Decompression Illness in SCUBA Divers
Gary Podolsky and Karl Neumann
Travelers planning trips to exotic beach resorts should be asked about their intentions of going scuba diving and if so, whether they understand the health
issues involved and are aware of the subtle signs of early decompression illness. Like any sport, scuba diving involves the risk of injuries. There are between three and
four illness/injuries reported for every 10,000 dives, with the vast majority of them minor, with complete resolution and no impact on future diving activities.
Permanent sequelae are rare.
Decompression illness (DCI) includes two conditions, decompression sickness (DCS) (also known as the bends or caisson disease), and arterial gas embolism (AGE). DCS is believed to be due to bubbles forming in body tissue, causing local damage. AGE results from bubbles entering the bloodstream, usually in the lungs, traveling through arteries and causing tissue damage at distant points by blocking blood flow in small vessels. Risk factors for both include deep/long dives, cold water, vigorous exercise at depth or immediately after surfacing, and rapid ascents. Obesity, dehydration, and pulmonary disease may play roles. And there are unknown factors involved; divers not at risk and who follow all the safety guidelines are sometimes affected.
Decompression Sickness
DCS results from inadequate decompression following exposure to increased pressure. The condition varies from mild with no immediate threat to serious injury requiring prompt treatment to ensure full recovery.
During a dive, the body tissues absorb nitrogen from the breathing gas in proportion to the surrounding pressure. As long as the diver remains at pressure, the gas presents no problem. If the pressure is reduced too quickly, nitrogen comes out of solution, forming bubbles in the tissues and bloodstream. This commonly occurs as a result of violating or approaching too closely to the diving table limits, but can occur when accepted guidelines are followed.
Bubbles forming in or near joints are the presumed cause of joint pain or "the bends." Bubbles forming in the spinal cord and brain may cause paralysis and other neurological symptoms. Bubbles entering the bloodstream can cause pulmonary and circulatory problems.
Symptoms of DCS
Joint pain and numbness or tingling are common manifestations of DCS, followed by muscular weakness and inability to empty a full bladder. Severe DCS is easily diagnosed but most cases begin subtly, with minor joint aches or paresthesias in an extremity. Often the symptoms are ascribed to another cause such as overexertion, heavy lifting or a tight wetsuit. This delays seeking help and is why it is often said that the first symptom of DCS is denial.
Even symptoms that remain mild and disappear spontaneously should be investigated promptly. Severe DCS may result in permanent problems such as bladder dysfunction, sexual dysfunction and muscular weakness. Rarely, damage to the spinal cord may decrease the likelihood of recovery from subsequent bouts of DCS. Untreated joint pain that disappears may still cause small areas of bone damage (osteonecrosis). Future bouts of osteonecrosis may cause additional damages, making bones brittle and causing arthritis.
Signs of DCS usually appear within 15 minutes to 12 hours after surfacing; but in severe cases, symptoms may appear before surfacing or immediately afterwards. Delayed occurrence of symptoms is rare, but does occur, especially if air travel follows diving. Symptoms include: unusual fatigue; pruritis; pain in joints/muscles of the arms, legs or torso; dizziness; vertigo; ringing in the ears; numbness, tingling and paralysis; and shortness of breath.
Also associated with DCSR are the following: e a blotchy rash on the skin, muscular weakness and paralysis, difficulty urinating, confusion, personality changes and bizarre behavior, amnesia and tremors, staggering gait, coughing up bloody and frothy sputum, and collapse or unconsciousness.
Prevention
Recreational divers should dive conservatively, following guidelines set forth in dive tables or computers. This is highly recommended for all divers, especially when diving in cold water or when diving under strenuous conditions. There are also published guidelines for flying after diving. Different sources advocate waiting a minimum of 12 to 24 hours after an uncomplicated dive before flying.
Arterial Gas Embolism (AGE)
This occurs when divers surface without exhaling. Air trapped in the lungs expands with ascent and may rupture lung tissue (pulmonary barotraumas) and release gas bubbles into the arterial circulation. Since the brain receives the highest proportion of blood flow, it receives the most bubbles. The bubbles become lodged in the small arteries of the brain and damage brain tissue. Pulmonary disease may be a predisposing factor.
