Diving medicine: A comprehensive review

As a primary care physician, you may be asked to assess the eligibility of a potential diver. A thorough evaluation can help you determine a candidate's physical, mental, and emotional fitness.

More than 3 million people dive for recreation or sport in the United States, and more than 250,000 new divers are certified annually. [1] Primary care physicians are frequently involved in examining scuba divers, both to treat diving-related injuries and to determine fitness to pursue training or continue diving.

As a branch of medical science, diving medicine is primarily concerned with the effects of changes in pressure on the human body. A basic understanding of the phases of diving is necessary background for a physician who is called on to evaluate a person's fitness to dive.

THE 3 PHASES OF DIVING

To enhance physiologic insight and aid diagnosis of potential problems, think of the dive as comprising 3 phases. These may be called the descent phase, time exploring at depth, and the ascent phase.

The descent

During descent the body is exposed to a linear increase in ambient pressure. The equivalent of atmospheric pressure at sea level is produced by 33 feet of seawater (FSW). The pressure at a depth of 33 FSW (10 meters) is thus 2 atmospheres absolute (ATA), or 2 ATA, twice what it is on the surface. At 66 FSW (20 meters), ambient pressure is 3 ATA, and so forth. Since the diver's body is largely composed of water, the increasing pressure primarily affects air-filled spaces such as the sinuses, middle ears, and lungs, which can cause significant problems if not equalized to ambient pressure (see Figure 1, page 21).

Sir Robert Boyle noted centuries ago that the volume of a given amount of gas is inversely proportional to the ambient pressure, and thus the higher the ambient pressure, the smaller the volume of a gas. Unequalized air spaces in the diver's body become smaller in volume with descent, which may result in barotrauma to the sinuses and middle ear--commonly referred to as a squeeze. For a squeeze to occur, a space must be filled with air, subjected to ambient pressure changes, lined by a membrane, and relatively enclosed. A cavity must also have rigid walls in order to suffer a squeeze.

A middle ear squeeze is one of the most common reasons for a diver to seek medical attention. The middle ear meets all the criteria required for barotrauma and relies only on a small, collapsible eustachian tube for pressure equalization. In contrast, the lungs are in constant free communication with air delivered at ambient pressure through a demand scuba regulator and are essentially never subjected to a squeeze.

When a squeeze occurs, surrounding tissues are pulled inward in an attempt to fill the void and equalize the pressure. The mucosa is stretched and becomes painful or bloody as nerves and capillaries are damaged. Continuous equalization of pressure during descent, usually accomplished by performing a Valsalva's maneuver (gently attempting to exhale through the nose while occluding the nares) or by swallowing or yawning, can help prevent these injuries. Air flows into the middle ear space, equalizing pressure on both sides of the tympanic membrane (TM).

Symptoms of middle ear barotrauma include a sensation of fullness in the ear, conductive hearing loss, vertigo, or occasional tinnitus. A tuning fork will help differentiate between conductive and a neurosensory hearing loss. Otoscopy reveals vascular congestion and a retracted TM.

In most cases, treatment includes decongestants, antibiotics (if perforation. has occurred, do not instill ear drops), and a follow-up examination before the next dive. Suspect an inner ear injury or round or oval window blowout when hearing loss, tinnitus, or fullness of the ear is present but without visible signs of ear disease. Consultation with an otolaryngologist is required if you see evidence of hemorrhage into the middle ear, TM rupture, or injury to the inner ear (persistent vertigo, tinnitus, nystagmus, or neurosensory hearing loss) causing a round or oval window rupture.

Fortunately rare, alternobaric vertigo is an inner ear phenomenon that can occur when rapid pressure changes are transmitted to the inner ear. Unequal vestibular stimulation and the resultant vertigo usually occur when one ear is cleared with a forceful Valsalva's maneuver and the other is not. Vertigo can be lethal for a diver when in deep, murky water. As long as the diver controls the feeling of panic or avoids vomiting into the breathing apparatus, the problem is usually transient. The same can be said for caloric vertigo, occasionally produced when water enters only one external auditory canal.

Exploring at depth

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During descent and while at depth, divers' tissues absorb gas from the mixture they breathe. This gas absorption is governed by Dalton's law of partial pressures, which states that the total pressure of a gas mixture is equal to the sum of the partial pressures of the individual gases, and Henry's law, which states that the quantity of a gas dissolved in a liquid is directly proportional to the partial pressure of that gas. The gases of most concern for diving are oxygen and nitrogen. As the total pressure increases with depth, so must the partial pressure of each gas. At sufficient depth, these normally harmless gases may become toxic.

