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What Will the Doctor Do?

Diagnosing decompression illness

Whether you’re exploring Australia’s coral reefs, drifting through warm Caribbean waters or diving into a crisp Canadian lake, nothing puts a damper on a dive vacation quite like a trip to the emergency room (ER). Anxiety and uncertainty accompany most illnesses and injuries — from cuts that need stitches to more serious problems like chest pain. Unfortunately, even the most well-planned dives by careful and experienced divers may result in ER visits. A little knowledge, whether about ear squeezes or decompression sickness (DCS), can go a long way in reducing anxiety around trips to the ER.

DAN’s medical staff is available to offer advice about dive injuries and provide recommendations about the need for medical care. In complex and more serious cases DAN can work with local facilities to help coordinate care or arrange emergency medical evacuations. If you experience symptoms after diving, activate local emergency medical services or safely get yourself to the nearest ER. Call the DAN Emergency Hotline at +1-919-684-9111 if you wish to discuss your symptoms with an expert in dive medicine.

One of the most common problems in the management of dive accidents is delay in seeking care. If you are worried you may be suffering from a diving-related medical problem, don’t hesitate to make the call. Whether a DAN medic advises you to seek care or you decide on your own to do so, the best course of action is to go to the nearest hospital — not the closest hyperbaric chamber. Chambers are not generally equipped to receive patients directly; patients must be evaluated in an ER first. People with severe burns don’t seek out the closest burn center — they go directly to the hospital. Symptoms after diving warrant the same approach.

The Doctor Meets the Diver


A detailed discussion of medical history and recent diving history is
essential for diagnosing DCI.

The doctor will ask about your medical history and conduct a physical exam. Provide as much information as you can about your symptoms and dives. Be prepared to tell the doctor the number of dives you made over the past few days, the depths and times of the most recent dives, the maximum depth of the deepest dive in the series and the gases you breathed. Also, make sure to mention any rapid ascents, omitted decompression or other problems.

Be honest and thorough when describing your symptoms and the events leading up to your injury. An unanticipated problem or error during a dive may provide clues that will help with the diagnosis. Bring your dive computer with you; it can provide information such as dive profiles and ascent rates that may be of interest to the doctor.

The Physical and Neurological Exams

In the course of the physical exam, the doctor will try to identify any abnormalities that will help in making a diagnosis and determining the best treatment. For a patient who was diving, the most important parts of the physical exam are the assessments of the ears, lungs, heart, skin and neurological function.


A thorough neurological exam may include patellar reflex, finger-to-nose, sharpened Romberg and eye-movement tests.

The doctor will check your ears for signs of barotrauma, such as visible damage to the eardrums and blood or other fluid in the middle ears, will listen to your lungs and heart for abnormal sounds and will examine your skin for any rashes that might be suggestive of DCS. The neurological exam may seem a little unusual, but it is a critical part of the evaluation, and subtle deficits may be significant. The exam is a series of observations, questions and measurements used to evaluate motor strength and sensation all over the body, the function of the 12 cranial nerves, reflexes, balance, coordination and cognition. Impaired balance or coordination is relatively common in people with neurological decompression illness (DCI). Some of the specific evaluations used to detect impairments include the Romberg and sharpened Romberg tests, in which you will be asked to stand still with your eyes closed and your feet close together, the finger-to-nose test and the heel-to-shin test. The doctor may also carefully examine your gait for signs of unsteadiness and evaluate your ability to perform rapid, alternating movements.

Making the Diagnosis


A heel-to-shin test assesses coordination, which may be impaired in people with DCI.

During the evaluation, the physician may make frequent adjustments to a list of possible diagnoses. This list is called the differential diagnosis. When it comes to diving-related medical conditions, diagnosis may be especially difficult since both forms of DCI — DCS (or “the bends”) and arterial gas embolism (AGE) — are clinical diagnoses. This means there are no definitive medical tests that can prove these conditions are present. The diagnosis is instead the result of a thorough history, identification of abnormalities during the physical exam and data gathered from other tests and observations.

Remember that just because you were diving you are not necessarily suffering from a diving-specific medical problem. Many medical conditions can mimic the symptoms of DCI, which further complicates the process of making a diagnosis. Other possible explanations of symptoms that commonly occur after diving include food-borne illnesses like ciguatera, infectious diseases including viral and parasitic syndromes and, perhaps most notably, exertion or trauma that leads to muscle strains or joint pain. But don’t be too quick to decide your symptoms are the result of something other than DCI; leave that decision to the doctor.

Other Tests

When you arrive at the ER, the nurses will check your vital signs: heart rate, blood pressure, respiratory rate, temperature, pulse oximetry (which measures oxygen saturation of hemoglobin) and level of pain.

If your symptoms are serious, a nurse will obtain intravenous (IV) access by inserting a needle into a peripheral vein, usually in your arm or hand. Blood will be taken and sent to the lab for testing, and a tiny plastic tube through which fluids and medications can be administered will be placed into the vein. Common blood tests that may be conducted include a complete blood count (which checks blood cells), a metabolic panel (which checks electrolytes, kidney function, blood sugar and liver function) and cardiac and other biomarkers (which check for heart and muscle damage).

Your doctor may also order a chest X-ray to check for problems with your lungs, including such conditions as pneumothorax (a collection of air in the space around the lungs) or evidence that air has leaked outside the lung into other areas such as the mediastinum (the area around the heart) or in subcutaneous (under the skin) spaces. In addition, a chest X-ray can identify fluid in the lungs that may suggest cardiac problems, immersion pulmonary edema or water aspiration.

Your doctor may also ask for an electrocardiogram (ECG or EKG). This test involves placing electrodes on your chest, arms and legs to collect information about your heart’s electrical system. It can identify an abnormal heart rhythm and reveal evidence of a recent heart attack.

If you had a loss of consciousness or are experiencing neurological symptoms, it is likely the doctor will order a computed tomography (CT) scan of your head. During this test you will lie on a table that moves you through a circular, donut-shaped X-ray machine. This machine will rapidly take a series of pictures of your head and brain as you pass through and will display a detailed three-dimensional image. The doctor will review this image for brain abnormalities such as evidence of AGE, bleeding or a stroke.