AGE can occur even when ascents are apparently normal. The most dramatic presentation of air embolism is the diver who surfaces unconscious and remains so, or the diver who loses consciousness within 10 minutes of surfacing. Obviously, these are medical emergencies. Rapid evacuation to a treatment facility is paramount. But usually air emboli merely cause tingling or numbness, weakness without obvious paralysis, or difficulty in thinking without obvious confusion. Individuals are awake or easily aroused. In these cases, there is time for more thorough evaluations, preferably by a diving medical specialist who can rule out other causes of symptoms.
As with DCS, ascribing mild symptoms to a non-dive cause delays or results in no treatment, and symptoms resolve, though damage has occurred. This increases the risk of residual symptoms after a future bout of AGE, even if the later bout is treated.
The signs and symptoms of AGE include dizziness, blurring of vision, weakness and paralysis, areas of decreased sensation, chest pain, disorientation, bloody froth from the mouth or nose, seizures and unconsciousness.
The percent of diving problems due to AGE has decreased substantially over the years, from 18% of reported cases of DCL in the late 1980s to less that 10% now, probably due to the advent of dive computers, which help chart the rate of ascent, reminding divers to slow down.
Preventing AGE
Breathing normally and relaxing during ascent helps prevent AGE. Asthma, respiratory infections, obstructive lung disease and other pulmonary pathology predispose divers to air embolism. Divers with these conditions should be evaluated by a physician knowledgeable in diving medicine.
Treatment
The treatment for DCI (DCS and AGE) is recompression. Although divers with severe symptoms require urgent recompression, it is essential that they be stabilized at the nearest medical facility before transportation to a recompression chamber. Oxygen may reduce symptoms substantially but should not change the treatment plan. Symptoms often clear after initial oxygen therapy, but may reappear later. A dive physician should always be contacted even if the symptoms and signs appear to resolve.
Care of the Diver with Decompression Illness
I. Determine the Urgency of the Injury
Make an initial evaluation at the dive site. Suspect DCI if signs occur within 24 hours of surfacing. The initial state of the affected diver will determine the order and urgency of the actions taken. The U.S. Navy uses a three-part category system:
- Category A. Emergency
- Category B. Urgent
- Category C. Timely
Category A - Emergency
Symptoms are severe and appear rapidly, within an hour or so of surfacing. Unconsciousness may occur. Symptoms may be progressing. The diver is obviously ill, may be profoundly dizzy, have trouble breathing or altered consciousness and abnormal gait or weakness.
If indicated, begin CPR and arrange for immediate evacuation. Check for foreign bodies in the airway. If ventilatory or cardiac resuscitation is required, the injured diver must be supine. Vomiting in this position, however, is extremely dangerous; if it occurs, quickly turn the diver to the side until the airway is cleared and resuscitation can resume in the supine position.
Caregivers should use supplemental oxygen if available during ventilatory support to the injured diver. Even if CPR is successful and the diver regains consciousness, 100 percent oxygen should be provided and continued until the diver arrives at a medical facility. Advanced divers are also encouraged to take oxygen provider course.
If trained healthcare personnel are available, an IV with isotonic fluids without dextrose should be started. Give an initial rapid infusion of 1 liter over 30 minutes to correct any dehydration and reduce hemoconcentration. Then reduce the rate of administration to 100-175 cc/hour maintenance rate. Additional fluids may be required to further correct dehydration and maintain blood pressure but only after weighing complications of fluid overload and discomfort from urinary retention. If possible, insert a urinary catheter.
Definitive treatment requires a facility with a recompression chamber. The Divers Alert Network (DAN) can assist in locating one. And DAN medical experts can contact the receiving facility to assist in diagnosis and, if necessary, treatment. This should be done even if the diver appears to be improving on oxygen. While awaiting evacuation, take as detailed a history as possible and try to evaluate and record the diver's neurological status. If air evacuation is used, cabin pressure should be maintained near sea level and not exceed 800 feet/244 meters unless aircraft safety is compromised.
Place the diver in the lateral recumbent position, also known as the recovery position. This puts the person on one side (usually left) with head supported at a low angle and the upper leg bent at the knee. If vomiting occurs in this position, gravity will assist in keeping airway clear.
Category B - Urgent Cases of DCI
Here, the only obvious symptom is severe continuous pain, no other signs of distress, and no obvious neurological signs, though a careful history and physical may elicit some findings.
