Chapter 3 Environmental Hazards & Other Noninfectious Health Risks
Scuba Diving: Decompression Illness & Other Dive-Related Injuries
Published estimates report anywhere from 0.5 million to 4 million people in the United States participate in recreational diving; many travel to tropical areas of the world to dive. Divers face a variety of medical challenges, but because dive injuries are generally rare, few clinicians are trained in their prevention, diagnosis, and treatment. The onus, then, is on the recreational diver to assess potential risks before diving, recognize signs of injury, and seek qualified dive medicine help when needed.
PREPARING FOR DIVE TRAVEL
Planning for dive-related travel should take into account chronic health conditions, any recent changes in health (including pregnancy, injuries, and surgeries), and medication use. Underlying respiratory conditions, such as asthma, chronic obstructive pulmonary disease, or a history of spontaneous pneumothorax, can challenge the breathing capacity required of divers. Mental health disorders (such as anxiety, claustrophobia, or substance abuse) and disorders affecting central nervous system higher function and consciousness (such as seizures) raise special concerns about diving fitness. Although medications should be reviewed for their compatibility with diving, it is usually the underlying condition for which the medication is taken that is of concern.
People with known risk factors for coronary artery disease, including but not limited to an abnormal lipid profile, elevated blood pressure, diabetes, and smoking history, who wish to either begin a dive program or continue diving, should undergo a physical examination to assess their cardiovascular fitness. This may include an electrocardiogram or exercise treadmill test. Diving is a potentially strenuous activity that can put substantial demands on the cardiovascular system. Serious injury and death are associated with poor physical conditioning; regular aerobic exercise should already be part of a diver’s routine before arriving for their dive physical.
Health care workers providing travel medicine examinations for divers should also remind their patients of actions they can take in advance to reduce or eliminate risks. Identifying and assessing potential hazards (such as weather, water conditions, planned depth, bottom time, and environment) better enables divers to make decisions about acceptable risk. Preparing for a safe dive also includes having an up-to-date emergency action plan, on-hand first aid supplies (with ample oxygen), and reliable communication devices. Using correct and well-maintained protective equipment, diving with supervision, and ensuring that medical care is available in the event of an emergency are other controls that can be implemented. Finally, a diver should never feel compelled to make a dive.
Barotrauma is an injury to soft tissues resulting from a pressure differential between an airspace in the body and the ambient pressure. The resultant expansion or contraction of that space can cause injury.
EAR AND SINUS
The most common injury in divers is ear barotrauma (Box 3-03). On descent, failure to equalize pressure changes within the middle ear space creates a pressure gradient across the eardrum. As the middle ear tissues swell with edema—a consequence of the increased pressure—the pressure difference across the eardrum pushes it into the middle ear space causing it to bleed and possibly rupture.
Forceful equalization under these conditions can increase the pressure differential between the inner ear and the middle ear, resulting in round window rupture with perilymph leakage and inner ear damage. To avoid these pathologic processes, divers must learn proper equalization techniques. The physician can coach this effort by observing movement of the tympanic membrane using simple otoscopy.
Paranasal sinuses, because of their relatively narrow connecting passageways, are especially susceptible to barotrauma, generally on descent. With small changes in pressure (depth), symptoms are usually mild and subacute but can be exacerbated by continued diving. Larger pressure changes can be more injurious, especially with forceful attempts at equilibration (such as the Valsalva maneuver).
Additional risk factors for ear and sinus barotrauma include:
- Use of solid earplugs
- Medication (such as overuse or prolonged use of decongestants leading to rebound congestion)
- Ear or sinus surgery
- Nasal deformity or polyps
- Chronic nasal and sinus disease that interferes with equilibration during the large barometric pressure changes encountered while diving
Divers who suspect they may have ear or sinus barotrauma should discontinue diving and seek medical attention.
A scuba diver reduces the risk of lung overpressure problems by breathing normally and ascending slowly when breathing compressed gas. Overexpansion of the lungs can result if a scuba diver ascends toward the surface without proper exhalation, which may happen, for example, when a novice diver panics. During ascent, compressed gas trapped in the lung increases in volume until the expansion exceeds the elastic limit of lung tissue, causing damage and allowing gas bubbles to escape into 3 possible locations:
- Pleural space. Gas entering the pleural space can cause lung collapse or pneumothorax.
