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Decompression Illness Scuba Diving Is a Common Leisure Activity in Australia, with Millions of Dives Taking Place Every Year

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Decompression Illness Scuba Diving Is a Common Leisure Activity in Australia, with Millions of Dives Taking Place Every Year RD_HTTMAR06_p17_20.qxd 2/2/06 10:45 AM Page 17 How TO treat RURAL HowAustralian to treat RuralDoctor PULL-OUT SECTION MARCH 2006 Decompression illness Scuba diving 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. Decompression illness 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 compressed air is associ- diving and ated with some risk of decompression hyperbaric medicine 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 deaths. 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, lungs and respiratory sinuses. interface (barotrauma) Under pressure: all scuba diving carries FRACGP Ill-effects associated with diving may be • immersion in water (eg, near drowning, 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 tissue/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 the last dive, 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 panic ascent and did not miss He feels weak and lethargic and deep tendon reflexes in both legs. Case outcome, page 20 March 2006 | Australian Rural Doctor | 17 RD_HTTMAR06_p17_20.qxd 2/2/06 10:45 AM Page 18 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 first aid protocol in the death or paralysis. 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 embolism (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 central nervous system 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: nitrogen 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- Fatigue 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- Headache 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 Dizziness 20 Pathophysiology Ataxia 17 During diving, air is breathed at greater bottle of carbonated water bubbles when ardiac shunt and is known as arterial Dyspnoea 13 pressures 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 ‘decompression sickness’, 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 endothelium is damaging due to Urinary dysfunction 1 During ascent, nitrogen must be elim- Bubbles may cause harm through surface tension effects: it removes the Other 13 inated as the ambient pressure decreases. mechanical distortion of tissues, vascular protective surfactant 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 hypoxia. 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 platelet 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 solution 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. 18 | Australian Rural Doctor | March 2006 RD_HTTMAR06_p17_20.qxd 2/2/06 10:45 AM Page 19 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 diabetes. 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, pneumothorax. 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 allergies 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 oxygen? How much clouding of thought revealed by oxygen was given and for how long? slowing or failure at complex mental tasks.
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