J R Army Med Corps 2003; 149: 15-22 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from REGULAR REVIEW

Common Medical Disorders Related To Diving – Prevention, Diagnosis And Fundamentals Of Treatment. Part 1: Diving Disorders That Do Not Require Recompression.

Extracts from Institute of Naval Medicine Report R98013, The Prevention and Management of Diving Accidents

Edited by DE Ayers, SJ Mercer, M Glover

recognition and initial management as well as the necessity or otherwise of referral.The details of therapeutic recompression have not been covered, with emphasis instead placed (in Part II of the paper) on recognising the need for recompression. Part I - Diving disorders that do not require recompression This section covers diving related illnesses and injuries not usually requiring therapeutic recompression. As general Introduction principles, any diver should either not dive This paper, which is published in two parts, or not remain in the water if they feel is aimed at the non-specialist and reviews in unwell, and any illness that occurs during or outline the more common medical after a dive should be considered to be due disorders related to diving. A more in-depth to that dive until proven otherwise (Table 1). account can be found in the medical section of BR2806, the UK Military Diving Oxygen deficiency http://militaryhealth.bmj.com/ Manual, and Institute of Naval Medicine (hypoxia/anoxia) Report R988013, The Prevention and This condition is rare when diving on air Management of Diving Accidents (1). The using open circuit breathing apparatus, but latter work, from which this paper has been if it occurs it is either due to interruption of extracted, contains the distilled wisdom of the breathing gas supply, or normal delivery generations of Royal Navy divers and diving but with insufficient oxygen in the gas medical officers including exchange officers mixture. In cases of inadequate supply such from allied Navies.This paper is intended as as when running low on air using SCUBA an introduction for those who may equipment, the diver notices increased work infrequently encounter these conditions, of breathing before being overtaken by the on October 1, 2021 by guest. Protected copyright. rather than a scientific treatise and so is Surg Lt Cdr DE symptoms of hypoxia. If the breathing gas is Ayers RN deliberately devoid of further references. It of adequate volume but contains is no substitute, however, for more detailed insufficient oxygen, the diver may notice Department of Plastics, Queen Victoria and systematic study and the Royal Navy’s few symptoms before losing consciousness Hospital, Standard Underwater Medicine Course is other than a sense of well-being. Loss of East Grinstead, commended to readers with an interest. judgement may, however, be apparent to the West Sussex, The work has been divided into two parts victim's buddy. The treatment is to restore RH19 3DZ – diving disorders that do not and those that interrupted supply or switch to another do require recompression, the latter to be supply and administer 100% oxygen when Surg Lt Cdr SJ published in a subsequent edition of The on the surface. Mercer RN Journal. The work focuses principally on Department of Surgery, disorders resulting from the use of open Queen Alexandra Oxygen toxicity Hospital, Portsmouth, circuit breathing apparatus in which the If oxygen is breathed at a high partial Hant, PO6 3LY diver does not rebreathe any previously pressure for long periods, it becomes toxic exhaled gas. Closed circuit systems do have Surg Cdr M Glover RN to many tissues, particularly the lungs and Institute of Naval a number of uses in the military setting but central nervous system. Medicine, Alverstoke, are generally beyond the scope of this work. Gosport, Hants, PO12 Both sections aim to explain the 1. Pulmonary oxygen toxicity 2DL mechanisms of the conditions covered, their At partial pressures greater than 0.5 16 Common Medical Disorders Relating To Diving Part 1 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from Atmospheres Absolute (ATA) oxygen will depths in excess of 30 msw. It manifests as become toxic to the lungs. For practical progressive shortness of breath, nausea, purposes this does not arise from normal air headache, dizziness, neuromuscular ‘bounce’ diving (i.e. where no planned twitching, convulsions and eventually loss recompression is required after the dive), to of consciousness. If it occurs at depth the less than 50 metres of seawater (msw), diver should reduce his activity and ensure because decompression considerations limit that there are no problems with his gas the period of exposure to oxygen within safe supply. Once at the surface recovery should limits. It can occur where pure oxygen be rapid, but a throbbing headache is a closed breathing sets are used and manifests frequent after-effect. as tickly throat, coughing then substernal burning. Advanced cases will manifest with Carbon dioxide deficiency physical signs and impaired lung function (hypocapnia) but, in most cases, complete recovery can This results from voluntary hyperventilation usually be expected.The treatment is simply prior to a breath-hold dive in an attempt to to reduce the concentration of oxygen in the extend endurance or from involuntary over- mixture, preferably to 0.2 atmospheres. breathing while undertaking a dive. It may be provoked by anxiety states or fear. 2. Cerebral oxygen toxicity Common symptoms include dizziness, poor Cerebral toxicity can be highly variable in coordination, headache and classical carpo- its presentation with signs and symptoms pedal spasm with peri-oral paraesthesia. It including dizziness, nausea, tunnel vision should be noted that the symptoms of and convulsion. Furthermore, there is no hypocapnia can be very similar to some of fixed oxygen exposure at which toxicity the constitutional and neurological occurs with susceptibility varying both manifestations of decompression illness and between individuals and within the same the distinction, though difficult, needs to be person from day to day. In most underwater made correctly. Once recognised, most breathing apparatus the inspired partial cases of hypocapnia can be successfully pressure of oxygen is limited to 1.4 ATA or managed by voluntary regulation of the less in order to make the risk tolerable. The breathing rate. If symptoms persist despite first sign of cerebral oxygen toxicity can be attempts to control this, the time-honoured generalised tonic-clonic seizure. If so, treatment of breathing from a paper bag will during the tonic phase, which lasts up to a alleviate symptoms. minute, it is dangerous to surface the casualty as spasm of the glottis can result in Nitrogen narcosis (‘narcs’) inadequate exhalation, lung overpressure If nitrogen is breathed under pressure, it and consequent pulmonary barotrauma. If acts like an anaesthetic and induces http://militaryhealth.bmj.com/ this occurs underwater the treatment is to narcosis. The severity of effect depends on keep the diver’s depth as constant as the depth of the dive, the rate of possible in the tonic phase and then return compression and the experience of the to the surface. In the clonic phase the victim diver. Some drugs, particularly alcohol and undergoes true convulsions. Once at the sedatives, may have an additive effect to the surface, breathing apparatus should be narcosis and should not be taken prior to removed and the casualty placed in the diving. Other gases also have a narcotic recovery position in fresh air to recover. If effect, the narcotic potency being further convulsions occur the airway should proportional to their lipid solubility. be protected. All cases should be kept under Individuals vary in their susceptibility to on October 1, 2021 by guest. Protected copyright. observation for twelve hours to ensure that nitrogen narcosis and some behavioural the seizures are not due to some cause other adaptation to the effects of narcosis can be than oxygen toxicity. If an uncontrolled achieved by frequent exposure. The effect ascent is made, an examination, including a varies with depth, ranging from light- neurological examination, must be carried headedness and euphoria at 30-60 msw out to exclude pulmonary barotrauma and through progressively poorer judgement decompression illness (see below). Loss of and hallucinations to eventual loss of memory almost always occurs but is usually consciousness at more than 120 msw. The short-term and resolves quickly. symptoms and signs of nitrogen narcosis are similar to those of drunkenness except that Carbon dioxide poisoning there is no hangover. There is no danger (hypercapnia) from the narcotic effect itself and the effect Carbon dioxide poisoning may occur with wears off rapidly on reducing depth. The or without a deficiency of oxygen. It may be hazard is that a narcosed diver may act caused whilst using open circuit apparatus inappropriately, sustain an injury or drown by incorrect or shallow breathing, by while his concentration is impaired. excessive resistance or dead space within Nitrogen narcosis is prevented by limiting the equipment, or by using dense gases such the depth of dives according to the as air or nitrox (nitrogen/oxygen mixture) at experience of the diver. Deep dives are DE Ayers, SJ Mercer, M Glover 17 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from preceded by a work-up, which does not Compression barotrauma prevent narcosis, but enables the diver to (squeeze) learn to cope with the effect. Deeper dives The body is mainly composed of are conducted using helium rather than incompressible fluid. However, any gas- nitrogen as the inert gas in the breathing filled space present within or next to the mixture. If narcosis occurs, treatment is to body can damage tissues when its volume reduce the depth of the dive and in rare changes in accordance with Boyle’s Law. serious cases the diver should surface. Once ‘Squeeze’ refers to the damaging effect of a the inspired pressure of nitrogen is reduced, reduction in volume of gas in a diver’s the effects of narcosis resolve rapidly. equipment or body cavity as pressure is increased. The opposite effect, barotrauma Caustic cocktail of ascent, is caused by the expansion of gas. Despite this article's focus on open circuit The predominant symptom of barotrauma diving systems, one important and is pain. In situations where the gas volume dramatic condition particular to closed- can be restored to the pre-dive volume, e.g. circuit systems needs to be considered. If by inflating a dry suit or ‘clearing’ the ears, water enters a closed circuit breathing squeeze can be avoided. Equally, where the apparatus it might mix with the carbon gas is contained within a flexible viscus such dioxide absorbent (usually a mixture of as the bowel, compression and subsequent calcium hydroxide with a small amount of expansion of gas can occur harmlessly. The sodium hydroxide). This strong alkali types of squeeze most frequently solution can cause severe chemical burns encountered in diving are in the ear, suit, to the face, mouth, lungs and stomach. In sinuses, lung, facemask and tooth. order to prevent this, equipment needs to Suit squeeze is caused when a pocket of be checked for leaks before diving and if air under a fold or fitting of a dry suit is one becomes apparent during a dive then compressed and results in the skin being the diver needs to surface as soon as he is pinched. Sinus squeeze may occur when the able. The diver should leave the water and passages that vent the sinuses into the nasal remove the set as quickly as possible. The cavity are obstructed. It presents as pain oropharynx should be inspected for signs because the pressure in the affected sinus of burning and, if apparent, the victim decreases relative to ambient, causing should wash his mouth out with fresh oedema of the mucosa and possibly water and drink more to dilute the alkali. If haemorrhage into the space. Lung salt water is all that is available at the time, (thoracic) squeeze is a very rare event, then this may be used to wash out the which may occur if the air in the lungs is mouth, but should not be swallowed as this compressed to a volume somewhat less than

may induce vomiting. Vomiting is http://militaryhealth.bmj.com/ dangerous and can cause further burning the residual volume of the lungs. Facemask to the oesophagus and oropharynx if the squeeze is caused by a failure to equalise air caustic cocktail has been swallowed. Any pressure in the mask by nasal exhalation. skin surface exposed to the injurious agent Facial oedema over the area covered by should be washed liberally with fresh or the mask as well as subconjunctival salt water. haemorrhages may result. Tooth squeeze Any patient with known or suspected results when a small pocket of trapped gas oropharyngeal burns should be referred exists under a poorly prepared or cracked urgently for endoscopy. Caustic burns to filling. If it is completely isolated, the pulp the eye should similarly be treated by of the tooth or the tissues of the socket can washing with large volumes of water and be drawn into the space causing pain. The on October 1, 2021 by guest. Protected copyright. subsequent referral to an ophthalmologist. treatment of all of these instances of Caustic cocktail readily provokes panic barotrauma is to stop the descent and if which may result in rapid ascent and efforts to equalise the pressure fail, ascend breath holding (to avoid inhaling further to a shallower depth. alkali). Consequently, divers who have accidentally inhaled a caustic cocktail External ear squeeze - should be carefully observed following the ‘reversed ears’ dive for evidence of pulmonary barotrauma External ear squeeze or ‘reversed ears’ or neurological decompression illness. occurs when the external auditory meatus (EAM) is blocked by an obstruction such as Table 1.Conditions caused by effects of O2,CO2 and N2. wax, a tight fitting hood, earplugs or otitis Oxygen deficiency Increased work of breathing, inappropriate sense externa and the pressure in the outer ear of well-being cannot equilibrate with the ambient Oxygen toxicity Dizziness, nausea, tunnel vision, generalized pressure. During descent therefore, a convulsions relative vacuum develops in both the outer Carbon dioxide Progressive shortness of breath, nausea, dizziness, and middle ear. When the ears are cleared, toxicity headache, eventual loss of consciousness which returns the middle ear pressure to Nitrogen narcosis Light-headedness and euphoria, poor judgement, ambient, the tympanic membrane balloons hallucinations, eventual loss of consciousness outwards, in the opposite direction to that 18 Common Medical Disorders Relating To Diving Part 1 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from which occurs in more conventional middle moving the jaw around. Some require a ear barotrauma – hence ‘reversed ears’. If it Valsalva manoeuvre against a closed nose persists for more than a few minutes, then and mouth (rather than a closed glottis) to injury to the epithelial lining of the EAM achieve this. and tympanum may occur with oedema and If the Eustachian tube is blocked, the ears petechial haemorrhages. Accordingly, divers cannot be cleared. During the initial phase should be told not to dive if they have an of descent, the decreasing volume of the outer ear infection and the use of tight middle ear is compensated for by the drum fitting hoods and earplugs should be being displaced inwards. Eventually, avoided. The condition is heralded by the however, the eardrum reaches the limit of onset of pain similar to that which occurs in its inward distensibility and the middle ear the more classic middle ear barotrauma pressure falls below the external water described below. There may also be mild pressure. This creates a relative vacuum in vertigo and on examination the external the middle ear space and so a pressure canal may be swollen or haemorrhagic. difference across the tympanic, round and Patients with reversed ears should be oval window membranes. This negative referred to an otolaryngologist especially if pressure causes the blood vessels of the tympanic rupture is suspected. Eardrops, eardrum and the lining of the middle ear to which may be ototoxic, should be avoided. expand, leak and eventually rupture. If descent is continued, then either the Middle ear barotrauma (‘ears’) eardrum will rupture allowing the Middle ear barotrauma is due to a failure to immediate equalisation of the middle ear equalise middle ear pressure with ambient and ambient pressure, or bleeding into the and remains the most common medical middle ear becomes sufficient to equalise problem associated with diving. It is both the pressure by replacing air with painful and potentially dangerous. incompressible fluid. The eardrum completely seals off the The first symptoms are pressure and outer ear canal from the middle ear space fullness in the ear followed by pain, usually and when the diver descends, the pressure experienced within the first 6-7 msw of on the outer surface of the drum increases. descent (Table 3). If the tympanic mem- To maintain the status quo, the air pressure brane ruptures, relief of pain occurs almost on the inner surface of the drum must immediately. If this results in ingress of increase by the same amount. This is water to the middle ear, caloric vertigo due accomplished by the diver allowing air to to thermal imbalance between the two ears pass down the Eustachian tube, which may occur. Following the dive there may be connects the pharynx to the middle ear (see some residual pain and a mild conductive

Figure 1).This process is known as ‘clearing hearing loss and the ears should be http://militaryhealth.bmj.com/ the ears’. In a few divers, the Eustachian examined with an otoscope. In milder cases, tube is open all the time, so no conscious signs range from a normal otoscopic effort is necessary to clear their ears. For appearance through to redness and most, however, the Eustachian tube is retraction of the membrane, possibly with naturally closed and some action must be haemorrhage within the membrane. In taken to allow this passage of air. Many can more severe cases, a bulging membrane accomplish this by yawning, swallowing or with free blood in the middle ear or tympanic membrane perforation with free haemorrhage is seen. Hearing loss usually recovers within two days but, if persistent, ossicular chain disruption may have on October 1, 2021 by guest. Protected copyright. Oval Window occurred. Round Window In order to prevent middle ear barotrauma, divers should avoid diving with a cold or nasal congestion, since the Eustachian tube may be blocked. Divers who cannot clear their ears on the surface should not dive. A diver who has suffered middle ear squeeze should not return to diving until healing is complete. If there is bleeding from the ear or vertigo following a dive, the medical officer should refer the diver to an otolaryngologist. Again, eardrops which contain drugs that may be ototoxic should not be used if a perforated tympanic membrane is seen or suspected. Tympanic Eustachian Tube Membrane Alternobaric vertigo This condition occurs quite commonly. It Fig1. A coronal section through the middle and inner ear. arises when either during descent, or more DE Ayers, SJ Mercer, M Glover 19 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from Table 2.Conditions caused by pressure changes. considered dead until they are completely re-warmed and continue to be unresponsive Middle ear barotrauma Pressure and fullness in ears, and reversed ears increasing pain in ears to resuscitation. A person with water in his lungs may not Tooth squeeze Pain in tooth on changing depth lose consciousness immediately, but may Sinus squeeze Headache or face pain on changing depth still die from later ‘secondary drowning’ due Alternobaric vertigo Transient dizziness and nausea to pulmonary oedema. This can result from reaction to the inhalation of either fresh or commonly ascent and (particularly when in salt water. For this reason all suspected near the upright position), the change of middle drowning victims should be observed in ear pressure between the two sides is hospital for 24 hours. asymmetrical. This can result in a transient sensation of vertigo, disorientation or Vomiting underwater nausea. If it occurs at depth, it can be This is an extremely dangerous and hazardous. These symptoms normally potentially life threatening event. It may be resolve rapidly once the diver equalises caused by diving with a gastro-intestinal pressure in the affected middle ear. upset, over exertion after recent intake of alcohol or food, or as part of another Caloric Vertigo underwater incident such as ingestion of Usually on immersion, water enters both caustic cocktail.The correct management is ears and the inner ear is cooled at a similar to get the diver out of the water as soon as rate on each side. Caloric vertigo, which has possible and remove the breathing been mentioned already, occurs when one apparatus. If unconscious, the airway ear is partially or completely blocked by a should be cleared and CPR begun if tight fitting hood or wax and the inner ears necessary. are stimulated unequally. Vertigo, which tends to be transient, results. Underwater blast injury Proximity to underwater explosions is Otitis externa (swimmer’s ear) dangerous and the resultant injuries are Repeated immersion breaks down the skin complex. In short, shrapnel injuries are which lines the external ear canal and this unusual as material displaced by the blast allows the bacteria and fungi normally does not travel far. The pressure waves present to multiply. The diver complains of propagate much further and release energy itching, a wet feeling or discharge and, if at density interfaces. Energy of a pressure severe, pain. It is a completely preventable wave is transmitted to the tissues of the condition. 7% Aluminium acetate solution body more efficiently from water than from

or Otic Domeboro® ear drops prevent air because of the similarity in densities. http://militaryhealth.bmj.com/ infection if applied after each wet dive. There is significant disruption, however, of These solutions are both bacteriostatic and tissues containing gas as destructive energy astringent and should be left in for a is released due to the sharp density changes minimum of 5 minutes. If the condition is at gas-tissue interfaces and the spaces contracted, treatment is a temporary distort with the pressure changes. cessation of diving so that the ear can be Accordingly, perforated eardrums may be kept dry and continued use of aluminium seen as well as pain or haemoptysis from acetate drops and appropriate antibiotic injuries to bowel or lungs. Casualties should drops if necessary. be assessed and treated for immediate life threatening conditions in accordance with Near drowning basic principles and evacuated immediately on October 1, 2021 by guest. Protected copyright. Drowning is the most common cause of for more detailed assessment. diving fatalities. Divers drown as a result of accidents, panic, over-exertion or the effects Cold exposure and hypothermia of cold. Near drowning describes the Cold immersion is thought of as acute and condition of those who survive such sub-acute. Acute cold immersion results submersion – at least, temporarily. The from sudden unprotected entry into cold victim is unconscious, often the body is water or the rapid influx of cold water into leaden-blue in colour and froth is visible a diving suit. As well as immediate increases around the nose and mouth. It should be in pulse and blood pressure this results in a noted that in 10-15% of cases water does period of rapid uncontrolled breathing. As not enter the lungs due to the effects of divers usually enter the water protected and laryngospasm. The mouth and throat should in a controlled fashion, this acute cold be cleared of debris and cardio-pulmonary reaction is rare. Immersion in water below resuscitation (CPR) commenced. Time about 32° C however, soon results in the should not be wasted trying to drain the unprotected diver becoming chilled. lungs but oxygen should be administered if Discomfort is followed by shivering and loss available. The victims of near drowning are of first manual then mental dexterity. Thus often severely hypothermic and may appear the diver may make mistakes which dead. Such victims should not be themselves could be fatal. If immersion is 20 Common Medical Disorders Relating To Diving Part 1 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from prolonged, heat loss reaches a point where rises further, conscious level is reduced and death occurs from hypothermia. The coma supervenes. The patient should be symptoms and signs of a falling core rested in a cool place, encouraged to drink temperature begin with pale skin and water and cooled by evaporative heat loss sporadic shivering at around 36° C, which through wetting and fanning. All but the then becomes uncontrollable (Figure 2). mildest cases should be transferred to Mental confusion takes hold around 35° C hospital as the condition can readily and and the diver is at risk of drowning. sometimes rapidly deteriorate to life- Gradually speech is impaired and threatening severity. It can take over 24 consciousness clouds when the core reaches hours for spontaneous thermoregulation to 33° C. Evidence from shipwrecks suggests be restored. that 50% of individuals will not survive this stage. Shivering may cease as the casualty Decompression pulmonary cools further and the heart rhythm may barotrauma become irregular. Loss of consciousness Decompression pulmonary barotrauma is a occurs at around 30° C and nearly all are syndrome that results in gas, which is dead by 27° C. Treatment of the casualty normally retained within the airways, begins with prevention of further heat loss leaving its natural confines and entering by removing the casualty from the water, either the interstitial space within the lung, maintaining them throughout in a the pleural cavity or the blood stream. The horizontal position to prevent cardio- mechanisms by which this happens are vascular collapse. The patient then needs to incompletely understood. At the simplest be gently re-warmed, ideally in a medical level, if gas, which has been breathed while facility, and CPR instituted if necessary. at depth, is trapped within the lung during Caution should be exercised in making the ascent, then the resulting expansion in decision to commence cardiac massage, as volume of that gas, in accordance with it can induce arrhythmias and will need to Boyle’s Law, may be sufficient to cause be continued until re-warming is complete. delicate pulmonary tissue to rupture. The Milder cases of hypothermia where gas may be trapped as a result of voluntary consciousness has been maintained or involuntary breath holding, or as a result throughout can be re-warmed by careful of pulmonary pathology. However, immersion in a bath at 40° C. numerous cases of decompression pulmonary barotrauma have occurred in Heat exhaustion which no evidence of pulmonary pathology This occurs as a result of over-exertion by a has been found and exhalation during diver in warm water (over 25° C), when ascent has been witnessed by independent

wearing either a dry suit or a wet suit that is observers. Consequently there probably http://militaryhealth.bmj.com/ too thick, or normal levels of exertion in remain other causes of the condition that water over 30° C. This should be a have yet to be identified. preventable condition but, when it does Divers should be screened, therefore, for occur, manifests as dizziness and headache evidence of obstructive lung disease which with a rapid pulse and a raised core could result in trapping of gas. Those temperature. Usually, but not always, there suffering short-term respiratory illness is excessive sweating. As the temperature should not dive while they remain on October 1, 2021 by guest. Protected copyright.

Fig 2. Symptoms of reducing core temperature. DE Ayers, SJ Mercer, M Glover 21 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from symptomatic. Decompression pulmonary administration of 100% oxygen, but large barotrauma manifests with a range of pneumothoraces will require draining. All symptoms and signs. Certain of these are tension pneumothoraces obviously require usual, such as sharp retrosternal chest pain, emergency decompression then siting of a shortness of breath, painful breathing and chest drain. productive cough with small amounts of blood staining in the sputum (Table 3). 3. Arterial gas embolism (AGE) Others depend on the route the gas takes If gas from a ruptured lung enters the after rupture and so are less consistently pulmonary veins, it will be carried to the left observed. side of the heart and from there be distributed to the body as arterial gas 1. Mediastinal and subcutaneous emphysema emboli.The two organs that are particularly If gas escapes into the interstitial tissue susceptible to functional disturbance as a space, it can track out of the airways and result of such emboli are the brain and the vessels to the hila and thence to the heart. Divers sustaining decompression mediastinum. This is often asymptomatic pulmonary barotrauma should, therefore, but if there is a substantial quantity, be examined for evidence of cardiac or retrosternal pain may be felt. Gas in the cerebral dysfunction. In the past it was mediastinum may migrate to the considered possible to make a diagnosis of subcutaneous tissues of the neck where it AGE in patients who experienced the onset manifests as crepitation. Rarely it may track of neurological symptoms during decom- down to the abdomen where it lies in the pression or shortly after surfacing from a retroperitoneum and though usually dive, even in the absence of any other asymptomatic, may outline the liver or evidence of pulmonary barotrauma. It is kidneys on plain radiography. now recognised that such a diagnosis is liable to be inaccurate as other conditions 2. Pneumothorax can present in a similar manner. This occurs when alveolar gas escapes into Accordingly, neurological symptoms or the pleural space. It is often painless, but signs presenting after a hyperbaric exposure may cause a sharp pain, worse on deep are termed ‘neurological decompression inspiration. Commonly the pneumothorax illness’ and are covered in the second part of is small with few physical signs, but a more this paper. substantial one demonstrates the classical signs of shortness of breath, cyanosis, Gastrointestinal barotrauma reduced chest movement on and tracheal Gas normally present within the intestine shift towards the affected side, hyper- expands during decompression and may

resonant percussion note and reduced result in eructation, flatus or abdominal http://militaryhealth.bmj.com/ breath sounds. If gas escapes into the discomfort. Occasionally such colicky pleural space with each breath but is unable abdominal pain and distension with to return a tension pneumothorax results. ‘tinkling’ bowel sounds on auscultation, The danger is the resultant collapse of one, may mimic bowel obstruction, but will then both lungs. Tracheal shift is now away resolve spontaneously. If gas is swallowed from the affected side, cyanosis is profound (aerophagia) when under pressure however, and shock, unconsciousness and death it may be dangerous as more serious ensue if untreated. A simple pneumothorax gastrointestinal barotrauma may result which occurs at depth may increase in size leading to rupture of a viscus during ascent.

during decompression and effectively on October 1, 2021 by guest. Protected copyright. become a tension pneumothorax. The Conclusion diagnosis should, therefore, be suspected in This review, based on the medical section of a diver whose respiratory symptoms worsen the Royal Navy Diving Manual, represents during ascent. current philosophy on the subject within the Asymptomatic mediastinal and subcuta- Royal Navy. It is intended as both a training neous emphysema will resolve gradually and a practical aid, and has briefly covered without the need for any specific treatment. diving related illnesses which do not usually If there are troublesome symptoms then require therapeutic recompression; part II breathing 100% oxygen on the surface will of this review, to appear in a future issue of accelerate resolution of symptoms. Small this journal, will cover diving disorders that pneumothoraces can be treated just by require therapeutic recompression. Table 3.Symptoms due to decompression barotraumas. Pulmonary Mediastinal or subcutaneous Retrosternal pain, skin crepitus emphysema Pneumothorax Shortness of breath, cyanosis, collapse. Often painless Arterial gas embolus Cardiovascular collapse, neurological disturbances Gastro-intestinal Colicky abdominal pain, abdominal distension 22 Common Medical Disorders Relating To Diving Part 1 J R Army Med Corps: first published as 10.1136/jramc-149-01-03 on 1 March 2003. Downloaded from As a general rule, no diver should dive or of Diving Accidents. Undersea Medicine remain in the water if they feel unwell, and Division of the Institute of Naval Medicine any illness occurring during or after a dive has provided advice and oversight to ensure should be considered to be related to that that, despite considerable editing, this paper dive until proved otherwise. retains a faithful description of the principles of diving medicine and the problems covered Acknowledgements by the original text from which it was drawn. We are indebted to those individuals who have contributed to the medical section of References the Military Diving Manual and successive 1. The Prevention and Management of Diving copies of Institute of Naval Medicine Accidents. Institute of Naval Medicine Report. No. Reports on the Prevention and Management R988013. http://militaryhealth.bmj.com/ on October 1, 2021 by guest. Protected copyright.