- Mediastinum. Gas entering the space around the heart, trachea, and esophagus causes mediastinal emphysema and frequently tracks under the skin (subcutaneous emphysema) or into the tissue around the larynx, sometimes precipitating a change in voice characteristics.
- Pulmonary vasculature. Gas rupturing the alveolar walls can enter the pulmonary capillaries and pass via the pulmonary veins to the left side of the heart, resulting in arterial gas embolism (AGE).
While mediastinal or subcutaneous emphysema may resolve spontaneously, pneumothorax generally requires specific treatment to remove the air and reinflate the lung. AGE is a medical emergency, requiring urgent intervention with hyperbaric oxygen therapy (recompression treatment).
Lung overinflation injuries from scuba diving can range from mild to dramatic and life threatening. Although pulmonary barotrauma is uncommon in divers, prompt medical evaluation is necessary, and clinicians must rule out this condition in patients presenting with post-dive respiratory or neurologic symptoms.
Decompression illness (DCI) describes the dysbaric injuries (such as AGE) and decompression sickness (DCS). Because scientists consider the two diseases to result from separate causes, they are described here separately. However, from a clinical and practical standpoint, distinguishing between them in the field may be impossible and unnecessary, since the initial treatment is the same for both (Box 3-04). DCI can occur even in divers who have carefully followed the standard decompression tables and the principles of “safe” diving. Serious permanent injury or death may result from AGE or DCS.
ARTERIAL GAS EMBOLISM
Gas entering the arterial blood through ruptured pulmonary vessels can distribute bubbles into the body tissues, including the heart and brain, where they can disrupt circulation or damage vessel walls. The presentation of AGE ranges from minimal neurologic findings to dramatic symptoms requiring urgent and aggressive treatment.
In general, a clinician should suspect AGE in any scuba diver who surfaces unconscious or loses consciousness within 10 minutes after surfacing. Initiate basic life support, including administration of the highest fraction of oxygen. Since relapses can and do occur, evacuate rapidly to a hyperbaric oxygen treatment facility even if the diver appears to have recovered fully.
Breathing air under pressure causes excess inert gas (usually nitrogen) to dissolve in and saturate body tissues. The amount of gas dissolved is proportional to—and increases with—the total depth and time a diver is below the surface. As the diver ascends, the excess dissolved gas must be cleared through respiration. Depending on the amount of gas dissolved and the rate of ascent, some can supersaturate tissues, where it separates from solution to form bubbles, interfering with blood flow and tissue oxygenation.
Other Conditions Related to Diving
Drowning: Any incapacitation while underwater can result in drowning (see Injury & Trauma in this chapter).
Nitrogen narcosis: At increasing depths, the partial pressure of nitrogen increases, causing narcosis in all divers. The impairment can be life threatening. This narcosis quickly clears on ascent and is not seen on the surface after a dive, which helps differentiate this condition from AGE.
Oxygen toxicity: At increasing partial pressures of oxygen, levels in the blood become high enough to cause seizures. This is not seen when diving on air at recreational depth limits.
Immersion (induced) pulmonary edema (IPE): The hemodynamic effects of water immersion account for a shift of fluid from peripheral to central circulation that can result in higher pressures within the pulmonary capillary bed, forcing excess fluid into the lungs. Symptoms and signs of IPE generally begin on descent or at depth and include chest pain, dyspnea, wheezing, and productive cough with frothy sputum. Although not entirely well understood, age, overhydration, overexertion, negative inspiratory pressure, and left ventricular hypertrophy are believed to increase IPE risk in otherwise healthy divers. Anyone experiencing acute pulmonary edema while diving requires a workup to rule out myocardial ischemia, evaluation of left ventricular function, hypertrophy, and valvular integrity.
Hazardous marine life: Oceans and waterways are filled with marine animals, most of which are generally harmless unless threatened. Most injuries are the result of chance encounters or defensive maneuvers. Resulting wounds have many common characteristics: bacterial contamination, foreign bodies, and occasionally venom. See Animal Bites & Stings (Zoonotic Exposures) in this chapter for prevention and injury management recommendations.