Given the relatively short exposure period involved in recreational diving, the most important effect of oxygen at depth is upon the CNS. Oxygen seizures may be produced by oxygen partial pressures greater than 3.0 ATA but may also occur at pressures as low as 1.6 ATA. Seizures in a hyperbaric chamber are essentially benign and can be treated by switching the chamber's gas from 100% oxygen to 21% oxygen, the percentage found in air.

For a recreational diver, however, seizures are almost universally fatal. Often a warning prodrome will signal impending seizure activity and the urgent need to quickly lower the oxygen partial pressure. The warning symptoms are best remembered by the acronym VENTID-C (see Table 1).

Nitrogen narcosis describes the narcotic effect of elevated nitrogen partial pressure on the CNS. The onset of symptoms, usually at about 100 FSW, is gradual, dose-related, and similar to ethanol intoxication. The associated loss of judgment, when combined with other high-risk activities such as cave- or wreck-diving, can result in accidental drowning, even in experienced divers.

Despite its narcotic effects, nitrogen is considered metabolically inert because it is not utilized by the body, as compared with oxygen, which is metabolically active. At elevated partial pressures, tissues take up the excess nitrogen until a new equilibrium is attained and the tissues become saturated with nitrogen at the new pressure. The time required to reach equilibrium differs with the type of tissue but can range from a few minutes to many hours. What goes into the tissues during descent and time at depth must eventually come out.

The ascent

The majority of medical problems encountered during ascent are associated with bubble formation and expansion. Inert gases previously dissolved in solution (tissue) at elevated ambient pressure must emerge from the tissue as pressure is reduced. This process continues until the partial pressure of the inert gas in the tissue achieves equilibrium during ascent with decreasing ambient pressure. If ascent is too rapid, the dissolved gas will form bubbles in blood or tissue.

The analogy of a well-shaken carbonated beverage is commonly used. Few bubbles form as long as the pressure is released slowly. A sudden release of pressure, however, results in an almost explosive formation of bubbles. Intravascular and interstitial bubbles cause mechanical damage, form emboli, and activate the complement system. If significant bubble formation occurs, it will usually do so in the low pressure venous system, in major joints, and in neurologic tissue. For recreational divers breathing air, the bubbles contain mostly nitrogen and can produce a group of neurologic symptoms referred to as decompression sickness (DCS) or the bends--the latter term deriving from the bent-over posture assumed by divers with joint pain.

DCS type I is characterized by unilateral joint pain or transient skin symptoms involving mild rashes or pruritus. DCS type II is more serious and involves dermatologic, neurologic, pulmonary or cardiac symptoms. Neurologic symptoms are by far the most common. Patients may experience a variety of them, including patchy paresthesias, constricting sensation around the abdomen or thorax, extreme fatigue, slow mentation, ataxia, paralysis, urinary retention, blindness, or coma.

Patients presenting with pulmonary and cardiopulmonary symptoms have very high mortality rates. Pulmonary DCS, caused by massive amounts of lung bubbles, produces symptoms that include cough, hemoptysis, and dyspnea. Cardiopulmonary DCS causes right-sided heart congestion and asphyxia.

The therapeutic mainstay for all types of DCS is recompression, which consists of placing the diver in a chamber pressurized to the equivalent of 60 FSW and giving 100% oxygen via face mask. The presumed mechanism of action is the compression of the bubbles to a smaller size or back into solution while enhancing nitrogen release from tissues by the breathing of pure oxygen.

Recompression treatment schedules for DCS type I are shorter than those for DCS type II. In addition to recompression therapy, various adjunct therapies are currently being investigated. Intravenous hydration is almost universally recommended, as is inhalation of 100% oxygen during transport to the recompression chamber.

One of the most feared complications from too rapid an ascent is an arterial gas embolism (AGE). This condition usually develops either during a panicked ascent when divers hold their breath, or with certain pathologic conditions in which air is trapped within the pulmonary system, resulting in pulmonary overinflation and alveolar rupture. Air is thus free to travel to the heart or brain.

AGE in the cerebral circulation can mimic symptoms of a thromboembolic stroke and should be suspected in any diver with new neurologic symptoms during or soon after a dive. Well over 90% of AGE symptoms appear within 10 minutes of surfacing. If neurologic symptoms develop during this time, treatment should be provided immediately for presumed AGE. This consists of recompression to mechanically compress the bubble, followed by gradual decompression to sea level. These complications can be avoided by obeying the rules of slow ascent and making a stop on ascent at 10 feet for 3 minutes.

FITNESS_FOR DIVING

The underwater environment is unique because those who enter it require the use of a life-support system. The physiologic changes that occur during diving can serve as a guide for the primary care physician when evaluating recreational divers, since diving-related medical problems often have a characteristic pathophysiology, differential diagnosis, and treatment. [2]

While commercial, military, and scientific divers are generally examined and certified according to standards set forth by the employer or agency involved, recreational divers often decide for themselves whether they can dive safely. A medical examination before diving instruction begins is not always mandatory, and no rules exist to define the training or experience of the examining physician. The decision to resume diving after illness or injury is made by divers themselves or by physicians who may lack experience in diving medicine.

