact, many studies report that subjects show improvement of overall function and a reduction in chronic pain.

Diving with Cerebral Palsy

September 2004

Q: My niece, who loves the ocean, wants to pursue scuba diving, but she suffers from cerebral palsy. Can she dive?

A: Cerebral palsy is a group of chronic disorders that impair control of movement. Such disorders appear in the first few years of life and generally do not worsen over time. The disorders, which are caused by faulty development of or damage to motor areas in the brain, disrupt the brain's ability to control movement and posture.

Symptoms of cerebral palsy include difficulty with fine-motor tasks (such as writing or using scissors), difficulty maintaining balance or walking, and involuntary movements. The symptoms differ from person to person and may change over time. Some people with cerebral palsy are also affected by other medical disorders, including seizures or mental impairment, but cerebral palsy does not always cause profound handicap.


Diving fitness depends entirely on the extent of disability in the individual. Candidates with mild problems may qualify; candidates with more severe disabilities may be eligible for a restricted certification. The absence of seizures and the ability to master water skills are particularly important. For participation in scuba, a case-by-case determination is needed.

For a full discussion of most central nervous system conditions and diving, read "CNS Considerations in Scuba Diving," an article by the late Dr. Hugh Greer III. It appears in The DAN Guide to Dive Medicine's Frequently Asked Questions (FAQs), available in the Dive Medicine section of the DAN web site (

Spontaneous Pneumothorax

October 2004

Q: I have had spontaneous pneumothorax. Should I dive?

A: Pneumothorax is a condition in which a lung collapses due to a leak, allowing air from an air sac to enter the pleural space surrounding the lung. When spontaneous pneumothorax occurs, it usually causes sharp pain on the affected side of the chest. Shortness of breath can occur if the volume of air leaked into the pleura is sufficiently large. Sometimes the lung leak acts like a one-way valve, allowing air to leak out, but not in. This is known as tension pneumothorax because the volume of air (and hence pressure) in the pleural space increases rapidly, and can compress the lung and heart. Extreme shortness of breath, low blood pressure, shock and even death can occur.

People who have experienced one episode of spontaneous pneumothorax are at higher risk of having another one. Up to 50 percent of people who have experienced one episode will have another occurrence. When pneumothorax occurs during diving, it is usually during decompression, when the tendency for the lung to overexpand is greatest. Pneumothorax occurring during a dive can be doubly dangerous because leaked gas within the pleural space will expand during decompression, making the buildup of pressure, and thus the development of tension pneumothorax, more likely.

In people predisposed to spontaneous pneumothorax, it is logical that the greater pressure changes that occur during a dive are more likely to precipitate a recurrence while under water, when the risk of tension pneumothorax is also highest. Therefore, most dive physicians recommend that individuals who have experienced spontaneous pneumothorax should never scuba dive, to any depth. This recommendation also extends to people who have had surgery to prevent recurrences.

Macular Degeneration and Diving

November 2004

Q: I have recently been diagnosed with macular degeneration. Is it still safe to dive? Do I have an increased risk of ocular DCS or ocular barotrauma?

A: No drug is completely safe. Drugs are chemicals and, by design, alter body functions through their therapeutic action. Moreover, they may have undesirable effects that vary by individual or environment. Most drugs have never been specifically tested in a diving or hyperbaric environment, but by understanding their usual actions and side effects it may be possible to predict what might happen when divers use them. So, research your medications. Learn their active ingredients. Warnings and directions provided by the manufacturer may alert you to the potential for a problem.Antihistamines are most often used to provide symptomatic relief of allergies, colds and motion sickness. They may have side effects including dryness of the mouth, nose and throat, and blurred vision. A side effect of many antihistamines is drowsiness, which could exacerbate nitrogen narcosis and impair a diver's ability to think clearly and react appropriately as needed. If an antihistamine is used by a diver, it should ideally be one of the less sedating type.

As the macular area in the center of the retina deteriorates, central vision worsens. AMD occurs in two main forms: a€?weta€ and a€?dry.a€ Dry AMD, the most common form of the disease, results in a gradual thinning and atrophy of the retina. Wet AMD develops as a result of leakage from abnormal new blood vessels that occur underneath the retina in the macular area. This leakage ultimately leads to scarring of the macular retina with loss of central vision, although peripheral vision usually is preserved.

Laser photocoagulation is a surgical procedure that may be used to treat the abnormal blood vessels in some forms of wet AMD. Recent evidence suggests that the progression of early AMD in some individuals who are at high risk for vision loss may be slowed with antioxidant dietary supplements.

There are no obvious restrictions for individuals diving with AMD, as long as his or her visual acuity is adequate to dive safely. There is no known increased risk of barotrauma or DCS from macular degeneration.