If a lung injury (i.e., pulmonary barotrauma) cannot be ruled out, the doctor may also order a CT scan of your chest. This can allow detection of a small pneumothorax or small collections of gas in the chest that may not be visible on the chest X-ray. A CT scan performed in conjunction with the injection of a contrast dye through your IV can help identify blockages in arterial blood flow from blood clots or gas bubbles.

The doctor, if concerned about your heart, may order an echocardiogram. This test uses ultrasound to create a video of your heart in action. It involves the placement of gel and a probe on your chest. Echocardiography checks for problems with the heart muscle, heart valves or the flow of blood through the heart.

What About Treatment?

If DCS or AGE is suspected, high-flow oxygen should be administered through a mask. In addition, unless you have an underlying cardiac problem, you will probably be given fluids through your IV to help address possible dehydration. If you are experiencing pain, the doctor may offer you pain medication either orally or via IV. If you are experiencing nausea or vomiting, you may also be given medication for that.

If you have a pneumothorax the doctor may need to place a tube through your chest wall to release air and allow your lung to reexpand. A pneumothorax can become life-threatening if it is not appropriately managed prior to treatment in a hyperbaric chamber.

Will I Need a Chamber?


Once a doctor has diagnosed DCI, the next stop is usually the chamber.

Hyperbaric oxygen therapy involves the administration of 100 percent oxygen during compression in a hyperbaric chamber. Both forms of DCI warrant chamber therapy, but other diving-related medical conditions do not.

Physicians in the ER who manage patients with diving-related illnesses are encouraged to call DAN for consultation and information about nearby dive-medicine specialists and hyperbaric chambers. As a patient, it is important to be your own advocate; ask your doctor to call DAN for consultation about your diagnosis and treatment.

If hyperbaric treatment is indicated, you may need to be transported to a chamber at a different location. This may involve transport in an air ambulance (helicopter or fixed-wing). Helicopter crews are typically instructed to minimize altitude exposure by flying as low as safely possible when transporting dive-accident patients. Most fixed-wing air ambulances are pressurized to very low altitudes or even sea level.

The Chamber


Hyperbaric technicians or nurses operate chambers from consoles just outside.

Once you arrive at a facility with a hyperbaric chamber you may experience déjà vu as it is likely you will pass through another emergency department where you will be registered, have your vital signs rechecked and be reexamined by a doctor.

You will meet the hyperbaric physician and staff who will take you to the chamber to begin your treatment. The most common hyperbaric treatment protocol used for DCS and AGE is the U.S. Navy Treatment Table 6. The initial descent will take you and the inside attendant (if the chamber can accommodate one) to 60 feet, the maximum depth of a Table 6. The total time of the treatment is at least four hours and 45 minutes. Dive physicians sometimes use other treatments, but they’re all long enough that a trip to the bathroom is highly recommended before you enter the chamber.

What Happens Next?

Depending on the severity of your symptoms and your response to treatment, you will either be admitted to the hospital or allowed to go home after you exit the chamber. If your symptoms were severe or your response incomplete, it is likely you will need additional “tailing,” or subsequent, hyperbaric treatments during the following days.

Once you are discharged, you should talk to your primary-care physician about what happened. Your recovery may take days, weeks, months or, in some rare cases, years. DAN is available as a resource for you during your recovery and can provide advice about safely returning to diving.

Once your recovery is complete, a doctor trained in dive medicine should evaluate you to make sure it is safe for you to return to diving. The doctor may recommend modifications in your diving procedures and habits.

Diving is a rewarding sport with beautiful and thrilling sites to see. The ability to explore the underwater world is a privilege that comes with significant responsibility. Divers must practice and sharpen their skills, demand excellence in education and training programs and adhere to the highest standards of diver etiquette. Education and preparation reduce the risk of dive accidents, but accidents can and do happen. Knowing how to handle a dive emergency and what to anticipate should one occur helps alleviate anxiety and empowers you to be an active participant in the process.

© Alert Diver — Fall 2012

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Two weeks in the Red Sea, February 2014

Mattijn’s dive blog – two weeks in the Red Sea, February 2014

 

Despite the recent political unrest, the Red Sea is still a good place for recreational and technical diving. It’s close to home, cheap and warm! Up till now there has been no violence in the Red Sea towns. Let’s keep our fingers crossed…

This was going to be a two tiered diving holiday. Joran (my 16 years old son) and Emiliano (long-time friend) joined me to do their courses. I finally persuaded Emi to do his OWC and this was the week it was going to happen (I thought). Joran was here to do his advanced nitrox course with Cat from Tekstreme.

We checked in at the old familiar Seagarden hotel in Hurghada. It was 3 yrs ago but they still remembered us. Must have been the tipping… The next day we were surprised to find the recently opened Hurghada Emperor Divers resort in Tia heights in the process of closing down. Declining tourist numbers has had its toll. It did not affect our diving but it was funny to see Joran clinging to the fridge to get a last coke while the whole thing was shifted out. Joran did very well in his advanced nitrox course. See you tube video. He has a natural build in buoyancy and had no trouble at all doing all the skills Cat Braun from Tekstreme threw at him. “Make him eighteen” was all she said. Both father and son can’t wait for that to happen so that Joran can do his tech courses and become an OC or CCR diver as well. Joran loved making dive plans, calculating SAC rates, OTU’s and a theoretical decompression plan. His SMB deployment is excellent. Yes, I am a proud father. I can’t wait for him to be eighteen so he can start with his tech courses OC or CCR.

Emiliano was a different story. He did all his skills but could not get further down then 1.2 meter. His ears just could not equalize. He had a history of glue ears and grommets but both of us thought he had grown out of it. Unfortunately this was not the case. After 3 days of trying he had a grade 2-3 barotrauma and he had to surrender. As there is absolutely nothing to do in Hurghada besides diving, he changed his flight and flew back the next morning.

My challenge was getting used to the combination off a dry suit and a CCR. I had been avoiding it for years but finally I bought a Bare trilaminate dry suit. In February even the Red Sea is cold at 60 msw. The first dives were OK. But my first zodiac entry was ehh….. Experienced dry suit divers can guess what happened. Slowly but surely my buoyancy control got better and after I had learned to squeeze out most of the air before rolling off the zodiac, I started to like my new suit.