In general, a thorough medical history should ascertain the reason for diving, whether for sport, commercial, or research purposes. The interview with a prospective diver should include the following questions:

* Does the prospective diver have any prior diving experience?

* How often and where will the diving occur?

* Does the prospective diver have a history of air embolism, DCS, barotrauma, vertigo, near drowning, oxygen toxicity, or prior disqualification from diving?

Senior divers

The age of the potential diver is an important consideration. Older divers appear to have an increased risk of DCS, which may be due to tissue hypoperfusion from advancing atherosclerosis or more subtle physiologic changes. Although no age limit exists for recreational diving, any person continuing to dive or desiring to participate in initial diver training after age 40 should be scrutinized closely for medical problems that might preclude diving. Senior divers are generally advised to progressively shorten times spent at depth with advancing age.

Junior divers

Despite the fact that some certifying agencies allow for junior scuba certification at age 12, several factors must be considered when qualifying a child or adolescent for scuba certification. Before children begin diving, their physical, intellectual, mental, and emotional readiness to dive should be evaluated. To wear properly fitted, standard dive gear, the young diving candidate should weigh at least 45 kg and be 150 cm tall. Equipment intended for adults may pose a serious hazard. Junior divers must have the physical strength necessary to respond to the extreme environmental conditions to which they may be exposed and to help a diving partner in trouble.

Young divers must also be able to understand the dynamics of compressed gas and the physiology of scuba diving, including its potential hazards. Children should possess the emotional maturity to cope with the stress of emergencies. Interest in diving should be personal and sincere and not the result of coercion by an overly enthusiastic parent.

The principles of basic pediatric physiology can be extrapolated to diving. Children's bodies cool faster than those of adults so they need well-fitted suits for adequate thermal protection. Divers with low body mass have greater buoyancy problems since subtle changes in suit or tank buoyancy exert more dramatic effects. Children succumb to dehydration secondary to evaporative fluid losses faster than adults because of an increased surface area-to-volume relationship. Tetanus and other immunizations should be current. The risk of damage to developing epiphy-seal plates from the effects of pressure and bubble formation is unknown. Although no data on gas uptake and elimination suggest a risk of damage to young divers, most agencies require a minimum age of 12 years for supervised scuba certification and 15 years for full scuba certification.

Physical conditioning and weight

Evaluation of general physical fitness is an essential part of diving-candidate assessment. Although recreational diving is often deceptively easy, the potential for any diver to get caught in an unexpected current or heavy surge always exists, necessitating a certain degree of muscular and cardiopulmonary reserve for survival. Diving can require vigorous physical activity such as carrying equipment (tanks), swimming with full gear, and climbing dive station ladders. All divers should maintain a certain level of physical fitness in order to manage unpredictable changes in water conditions.

Obesity is an important consideration because adipose tissue absorbs nitrogen gas more readily, retains it longer, and releases it more slowly, placing obese divers at greater risk for DCS. Any diving candidate deemed unfit by standards of body mass index should consider a weight-loss regimen and an exercise program that includes aerobic conditioning and strength training prior to diving.

Disqualifications for female divers

Although anecdotal evidence supports favorable outcomes in the pregnancies of women who, not knowing they were pregnant, went scuba diving during the first trimester, the potential risk makes pregnancy an absolute disqualification. Adequate information about the rates at which fetal tissues load and unload nitrogen is unavailable. Uterine flow dynamics may allow gas emboli to accumulate in the uterine circulatory beds, obliterating uterine blood flow and effective fetal gas exchange. Pregnant women should not dive, and female divers who are actively trying to conceive should stop diving.

DIVER EVALUATION SYSTEM BY SYSTEM

Although fitness for diving must be determined on an individual basis, a list of disqualifying conditions can be used as a guide for screening divers and treating diving-related conditions. Diving candidates with pathologic processes that make autoinflation impossible and predispose them to possible barotrauma should be excluded from diving. Potential divers suffering from conditions that would place them at risk of decompression illness (DCI), AGE or DCS should also be disqualified.

Ophthalmology

As a liquid, the eye is incompressible and relatively unaffected by pressure changes. Divers must have adequate visual acuity and visual fields for safe diving practice and underwater orientation. Unfortunately visibility is markedly diminished in most diving environments. Near vision should be adequate for reading devices such as pressure gauges and watches. Sight acceptable for obtaining a driver's license is a standard for distance vision. Soft contact lenses, prescription-ground diving mask lenses, or corrective lenses bonded into the face-mask surface are the preferred choices for underwater refractive correction. Symptoms related to bubble formation have been reported with hard contact lenses and rigid gas-permeable contact lenses.