Divers with macular degeneration should have the approval of their physician before diving. If youa€™ve had laser photocoagulation therapy for AMD, you should wait two weeks and be cleared by an ophthalmologist before returning to diving. -a€”Darren Lovecchio, with reports from Brooks McCuen, M.D.


Tooth Wisdom

December 2004

Q: My wife had oral surgery about six weeks ago for the removal of a wisdom tooth. The dentist said that there was no infection, and the wound was healing nicely. But it was deeply rooted, and the nerve was traumatized. She's still taking painkillers. We are going on a trip to Hawaii next week, where we planned to dive. Her oral surgeon, who's not a diver, said that it's probably not a very good idea for her to dive. What's your read?

A: If your wife's surgery had been routine, with normal healing, uncomplicated by infection or pain and she could hold a regulator without discomfort, then four to six weeks would be sufficient time to allow for the risk of infection, provided there has been good healing and gum tissue has begun to fill in the empty socket.

However, the nerve trauma indicates that her case may be different. Occasionally, proper healing may be delayed, often in smokers or older people. In such cases, air can be forced into the subcutaneous tissues by the increased pressures in the mouth during a dive. This condition could further delay the healing process and also cause discomfort.

Pain can impede the ability to hold the mouthpiece in place, a possible drowning hazard. One consultant also cautions on returning too early to diving based on the softness of the lower jawbone after a wisdom tooth extraction. The end of the mandible remains fragile until it has fully healed. Additionally, it is subject to fracturing when pressure is placed on the bone, such as when gripping a regulator in place.

Finally, some types of pain medicine (those containing codeine, oxycodone or other narcotics) could promote nitrogen narcosis and impair performance and judgment under water. If a diver still has symptoms, diving is not a good idea. --Joel Dovenbarger, Vice President, DAN Medical Services

Diving After Liver Transplant

January/February 2005

Q:A year ago, my wife's liver was removed and replaced with a portion of mine. She takes anti-rejection medicine, including tacrolimus and prednisone. Soon after I donated, I was cleared to dive. What are the diving indications for each of us?

A: After the acute effects of the transplant operation pass and your wound heals, you, the donor, should be able to return to normal scuba diving. Under similar conditions, your wife, the recipient, should also be able to dive. However, she should take a few precautions. Immunosuppressive drugs can cause high blood pressure and impair kidney function. Immunosuppression will also predispose your wife to infections.

Some recreational divers without health complications experience mild elevations of liver enzyme levels after repetitive dives. While enzyme levels always return to normal, it is conceivable that local bubble formation could cause a slight leakage of enzymes from liver cells. However, there is no evidence that the liver is damaged in any way by diving.

Your wife should avoid diving deeper than 60 to 70 feet, limit herself to two dives per day and take a day off in the middle of a diving week. --Joel Dovenbarger, Vice President, DAN Medical Services


Hand and Foot Edema After a Dive

Macrh 2005

Q: After a recent dive, I noticed my right hand appeared swollen about an hour after my second dive. There was no pain or numbness, and I didn't notice any difference in strength. I've never injured this hand nor had this happen before while diving. I've been diving about a year, and all my equipment is pretty new. I don't think this is decompression sickness, but why would my hand swell?

A: Although it's not frequently reported, slight swelling in a diver's hand or foot is not unusual--DAN periodically receives questions on this issue. Swelling, or edema, is not a typical symptom of decompression sickness (DCS) and would rarely occur alone. If it were related to DCS, it would more likely occur with pain, numbness or change in skin sensation.

The most likely explanation for edema is a constrictive cuff on a wetsuit or dry suit. Prolonged or repeated exposure to tight wetsuit cuffs could produce swelling in your hands or feet. Even if you have worn the suit before, you may not have worn it long enough to get this effect.

Something as simple as a new wristwatch can add compression around that area. It's important that new suits fit correctly and not too tightly. If you're using an old wetsuit, it's equally important that you can still fit into it comfortably.

Cold water and wrist activity may add to a constrictive effect. If constriction is the cause, it should resolve shortly, with no other symptoms.

Other possible causes include lymphatic decompression sickness (this usually affects the chest or abdomen rather than the extremities) and cold-induced angioedema (swelling that can occur in susceptible people, triggered by exposure to cold or water). If the swelling occurs again, and does not appear to be due to a tight cuff or watch, you should seek evaluation by a physician while the swelling is present. --Joel Dovenbarger, Vice President, DAN Medical Services

Diving Into Advanced Age

April 2005

Q: I am a 64-year-old healthy male working full-time in construction. I have been diving since 1953 and continue to do so as frequently as my schedule permits. Work takes me to all parts of the world, where I take the opportunity to dive. I normally limit my dives to a maximum depth of 40 feet. How long should I be able to continue diving? Are there special physicals that are recommended on an annual or semiannual basis?