The Emperor Elite

Friday I boarded the Emperor Elite for the technical safari. Joran played hideaway for one night in my cabin and flew back to Schiphol very early in the morning. At 9 AM the boat left for Gota Abu Ramada to do our check out dive. I use an Evolution plus with PLDT travel frame.  Two x 3 litre cylinders,  2 x 10 L bail cylinders and the dry suit created the need for 12 kg of lead. Who said that CCR is less heavy compared to OC….

Tekstreme is a red sea based company. Apart from doing technical courses the whole year round, they organize technical safari’s 3 times a year. I have done practically all of my OC and CCR training with them. This time there were 13 divers plus 3 Tekstreme staff members. A German, a Fin, Brits, a Russian and the odd Dutchman. Experience varied from a recreational CCR diver up to very experienced hard core OC divers who do 120 m plus. It is a bit like a floating hotel. This time there were two chefs in the little kitchen, one was a pastry chef! Everybody has put on weight, that’s for sure. The dive deck is very impressive. Loads of equipment, cylinders and a blending panel.

Time to set up my equipment, check the rebreather. Oh no…. cell failure of nr 3! Before leaving Holland I had replaced all of my cells as they were getting old. Now I had no spares left. Cat Braun was kind enough to give me a replacement cell. Scrubber changed, zipper waxed and fluid repleted, I was ready for the safari’s first dive.

Date Location Max depth Run time Dil mixture  
22-2-14 Gota Abu Ramada (reef) 13 44 air Check out dive
22-2-14 Umm Gamar (reef) 40 51 air  
23-2-14 Rosalie Muller (wreck bombed in 1941) 40 61 air Explored stern section
23-2-14 Rosalie Muller bow section 43 69 air Bow section, engine room too silted out to enter
24-2-14 The Lara (wreck) 60 20 min @ 60 msw, TRT 71 min Tx 16/35 Searched for 10 min!, could only explore the top part
24-2-14 Reef dive       Skipped the second dive because of N2 load
25-2-14 Thomas canyon 60 20 min “60msw, 10 min@45msw, TRT 80min Tx 16/35 Very nice dive!

See you tube video

25-2-14 The Dunraven (wreck sunk in 1876)       Grrrr

Cell failure again, no dive…..

26-2-14 Jolanda and shark reef 34 61 Tx 18/25 No deco dive, see you tube video for all the bath tubs and toilets
26-2-14 Abu Nuhas 30 110 Tx 18/25 Crazy dive
27-2-14         Very strong wind and waves, skipped the dive

The last dive was a memorable one. My two dive buddies, Ron and Craig wanted to do all four wrecks at Abu Nuhas in one two-hour dive! Kimon M, Chrissola K, the Carnatic  and the Giahannis D (all in the 20-30 msw range) We spent 15 min at each of the first three wrecks and all was fine. However, it was the swim between the wrecks that got us. After 90 min, with the Giahannis D looming in the distance, Ron was knackered (at least that was what he wrote on his slate) and it was time to abort the dive. He went up and then it I found out that Craig still had 25 min of deco to do. He was on OC, me and Ron were on CCR and had no deco time! LOL.  See Abu Nuhas: The Movie

Dive medicine

I had brought my V-scan (a very portable transthoracic echo machine) to get experience in doing post-dive TTE’s to look for bubbles. As the resolution of this midget machine is not as good as that of his big brothers I needed an echogenic diver with a considerable nitrogen load to begin with. Guess who was the Guiney pig. Joran did an air dive very close to his NDL. Fourty minutes post-dive some bubbles were discernable in his right ventricle. Then I echoed two technical divers 40-60 min post-dive. No bubbles! Perhaps not surprising as they had a thorough decompression with 80% oxygen.  Next step is to look at a technical diver at the end of a week of repetitive diving. Most technical divers are very interested in dive medicine. I gave a talk about decompression theory/ physiology and pre-dive optimisation strategies. Especially pre-dive exertion and the use of post-dive oxygen got their attention.

It was a very good trip. I have learned to dive with a dry suit and I have made new friends.  The after party was memorable as well! See Tekstreme diving blog. My next tech safari will be in September this year.

Mattijn Buwalda, anaesthesiologist-intensivist DMP DESA EDIC

Hyperbaric physician @ London Hyperbaric Medicine

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Dangerous Marine Life 2

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Dr Oliver Sykes  In the dangerous marine life series, this month I will cover injected toxins.

CONE SHELLS

Cone shells or snails have attractive shells, and may be picked up by children or visitors to the reef who may be unaware of the danger. The cones possess a detachable, dart-like tooth, with venom that can cause sustained muscle contractions, numbness and weakness.

Symptoms: Small puncture wound with localized blanching, cyanosis and swelling. Severe pain, numbness, and tingling of the mouth and lips. Sometimes there is difficulty breathing and paralysis.

Treatment: Immobilize the limb, apply a pressure dressing, administer CPR if needed. Cleanse the puncture site, give analgesics and give tetanus prevention. Be prepared to support and monitor rate and depth of breathing. There is no anti-venom.

 

BLUE-RINGED OCTOPUS

The salivary glands of the blue-ringed octopus produce venom.

Symptoms: The bite is usually painless and is followed by painless paralysis. Beginning with abnormal sensations of the mouth, neck and head, then nausea, vomiting, shortness of breath and sometimes lack of respirations. There can be visual disturbances, impaired speech and swallowing, and generalized weakness and paralysis. The duration is from 4 to 12 hours.

Treatment: Immobilize the limb, apply pressure dressings, cleanse the bite, treat for tetanus and monitor rate and depth of breathing.

 

STINGRAY

These possess a serrated bony spine at the base of the dorsal surface of the tail. Most injuries occur when the ray is stepped on.

Symptoms: Intense pain at the site; there is local loss of blood supply and swelling. Edges are jagged and may contain pieces of spine. Therefore secondary infection is common. Systemic effects include salivation, sweating, vomiting, diarrhoea, cramps, low blood pressure, and fast heart rate.