Box 3-03. Symptoms of ear barotrauma
- Tinnitus (ringing in the ears)
- Vertigo (dizziness or sensation of spinning)
- Sensation of fullness
- Sense of “water” in the ear (serous fluid/blood accumulation in the middle ear)
- Decreased hearing
Box 3-4. Decompression illness syndromes—clinical findings
|ARTERIAL GAS EMBOLISM||DECOMPRESSION SICKNESS|
|Chest pain or bloody sputum
Loss of consciousness
Personality change, difficulty thinking, or confusion
Numbness or paresthesias
|Coughing spasms or shortness of breath
Collapse or unconsciousness
Numbness or tingling
Staggering, loss of coordination, or tremors
Mottling or marbling of skin
Loss of bowel or bladder function
Joint aches or pain
FLYING AFTER DIVING
The risk of developing decompression sickness increases when divers go to increased altitude too soon after a dive. The cabin pressure of commercial aircraft may be the equivalent of 6,000–8,000 ft (1,829–2,438 m). Thus, divers should wait before flying at an altitude >2,000 ft (610 m) for:
- ≥12 hours after surfacing from a single no-decompression dive
- ≥18 hours after multiple dives or multiple days of diving
- 24–48 hours after a dive that required decompression stops
These recommended preflight surface intervals reduce, but do not eliminate, risk of DCS. Longer surface intervals further reduce this risk.
DIVING AFTER FLYING
There are no guidelines for diving after flying. Divers should wait a sufficient period of time to acclimate mentally and physically to their new location in order to focus solely on the dive.
PREVENTING DIVING DISORDERS
Recreational divers should dive conservatively and well within the no-decompression limits of their dive tables or computers. Risk factors for DCI are primarily dive depth, dive time, and rate of ascent. Additional factors such as repetitive dives, strenuous exercise, overhead situations (such as caves or wrecks), dives to depths >60 ft. (18 m), altitude exposure soon after a dive, difficult diving conditions (for example, decreased visibility, currents, wave action) and certain physiologic variables also increase risk. Caution divers to stay well hydrated and rested and dive within the limits of their training. Diving is a skill that requires training and certification and should be done with a companion (or buddy).
TREATMENT OF DIVING DISORDERS
Definitive treatment of DCI begins with early recognition of symptoms, followed by recompression with hyperbaric oxygen. Any unusual symptoms occurring soon after a dive should be suspect and properly evaluated. Breathing a high concentration (100%) of supplemental oxygen is recommended. Surface-level oxygen given for first aid may relieve the signs and symptoms of DCI and should be administered as soon as possible.
Because of either incidental causes, immersion, or DCI itself, which can cause capillary leakage, divers are often dehydrated. Administration of isotonic glucose-free intravenous fluid is recommended in most cases. Oral rehydration fluids may also be helpful, provided they can be administered safely (for example, if the diver is conscious and can maintain his or her airway).
The definitive treatment of DCI is recompression and oxygen administration in a hyperbaric chamber. It is worth noting that stable or remitting symptoms of mild DCI (such as limb pain, constitutional symptoms, some cutaneous sensory changes, or rash) in divers reporting from remote locations without a hyperbaric facility may not require recompression. Such conditions involve reasonable decision making with a qualified dive medicine physician and should take into account the prevailing circumstances, complicated logistics, the hazardous nature of evacuation, and the likelihood of disadvantaging the patient by failing to recompress.
Divers Alert Network (DAN) maintains 24-hour emergency consultation and evacuation assistance at 919-684-9111 (collect calls are accepted). DAN can help with the medical management of injured divers, deciding if recompression is needed, providing the location of the closest recompression facility, and arranging patient transport. Divers and health care providers can also contact DAN for routine, nonemergency consultation by telephone at 919-684-2948, extension 6222, or by accessing the DAN website (www.diversalertnetwork.org).
Travelers who plan to scuba dive may want to ascertain whether recompression facilities are available at their destination before embarking on their trip.
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