Give the injured diver 100 percent oxygen and fluids by mouth. Do not treat pain with analgesics until advised to do so by experienced medical personnel. Continue oxygen until arrival at the medical treatment facility. Even if symptoms improve, contact a medical facility or DAN on what sort of transport is indicated. Emergency air transport may not be necessary. As with category A patients, take a history and evaluate and chart neurological status.
Category C - Timely Cases of DCI
Symptoms are vague, perhaps complaint of some pain or abnormal sensations over a few days. The diagnosis of DCI may be in question. Take a complete diving history and do a neurological evaluation. Call the nearest medical facility or DAN for advice, or go to the nearest medical facility, if nearby, for evaluation.
In all cases of DCI try to document the 48 hours preceding the injury:
- Depths/times of dives, ascent rates, intervals between dives, breathing gases, problems or symptoms at any time before, during or after dives;
- Times of onset of symptoms and progression after the diver surfaced from last dive;
- First aid measures taken (times, method, and percent of oxygen delivery) and their effect on symptoms since the injury;
- Results of on-site neurological examination;
- Joint or other musculoskeletal pain including: location, intensity and changes with movement or weight-bearing;
- Distribution of rashes; and
- Traumatic injuries before, during or after the dive.
Information regarding the injured diver's neurological status will be useful to medical personnel in not only deciding the initial course of treatment but also in the effectiveness of treatment.
Returned Travelers
Although unlikely, with modern transport it is possible that travel medicine practitioners will see a returned traveler with symptoms of DCI. Such patients should receive oxygen immediately and be sent to an emergency facility for assessment for hyperbaric treatment.
Finding a Dive Physician
Dive physician may be available through local military hospitals. Many Navy and Air Force physicians are knowledgeable about the subject and so are some occupational medicine, emergency medicine and sports physicians. Practitioners may vary in experience from doing simple dive physical clearances to full certification in hyperbaric medicine.
Becoming a Dive Physician
Learning to screen candidates for diving can be very useful for travel medicine practitioners. Guidelines for diving fitness are straightforward although there are some differences in the American, British and Australian definitions of fitness and precluding conditions (see references). Introductory courses in Dive Medicine are regularly scheduled through the Divers Alert Network.
Advocating Safe Diving
Many dive related injuries are also associated with poor technique and with "quickie instructions at resorts." Proper certification by qualified dive shops can decrease this risk.
Divers and Malaria
Mefloquine has been associated with a decrease in fine motor reflexes and is listed as a contraindicated medication for divers (although some authors dispute this). It is best to use an alternative antimalarial in divers.
References:
1) Dive and Marine Medicine (3rd Conference. March 2000, sponsored by The Undersea and Hyperbaric Medical Society.
2) Dive and Travel Medical Guide Ed Thalmann, Editor, Revised 1999, published by D.A.N.
3) Bore, Alfred A and Davis, Jefferson C. (1990) Pub W.B Saunders. Diving Medicine.
4) Edmonts (1978) Diving and Sub Aquatic Medicine 2nd Edition. 6) Divers Alert Network. Report on Decompression Illness and Diving Fatalities 2000 Edition.
5) Undersea and Hyperbaric Medical Society Inc. (July 21, 1995) Published meeting. Are Asthmatics Fit to Dive?
6) D.A.N Website link: http://www.divers
alertnetwork.org/
Gary lives in Winnipeg, Canada where he operates a travel clinic. Karl is the editor of this Newsletter. We thank DAN for allowing us to freely use their information and data. Gary adapted the material for travel medicine practitioners.
About Dan
Divers Alert Network (DAN) is non-profit medical and research organization dedicated to the safety and health of recreational scuba divers and travelers. Associated with Duke University Medical Center (DUMC), DAN is supported by the largest association of recreational divers in the world.
Founded in 1980, DAN has served as a lifeline for the recreational scuba industry by operating scuba diving's only 24-hour emergency hotline, a lifesaving service for injured divers. DAN members have access to full-time travel assistance and emergency medical evacuation as well as help with legal, personal and travel information.
Additionally, DAN operates a diving medical information line, conducts vital diving medical research, and develops and provides a number of educational programs for everyone from beginning divers to medical professionals.
DAN also supports, through education and training, a network of recompression chambers worldwide for the treatment of injured divers.
Divers Alert Network is supported by membership dues and donations. In return, members receive a number of important benefits including $100,000 emergency medical evacuation assistance, DAN educational publications, a subscription to Alert Diver magazine, and access to diving's first and foremost accident insurance coverage.