Treatment: Irrigate and remove remaining spine. Immerse in hot (50 C) water until pain subsides. Give local or systemic pain relief. Cleanse, debride and suture the wound. Give tetanus protection, infection prophylaxis and monitor heart rate, blood pressure, rate and depth of breathing.

 

SALT WATER CAT FISH

Catfish are a common and widespread group of fish, found in rivers, estuaries, seagrass flats, mud flats and reefs. They are furnished with three venomous spines – one on the back and one on each side. These spines are very sharp and easily effect a serious injury, resulting in severe pain at the site. The pain usually only lasts a few hours The fins have a complex toxin which is believed to be destroyed at temperatures above 40 C.

Symptoms: Intense pain out of proportion for the physical injury, generalised symptoms are rare, including muscle cramps, tremor, fatigue, syncope and even cardiovascular collapse.

Treatment: Immerse in hot (50 C) water, cleansing of the wound and liberal irrigation with hot water. Give tetanus protection and antibiotics that cover Vibrio vulnificus. Severe allergic reactions can occur.

 

SCORPIONFISH

There are many species, including lionfish and stonefish. The venom is similar to stingray and is destroyed over 50 C. An antivenin is available through the Australia Commonwealth Serum Lab.

Symptoms: Immediate intense pain, redness, swelling, cyanosis, nausea, vomiting, low blood pressure, delirium and cardiovascular collapse.

Treatment: Irrigate and remove debris. Immerse in hot (50 C) water. Give analgesia, antibiotics, tetanus and antivenin if available.

 

SEA SNAKES

The sea snake is an inquisitive but usually non-aggressive air-breathing snake. Sea snakes are readily identified by their flattened tails and valvular nostrils. The venom is extremely toxic and, while not destroyed by heat, many bites are not envenomated.

Symptoms: No symptoms for10 minutes to 6-8 hours post bite then there is malaise, anxiety and stiffness, aching and paralysis, especially of the jaw and eye lids. Ten percent of untreated cases are fatal.

Treatment: Immobilize the site of the bite. Hospitalize, obtain the antivenin and give CPR if needed. Try polyvalent land snake anti-venom if specific anti-venom is not available. Haemodialysis can be helpful and respiratory support is often needed.

 

Question 1

What is venom?

 

Venom is made up of poisonous chemicals called toxins. Many animals have developed ways of injecting venom into other animals. When the toxins in the venom are absorbed into an animal’s body, they have a harmful effect on that animal. Venom is part of some creatures’ survival kit-they use their toxic weapons to survive. Some animals inject venom to gather and kill their food. Other animals use it to repel their attackers. Some animals use venom for both attack and defence.

 

Question 2

How do anti venoms work?

 

Anti-venoms are purified antibodies which act as a kind of molecular sponge to soak up venoms or venom components (toxins). The most commonly used animal in the production of Australian anti-venoms is the horse. Sheep, rabbits and dogs are also currently used in Australia. Venom is obtained in a number of different ways. Snakes and funnel web spiders are milked for their venom. Stonefish, red back spider and box jellyfish venoms are extracted from dissected glands and tissues. This can be a dangerous process

 

Question 3

What is a pressure dressing for?

 

The principle of pressure-immobilisation bandaging as a first aid measure is to prevent the spread of toxins through the body. This is done by applying enough pressure to compress the lymph vessels, and by preventing movement of the affected limb. Correct application of the technique can buy valuable time to get the patient to medical assistance.

 

Question 4

Which antibiotics should be used initially?

 

Tetracycline deriviatives, chloramphenicol, penicillin and aminoglycosides are useful broad spectrum antibiotics that will also cover Vibrio vulnificus.

 

Question 5

What do the blue rings on the blue ringed octopus mean?

 

The usual colour of this animal is a mottled brown, but when disturbed, bright blue rings appear on its skin, warning of the danger of a bite.

 

Question 6

Where can I find more information?

 

Australian venom research unit

http://www.avru.org/

A key activity of the Unit is to provide medical advice on envenomations, anti-venoms and related issues to doctors, veterinarians, paramedical staff and poisons information centres, as well as zoos, reptile parks and keepers, various workplaces, government departments and the military, Australia-wide and internationally. A 24 hour consultancy service is available for DOCTORS AND PARAMEDICAL STAFF ONLY. The Unit also aims to increase public awareness of the dangers of venomous creatures, and the first aid measures for such bites and stings. It also works closely with the World Health Organisation in matters of anti-venom standardisation as well as patient care.

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Tips for Reducing Pre-dive Nervousness

Zenobia

Zenobia

 

You had been saving up for it for many months, have upgraded your gear, may have travelled overseas, and finally made it to the dive site you’ve been dreaming of.

Yet, with the big wide ocean now in front of you, and your dive buddies all excited and gearing up next to you on the boat, all of a sudden you start feeling funny.  Butterflies in your stomach? Sweaty hands?  Having a little difficulty breathing, perhaps?  You’re not alone.  Many divers experience this once in a while, from beginners to old-timers — especially those who haven’t gone underwater for a long time.  So you wonder how others deal with pre-dive jitters and still manage to enjoy a great dive.

One can easily recognize a diver who is uncomfortable or nervous before a dive:

 

  1. A friendly or sociable person suddenly becomes withdrawn;
  2. One who’s quiet becomes too talkative;
  3. Somebody normally upbeat and enthusiastic becomes negative about the dive;
  4. One who’s relaxed and easygoing stiffens up and starts to turn pale; and
  5. The person keeps going to the loo too often.

 

These are just some of the outward indications of pre-dive jitters.  But much of the problem lies internally, within the person’s mind.  He or she may have had problems in the past that he hasn’t overcome yet.  Mishaps like getting entangled, getting lost or trapped while doing a wreck penetration, getting separated from one’s buddy and going out of air, being swept by a strong current or being hit by a boat, perhaps.  Others may have had traumatic experiences outside of diving – such as drowning while on a regular swimming trip.

 

What can we do to reduce the pre-dive nerves, and get the most amount of joy and satisfaction from each plunge?