A: The cornerstone of health maintenance and disease prevention is a periodic medical examination by your physician. Physical fitness and good health are necessary to participate in scuba; a lack of physical fitness or any type of acute illness usually restricts some normal activities, including diving.

Some people continue diving into their 80s. Provided you are healthy, there is no reason that you should stop diving, particularly given your conservative depth limit. In terms of a general level of physical fitness, you should have the ability to perform activities like surface swimming and entering a boat after a dive. Before you dive, you should be free of symptoms such as coughing, congestion, shortness of breath or difficulty breathing.

More specifically, if you havena€™t already done so, you should undergo an evaluation of your lungs and a screening evaluation to determine your risk of coronary artery disease. This may include an exercise stress test. A program of regular exercise as prescribed by your physician is also recommended.

The final decision on when to quit diving should be made based on your physiciana€™s advice, your overall health and your confidence in your abilities as a diver. a€”Joel Dovenbarger, Vice President, DAN Medical Services --Joel Dovenbarger, Vice President, DAN Medical Services {mospagebreak}

Diving After Ear Surgery

May 2005

Q: I underwent surgery to remove a benign tumor in the auditory canal between the inner ear and the brain stem. The surgery took place more than four years ago and I'm in good health. I've had no perceptible signs or symptoms since surgery. I'm very active in outdoor and indoor activities that require good balance and coordination. Now I'm interested in learning to dive. What do you think?

A: Scuba diving would not be recommended for you or for anyone who has undergone ear surgery, specifically vestibular (inner ear) surgery. The vestibular system contains the labyrinth, one of the organs that give us our sense of balance. In cases where one of either vestibular systems (i.e., the right or left) no longer functions because of disease or trauma, our bodies compensate over time. Recovery can appear complete, often with therapy and retraining, to the degree that a balance deficit is imperceptible.

Most people are able to return to their normal activities. However, any damage or injury to the opposite vestibular organ in addition to the previous injury could cause permanent and untreatable balance disturbance, in which even one's ability to walk and activities of basic coordination become affected.

The most commonly reported injuries among divers involve barotrauma to the middle ear. Barotraumatic injury to the inner ear, while less common, often has permanent aftereffects that can manifest as hearing loss or disturbances in balance. In your case, an injury of this kind could spell even more serious trouble. We recommend that you pursue sports that don't pose a threat of inner-ear injury. a€”By M. Celia Evesque, DAN Medical Information Specialist --M. Celia Evesque, Vice President, DAN Medical Information Specialist

Predator Provocation

June 2005

Q: I have just completed detailing a wetsuit with ocean art on the chest area, both arms and both legs. Do bright colors or art pose a danger of shark attack?

A: With respect to art as a visual stimulus, there is one shark attack worthy of mention. The International Shark Attack File (ISAF), based in Gainesville, Fla., has recorded an attack on a diver in the waters of Southeast Asia, where a shark removed significant amounts of tissue from both thighs of a male swimmer.

Prior to the attack, the diver had displayed two elaborate animal tattoos near the area of the wounds. The ISAF has theorized that the stark contrast of the skin to the colorful design of the tattoos may have attracted the shark's attention. Also, the diver may have intruded upon the territory of the shark. The true reason for the attack is unclear.

Because contrasts and bright colors may draw attention to you as a diver, certain environments may pose a risk. The cautious opinion of marine animal behavior specialists is that divers should avoid behaviors and appearances that can arouse the attention of marine predators. --Dan Nord, Director, DAN Medical Services {mospagebreak}

Can I Exercise After Diving?

July 2005

Q: After a couple of morning dives, I like to take the afternoon off to do some exploring on bike, foot or horseback. I've heard that a four-hour a€?activity bana€ before and after dives is generally a good idea to help prevent decompression sickness. Is this true?

A: There is solid evidence that exercise immediately after very long or deep dives (or during extreme altitude exposures) increases the risk of decompression sickness. However, we do not know what the risk is after mild to moderate dives or how quickly the risk decreases as the time between diving and exercise increases. In addition, aches and pains can occur as a result of exercise and can be very similar to symptoms of decompression sickness.

These are the reasons for the recommendation not to exercise for four hours after diving, but this recommendation may be very conservative. Post-dive exercise is common in the real world. In fact, many of us do it without apparent problems.

So what reasonable recommendations about post-dive exercise can be made, given our incomplete knowledge? First, avoid exercise after very long or deep dives. Second, as severe exercise may be more of a problem than mild exercise, avoid heavy exertion after diving. Third, the longer you can wait after diving, the lower the risk becomes, so wait an hour or more.

Exercise before diving may be a better idea, though you shouldn't dive immediately after exercise. Two hours may be a reasonable minimum wait. A more conservative suggestion would be four hours to allow your body to cool down and rest before you add nitrogen exposure.