The diver's ophthalmologist should be consulted before diving is resumed after any eye surgery. Corneal incisions in radial keratotomy (RK) may rupture from the pressure differential across the cornea, making RK a relative contraindication to diving. Orbital implants can cause a pressure-induced collapse of the orbit, disqualifying candidates who have undergone any enucleation procedure.

Otorhinolaryngology

The key to preventing barotrauma (squeezes of the middle ear and sinuses) is adequate patient education about pressure equilibration techniques (autoinflation). Those who cannot equalize their ears and sinuses should not dive. A history of frequent ear or sinus problems while flying should prompt further investigation.

If the pressure differential exceeds 90 mm Hg during descent, the eustachian tube clamps down on itself, making further attempts at equalization futile. The importance of equalization techniques as divers descend in the water column should be stressed, with particular emphasis on equalizing the pressure in their middle ears and ascending a few feet until autoinflation is possible.

Techniques to equalize pressure in the middle ear are fairly intuitive. Performing Valsalva's maneuver, especially forcefully is not without the risk of round window rupture. The technique of contracting the levator and veli palatini and tensor veli palatini muscles through yawning or swallowing is safer and more effective. This method opens the compressed eustachian tubes and allows autoinflation of the middle ears.

First developed by German dive bomber pilots at the beginning of World War II, the Frenzel maneuver is a safe, effective method of middle ear equalization. With the nose, mouth, and glottis closed, the back of the tongue is thrust against the soft palate, creating a compressed pocket of air and forcing it up into a now opened eustachian tube.

Potential divers should be educated about these techniques, and their ability to autoinflate their middle ears should be assessed. If TM mobility is not clinically obvious, office tympanometry is often indicated.

Any obstruction of the external ear canal could create an unvented air space lateral to the TM, causing an external ear squeeze as the ambient water pressure increases during descent. Divers with a large plug of ear wax, significant otitis externa, obstructive bony exostoses (found commonly in cold water swimmers), or congenital or acquired stenoses should not dive until the underlying obstruction is resolved. Ear plugs or tight-fitting hoods that could potentially cause an external ear squeeze should be avoided. Patients with residual inner ear dysfunction following inner ear DCS, Meniere's disease, or other recurrent vertiginous condition should not dive, since diving could invariably confuse the diagnosis of DCS or AGE.

Normal nasal function is required for adequate sinus ventilation since the sinuses drain through various ostia in the nasopharynx. Generally any abnormality in the nose can result in failure to properly ventilate the sinuses, causing either a frontal (the most common), ethmoid, or maxillary sinus squeeze. Mucosal abnormalities resulting from an infection, inflammation, or allergy are the most common and should temporarily restrict diving activity until they have been resolved. Common decongestants, especially topical oxymetazoline, are often effective if used appropriately. Prolonged daily use should be regarded with caution, however, because of the risk of habituation and rebound congestion. Anatomic obstructions such as a deviated nasal septum, nasal polyps, other nasal masses, and chronic sinusitis should all be evaluated and properly treated by an otolaryngologist before clearance is given for diving.

Psychiatry

Divers need to be mature, emotionally stable, and capable of good judgment. Diagnoses of concern in potential divers include severe claustrophobia, suicidality psychosis, severe anxiety and severe depression. The comprehensive prediving evaluation should include an assessment of a candidate's psychological suitability for scuba diving.

The interview should include questions about the patient's motivation for diving, number and nature of emergency department visits, previous experience with aquatic sports, history of psychiatric diagnoses and hospitalizations, use of psychotropic medication, and arrests for drug or alcohol use. The Cut down, Annoyed, Guilty Eye-opener (CAGE) screening questionnaire for alcoholism should also be incorporated into the discussion. A history of patients' responses to stressful situations and of hyperventilation or panic attacks is important, since panic is the single biggest killer of sport scuba divers. These particular questions can be useful in identifying a diving candidate who is pressured into diving by an overzealous friend or spouse. Psychotropic medication use should disqualify prospective divers since these compounds can cause somnolence, which enhances the effects of nitrogen narcosis while diving, or provoke extrapyramidal crises that could incapacitate a diver under water.

Pulmonology

Candidates with pulmonary conditions that increase the risk of air becoming trapped during ascent must be excluded from diver training. Trapped air predisposes to pulmonary overinflation syndromes (POIS), which lead to life-threatening cerebral AGE or pulmonary barotrauma like pneumothoraces, pneumomediastinum, pneumopericardium, and subcutaneous emphysema.

All patients with asthma, even those who are currently asymptomatic, generally have some degree of inflammation of the bronchial mucosa which can cause a pulmonary overpressure accident. Common triggers of asthma that are applicable to diving include exertion, cold or dry air, extremes of emotion, and irritant inhalants. Any of these conditions could be disastrous to people with asthma.