 

  1. Keep your mind focused on the joy of diving and not on any possible problem. Most fears are psychological in nature – drowning or being eaten by a shark tops the list. To prepare yourself mentally, it would help to do these things:
    1. Watch underwater videos like those of the BBC, National Geographic and Discovery. Try to recall and think about the positive underwater experiences you yourself have had in the past.  By keeping your mind focused on the good things, you won’t be dwelling on the roughness of the sea in front of you or whatever dangers you perceive to be lurking in the water.  If you’re feeling some shortness of breath, take a deep breath and just imagine all the good stuff you will be seeing during the dive.
    2. Before the trip, read about the exciting marine life or wreck you will be exploring.  During the trip itself, talk to your guide, the boat crew or any of the locals who live, swim, sail and dive in the area.  Find out as much as you can about the terrain.  Knowledge is power, and with power comes much confidence.
    3. Share some of your apprehensions with other — more experienced — divers.  They can give you tips on how they’ve overcome their own fears, reassure you about the concerns you have, and even quell any unfounded fears.

 

  1. Buoyancy is crucial. Most divers are over weighted. You need to make sure you are neutrally buoyant at the surface. That means your weights are enough to make you float at eye level with an empty tank and no air in your BC and drysuit. Doing so will allow you to move comfortably underwater, consume less air and, most of all, you will be certain of your equipment’s ability to keep you afloat.

 

  1. Make sure your regulator is properly serviced — it will give you the added assurance that your gear will always function properly during the dive.

 

Above all else, be excited! You have been waiting for this for a long time, so relax and just DIVE!

 

Scuba Diving opens a whole new world.

Scuba Diving opens a whole new world.

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Dangerous Marine Life

 Dr Oliver Sykes

Marine life in tropical waters that pose hazards to man can be divided into four general categories: Contact irritants and toxins, Injected toxins, Ingested toxins and Predators . This month I will cover contact irritants and toxins.

 

JELLYFISH, HYDROIDS and ANEMONES

All these animals possess nematocysts, a stinging apparatus that discharges on contact. Floating tentacles can retain active nematocysts, even after drying and there is a wide range of toxicity, from mild to severe.

Symptoms: Rapid onset of pain, varying from mild to severe. The rash is red, hot and swollen, usually linear. There is frequent pustule and vesicle formation and severe stings may cause muscle cramps, abdominal pain, fever, chills, nausea, vomiting, respiratory distress, and cardiovascular collapse. Fatalities are increased if there is pre-existing cardiac and respiratory disease. Box jellyfish (aka chironex, irukandji or sea wasp) may cause death in healthy individuals in less than 15 minutes.

Treatment: Use topical vinegar to neutralize undischarged nematocysts or sea water if copious volumes of vinegar are not available and then removal of remaining tentacles. Apply topical analgesics and steroids or intravenous versions if available. Treatment for shock or cardiac arrest may be required and therefore monitoring of pulse and blood pressure is required. Box jellyfish anti-venom is not universally available at all dive sites or smaller hospitals or clinics. Avoiding box jellyfish contact is of paramount importance. When diving in remote resorts in south-east Asia it is wise to ascertain the availability of anti toxin.

 

CROWN OF THORNS

This is the only known venomous starfish, its arms having large spines with venom producing integument.

Symptoms: Rapid onset of swelling, redness and pain.

Cleanse the wound and apply topical antibiotics. Give tetanus protection.

 

 

SEA URCHIN

Multiple slender spines puncture the skin and break off.

Symptoms: Immediate pain, joint pain, swelling and numbness.

Treatment: Remove spines, cleanse, topical antibiotics and tetanus protection. Soaking in hot water for 60-90 minutes is said to offer relief from the pain and swelling. Surgery is indicated for a foreign body reaction and if a joint capsule is punctured. Topical antibiotics and tetanus protection should be offered.

 

SEA CUCUMBER

Some species eject a visceral liquid.

Symptoms: Redness, itching and pain. If eyes are involved, symptoms are similar to chemical burns and blindness can occur.

Treatment: Copious irrigation of the affected area.

 

SPONGES

Three species of sponges produce a rash on contact, including the red-beard sponge, fire sponge and poison-bun sponge.

Symptoms include: redness, joint pain and swelling.
Treatment: symptomatic with soothing lotions and topical steroids.

 

CORAL:

Coral may cause abrasions that become infected but there are no toxins associated with coral. Fire coral is not actually coral. It has nematocysts and is more closely related to jellyfish. On close inspection, fire coral has tiny hair like tentacles, unlike coral.

 

 

Question 1: What is shock?

Shock is a medical term for poor organ perfusion. The casualty looks pale, has a weak pulse, low blood pressure and may be drowsy or confused. There are many causes of this, but severe decompression sickness, arterial gas embolism, severe bleeding or anaphylaxis are the likely causes in divers. The treatment requires intravenous fluid resuscitation and needs medical support urgently.

 

Question 2: What is anaphylaxis?

Anaphylaxis is a life threatening reaction which is rare but can occur due/ as a result of to medications, commonly penicillin or stings, such as bee stings. Therefore it is possible to have an anaphylactic reaction to any of the above sea animals. The symptoms come on within minutes of exposure and include wheeze, itching, redness, confusion, drowsiness and shock.

 

Question 3: How do I treat anaphylaxis?

This may be indistinguishable from a severe jelly fish sting, but the treatment is the same. Therefore remove the cause, apply oxygen and intravenous fluid resuscitation but also adrenaline. People who are known to suffer anaphylaxis often carry adrenaline around with them. Also known as epinephrine, the injection is known as an epi-pen. Steroids, such as hydrocortisone and anti-histamines, such as chlorpheniramine, are used to prevent the reaction recurring. This is a life-threatening condition and patient’s should be taken to hospital for stabilisation or observation if responding to emergency treatment

 

Question 4: How do I avoid getting stung?

Find out about the dive site beforehand. Jellyfish appear seasonally and most others are rooted to the spot or at least move slowly. The best plan is not to touch anything but a thin wet suit is very effective at preventing stings. Be careful when it comes to washing the suit afterwards, as the nematocysts will still be active!

 

Question 5: What is Irukandji syndrome?

