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How TO treat RURAL HowAustralian to treat RuralDoctor PULL-OUT SECTION MARCH 2006 illness is a common leisure activity in Australia, with millions of dives taking place every year. Diving may also be part of a job such as abalone harvesting or underwater cleaning services. Local and overseas dive holidays are increasingly popular, and divers may consult inland or rural GPs on their return, The author: particularly as relatively late presentations Dr Michael Bennett are common in diving-related conditions. may seem a myste- Dr Bennett is an rious condition to many medical practition- anaesthetist and a ers but understanding the pathophysiology former medical behind diving-related illness is relatively easy director of the and treatment is usually highly successful. department of All diving with is associ- diving and ated with some risk of decompression illness and the incidence rises steeply when at Prince of Wales the dive tables or computer algorithm Hospital in Sydney. limits are breeched. He has a long However, half of all divers diagnosed with interest in the decompression illness have not exceeded the retrieval and limit of their dive table or computer. management of Each year about 350 people in Australia acute diving are treated using recompression and there injuries. are 5-10 dive-related . Many divers also present to medical practitioners for Editor: advice and treatment of other problems Dr Ellie Brusasco, related to diving – such as disorders of the MBChB (UK), ear, and respiratory sinuses. interface () Under : all scuba diving carries FRACGP Ill-effects associated with diving may be • immersion in (eg, near , some risk of decompression illness. caused by: salt water aspiration syndrome). GP reviewer: • the generation of bubbles within the This article deals specifically with decom- Dr Alex Ghanem tissues or vasculature (decompression pression illness, but it is important to con- MBBS (hons), Dip illness) sider all of these mechanisms when consid- Paeds, • changes in pressure at the /gas ering a diagnosis. DRANZCOG, FRACGP, Dip Rural Health, MFM (Clin) CASE HISTORY

Dr Ghanem is a Alex, age 38, presents three days after any obligatory decompression stops. complains of intermittent paraesthesia in VMO at Mudgee returning from his first diving holiday near But since about one hour after both legs. Alex also noticed aches and Hospital in NSW Cairns. surfacing from , Alex has pains in his limbs on the flight back from and a part-time He did 11 dives over three days without felt unwell and has had difficulty Cairns, which receded on landing. educator with incident. Alex reported no episodes of concentrating at work. Examination reveals little except weak Rhedwest. rapid or ascent and did not miss He feels weak and lethargic and deep tendon reflexes in both legs. Case outcome, page 20

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HOW TO TREAT Making the diagnosis

HOME TRUTH Decompression illness has many pos- sible manifestations, ranging from All injured divers should be mild and vague constitutional symp- treated with the same stan- toms to sudden loss of consciousness, dard protocol in the or . emergency situation. The dif- It’s important to seek advice from a ference between decompres- recompression facility for any medical sion sickness and cerebral problem arising within 24 hours of arterial gas (AGE) diving (for which there is no probable can be subtle and has no alternative cause). clinical significance in the The most important affected tissues acute phase. are the and musculoskeletal system. Single or multiple limb pains are common but general, constitutional symptoms (similar to those experienced during viral illness) have been recognised as a primary manifestation in up to 40% of cases. COMMON SYMPTOMS Severe illness is now uncommon in Decompression illness can the developed world, but severe affect any system and decompression illness leading to per- symptoms are remarkably manent disability or death remains a diverse. This table lists the significant problem in poorly trained more than 12 hours after emergence In deep now: gas bubbles commonly cited symptoms indigenous commercial divers in the from the water) are unlikely to be forming in the tissues causes most cases of decompression illness. reported by divers suffering a developing world. related to decompression illness, it is decompression disorder from important to remember that divers a recent case series of 76 History with diving-related symptoms often Important elements of the history in patients. The diagnosis of decompression illness present late for assessment. a suspected case of decompression rests almost entirely on taking a For example, the average time to illness are listed in the table at right. SYMPTOMS % OF PATIENTS careful history. The temporal relation- first presentation in a series of cases In a case of early presenting, Pain 67 ship between symptoms and diving is at the Prince of Wales Hospital in serious or rapidly progressive symp- 54 particularly important. Typically, Sydney was more than 24 hours, yet toms of dive compression illness, the Tingling 46 symptoms begin within minutes or a the interval from the end of a dive to history should be significantly trun- 46 few hours after surfacing. the first symptom in these patients cated in order to recompress the Numbness 35 Although new symptoms (that start was less than two hours. patient as quickly as possible. Weakness 26 Cognitive difficulty 25 20 Pathophysiology 17 During diving, air is breathed at greater bottle of carbonated water bubbles when ardiac and is known as arterial Dyspnoea 13 than normal, causing an the pressure is acutely reduced after gas embolism (AGE). Itch 10 increase in the quantity of nitrogen dis- opening the cap. Nitrogen gas bubbles The central nervous system is particu- Visual disturbance 8 solved in tissues of the body. The longer forming in the tissues, sometimes called larly susceptible to this type of injury Rash 7 and deeper the dive, the greater the ‘’, is the mecha- (cerebral AGE or CAGE). Loss of consciousness 5 amount of nitrogen to be dissolved until nism responsible for most cases of The passage of bubbles along the vas- Cough 3 all tissues are saturated. decompression illness. cular is damaging due to Urinary dysfunction 1 During ascent, nitrogen must be elim- Bubbles may cause harm through effects: it removes the Other 13 inated as the decreases. mechanical distortion of tissues, vascular protective layers and whole Ideally, during a planned ascent with a obstruction or stimulation of immune endothelial cells. Source: controlled reduction in ambient pressure, mechanisms that lead to tissue oedema, The damaged endothelium is a pow- Mitchell S. Diving Injuries 1: the nitrogen diffuses down a pressure haemoconcentration and . erful stimulus to leucocyte adhesion and Decompression Illness. Australia and New Zealand Hyperbaric Medicine gradient from the tissues to the venous The other, much less common, form of aggregation, and restricts flow Group Introductory Course Notes. blood and into the alveoli to be exhaled. decompression illness occurs when dis- in small vessels. This secondary injury Sydney 2005 However, if the rate of ascent is too creet gas bubbles pass to the arterial cir- may explain the later deterioration after great, gas may come out of and culation, either through pulmonary early recovery seen in many cases of sus- form bubbles in the tissues, much like a damage or across a (right to left) intrac- pected cerebral AGE.