Recently, a workshop published by the Undersea and Hyperbaric Medical Society (UHMS) concluded that a person with normal resting and postexertional pulmonary function testing (forced expiratory volume in 1 second greater than 75% of predicted value) is not at risk when diving. The UHMS recommends that acute asthma be considered an absolute contraindication to diving, while chronic asthma with adequate lung function not be designated a contraindication. An asthma patient should not dive if medication was used within the previous 48 hours.

A history of spontaneous pneumothorax is considered an absolute disqualification for diving because of the high risk of recurrence (50% by some reports), even without the pressure changes encountered in diving. This condition most commonly affects healthy, thin, male smokers in their third to fifth decades. It theoretically results from the rupture of an undetectable apical emphysematous bleb, causing tension pneumothorax during ascent. A history of traumatic hemopneumothorax or thoracotomy is controversial regarding fitness for diving.

Any active pulmonary infections--including tuberculosis, mycotic infections, bronchitis, or pneumonitis--or sequelae such as fibrosis, cavitation, emphysema, or calcifications that obstruct bronchi are considered at least temporary disqualifications from diving. Congenital pulmonary defects like cysts, blebs, or emphysema also temporarily restrict a person from diving.

Cigarette smoking decreases cardiopulmonary reserve, increases the risk of mucous plug formation and bronchospasm-induced local air trapping, causes nasal irritation interfering with sinus and ear autoinflation and ventilation, and increases the risk of coronary artery disease (CAD). All divers should understand this information and avoid smoking. A baseline screening chest film before diver training is recommended in candidates with any history of pulmonary disorders or cigarette use.

Cardiology

The underwater environment affects the physiology of the cardiovascular system in unique ways. Immersion and cold diuresis place divers at risk of dehydration and could potentially stress those whose underlying cardiac reserve has become diminished. Certain cardiovascular conditions can produce sudden incapacitation without warning, and drowning or pulmonary barotrauma may ensue if such an emergency occurs under water.

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All potential divers should have adequate exercise tolerance to survive unexpected changes in current, entanglement, threatening marine and ventricular septal defects can be cleared for diving only after evaluation by a cardiologist and a pulmonologist. Diving may be allowed for patients with mitral valve prolapse only if they are totally asymptomatic and not taking medications. Those with first degree and Mobitz type I atrioventricular block may be cleared for diving only if a full cardiac evaluation with EST is normal. Third-degree or complete heart block and Mobitz type II block disqualifies patients from diving.

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Patients with right bundle branch block may be cleared to dive after cardiac evaluation with EST. Those with Wolff-Parkinson-White syndrome are unfit for diving, unless catheter ablation and a postablation electrophysiologic study are negative. Patients with certain valvular diseases, such as mitral regurgitation and aortic insufficiency, may be cleared for diving only if they are asymptomatic and without left ventricular hypertrophy or left ventricular dilation on echocardiography. Any degree of aortic or mitral stenosis is a disqualification from diving. Arteriosclerotic disease or a history of intermittent claudication could limit exercise tolerance and are contraindicated. A pacemaker also excludes potential divers. Idiopathic hypertrophic subaortic stenosis is an absolute contraindication to diving.

Neurology

A complete neurologic examination should be performed on all potential divers and used as a baseline for future comparison. Certain neurologic conditions such as demyelinating disorders, peripheral neuropathies, and degenerative nervous system disorders may confuse the diagnosis of DCS or AGE and exclude candidates from diving. A history of stroke or transient ischemic attacks also eliminates potential divers since local cerebral hypoperfusion makes serious CNS DCS more likely.

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Other neurologic conditions should be addressed on a case-by-case basis. Various complaints may mimic DCS or AGE and interfere with diving safety. Severe or refractory migraines with any neurologic sequelae would disqualify would-be divers. In addition, decompression is a known trigger for migraine cephalgia. Head injuries and traumatic brain injury may exclude diving candidates, depending on the severity of the injury, the amount of amnesia, and EEG results in terms of the likelihood of further neurologic sequelae.

Seizure disorders disqualify divers because of the possibility of drowning and the known periodic breath-holding during the tonic/clonic phases, which could place a diver at risk for POIS and AGE. Patients who have had seizures should only be cleared for diving if the seizures meet the following criteria: they occurred only in childhood (and were febrile seizures that did not result in an abnormal neurologic examination, did not last more than 15 minutes, were not focal seizures or associated with transient or permanent neurologic deficit, and did not occur in a family with a history of nonfebrile seizures); the seizures occurred in the neonatal period without sequelae; the seizures were secondary to sepsis or meningitis without sequelae; or the seizures were secondary to drug ingestion or breath-holding spells.