Irukandji syndrome is similar to anaphylaxis and is produced by a small amount of venom from a box jellyfish. There are muscle cramps, severe pain, a burning sensation in the skin and face, headaches, nausea, restlessness, sweating, vomiting, an increase in heart rate and blood pressure, and psychological phenomena such as the feeling of impending doom. The syndrome is delayed for 5–120 minutes and the treatment is symptomatic, with anti-histamines and anti-hypertensive drugs used to control inflammation and high blood pressure; intravenous opiates are used to control the pain. Irukandji are usually found near the coast, attracted by the warmer water, but blooms have been seen as far as five kilometres offshore. When properly treated, a single sting is normally not fatal, but two people in Australia are believed to have died from Irukandji stings in 2002.

 

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Decompression Modelling

Dr Oliver SykesScuba diving may seem a long way from the class room and the point of theory may not be obvious, but it can be vital in making important decisions, especially about decompression models (aka tables). This article will outline some important theory and hopefully remind you that no dive profile is completely safe. Bear in mind that a model is only as good as it has been verified to be and there are too many factors involved to guarantee prevention of DCI.

A fundamental problem in the design of decompression models is that the rules that govern a single dive and ascent do not apply when bubbles already exist, as these will delay nitrogen elimination and equivalent decompression may result in decompression illness (DCI). Therefore repetitive diving, multiple ascents within a single dive and surface decompression procedures are significant risk factors for DCI.

The ideal dive profile creates the greatest possible gradient for nitrogen elimination from the tissues without causing bubbles to form. However it is far from clear whether this is possible. Some decompression models assume that stable bubble micro nuclei always exist. However, the dissolved phase decompression models are based on the assumption that bubble formation can be avoided. The bubble models make the assumption that there will be bubbles, but there is a tolerable total gas phase volume or a tolerable gas bubble size and limit the maximum gradient to take these tolerances into account. A number of empirical modifications to dissolved phase models have been made since the identification of venous bubbles by ultrasound in divers soon after surfacing.

Building Bert’s observation that dissolved nitrogen causes DCI, the first model that was verified experimentally, was developed by Haldane and is based on the following principles and concepts:

  • Nitrogen dissolves into tissues and becomes completely saturated after a certain amount of time. (Henry’s law)
  • The degree of saturation is determined by the ambient pressure, so that a given tissue above atmospheric pressure contains more nitrogen than the same tissue at 1 atmosphere.
  • The difference between the ambient pressure and a tissue’s partial pressure is called the pressure gradient.
  • On ascent, the partial pressure may be higher than the ambient pressure. But the body can tolerate some amount of pressure gradient without DCI.
  • If the pressure gradient becomes too high, the dissolved nitrogen cannot be eliminated quickly enough (by exhalation) and nitrogen bubbles form.
  • Partial pressure is the fraction of the total pressure that a single gas exerts in a mixture.
  • Tissue compartments are areas of the body that absorb gas at different rates and are categorized by how fast they uptake gas. Haldane introduced the concept of halftimes and suggested 5 tissue compartments with half times of 5, 10, 20, 40 and 75 minutes.

Tissue compartments do not correspond to anatomic tissues but one compartment will on gas and off gas at the same rate. Fast tissues on-gas and off-gas in shorter half-times than slow tissues. Areas that are well supplied by blood, such as the lungs and abdominal organs, absorb nitrogen faster than other tissues. Slower tissues include fat, fatty marrow and cartilage and saturation is reached when the pressure gradient is 0. This means after one half-time a compartment is 50% saturated, but it is not 100% saturated after two half-times, since each time the pressure gradient is halved. After two half-times a compartment is 75% saturated. After three, 87.5%. Four, 93.8 and for simplicity, we say a compartment is 100% saturated after 6 half-times.

How large can a gradient become before it’s a problem? Haldane assumed from his observations that the gradient could be a maximum of twice ambient pressure for all tissues. He assumed that an ascent from 30m (4 bar) to 10m (2 bar), or from 10m (2 bar) to the surface when saturated would not cause DCI. This was very conservative for shallow dives and not conservative for deep dives. In the 1960s Robert D. Workman of the U.S. Navy Experimental Diving Unit revised Haldane’s model with further experimental work to allow each tissue compartment to tolerate a different amount of supersaturation which varies with depth. This required a standardised ascent rate, which he took to be 18m per minute. His work allowed greater flexibility and safety to be built into tables for a range of depths and he introduced the term “M-value” to indicate the maximum amount of supersaturation each compartment could tolerate at a given depth. There are M-values for each compartment for each decompression stop. In no-decompression diving, however, we only have to be concerned with the values for the pressure at the surface. The PADI recreational dive planner grew out of Workman’s work and this is the reason why 18m per minute is the ascent rate required. The precise algorithms used in dive computers and tables are proprietary and therefore not available, but the PADI recreational dive planner now has a long safety history and is a useful benchmark.

We now have a complete model for predicting how nitrogen moves in and out of the tissues and at what point this process becomes a problem. However it remains a model and is therefore not true for every dive for every diver. So keep it conservative and stay within the limits of your computer!

 

PADI Recreational Dive Planner

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Oxygen Toxicity: Too much of a good thing.

Oxygen is necassary for life, but as divers we are exposed to higher partial pressures of oxygen (pO2 or ppO2) than normal. A partial Dr Oliver Sykespressure is simply the fraction of the total pressure that an individual gas takes up in a mixture of gases. Therefore 21% oxygen at sea level has a pO2 of 0.21 bar.

There are 2 main types of oxygen toxicty that we need to limit, which are pulmonary (lung) and neurological oxygen toxicity. In order to obtain energy from food, oxygen is used to break strong molecular bonds at the cellular level and is necessarily a fairly reactive species. As humans, we have evolved to use oxygen at 0.21 bar and even a pO2 of 0.5 bar begins to overwhelm the body’s repair mechanisms very slightly. This pO2 is only 50% O2 at sea level or 25% O2 at 2 bar or 10m. Therefore 50% oxygen is not recommended for over 24hrs in healthcare settings due to lung oxygen toxicity. Unless absolutely necassary. With much larger increases over shorter periods, such as a pO2 of over 1.4 bar during diving, neurological oxygen toxicity becomes the main worry. This is manifested in violent fitting (uncontrolled movements of the arms and legs) and is often fatal when diving. Unfortunately drowning is common and ascent is dangerous due lung barotrauma from a closed wind pipe. Therefore even a full face mask is not safe and the only treatment is to reduce the high pO2. Unfortunately stressors make neurological oxygen toxicity more likely during diving and include exercise, cold, poor vis, nitrogen narcosis, raised blood carbon dioxide levels and psychological stress. These are present on all dives and for everyone to some degree.