Pneumothorax and Its Consequences

August 2005

Q: I suffered a fractured rib and pneumothorax during a sports injury. Can I ever dive again? What is the risk of a spontaneous pneumothorax? Can scarring of the pleura cause any problems?

A: The lungs are contained in the chest cavity within the pleural membrane. The pleura lines the exterior of the lungs and the interior of the chest cavity with a potential space between the two layers. If air enters the area between the pleural tissues, the potential space becomes an actual space. If the space expands, the lung expansion is reduced, and respiration is compromised. We assume your pneumothorax was a result of blunt trauma that fractured the rib and the pneumothorax, but that the broken rib did not penetrate the pleura and lung. If this is the case, the injured area should have healed adequately with very little risk of a spontaneous pneumothorax. The lung itself probably suffered little if any damage from this injury.

However, if a chest injury results in penetration of the lung by a broken rib, a gunshot, a knife or something similar, then the underlying lung tissue is damaged, and scarring of the lung and pleura may increase the risk that pulmonary barotrauma will occur during diving.

A spontaneous pneumothorax can occur with no warning. This is due to a lung defect, which may be congenital or may appear later in life. The recurrence rate of this type of pneumothorax is high, and these individuals are usually advised not to dive. A spontaneous pneumothorax might occur while diving, resulting in a closed air space, which can't be equalized as the diver ascends. The resulting expansion of this air space with decreasing ambient pressure would affect the heart and the other lung, with possibly disastrous consequences.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web: {mospagebreak}

How To Beat Ear Trouble

September 2005

Q: I have been certified for four years but do little diving because I have so much trouble with my ears. Sometimes I have no problems on the first dive, and then on the next dive it seems I can't equalize. What can I do?

A: Difficulty equalizing the air spaces of the middle ear and sinuses is the most common problem and injury among recreational divers. The first thing to do is consult with your personal physician or an ear, nose and throat specialist. Your issue may be something as simple as a chronic inflammation from allergies. Irritation and inflammation resulting from an allergy can narrow the air passages and restrict the flow of air into and out of the middle ear.

Your problem may also be from damage to your eustachian tube from an infection that occurred years ago. There may not be anything your physician can do for such a chronic problem, but decongestant medications may be available that can shrink swollen tissue and allow air to move freely in and out of the middle ear space. Your physician can assist you in finding the best and most effective medication for you.

Finally, test your ability to clear before you get into the water. This helps make sure you don't have a problem that could be corrected before you dive, such as by taking a drink of water to keep your mouth moist. You may need to clear more frequently--as often as every one to two feet in order to prevent injury.

Make sure that when clearing, you do it gently and before the problem becomes severe. Waiting too long will cause unnecessary pain, and a forceful clearing attempt by pinching your nose may cause middle ear damage. Several gentle maneuvers and switching back and forth between swallowing and pinching your nose and gently blowing may be the ticket to a trouble-free dive. Above all, if you cannot equalize, then abort the dive. a€”Joel Dovenbarger, DAN Director of Medical Services

Diving with Attention Deficit Disorder

October 2005

Q: I have a 16-year-old son who has been diagnosed with attention deficit disorder. He's eager to take a certification course so that he can dive with my husband and me, but I have reservations. What are the safety concerns relative to a diver with ADD?

A:Attention deficit disorder is usually recognized early in life and is manifested by an inability to concentrate or sustain attention. It may or may not be accompanied by physical hyperactivity. ADD is a significant (but overdiagnosed) cause of learning disability. The problem usually improves with age.

At its worst, attention deficit disorder can be so pronounced as to prevent a prospective student from learning the simple skills necessary for safety. This could present a significant hazard in many areas, including both driving and scuba diving. For many individuals, however, ADD is usually not that intense. Fitness to dive can best be assessed by looking at the student's social, school, athletic and job performance. Note that because some ADD patients take medications, they should consider the potential impact of these medications while diving.

No testing has ever been done to determine interactions between high partial pressures of nitrogen and the medications used to treat attention deficit disorder. Two drugs currently in use are Ritalin (methphenidate) and Dexedrine (dextroamphetamine). Both are heavy-duty stimulants that leave most adults "wired." However, they often have a calming and somewhat paradoxical effect on children with attention deficit disorder. This desirable effect is less apparent as children grow older.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web: {mospagebreak}

Diving After Eye Surgery

November 2005

Q: Is it safe to dive after radial keratotomy?

A: Radial keratotomy (RK for short) is a surgical procedure designed to cure myopia (nearsightedness). In this operation, the surgeon makes a small number of radially oriented incisions in the cornea of the eye. These incisions cause a decrease in the strength of the cornea and may increase the risk of serious injury if the eye is subjected to subsequent trauma, including barotrauma such as a mask squeeze. Despite this theoretical risk, there have been no reports of which I am aware of involving a traumatic rupture of the cornea resulting from diving after RK.