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HOW TO TREAT

IMPORTANT ELEMENTS TO CONSIDER Examination IN TAKING A DIVING HISTORY ELEMENT OF HISTORY NOTES and investigations

Demographic data Decompression illness is more common in There are no reliable haematological older divers, as are many other possible or biochemical markers of decompres- diagnoses such as angina or . sion illness. Method used to control May help decide the gas burden and Supposedly sensitive radiological decompression status: likelihood of decompression illness. investigations, such as MRI, may fail table or computer to show an abnormality even when Number of dives and surface May help decide the gas burden. florid neurological signs are present. intervals Therefore, clinical history and exam- Dive history – maximum Divers are generally able to tell us if the ination are the most sensitive indica- depth, duration, number and dive was ‘outside the tables’ – that is the tors for diagnosing decompression speed of ascents to surface, depth and duration were longer than illness and assessing progress during violation of tables, level of recommended. treatment. activity Such violations are not required to make When performing an examination, the diagnosis, but make the diagnosis the priority of the elements to consider more likely. will depend on the history. Any problem with ears? May help differentiate barotraumas from Chest: Particularly if there are any res- decompression illness. piratory symptoms. Look for surgical Temporal account of Related to the diving as discussed in emphysema, . symptoms and signs the text. Neurological: It is important to Past diving history Experience level may assist diagnosis. perform a thorough examination of Past medical history, Includes any reason for illness and higher functions, cranial nerves and medications and whether diving has previously resulted in peripheral nerves. illness. The most commonly affected elements Response to first aid Did the symptoms improve with the are: administration of ? How much clouding of thought revealed by oxygen was given and for how long? slowing or failure at complex mental tasks. (Many diving specialists use a standard mini mental-state question- naire.) COMMON PITFALLS impaired balance and/or co-ordina- tion. Don’t be falsely reas- lower limb weakness (may be uni- sured by a “sensible” lateral or bilateral) dive history: About 50% patchy, non-dermatomal, reduced of divers treated for In practice, pulmonary disruption headache, and bilateral sensation decompression illness in or intracardiac shunt is rarely proved lower limb parasthesia. upgoing plantar response. Australia have not vio- and the distinction between cerebral Evolution: the chronology and Ears: Bleeding and rupture of the tym- lated their dive tables or AGE and decompression sickness is intensity of symptoms over time in panic membrane indicates significant computer limits for often difficult to make. relation to the time of the dive. barotrauma. depth and duration of It is now accepted practice to define Gas burden: an estimate of nitro- : A patchy erythematous rash is the dive. the whole group of related conditions gen still left in body. It is highest common and is usually short lived and Ensure patients lie down under the heading decompression with increasing dive depth and mobile. The area affected may change throughout physical illness and to characterise the type of duration, and if decompression while being observed. examination, chest X-ray illness by outlining the manifestation, stops are missed. Response to oxygen: 50% of cases or during transfer: sitting evolution, time of onset, estimation Barotrauma: if present, look espe- respond rapidly to high flow oxygen or standing can result in of gas burden and presence or cially for indications of injury. therapy, but a good response does not movement of intravascu- absence of evidence of barotrauma. Also, chest pain, dyspnoea, cough indicate that recompression can be lar bubbles and neuro- Manifestations: these cover signs or surgical emphysema (with or avoided. logical deterioration and symptoms, as well as organs without clear cerebral injury) all during acute illness. affected. For example, neurological suggest serious illness that may decompression illness with deteriorate quickly.