During recompression treatment, the chamber environment does not risk drowning and we minimise the stressors. We also use air breaks to limit the time spent at high pO2 levels and therefore use 100% O2 to greater depths than in water.

Overall, neurological oxygen toxicity is a very rare event in chambers and simply requires the diver to be taken off oxygen. Given that recompression is a treatment, the additional risk from oxygen toxicity is therefore acceptable and the pO2 limit is significantly higher in chamber treatments. But only with good reason.

 

Question 1:

What do you do if a diver fits underwater?

100% O2 should not be breathed below 4-6m, as this gives a pO2 of 1.4 to 1.6 bar. If a diver is using breathing gas mixes enriched with oxygen and then fits at depth, the cause is likely to be oxygen toxicity and switching to the wrong mix can cause this. Ascent is clearly dangerous due to lung over expansion injury, but may be the only way to ensure help can be given. Make sure you are aware of this problem and are able to cope with it. Essentially, follow the guidence from your training agency at all times.

 

Question 2:

Are there any preceding symptoms prior to an oxygen toxicty fit?

Yes there are. These include blurred vision, ringing in the ears, nausea, twitching, irritability (anxiety, restlessness) and dizziness, which can progress to convulsions (fitting). These can be remembered with the letters VENTID-C  and can be difficult to pick up when diving. (Vision, Ears, Nausea, Twitching, Irritability, Dizziness, Convulsions)

 

Question 3:

What happens if someone has an oxygen fit in the chamber?

Our chamber attendants are trained to recognise the preceding symptoms and will take the diver off oxygen. If there is a convulsion, then they will pad the moving limbs and the fit will stop once off oxygen. Chamber pressure must not be altered during a fit. There is no long term damage, it is not epilepsy and has no impact on future diving or driving. We would then decide whether to continue the treatment or shorten it, depending on the reason for treatment and the state of the patient.

 

Question 4:

What is pulmonary (lung) oxygen toxicity?

The airways become narrower as a result of inflammation. There is often midline chest pain, cough and reduced lung function tests. Diving is unlikely to produce sufficient oxygen exposure. However some of the more extensive treatments for decompression illness may cause a degree of pulmonary oxygen toxicty. Thankfully this is often completely reversible.

 

Question 5:

Are air breaks useful in preventing oxygen toxicity at sea level?

Important: Do not use air breaks when using oxygen at the surface in an emergency situation, this is unnecessary and deprives the diver of a very important treatment.

 

A video from Divers Alert Network DAN follow the link below :

CNS Oxygen Toxicity – Richard Vann PhD

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Flying after diving and flying after recompression

Dr Oliver Sykes

Dr Oliver Sykes

Many divers fly home after a diving holiday, but how many realise that this might have consequences and there are guidelines on how long they should wait? We often see divers at the hyperbaric unit who clearly have not waited long enough before flying and have developed decompression illness during the flight. Thankfully these are a tiny minority of divers and are not usually severe cases, but time to treatment is often delayed and can result in residual symptoms.

 

Why do we decompress during a flight? Commercial aircraft are pressurised to less than an atmosphere for a number of reasons, primarily financial. No planes are airtight and therefore leak. This requires compressors to maintain cabin pressure, which requires expensive fuel. However the pressurised plane is then heavier and this requires more fuel too. Therefore pressurising the fuselage to less than 1 atmosphere makes flying cheaper and we all decompress on the flight home. This is not a problem unless you’ve been diving recently. PADI appears to follow the DAN guidelines on flying after diving:

 

The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. (Alert Diver, November/December 2002, www.diversalertnetwork.org/files/FADWkshpBook_web.pdf) They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further. For a single no-decompression dive, a minimum preflight surface interval of 12 hours is suggested. For multiple dives per day or multiple days of diving, a minimum preflight surface interval of 18 hours is suggested. For dives requiring decompression stops, there is little evidence on which to base a recommendation, and a preflight surface interval substantially longer than 18 hours appears prudent.

 

In reference to these guidelines, scubadoc states (http://www.scuba-doc.com/flyngaft.htm):

The above is for sports diving and should not apply to commercial diving or nitrox diving. Because of the complex nature of DCS and because decompression schedules are based on unverifiable assumptions, there can never be a fixed flying after diving rule that can guarantee prevention of bends completely.

 

After treatment for decompression illness, there also should be some time for recovery before flying. Damage from the bubbles of decompression illness is the result of many interactions, but one of the most basic problems is lack of oxygen (low partial pressure of oxygen) in the tissues. Unfortunately a lower partial pressure of oxygen in the tissues also occurs with the decompression and lower cabin pressure involved in commercial flights. Therefore flying after treatment for decompression illness should be discussed with the diving doctor. The US Navy Diving Manual (Rev 6) states: Patients with residual symptoms should fly only with the concurrence of a Diving Medical Officer. Patients who have been treated for decompression illness or arterial gas embolism and have complete relief should not fly for 72 hours after treatment, at a minimum.

 

Question 1:

Can I fly home immediately after a 40 min Discover Scuba session to 5m?

 

No. This is a single no decompression dive and you must wait at least 12 hours.

 

Question 2:

I am going to drive home over some hills that are around 1000ft above sea level. Is this OK within 12hrs of surfacing?

 

This is probably OK, but be aware that symptoms may still occur,especially if you ascend to altitude sooner rather later after surfacing. Anything below 2000ft (610m) should be fine. There are plenty of hills within the UK that are over this height and I have seen divers develop decompression illness as a result of driving home over the Pennines, for example.