Divers who have had this procedure should wait at least three months after the surgery before returning to diving and should be careful to avoid a mask squeeze--it's important to avoid imposing the "Boyle's Law Stress Test" on these corneal incisions.

If you are a diver and considering having this procedure done, we recommend that you also ask your eye surgeon to discuss the potential advantages of photorefractive keratectomy, the alternative refractive surgical procedure discussed below.

Q: Is it safe to dive after having had the new laser refractive surgery (photorefractive keratectomy, or PRK)?

A: Yes. This procedure uses laser reshaping of the cornea instead of incisions to treat myopia. This method results in no decrease in the structural integrity of the cornea and no risk of corneal rupture as a result of mask squeeze. It should be safe to dive approximately two weeks after this surgery. Discuss your plans with your physician and have a final evaluation before you dive.

Diving Fitness

December 2005

Q: Can you offer some general suggestions on diving fitness?

A: Here are some general guidelines:

Check yourself. Divers check and maintain their gear before leaving on vacation, but how many divers check their personal health and fitness before diving? Fitness for diving adds to the comfort and enjoyment of each dive you make.

Be heart-smart. Cardiovascular disease is the most common cause of death in divers over the age of 40. If you're over 40, have an annual physical with a physician knowledgeable in diving medicine. A cardiac stress test may also be a beneficial preventative measure for you.

Bag it. If you're fatigued, sick or just not feeling well, don't dive. Illness and injury increase your risk of decompression illness (DCI), and your performance under water will suffer, too. Dehydration may also contribute to DCI. Hot and humid climates, the hot sun, dry compressed air from your scuba cylinders and immersion diuresis all help to dehydrate you. When you're traveling and diving, make sure you drink at least eight glasses of water a day.

Know your limits. Overall physical fitness is important, but knowing your physical limits may be more so. When you begin to feel overexerted or tired, rest and discontinue diving until your energy level has returned. Watch for signs of overexertion in your buddy, too. While you can't necessarily control the tides and currents, you can improve your fitness and your preparedness for those environmental changes.

Be aware. Take note of your body's signals. If you don't feel up to making a dive, it will be there another day. If you have questions about your health, check with your physician. If you or your doctor have dive health questions, call DAN. We're here to help.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

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Diving After Rupturing an Eardrum

January 2006

Q: I have had trouble clearing my ears, and recently had an eardrum (tympanic membrane) rupture. My ENT (ear, nose and throat) doctor found no problems that would lead to clearing trouble. I never had a broken nose, nor suffer from allergies or ear infections. Even though my eardrum has healed completely, he has advised caution in returning to diving. Is it safe to dive again?

A: Once a ruptured tympanic membrane has healed, a diver can usually return to diving. Divers with this injury should exercise caution, however, because a small scar is left in the layer of tissue that makes up the membrane. Forceful clearing could cause repeated problems with the membrane.

Although your doctor found no ENT problems, it is possible for you to irritate the eustachian tube (which connects the middle ear with the back of the throat and regulates air pressure on both sides of an eardrum) when youa€™re trying to clear your ears and sinuses. You may even have small eustachian tubes, sensitive to rapid pressure changes.

Remember to clear before you get into the water. This helps ensure you dona€™t have a problem that could be corrected at the surface before you dive. You may simply need to add something new to your current clearing technique, such as clearing as often as every one to two feet in order to prevent further injury.

Make sure that when clearing you do it gently and before the problem becomes severe. Waiting too long will cause unnecessary pain, and a forceful clearing attempt by pinching your nose at that time may cause middle ear damage. Several gentle maneuvers and switching back and forth between swallowing and pinching your nose and gently blowing may be the ticket to a trouble-free dive. Above all, if you cannot equalize, abort the dive.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

Preventing Heart Disease

March 2006

Q: I know cardiovascular disease can be a serious danger for scuba divers. What are the factors that contribute most to cardiovascular disease?

A: The major risk factors for cardiovascular disease include cigarette smoking, high blood pressure, a diet high in cholesterol and saturated fat, a family history of cardiovascular disease and a sedentary lifestyle.

Here are some other facts of life:

>> Even with all other factors being equal, men have a higher risk of developing cardiovascular disease at a younger age than women;

>> Cardiovascular disease increases in prevalence with increasing age; and

>> You cannot alter risk factors for cardiovascular disease such as age, gender and family history.

Knowing these unalterable factors, your goal should be to minimize the risk factors that are known to reduce your chances of developing cardiovascular disease-smoking, diet and serum cholesterol level, blood pressure-and maximize your activity level.