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HOW TO TREAT Treating suspected decompression illness

THE GEMS If decompression illness is suspected, there are a few standard simple first In any acute diving injury, aid measures that should be instituted give high-flow oxygen, while seeking advice and referral to a administer intravenous recompression facility. crystalloid fluids and keep the patient lying down. Acute illness Seek advice from a recom- If a diver presents within 12 hours of pression facility for any a dive and is significantly unwell, the medical problem arising recommended approach is: within 24 hours of diving • Institute standard emergency man- (for which there is no prob- agement protocols to support able alternative cause). airway, and circulation. Tissue injuries • Administer 100% oxygen (or as (decompression sickness) close to it as possible) with avail- are most unlikely if symp- able equipment. toms begin before the end • Keep lying flat – sitting or of a dive. standing has resulted in movement A recompression chamber: the only definitive treatment for decompression. Timely first aid and recom- of intravascular bubbles and neu- pression results in a high rological deterioration. In particu- and oral fluid can be administered for greatly increased of rate of complete recovery. lar, don’t sit or stand for physical presentations occurring up to 24 oxygen to the tissues. A return to diving after examination, chest X-ray or during hours after the dive, while awaiting At the same time, the volume of decompression illness is transfer. transfer to a recompression facility. bubbles is directly reduced through best managed by a • Administer crystalloid fluid Low-level transfer – such as pres- the operation of Boyle's Law (volume specialist diving physician. replacement. Adults should receive surised fixed-wing aircraft, special hel- of a given mass of gas is inversely pro- 1L of fluid (usually normal saline icopter or even road transport – portional to the ambient pressure). or Hartmann’s solution) over 30 avoids the risk of symptom deteriora- Treatments typically involve pres- minutes, followed by appropriate tion from hypoxia and further depres- surisation to 2-6 atmospheres absolute maintenance. All divers should be surisation. The specific type of low- (ATA) for between two hours and treated as significantly dehydrated level transfer is best decided by the several days as a single treatment. until passing urine copiously (but recompression chamber staff and NSAIDs may offer symptomatic being careful to avoid fluid over- retrieval team. relief and may shorten the amount of load). recompression needed. • Urgently seek advice and referral to Specialist advice a recompression facility. Once first aid measures have been instituted, discuss all cases with the Life after Subacute illness local recompression facility. There is at decompression When the presentation is less acute, least one such facility in each state illness first aid measures are likely to be and territory (except the ACT). In most cases, the outcome of unnecessary and unhelpful. In addition, even serious decompression However, oxygen administration Hospital’s hyperbaric medicine unit illness is for a return to full runs a 24-hour emergency advice line, health. In up to 10% of cases, Divers Emergency Service. Call 1800 CASE OUTCOME any of the presenting symptoms 088 200 (Australia) or +61 8 8212 and signs may persist for months From page 17 9242 (from overseas). or years, particularly if there has Alex is probably suffering from decompression illness. Although he would been a delay in first aid or technically be described as having “static neurological decompression Recompression recompression. It is most unusual illness with no features of cerebral AGE or barotrauma and a moderately Recompression is the only definitive for new problems to develop after high gas burden”, the illness is affecting his life and work. treatment for decompression illness. definitive treatment. The natural history suggests he would recover slowly, over weeks or It involves placing the patient in an The most serious sequelae are months, but referral to a hyperbaric centre via low-level transfer for airtight vessel, increasing the pressure those following severe neurological recompression is preferable and appropriate. and administering 100% oxygen. decompression illness where leg After three sessions of hyperbaric oxygen recompression and a regular This greatly enhances the move- weakness, loss of balance and/or NSAID, Alex feels well and is normal on examination. He agrees to dive less ment of nitrogen out of any remain- fine co-ordination may be intensively in the future – a maximum of two dives a day is safest. ing bubbles down a steep permanent and disabling. gradient, as well as delivering a

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