 

Question 3

As a diving officer, what should I advise helicopter crews, if a diver requires airlifting to a chamber?

This needs to be discussed on a case by case basis with the diving doctor and the service providing the aircraft as there is a risk of worsening the decompression illness but there are also significant risks to flying low.

Advice usually includes:

Keep the diver on 100% oxygen

Use an aircraft pressurised to 1 atmosphere if available

Fly as low as possible, preferably below 1000ft

 

Question 4

I have a commercial diving medical from the Health and Safety Executive, what are their recommendations about return to diving after DCI?

Commercial diving is very different to sports diving, with far more control over depths, times, ascent rates, multilevel diving and number of dives per day. However the diver has less control over when he/she actually dives. Its therefore not really reasonable to compare the two. I would recommend that you discuss it with the diving doctor that treated you. The HSE guidelines can be found at: www.hse.gov.uk/diving/ma1.pdf

 

Question 5

Where can I get more advice on flying, diving and decompression illness?

 

The Divers Emergency Service
Telephone: +44 (0) 7999 292 999

 

We are based at London Hyperbaric Medicine in the East end of London. You can phone us from anywhere in the world and we will help you find your nearest chamber and diving doctor

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Clearing your Ears In Water and Other Pressurised Environments.

As a diver, clearing your ears may be second nature. However we all had to learn at some stage and damage to your ears from over forceful clearing techniques is possible. So a quick reminder of the many techniques available may be useful.

The theory:

Your ears have an external tunnel that ends with a flexible ear drum. Imagine a real drum that gets compressed if you increase the pressure around it. (See a. in Figure 1.) The frame of the drum is like your skull and the skin of the drum is like your ear drum. Thankfully your ears differ significantly from a real drum! (See Ear anatomy picture below) For example, ach ear has a tube (See b. in Figure 2), which runs from behind the ear drum to the back of your throat. To stop your ear drum being pushed inwards, you need to increase the internal pressure behind your ear drum. You can do this by actively pushing air up these tubes. Unfortunately these tubes can work like flutter valves, hence can get stuck closed if you try too hard or allow the pressure to get too great before clearing your ears. Blockage can also occur when you have a cold and diving may not be possible. So you must not dive if you can’t clear your ears.

The external water pressure on the drum (Figure 1) and internal pressure generated by you (Figure 2):

 

The Techniques:

Try any of the techniques below early and often but perhaps start with 1. and  2. Everyone does it differently and works out which method works best for them. You will know when you have been successful when your ears “pop” and your hearing and perhaps balance returns to normal. Some of these are easier, in a recompression chamber rather than when diving.

1.         Swallowing, which is known as the Toynbee manoeuvre, drinking, sucking sweets, yawning, coughing, blowing your nose are all things we are used to doing and can be useful.

2.         Pinch your nose, close your mouth and try to blow out of your ears gently. Too hard will not work and can do damage. Watch other divers if you need to know how hard to try. This is known as the valsalva manoeuvre.

3.         The Lowry technique involves using all the above.

4.         Edmonds technique involves rocking the lower jaw from left to right and up and down and forwards and backwards, so that the lower teeth project in front of the upper teeth.

5.         Edmonds 2 advice: “Block your nose, close your mouth, then suck in your cheeks then puff them out quickly.”

6.         Try an otovent. (In chamber only) Occlude one nostril and blow up the balloon with the other nostril.  [youtube]http://www.youtube.com/watch?v=yr5wdwn_Xmk[/youtube]

7.         A difficult one to describe is the Frenzel manoevre. This involves closing the mouth and nose and push the back of your tongue up to the roof of your mouth as you swallow.

8.         Some people get good at clearing their ears and can do it without seeming to do anything. This is an advanced technique not discussed here, but everyone started off by holding their nose and blowing gently out of their ears!

Blocked or painful ears are very common while the pressure is increasing and difficulty clearing your ears is nothing to be ashamed of, but pain is a sign of possible barotrauma and definitely to be avoided. Some people simply find it difficult, but the longer and deeper you leave it, the less likely you will be able to clear your ears.

Ear Anatomy

 

(Kindly reproduced from Wikipedia)

Question 1: Who was Valsalva?

He was a 17th Century Italian anatomist, who described this method for expelling pus from the middle ear through a perforated ear drum.

Question 2:

Can I cause a perforated ear drum by clearing my ears too hard?

Yes, but this thankfully only happens rarely and is probably most commonly associated with a pre-existing weakness in the ear drum. Round window rupture and disruption of the middle ear bones are also possible and barotrauma is possible from as little as 2m. Grommets are artificial tubes placed in the ear drum to allow passive ear clearing, but completely preclude diving. Perforated ear drums seem to me to be most commonly caused by jumping into water ‘ear first’

Question 3:

Can I use decongestants to help clear my ears?

Definitely avoid these and do not dive if you cannot clear your ears. If the medications wear off, the ‘reverse block’ may cause barotrauma, intense dizziness and prevent ascent due to pain.

Question 4:

How can I be sure that I am clearing my ears properly?

Practise gently in water and follow the advice from your instructor. If clearing your ears is still causing pain, avoid diving with an upper respiratory infection. Try descending feet first to reduce venous congestion and using the anchor chain to fine tune to the speed of descent. Small ascents may relieve a blockage due to the flutter valve effect. Finally, there may be a correctable cause and a visit to your doctor may be useful.

Question 5:

How can I tell the difference between inner ear DCI and inner ear barotrauma?

This is an important question as the treatments are entirely different. Inner ear DCI requires recompression, but this will worsen inner ear barotrauma. However both may present with dizziness, nystagmus, (eye flicking) nausea, vomiting and unsteadiness. Both are serious conditions and require assessment by a doctor experienced in diving medicine. Inner ear barotrauma is more likely when symptoms begin on compression, with a shallow dive profile and forceful ear clearing. There may be associated ear barotrauma signs and symptoms, such as pain, fullness, unable to clear your ears and red/damaged ear drum.

Whereas the symptoms of inner ear DCI may start after the beginning of the ascent from longer, deeper, mixed gas dives and there may be signs and symptoms of neurological DCI, such as numbness and weakness in the limbs