Diving is an activity that requires at least a modest amount of physical exertion. Under emergency conditions, a diver can potentially be faced with a large amount of strenuous activity for at least a brief period of time. It's a good idea for divers to:

>> maintain a regular exercise regimen;

>> eat a diet low in salt, cholesterol and saturated fat;

>> abstain from smoking or the use of other tobacco products; and

>> have regular medical evaluations, with periodic measurements of blood pressure and serum cholesterol levels in consultation with your healthcare provider.

Older individuals and those with pre-existing risk factors for cardiovascular disease will need more frequent and in-depth medical evaluations.

Pre-existing cardiovascular disease does not necessarily mean that an individual cannot participate in recreational diving safely. Most physicians who provide medical care to divers agree on these facts: adults with high blood pressure controlled with medication can safely continue to dive; and divers who have undergone coronary bypass surgery may be able to dive safely after a period of recovery and rehabilitation. This group of divers must be free of symptoms of coronary heart disease and demonstrate a high level of exercise tolerance. Additionally, their decision to return to diving must be made in consultation with a cardiologist.
-Dr. James Caruso

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

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Can Vitamins Prevent DCS?

April 2006

Q: Is there any benefit to taking vitamins while on a dive vacation? Can this help prevent decompression sickness?

A: There's really no benefit to taking excessive amounts, or more than the recommended daily values of either vitamins or minerals. Nor is there a specific protective value to increasing vitamin intake, except to help you maintain good health. The body will use only what it needs and excrete the rest.

We shouldn't mention vitamin intake without acknowledging that eating a balanced diet with protein, fruits, vegetables and whole grains is not only nutritional, but contains the necessary minerals and vitamins the body needs every day.

The best advice is to eat a balanced diet when you're on a dive trip. If your physician has recommended taking a specific vitamin or a daily multiple vitamin, then follow that advice. But remember, vitamins do not make up for a skipped or inadequate meal plan.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

Sting Relief

May 2006

Q: What's the best way to treat a jellyfish sting?

A: Regardless of the species of the stinger you encounter, some basic first-aid guidelines will aid in treating jellyfish stings:

>> Stabilizing the injured person's vital signs is the top priority. First check the ABCs-airway, breathing and circulation. If necessary, proceed with CPR or artificial resuscitation.

>> Keep the victim quiet and comfortable. Stings from some jellyfish can be very painful, and if left unchecked, the pain and excitement will stimulate muscular activity, circulating the venom-in larger doses-through the body. Depending on the victim's condition, you might need to administer analgesic drugs.

>> Treat the affected areas. Jellyfish release nematocysts, which can result in painful injury. Many stingers can remain on the skin, and unless they are removed or neutralized, they will continue to break and sting, especially when they're rubbed.

>> Apply vinegar or use a 50/50 mixture of water and baking soda on the affected area. In the waters of the Gulf and Atlantic coast south of Chesapeake Bay, a good rule of thumb for neutralizing nematocysts is to apply vinegar in liberal amounts. North of Chesapeake Bay and on the central and northern Pacific coasts, a thin mixture-50 percent water and 50 percent baking soda-is the recommended application.

These measures don't always stop the pain or swelling. The venom-coated nematocyst thread has already penetrated the outer layer of skin, where topical agents exert their action, so topicals are ineffective in relieving pain. In cases where the patient has signs of post-envenomation, a physician should be consulted to recommend proper treatment.
-Dr. Joseph W. Burnett

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

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Diving with Diabetes

June 2006

Q: I have been diagnosed with insulin-requiring diabetes (Type 1). Can I still scuba dive?

A: Insulin-requiring diabetes mellitus (IRDM) has traditionally been considered an absolute contraindication to diving. However, there has been a growing shift away from the blanket prohibition in recent years. Persons with IRDM are now able to receive training and dive openly in several countries.

A recent international workshop, jointly sponsored by the Undersea and Hyperbaric Medical Society and DAN (June 2005), produced a consensus agreement that dive candidates who use dietary control or medication to treat diabetes but who are otherwise qualified to dive may undertake recreational scuba diving, provided certain criteria are met. A summary of the guidelines can be found at

Among the guidelines are practical recommendations for rescue medications and procedures in case of hypoglycemic problems developing under water. The person with diabetes, his or her buddy, and dive leaders should all be aware of the status of the diver or divers, signs and symptoms of hypoglycemia, and procedures required to assist in case of a problem.

Rescue medications should be carried on all dives and parenteral glucagon should be available at the surface. If hypoglycemia is noticed under water, the diver should surface, ingest glucose and leave the water.

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

Ciguatera Poisoning

July 2006

Q: I’ve heard of ciguatera poisoning. What is it?

