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J R Army Med Corps 2005; 151: 256-263 J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

Diving

K Robinson, M Byers

with diving. This article aims to review the physics and of diving, discuss the common medical conditions that occur whilst diving, and consider the thinking in relation to aetiol- ogy and treatment. A Brief History of Diving Breath-hold diving has probably been around from before written history. Divers were reportedly used in the Trojan Wars (1194-1184 BC) to disrupt the enemy navies. Aristotle described ruptured tympan- ic membranes and ear in sponge divers, and Marco Polo wrote of pearl divers reaching depths of 27 metres. Alexander the Great is supposed to have made a dive in a primitive , Roger Bacon described men walking on the seabed in 1240, and in 1535 Guglielmo de Lorena developed the first true diving bell (3). In 1774 Freminet used a bellows to deliv- er air from the surface to a diver and Siebe Introduction developed the in 1819 (3). This It could be argued that diving is the most consisted of a copper helmet and jacket, extreme sport of all. Survival in such a which was modified in 1839 to resemble the

hostile is waterproof suit recognised and in regular use http://militaryhealth.bmj.com/ dependent on sophisticated to the present day. apparatus and an understanding of the Self-contained underwater breathing inherent risks. Diving incidents are well apparatus (SCUBA) was also developed in publicised, not least because of the the 19th century and in 1943 Jacques severe injuries that ensue, but remain an Cousteau and Emile Gagnan demonstrated uncommon occurrence. Yet despite, or the aqualung (3). perhaps because of its dangerous and challenging profile, Physics and Physiology Air is composed of approximately 21% oxy- is on the increase with more people gen and 79% . Each of these gases learning to dive each year. There are exerts a partial in proportion to on September 30, 2021 by guest. Protected copyright. currently an estimated 700,000 recre- their . At sea level man is sub- ational divers in the UK (1). ject to 1 atmosphere (101.32 kPa). Water, Diving within the military may be being denser than air, exerts a greater pres- occupational or recreational. sure per unit volume such that for each 10 Occupational diving involves a long and metres of sea water (msw) of descent adds rigorous training package designed to another atmosphere of pressure. A diving provide with the necessary Miss K Robinson, cylinder filled with compressed air will con- skills to complete their task, be it in Specialist Registrar in tain the same partial of nitrogen , mine clearance, underwater engineering and as environmental air but contain Derriford , or as a combat swimmer. It is Ministry a considerably larger volume, thus allowing a of Defence policy that diver to breath air from the tank for extend- Email: complies with Health and Safety at Work ed periods. For example a 12 litre cylinder of [email protected] guidance and with the Diving at Work air compressed to 232 will hold 2784 Regulations as far as reasonably practi- Lt Col M Byers litres of air (12 x 232). Normal air pressure cable (2). MRCGP Dip IMC DA (1 atm) = 1.01 bar, 760mmHg or 101 kPa. Diving injuries can be encountered in Dip SEM RAMC The pressure increases relating to diving barracks, on exercise and on operations 3 CS Med Regt, Gaza affect the inspired gas and also the gas filled and Medical Officers need to have an Barracks, Catterick spaces within the diver such as the , Garrison understanding of the presentation and sinuses, ears and gastrointestinal tract. The Email: [email protected] management of conditions associated K Robinson, M Byers 257 J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