Clearing a person to resume diving after suffering from DCS or AGE on a previous dive is controversial. The consensus is that if the initial neurologic deficit completely resolved itself within the first 24 hours with or without recompression therapy, irreversible nerve cell damage may not have occurred. Even in this setting, however, diving after neurologic DCI may not be recommended because of the increased risk of recurrence. Furthermore, the existence of persistent neurologic deficits indicates some degree of irreversible damage to those areas of the body that may be selectively vulnerable to further damage under circumstances of decreased blood flow

Hematology

Polycythemia or leukemia is disqualifying because impaired tissue perfusion may inhibit gas uptake and release, resulting in DCS. Sickle cell disease and trait are relative contraindications given the risk of breathing hypoxic gas mixtures. Patients in a hypercoagulable state generally should not dive, and those receiving anticoagulant therapy but wish to dive should be advised about the possibility of bleeding.

Endocrinology

In general, type 1 diabetes mellitus is a disqualification for diving since an insulin reaction underwater and subsequent hypoglycemia could result in unconsciousness and drowning. In addition, the small vessel disease secondary to diabetes may increase the risk of DCS because of the impaired release of gas from bodily tissues. Patients whose type 2 diabetes is controlled with diet or oral hypoglycemic drugs and who have no significant history of hypoglycemic episodes are generally cleared to dive.

Gastroenterology

Absolute contraindications to diving relevant to the GI tract include conditions that cause the trapping of air from gas expansion during ascent and that increase the risk of vomiting underwater. Relative contraindications include transient infectious or inflammatory conditions that may predispose divers to diarrhea or emesis and subsequent dehydration, placing them at risk for DCS and other possible adverse sequelae because their bodily tissues cannot readily release gas.

Divers may occasionally experience abdominal pain during ascent because of gas expansion in the stomach or intestines. This expansion is caused by the generation of gas in the intestines during a dive or more commonly by the swallowing of air (aerophagia). Although these pockets of gas will usually work their way out of the system through the mouth or anus, the pockets could expand, resulting in enteric distention. In this case, ascent should be halted and the diver should descend to depth of relief and attempt to ventilate. Most intestinal gas expansion can be avoided by not diving with an upset stomach, forgoing foods that are likely to produce intestinal gas, and minimizing the swallowing of air during a dive by avoiding a steep head-down angle during descent.

Musculoskeletal

Because symptoms of type I or musculoskeletal DCS include joint pain, any preexisting musculoskeletal problem that could confuse the diagnosis of DCS should be carefully evaluated and discussed with the diving candidate. Patients with any musculoskeletal injury should not be cleared for diving until the injury has healed enough to permit a full range of motion and strength without residual pain. A limited range of motion could impair ability to perform in diving emergencies or confuse the diagnosis of type 1 DCS.

Scoliosis need not be an absolute disqualification, but divers must demonstrate normal pulmonary function and the curvature should not be so severe as to place them at risk for further spine trauma from straps and heavy compressed air tanks. A diver with aseptic bone necrosis, whether related to previous diving with dysbaric osteonecrosis or resulting from other causes, must be aware of the increased risk of progression due to compressed gas diving. Although dysbaric osteonecrosis usually occurs in working saturation divers, the advent of mixed-gas diving among sport divers might place them in jeopardy as well. Although a handicap such as blindness, deafness, amputation, or paraplegia usually precludes diving, scuba certification courses for the handicapped are available.

Dermatology

Sunburn is the most common problem encountered by sport scuba divers in warm climates. The examining physician can minimize the likelihood of sunburn by evaluating the diver's skin type and making recommendations regarding photoprotection. At the initial assessment of any diver, the patient should completely disrobe and be inspected thoroughly for signs of skin cancer.

Patients with systemic lupus erythematosus or dermatomyositis should not dive since the photosensitivity and joint pain resulting from these disorders can be exacerbated by a diving environment and confuse the diagnosis of DCS. Severe cystic acne and hidradenitis suppurativa are worsened by heat, occlusion, and mechanical trauma and should be controlled prior to clearance for diving. Allergic contact dermatitis associated with the rubber in a diving suit is often caused by the fabric dye or the accelerator used in the manufacture of the suit.

Gynecology

Menstruation does not restrict a woman from diving. Oral contraceptive (OC) use also does not appear to be a contraindication. Although OCs are known to increase the risk of spontaneous thrombotic events 3-fold, no case reports suggest they increase the likelihood of DCS. Intrauterine devices are safe for use. Women should not resume diving for at least 1 month after a routine vaginal delivery. Following a cesarean section, 8 to 12 weeks of recovery are recommended prior to returning to diving activities. Tampons, diaphragms, caps, and sponges in the vagina pose no problem during diving. Breast implants are safe and will not rupture since they behave according to fluid dynamics, not gas laws.

MEDICATIONS AND DIVING

Some medications and the underlying disease they are used to treat can both disqualify a candidate from diving. Physicians must determine on a case-by-case basis when diving eligibility is affected. The possible effect of a medication's sedative properties on performance in the water should be considered in making a decision (see Table 2, page 51).

FINAL CONSIDERATIONS

A screening questionnaire can be helpful in determining a candidate's fitness for diving (see "Recommended medical history screening questionnaire for divers," page 52). Unfortunately, people regularly dive when they should not. Patients should understand the pathophysiology of a given condition once a diagnosis has been made, as well as the rationale for why a condition places them at increased risk for injury while diving. After discussing the risks with the patient, a physician can ask the diver to sign a statement explaining that he or she understands and accepts the increased liability. Alternatively, the patient is free to consult another physician for a second opinion. Physicians can be a valuable resource to their patients and provide the Divers Alert Network emergency line number--(919) 684-8111--to all potential divers, so that emergency recompression can be arranged in the event that it should be necessary.

ARTICLE CONTRIBUTORS

CONSTANTINE LAN FOTOPOULOUS, MD, is a LT, MC, USN, and Undersea and Diving Medical Officer, Naval Station, Norfolk, Va.

JON LYNOTT, MD, is a LT, MC, USN; and Undersea and Diving Medical Officer, Naval Station Norfolk, Va.

DALE MOLE, DO, is a CT, MC, USN; COMSUBLANT (Atlantic Fleet Submarine, Force); and Senior Undersea and Diving Medical Officer, Emergency Medicine, Norfolk Va.

JAMES P OBERMAN, MD, is a LT, MC, USN, and Undersea and Diving Medical Officer, Naval Amphibious Base, Little Creek, Va.

REFERENCES

(1.) Kizer K. Diving medicine. Emerg Med Clin North Am. 1984;2:513-530.

(2.) Bove AA. Medical aspects of sport diving. Med Sci Sport Exerc. 1996;28:591-595.

SUGGESTED READING

Beckman TJ. A review of decompression sickness and arterial gas embolism. Arch Fam Med 1997;6:491-494.

Bennett PB, Elliott DH, eds. The Physiology and Medicine of Diving. Philadelphia, Pa: WB Saunders: 1993.

Bove AA and Davis JC. Diving Medicine. 3rd ed. Philadelphia, Pa: WB Saunders; 1997.

Butler FK. Diving and hyperbaric ophthalmology. Surv Ophthalmol. 1995;39: 347-366.

Camporesi EM. Diving and pregnancy. Semin Perinatol. 1996;20:292-302.

Melamed Y. Shupak A, Bitterman H. Medical problems associated with underwater diving. New Engl J Med 1992;326:30-35.

Millington JT. Physical standards for scuba divers. J Am Board Farm Pract. 1988;1:194-200.

Morgan WP. Anxiety and panic in recreational scuba divers. Sports Med 1995;20:398-421.

Neuman TS. Diving medicine. Clin Sports Med 1987;6:647-661.

Neuman TS. Bove AA, O'Connor RD, et al. Asthma and diving. Ann Allergy 1994;73:344-350.

Wolf SL, Twarog F, Weiler JM, at al. Discussion of risk of scuba diving in individuals with allergic and respiratory diseases: SCUBA subcommittee. Allergy Clin lmmunol.1995;96:871-873.

This article at a glance

The 3 phases of diving

* Symptoms of middle ear barotrauma during descent include a feeling of fullness in the ear, conductive hearing loss, vertigo, or tinnitus. Treatment usually includes decongestants, antibiotics in cases of tympanic membrane perforation, and a follow-up exam.

* The most important effect of oxygen while at depth is upon the CNS.

* Decompression sickness (DCS) type I during rapid ascent causes symptoms of unilateral joint pain or transient skin symptoms involving mild rashes or pruritus. DCS type II is more serious and involves dermatologic, neurologic, pulmonary, or cardiac symptoms.

Fitness for diving

* The interview with a prospective diver should include questions regarding the reason for diving, the diver's experience level, the frequency and location of diving activity, and the diver's history of air embolism, DCS, barotrauma, vertigo, near drowning, oxygen toxicity, and prior disqualification.

* The age and overall physical fitness of the potential diver are important considerations.

Diver evaluation: System by system

* Exclude from diving candidates with pathologic processes that make autoinflation of the middle ear and sinuses impossible and predispose them to possible barotrauma.

* Disqualify potential divers suffering from conditions that would place them at risk for arterial gas embolism or DCS.

"Diving medicine: A comprehensive review" Patient Care, June 30, 2000.

Mnemonic for signs of CNS toxicity

Visual

Ear disturbances

Nausea

Twitching

Irritability

Dizziness

Convulsions

Diving resources on the Web

Divers Alert Network (DAN)

The Peter B. Bennett Center 6 West Colony Place Durham, NC 27705

24-hour diving emergency hotlines: DAN America (919) 684 8111 or (919) 684 4DAN (collect)

DAN South East Asia Pacific (SEAP), Diver Emergency Services (DES) 011-61-8-8212-9242

DAN Europe 011-41-1-1414

DAN Japan 011 81-3-3812-4999

Medical information line: (919) 684-2948, extension 222, Monday through Friday, 9AM to 5PM eastern time

Fax: (919) 493-3040 (medical department)

World Wide Web: www.diversalertnetwork

DAN, an international nonprofit organization dedicated to diver safety, is the largest diving medical association in the world. It provides expert medical information and advice for the benefit of the diving public. Services include a 24-hour emergency hotline, a medical information line for nonemergency situations and inquiries, diving safety seminars, and educational materials. Membership benefits include dive accident insurance and enrollment in TravelAssist, an emergency medical, travel, and personal assistance program. DAN also maintains a database network of world-wide recompression chamber facilities and conducts research on diving physiology and safety. Books on diving-related topics and, reports on decompression illness and diving fatalities are available from the online store.

Diving Medicine Online

Ernest S. Campbell, MD, FACS

31681 Shoal Water Dr Ono Island, AL 36561

Phone; (334) 980-1384

Fax: (334) 980-1001

E-mail: scubadoc@gulftel.com

World Wide Web: http://www.gulftel.com/[sim]scubadoc/

Diving Medicine Online is a resource for divers and medical professionals. Visitors can e-mail a question to a diving medicine specialist, browse a list of frequently asked questions, or find information on a select topic of interest. A list of seminar and course announcements is posted. A glossary of diving medicine terminology is provided. Physicians can click on the positions and employment link to find opportunities in diving and hyperbaric medicine. The bookstore offers books on diving medicine. An online newsletter is available free of charge.

Undersea and Hyperbaric Medical Society (UHMS)

10531 Metropolitan Ave Kensington, MD 20895

Phone: (301) 942-2980

Fax: (301) 942-7804

E-mail: uhms@uhms.org

World Wide Web: http://www.uhms.org

The UHMS is an international, nonprofit organization whose membership is largely composed of hyperbaric medicine physicians and scientists.. It provides information regarding diving and hyperbaric medicine and physiology, with the goals of protecting the health of divers while furthering knowledge of hyperbaric oxygen therapy, promoting standard of care treatment for diving injuries and other conditions using hyperbaric protocols, and offering continuing medical education accreditation. Members can register electronically for meetings and find out about courses. that may earn them CME credit hours. Books, slides, and other materials are available through the online store. A subscription to Pressure, a bimonthly newsletter, and Undersea and Hyperbaric Medicine, a quarterly journal is included in the membership fee. A useful area of the Web site discusses the indications for hyperbaric oxygen therapy and lists journal references for those wanting further information.

Substances to be avoided by active divers

Adrenergic blockers

Alcohol

Anticonvulsants

Antidepressants

Antigout medications

Antihistamines

Antihypertensives

Antipsychotic agents

Antituberculous agents

Chemotherapeutic agents

CNS stimulants (anorexics)

Coronary vasodilators

Hallucinogens

Hypoglycemic agents

Narcotics

Sedatives and tranquilizers

Steroids

Thyroid drugs

Recommended medical history screening questionnaire for divers

Do you have or did you ever have the following? (Yes/No)

Asthma

Back injuries

Bleeding tendencies/disorders

Blood disorders

Chest pain or angina

Claustrophobia

Decompression sickness (DCS) (bends) or other diving accident

Diabetes

Ear infections, mastoid infections

Epilepsy or other seizures, convulsions or fits

Fainting or blackouts

Frequent colds, bronchitis

Hay fever

Head injury

Heart attack

Heart disease

Hernia

High blood pressure

Migraines

Nervous disorders

Other allergies

Pneumothorax (collapsed lung)

Seasickness

Trouble clearing your ears (equalizing pressure in airplanes/diving)

Ulcer disease

Wheezing on breathing cold air or with exercise

In addition

Are you accustomed to exercise?

Do you drink alcoholic beverages?

Do you smoke?

Do you take any medications?

Do you use any drugs?

When was your last chest x-ray?

Source Citation:FOTOPOULOUS, CONSTANTINE LAN, JON LYNOTT, DALE MOLE, and JAMES P. OBERMAN. "Diving medicine: A comprehensive review." Patient Care 34.12 (June 30, 2000): 20. Academic OneFile. Gale. BROWARD COUNTY LIBRARY. 2 Sept. 2009
.

Gale Document Number:A63669556

Disclaimer:This information is not a tool for self-diagnosis or a substitute for professional care.