A: Ciguatera is a bad actor, best avoided. One of the most serious of marine toxins, ciguatera is mainly a tropical disorder, but it does occur in semitropical and temperate areas when we consume contaminated, imported fish. Occasionally a traveler will return home with an undiagnosed illness that turns out to be ciguatera. Distribution is worldwide, and the ciguatera-toxic fish are found between latitudes 35 degrees north and 35 degrees south. The fish are usually large reef fish, but are not identifiable as toxic by their external appearance. The dinoflagellate Gambierdiscus toxicus is thought to be the originator of the toxin, which is harmless to fish and moves up through the food chain. The toxin is heat-stable, and neither cooking nor freezing will remove it.

Symptoms begin within two and 12 hours after ingestion, with generalized nonspecific symptoms and mild weakness. Symptoms increase in severity, with dull aches, cramps and numbness around the mouth, tongue and throat. Gastrointestinal symptoms include loss of appetite, nausea, vomiting and diarrhea. Neurological symptoms include delirium, lack of coordination, difficulty walking, reversal of temperature perception, convulsions, coma and-in rare instances-death.

The main symptoms clear up in one to two days, but residual weakness, alteration of temperature perception and other symptoms may persist for months. Ingestion of alcohol can cause a recurrence of the symptoms even months after the illness. A reddened skin area, with burning sensation developing after alcohol consumption, is a characteristic of the disease.

Preventive measures include not eating:

  • Viscera (internal organs)

  • Large reef predators and other species implicated in poisoning: barracuda, grouper, snapper, sea bass, surgeonfish, parrotfish, wrasses, jacks and others.

  • Moray eels.

-From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

Stay Healthy Overseas

August 2006

Q: I’m getting ready to do some overseas traveling and diving. Do you have any general advice about some of the shots I might need?

A: Travel can be a portal for discomforts and even disease for the unwary traveler. Read on.

Travel-Related Illness
If you’re a student helping to build schools in undeveloped areas of an equatorial country, you’re at much greater risk than the diver on a well-organized dive boat operating over the coral reefs of the same area. In other words, there may be very little risk of acquiring a tropical disease aboard the dive boat, but a very high risk for the land-based traveler. Divers and travelers journey to sites in remote countries as well as more developed areas. Certain illnesses can be associated with travel anywhere; many can be prevented, but some of them may be life-threatening. Appropriate prophylaxis and counseling by professionals can reduce the health risks of travels.

Pretravel Precautions
The four most important categories of pretravel precautions are:
» Vaccinations and immunizations
» Diarrhea management
» Malaria prophylaxis
» Behavioral counseling
Review your immunization status, especially the routine vaccinations such as tetanus/diphtheria, measles, polio, hepatitis B, Varicella and influenza, with your physician. A current test for tuberculosis exposure (PPD) is advised. The World Health Organization currently requires a yellow fever vaccination, but some countries may require proof of cholera vaccination as well. Other vaccinations will depend on your itinerary, your lifestyle and the length of your trip.

Prophylactic Treatment and Counseling
Giving general recommendations on vaccinations and immunizations can be difficult, and detailed recommendations are beyond the scope of this article.

Check with the Centers for Disease Control and Prevention web site (, visit your doctor or go to a travel clinic for the latest recommendations on immunizations. If you’re a DAN member, you can call DAN TravelAssist at 1-800-326-3822 (DAN EVAC).

When you visit a travel medicine clinic, ask the staff there to review your itinerary in order to determine the precautions needed: Disease exposure differs according to destination. Schedule your visit at least four to six weeks ahead, because some vaccinations need time to become effective, or they may be given in a series. Lifestyles, pre-existing illnesses and current medications can all influence risk assessment, and this requires knowledge of what you will do abroad.

-From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

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Motion Sickness and Diving

September 2006

Q: If I experience motion sickness, should I cancel my dive?

A: Motion sickness itself is not a serious medical problem, but it can set the scene for more serious incidents. Because affected individuals can develop an almost desperate inattentiveness: the desire to get into the water quickly in an effort to reduce motion sickness can affect how well you set up your equipment, watch your buddy or mind the surrounding conditions.

Plus, once you're underwater, vomiting can foul your second stage, and you might inhale water. Removing a regulator to vomit underwater keeps it from being fouled, but it must be done carefully.

What helps? Close your eyes, or sit where the rocking motion of the boat is clearly visible. Gazing at the horizon works, too. And stay away from areas with strong fumes (like those from fuel). Mild nausea from motion sickness must also be differentiated from the dizziness and nausea that may signal a more serious injury. This can be difficult at times, as motion sickness can often recur and persist for several hours after you return to land.

Drugs should be taken with caution when you dive, as they can cause mild drowsiness and a decrease in mucus secretions. Since both effectiveness and the level of side effects vary with individuals, no single drug is clearly best for every diver.

If you have any doubts as to your health, it's wise to cancel the dive.