Gas Laws make these changes clear. Vision underwater is altered due to the Boyle’s Law states that if refraction of light making objects seem larger remains constant, the volume of a fixed mass and closer. Light has a differential absorption of gas is inversely proportional to the in water causing loss of colour (especially absolute pressure. As pressure increases by 1 red) at depth and many diving environments atmosphere for every 10m of descent in have poor visibility due to turbid water. water, a given volume of gas will halve in Sound travels more than four times faster in volume at 2 atmospheres. At 20m below the water than in air making it much more diffi- surface (3 atmospheres) the gas will be a cult to localise sound (4). If the diver is using third of its original volume and so on. The a gas mixture containing , the pitch of converse is true on ascent. A volume of gas the voice will increase making underwater will double in volume from ascending from voice communication, with wired or wireless 10m deep to the surface. This helps to systems, almost impossible without the use explain . of expensive electronic equipment (5). Dalton’s Law states that in a mixture of Hearing acuity is reduced by around 60dB gases, the of each gas present especially in the higher frequencies, localisa- is equal to the pressure that gas would exert tion is poorer and there are the thermal and if it alone occupied the original volume pressure effects due to being under water. (Table 1). From this it can be seen that with There is decreased sensation affecting dex- every 1 atmosphere increase in pressure, terity, 2-point discrimination, vibration and although the proportions of the gases stay other functions caused by the cold, the gases the same the partial pressure increases. The used for , pressure and the protec- effects of this will be seen when decompres- tive equipment worn to survive in the envi- sion sickness is considered. ronment. Henry’s Law states that at a constant The increased density of water leads to an temperature the amount of gas that will dis- increased heat loss. Water vary o solve in a liquid is proportional to the partial between –2 to above 30 C but are usually pressure of a gas over the liquid.The amount below the body’s thermo neutral point o of gas that dissolves will also be affected by (31 C). Greater depth leads to lower temper- Bunsen’s coefficient of , time and atures and water conducts heat 25 times temperature. This is important in the theory faster than air. Peripheral vasoconstriction of sickness. occurs to maintain the core temperature, but this can cause loss of manual dexterity, and Physiological Demands of the alteration in blood flow may contribute Diving to . Protective ther- Being underwater affects many body systems mal equipment worn to survive the cold envi-

and creates increased phys- ronment causes an additional loss of dexteri- http://militaryhealth.bmj.com/ iological demands on the body.The diver has ty. to move in a medium that is more viscous than air, breathe gases at increased density, The Gases cope with an increased hydrostatic pressure, and carry heavy and bulky equipment. Nitrogen As the diver descends the hydrostatic pres- Nitrogen is an inert gas that constitutes 79% sure around his legs may increase the of air and at 1atm has a partial pressure of intrathoracic blood volume by up to 700mls. 0.79atm. It is a weak anaesthetic agent. This alters the ventilation balance Diving below 30 metres of sea water (msw) and may cause gas trapping. The increased equivalent to 4 atmos and a piN2 of 320kPa pressures in the right atrium and pulmonary will lead to a narcotic effect.This is similar to on September 30, 2021 by guest. Protected copyright. stimulates a , which, com- the effects of alcohol, gets worse with depth pounded by cutaneous vasoconstriction in and causes cognitive and manual impair- cold temperatures, causes dehydration. ment. Similar effects will occur with other inert gases including helium and hydrogen Table 1.Effects of Depth on Volume and Partial Pressures. (4). While the gas itself is not poisonous, it leads to a condition called Effects of Depth on Partial Pressures (“being narked”), which can be fatal due to the effect of this condition on decision mak- Depth Lung Volume Pressure pO2 pN2 ing. Divers can be taught to acclimatise to Surface 100% 101kPa 21.2kPa 79.8kPa the milder effects of narcosis by building up 1 atmos to deeper dives gradually and regularly. It is not thought to be a physiological adaptation 10m 50% 202kPa 42.4kPa 159.6kPa but a learned response to repeated drills. As 2 atmos nitrogen is inert it is not metabolised by the body. It does, however, enter the body tis- 20m 33% 303kPa 63.6kPa 239.4kPa sues. During a dive the amount of nitrogen 3 atmos that enters the tissues is proportional to its 30m 25% 404kPa 84.8kPa 319.2kPa partial pressure in alveolar air. Therefore, as 4 atmos the dive becomes deeper, the amount of 258 J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

nitrogen entering the tissues will be greater. exposure to lower partial pressures causes Different tissues ‘on-gas’ at different rates progressive pulmonary fibrosis. A reduction but eventually all the body tissues will of 10% of Vital Capacity associated with become saturated with nitrogen. cough and chest pain is usually reversible in On ascent (or decompression) the nitrogen a few days. Divers using elevated partial pres- will move out of the tissues into the blood sures of oxygen in their gas mixtures and per- and be eliminated by the lungs. If the ascent forming repeated or long dives calculate their is not controlled the nitrogen may form bub- Oxygen Tolerance Units over 24 hours bles within the or blood, much like the (where 1 OTU is equivalent to exposure to opening of a carbonated drink. These bub- 100% oxygen at 1atm for 1 minute), to pre- bles may cause damage to their surrounding vent . vessels or block the circulation to a tissue. Oxygen has been shown to adversely affect This manifests as decompression sickness vision by causing progressive myopic and may result in a wide array of signs and changes. In 1971 Clark and Lambertsen symptoms. demonstrated a loss of peripheral vision after breathing oxygen at 3atm for 2.5 hours. Recovery was complete after 45 minutes breathing air (6). The middle ear can also be affected by high of oxygen as demonstrated by US Navy divers breathing 100% oxygen from a closed circuit system (the ).They experienced a popping sensation in the ear and a mild conductive hearing loss and were found to have fluid in the middle ear caused by absorption of the oxygen. This spontaneously resolved (6).

Gas Choice Oxygen Recreational divers are taught to dive using Oxygen makes up 21% of air and has a par- air, but soon realise the benefits of altering tial pressure of 0.21atm at 1atm. It is vital for the gas mixture to reduce the risks of narco- life and, therefore, must be a part of a diving sis and . Divers will gas mixture. However, at higher partial pres- either carry their own gas cylinders in open sures it becomes toxic to the lungs and cen- circuit systems (Self Contained Underwater tral . The precise mechanism Breathing Apparatus SCUBA) or closed cir- of this is unknown, but is thought to involve cuit systems (“”, which utilise

a depression of cellular by the soda lime to remove exhaled carbon dioxide, http://militaryhealth.bmj.com/ production of free radicals and inactivation and then recirculate the gas adding small of enzymes (6). amounts of oxygen). Central Nervous System (CNS) toxicity Military divers use SCUBA and rebreather shows extreme variability between individu- kits, as well as surface-supplied equipment in als such that time to onset of symptoms can- which the gas is pumped to them through a not be related to a particular depth or time of long hose.The choice of gas and delivery sys- exposure. Symptoms include facial twitch- tem is task dependant. SCUBA may be used ing, nausea and vomiting, , dys- for under ship inspection tasks, self con- phoria, tinnitus and . Exercise tained closed-circuit rebreathers for mine and have been shown to hasten clearance operations where the absence of the onset of symptoms. CNS Oxygen bubbles is beneficial, and surface supplied on September 30, 2021 by guest. Protected copyright.

Toxicity can occur at a piO2 above 200kPa or systems for engineering tasks (7). Pure oxy- 2 atmospheres. The recreational diving limit gen systems can greatly increase the maxi- is set at 1.4atm, the Health and Safety mum duration of the dive but limit the depth Executive limit to 1.5atm and the maximum to around 7m. limit of 1.6atm to prevent toxicity occurring. Breathing air and oxygen at pressure caus- Chamber dives providing therapeutic oxygen es problems as outlined above. To overcome for treatment of decompression sickness or some of these problems gas mixtures such as other conditions are limited to 2.8atm. (a gas mixture that reduces the nitro- Pulmonary occurs after gen content by replacing it with oxygen) are longer duration of exposure or after high used. As the absorption of nitrogen is less this inspired partial pressures. Again individual lowers the risk of decompression illness and susceptibility varies greatly. Signs and symp- extends the diver’s time in the water. For toms often start with a tickle in the throat instance a dive to 20m on air for 35 minutes and progress onto a cough and retrosternal could be extended to 51 minutes using pain (5). Dyspnoea, crackles and wheeze Nitrox 32 without increased risk or decom- may ensue with a loss of lung Vital Capacity. pression time. Partial pressures of more than 0.8atm cause (helium, nitrogen and oxygen) is acute toxicity which leads to exudative and also used. Helium replaces some of the oxy- proliferative changes in the lung. Chronic gen and nitrogen in the mixture. Helium is K Robinson, M Byers 259 J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

an inert gas, which does not normally cause incorporate the need for high levels of phys- narcosis, and so this mixture can be used ical fitness to accomplish strenuous tasks. when diving at greater depths. Oxygen toxic- The demands on a recreational diver are ity is less of a problem as the oxygen content generally considered to be less and current- is reduced, making a gas safe to breathe at ly self-certification via a questionnaire is all depth although potentially harmful on the that is required. surface. Helium enters and leaves tissues up Poor physical fitness is a risk factor for to 2.65 times faster than nitrogen, therefore, DCS. Broome et al (1994) experimented on causing a different set of issues during pigs to show that sedentary pigs were more ascents. likely to get DCS than those that ran twice a day (9). Increased body fat was presumed to Decompression Illness (DCI) be a risk for DCS due to its slow off-gassing DCI is a term that includes decompression characteristics, but studies have not shown sickness (DCS) and arterial gas embolism this to be statistically true (10). (AGE). Both conditions are caused by gas Repetitive increases the likeli- bubbles that have either escaped due to baro- hood of getting DCS as the surface time for trama to the lung or have evolved in the tis- off-gassing is reduced, causing a build-up of sues. Data collected by the Divers Alert residual nitrogen within the body tissues. Network show that 50% of cases of DCI Both recreational and military diving follows occur within 1 hour of a dive, 90% within 6 guidelines on safe surface intervals between hours, and less than 1% present after 36 dives to reduce this risk. hours (8). Research into whether women are more or less susceptible to DCS remains inconclu- Decompression Sickness sive. The effect of the menstrual cycle on During a dive, gas dissolves in the body and DCS risk was investigated by Lee et al (11) is eliminated on ascent by the lungs. A large and showed an increased incidence of DCS amount of work has been done looking at the symptoms in the first week of the menstrual optimum rates at which to ascend after each cycle and immediately prior to menstrua- dive to maximise the efficiency of this pro- tion. This variation in distribution of DCS cess. In 1906 was com- symptoms across the menstrual cycle differs missioned by the Royal Navy to minimise further between users and non-users of the DCS among fleet divers, and published his oral contraceptive pill. work in 1908. He concluded that different Advancing age, pre-dive dehydration and compartments in the body absorb and having a patent foramen ovale are other con- release nitrogen at different rates, and that ditions thought to increase the likelihood of decompression stops should be staged to getting DCS. A patent foramen ovale (PFO) minimise the chances of decompression sick-

is a persistent embryological remnant http://militaryhealth.bmj.com/ ness. His work produced the first Royal between the two atria in the heart. It is Naval decompression tables. Although the formed by the failure of fusion of the ostium US Navy has further modified these tables, primum to the ostium secondum after birth. the basic Haldanian model is still used today PFO occur in approximately 25% of the in recreational dive tables and computers (4). population and are usually asymptomatic Decompression sickness is caused by bub- (12). An association between neurological bles that have come out of in the tis- DCS and the presence of a PFO was sues. Bubbles formed while diving on air are observed and various studies have been con- predominantly made of nitrogen and may ducted which have established that paradox- grow in size to cause arterial obstruction. ical gas emboli can occur causing neurolog- Intravascular bubbles block blood and lymph ical defects (13). Divers that present with on September 30, 2021 by guest. Protected copyright. circulation, causing ischaemia, endothelial neurological or cutaneous DCS after a non- damage and impaired waste removal. provocative dive (that is one with no other Extravascular bubbles distort and compress obvious predisposing risk factors) should be blood vessels and nerves and may also set up considered for investigation of a potential an inflammatory response activating comple- PFO. ment and coagulation pathways. It is these pathophysiological changes that create the The Dive symptoms and signs of pain, swelling, oede- The biggest risk factor with the dive is a ma, rash and . rapid ascent after a long deep dive. Being cold on ascent and on any decompression Risk Factors for DCS stops has also been shown to reduce the There are many individual factors thought to nitrogen off-gassing and, therefore, increase play a part in DCS. These can be divided DCS risk. Exercising at depth, for example into those relating to the diver, the dive, and swimming against a current, also requires post dive situation. longer decompression times to avoid DCS. The estimate the The Diver overall risk of DCS in a diver is 1 in 42000 All military divers are required to undergo dives above 30msw, but this reduces to 1 in regular ‘’ medicals (7). These 7000 if the dive is deeper than 30 msw (8). 260 Diving Medicine J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

Post dive Divers should be advised not to exercise, ascend to altitude or have a hot bath after a dive as all these factors will cause a sudden increase in off-gassing and bubble size. Types of DCS Bubbles can form and travel anywhere with- in the body and therefore DCS may mani- fest itself in a wide variety of . Traditionally these were divided into Type 1- relating to musculoskeletal pain, rashes and oedema (Figure 1), and Type 2- relating to more serious neuro- logical and cardiopulmonary symptoms. This system was often confusing to use and so is now being replaced by ‘The Descriptive Protocol’ (Table 2).This divides DCS into ‘Manifestation’ meaning the site(s) of symptoms and ‘Evolution’ to Fig 1.Cutaneous rash. assess the development of symptoms over time. Neurological and limb pain are the Treatment of DCI most common manifestations of DCS. The DCS and AGE are often indistinguishable Evolution of a symptom or sign may be pro- in their manifestations and the treatments gressive, static, spontaneously improving, or are the same in the early stabilising phases. relapsing, and reinforces the important principle of repeated examinations in Initial Treatment patients with DCS. Management of DCI should start by assess- ment and management of airway, breathing Table 2.Decompression Illness – Descriptive protocol. and circulation. In addition 100% oxygen is Evolution Progressive, Static, Relapsing, Spontaneously administered via a tight fitting mask. The benefits of oxygen have been Improving shown in several studies, (Divers Alert Manifestation Pain: Limb, Girdle Network 1996). Divers who received oxy- gen prior to arriving at a recompression Neurological: Any symptom related to neurological chamber were statistically more likely to deficit have an improved clinical condition (8). http://militaryhealth.bmj.com/ Audiovestibular:Vertigo,Tinnitus, nystagmus. As dehydration is usually a feature of the May mimic inner ear damage disease, rehydration should be commenced early, either orally or intravenously. Pulmonary: Chest pain, cough, haemoptysis, dys Crystalloids are preferred when intravenous pnoea. Maybe due to AGE rehydration is required (15). Analgesics may Cutaneous: Itching, erythematous or marbling mask the disease process and nitrous oxide rash (present in entonox) should never be used, as it is highly soluble and will diffuse into Lymphatic:Tender lymph nodes, oedema any gas bubbles exacerbating the disease. Care should also be taken to lift an

Constitutional: Headache, fatigue, general malaise on September 30, 2021 by guest. Protected copyright. immersed diver in a horizontal position as a Depth,Type, Describes sudden loss of the hydrostatic pressure from Duration around a cold diver may induce hypoten- sion and loss of consciousness if vertical. AGE Traditionally patients were placed in the left Arterial gas embolus (AGE) originates decubitus head down position but due to from alveolar barotrauma when quickly concerns of worsening cerebral oedema, the expanding air ruptures the alveolar diver is now kept horizontal and supine. parenchyma and gas enters the pulmonary Patients must be transferred to a recom- venous system. Bubbles are delivered to the pression chamber as quickly as possible, but left side of the heart and from here to the be aware that if a helicopter is to be used, cerebral circulation. If bubbles block the then the crew must fly at low level (less than circulation, irreversible damage to nervous 300m) if possible to avoid exacerbating the tissue may occur within 10 minutes. problem. Symptoms appear suddenly upon surfacing and may include confusion, vertigo, motor Recompression or sensory deficits, frothy sputum, , Recompression provides definitive therapy loss of consciousness or arrest. There may and is best conducted in a purpose built be associated pneumothorax, pneumome- chamber under the supervision of a Diving diastinum or subcutaneous emphysema. Medicine Specialist (Figure 2). Recom- K Robinson, M Byers 261 J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

cidated, but the infusion should start as early as possible after the initial insult and continue for 24-48hrs. Patients with minor symptoms (limb pain or skin manifestations) should not fly for 24 hours or return to diving for 48 hours (18). If ever in doubt a diving medicine specialist should be contacted Barotrauma Barotrauma is trauma caused by pressure in any gas filled space. Boyles Law shows that trapped gas will be compressed on Fig 2. Recompression chamber. descent and will expand on ascent. If this pression is thought to reduce the size of the gas is trapped in a body space barotrauma gas bubbles, and hyperbaric oxygen pro- may occur to the surrounding structures. It motes absorption of the bubbles and can be difficult sometimes to differentiate increases tissue oxygenation. between the signs and symptoms of baro- Initially casualties are compressed to an traumas on ascent and DCS. If this is the equivalent depth of 18msw on 100% oxy- case it is safer to treat for DCS while fur- gen and then reassessed. Treatment contin- ther tests are carried out. ues according to the treatment recompres- Otobarotrauma. The ears are the site sion protocols. At 18msw (2.8 atmospheres) most commonly affected by barotrauma. it is possible to see oxygen toxicity in the Divers manage this by equalisation of air patient, as previously described, although pressure in the middle ear via the eustachi- this is usually easily managed. Patients an tubes. On descent the diver equalises the require careful monitoring and constant middle ear pressure to the ambient pres- attention. sure. If the eustachian tube is blocked, pre- There are many different protocols in venting equalisation, the lining of the mid- existence, but their aim is to compress the dle ear can and blood vessels dilate bubbles to a smaller size and administer and rupture. The tympanic membrane will hyperbaric oxygen, which speeds up gas become retracted and eventually rupture. elimination and improves oxygenation to Otoscopic examination of the tympanic ischaemic tissues, relieving clinical symp- membrane after barotrauma shows these toms and preventing secondary damage. epithelial changes and is graded 1-5 in The main treatment tables used in the UK severity with 5 equalling rupture.Tympanic membrane rupture normally heals after 6-8 are derived from the Royal Navy, the US http://militaryhealth.bmj.com/ Navy, and diving companies such as weeks. Rarely middle ear barotrauma can Comex. The choice of table may depend on cause facial nerve palsy due to compromise the facility preference, the gas mixture used of its vascular supply.This may be confused and the depth of the dive. Treatments may with DCS but usually resolves 1-2 hours need to be repeated over many days to after decompression of the middle ear. achieve complete resolution of symptoms. Outer ear barotraumas can also occur Various other adjuncts to treatment have on descent, commonly caused by wax in been proposed. Aspirin was introduced in the ear canal, or too tight a hood.These will the 1960’s by the French after they noticed resolve on removal of the obstruction. rouleaux formation in the blood. This Inner ear barotrauma is a more serious appearance is now thought to be due to condition, but also less common. It can be on September 30, 2021 by guest. Protected copyright. dehydration and as aspirin may also pro- caused as a result of middle ear barotrauma voke or sustain haemorrhage into central or due to the diver’s efforts at middle ear nervous system lesions, it is not routinely equalisation. Increased middle ear pressure used (6). Non steroidal anti-inflammatory causes either the round or oval windows to drugs have been shown to improve relief of rupture producing vertigo, tinnitus, vomit- symptoms and an Australian randomised ing, and deafness. Round window rupture controlled trial showed a reduction in may require , should be considered chamber episodes required to achieve a surgical emergency, and will probably symptom resolution (19). prevent future diving. High dose steroids have been suggested as Sinus Barotrauma occurs if the ostia a way of reducing oedema, and are used in are blocked before or during a dive, for some centres in cases of spinal cord DCS example due to a cold. If the sinus pres- but there is concern that they may reduce sures are not equalised the mucosa may the body’s tolerance to high partial pres- swell and haemorrhage, leading to pain and sures of oxygen (6).There is a growing body epistaxis. of evidence that intravenous lignocaine has Pulmonary barotrauma occurs on ascent a role to play in the treatment of cerebral due to expanding gas being unable to arterial gas embolism (15, 16). The exact escape through the airways.This can be due mechanism of action has not been fully elu- to the diver holding his breath, a mucus 262 Diving Medicine J R Army Med Corps: first published as 10.1136/jramc-151-04-07 on 1 December 2005. Downloaded from

plug or bronchospasm. The gas may rup- References ture the alveolar membrane and will enter 1. Jagger RG, Jackson SJ, Jagger DC. In at the deep the pulmonary veins causing an arterial gas end–an insight into and related dental embolism or enter the pleural cavity caus- problems for the GDP. Br Dent J 1997; 183(10):380-2. ing a pneumothorax, a pneumomedi- 2. Defence Council Instructions Joint Service April astinum or subcutaneous emphysema. 2003 p2 BR2806 UK Military Diving Manual 1993 Treatment is by conventional , but Volume 1. recompression may be required for severe 3. Kindwall EP. A short History of Diving and Diving Medicine; in Bove and Davis Diving Medicine 4th persistent emphysema. Edn, Saunders; Philidelphia:2004. Barotrauma may also occur in teeth, in 4. Diving and Review for the gastrointestinal tract, from the mask . Jolie Bookspan. PhD 2000 p31. (which can cause conjunctival bleeding and 5. 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Ann Emerg Med 1997;29(2):284-6. in a hostile environment. Environmental 18 Benton PJ. Resumption of diving after illness or conditions and the effects of pressure on injury. J R Nav Med Serv 1998;84(1):14-8. tissues and inspired gases produce a range 19 Bennett M, Mitchell S, Dominguez A. Adjunctive on September 30, 2021 by guest. Protected copyright. of conditions that, although not unique to treatment of decompression illness with a non- this environment, are associated with steroidal anti-inflammatory drug (tenoxicam) reduces compression requirements. Undersea Hyperb underwater work and recreation. The mili- Med 2003;30(3):195-205. tary community has a significant popula- tion that works and plays underwater and Further Reading who are at risk of developing any of the dis- C Edmonds, CJ Lowry, J Pennfeather and R Walker. eases described above. 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