--From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

The Cold Facts About Hypothermia

November 2006

Q: What's hypothermia, and how do you manage it?

A: Hypothermia is a condition of reduced body core temperature. It may be mild or severe. A variety of rewarming strategies may be used, depending on the degree of hypothermic injury, the level of consciousness of the injured person and the availability of resources and additional medical aid. Most cases involving scuba divers are mild.

The mildly hypothermic individual will be awake, conversing lucidly, complaining of cold and probably shivering. Assuming no other injuries, here's how to rewarm a person with mild hypothermia. Remove wet clothing and replace with dry insulating inner and windproof outer layers, including the head, whenever possible. Shivering will provide effective rewarming. The individual who feels comfortable exercising at this point can increase the rewarming rate. The fully alert hypothermic individual can have warm liquids to drink. These deliver negligible amounts of heat, but will help to correct the inevitable dehydration and provide a sense of comfort. Most beverages can be used, but avoid alcohol, as it can compromise awareness and contribute to dehydration and inappropriate vasodilation. Food supplements caloric reserves, but only a little.

The prevention of hypothermia requires preparation, using protective garments to conserve body heat and control heat loss. Most divers will benefit from wearing thermal protection in water cooler than 80 degrees. Significant thermal stress can be expected in water colder than 75 degrees. Divers should ensure that they have the proper protective equipment and experience to dive safely in cool or cold waters.

--From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web:

Treating Stingray Injuries

December 2006

Q: How common are wounds from stingrays, and what's the best first aid for such an injury?

A: A stingray wound from a spine puncture is both a traumatic injury and envenomation. When it occurs, envenomation classically causes immediate intense pain, edema and variable bleeding at the site of the wound. The pain may radiate centrally (toward the chest), peaks at 30 to 60 minutes, and may last for up to 48 hours. The wound is initially dusky or bluish and rapidly progresses to redness and bruising, with rapid onset of bleeding into fat and muscle, followed by tissue death and destruction. If discoloration around the wound edge is not immediately apparent, it often extends a few inches from the wound within two hours. Bloody blisters resembling a severe thermal burn or frostbite may occur. Manifestations of envenomation include weakness, nausea, vomiting, diarrhea, sweating, dizziness, rapid heart rate, headache, fainting, seizures, groin or armpit pain, muscle cramps and twitching, generalized swelling (with wounds involving the trunk), paralysis, low blood pressure, serious abnormal heart rhythms and death. Paralysis may represent spastic muscle contractions induced by pain.

Here are some basic steps for treating spine punctures:

  • Remove any visible pieces of spine or other foreign material with forceps. Although it’s standard to remove the spine and fragments as soon as possible (to limit the extent of envenomation and pain, usually in a foot, leg, or arm), if a spine is lodged deeply into the victim’s chest, abdomen or neck (extremely rare) and may have penetrated a critical blood vessel or the heart, it should be managed as would be a weapon of impalement (e.g., like a knife). In this case, the spine should be left in place (if possible) and secured from motion until the victim is brought to a controlled operating room environment, where emergency surgery can be performed to guide its extraction and control bleeding that my occur upon its removal.

  • Immerse affected areas in hot water (113°F/45°C maximum) for 30 to 90 minutes.

  • Scrub with soap and water and irrigate vigorously with fresh water.

  • Seek evaluation by a medical professional.

--From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

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Treating Stings And Punctures

February 2007

Q: I inadvertently dragged my hand across what looked like a scorpionfish on a recent dive. My hand was red, swollen and painful for a few days. What's the general advice on wounds from fish?

A: First-aid treatment for fish lacerations, stings and punctures calls for immediate attention. The wounds produced by the various species of animals with venomous spines are quite painful. These wounds are frequently lacerations and punctures containing a venom or foreign material (i.e., dirt or sand) and are contaminated with bacteria. Irrigation of the wound can help remove venom, sand and other contaminants. If any foreign material remains, healing will be delayed, so it's important to monitor any marine puncture wound. Many of these venoms are heat-labile--meaning they will break down at certain temperatures--and a hot soak at as high a temperature as you can tolerate (not higher than 113 degrees) can help. Try it for 30 to 90 minutes, and you'll likely get some pain relief.

Some of these wounds will be severe either due to the size of the animal or the potency of the venom. Some wounds may require surgical exploration and debridement to remove foreign material and damaged tissue. Other injuries may require an antivenin, which itself may be hazardous.

Divers Alert Network can frequently assist in advice concerning immediate care of these injuries and referral to appropriate medical centers.

--From the DAN Dive and Travel Medical Guide

DAN Dive Safety and Medical Information Line: (919) 684-2948

DAN 24-Hour Diving Emergency Hotline: (919) 684-4DAN (4326) collect, or (919) 684-8111

DAN on the web: