Scuba Diving

Scuba diving presents a variety of unique medical challenges for the travelling diver. Because diving injuries are generally rare, few health-care providers are trained in their diagnosis and treatment. Thus, the recreational diver must be able to recognise the signs of injury and ensure the availability of dive medicine help when needed.

Fitness to Dive

Planning for dive-related travel should consider any changes in health status, recent injuries, or surgery. In general, respiratory disorders, as well as any disorders affecting higher function and consciousness (e.g., diabetes mellitus or asthma) and psychological problems (e.g., anxiety) raise concerns about diving fitness.

Diving Disorders

Ear Barotrauma

Ear barotrauma is the most common injury in divers. On descent, failure to equalize pressure changes within the middle ear space creates a pressure gradient across the eardrum, which can cause bleeding or fluid accumulation in the middle ear and stretching or rupture of the eardrum and the membranes covering the windows of the inner ear. Symptoms can include pain, ringing in the ear, vertigo, a sensation of fullness in the ear and decreased hearing. With small pressure differences, symptoms are usually short lived, but will be exacerbated by continued diving. Larger pressure differences, especially with forceful attempts at clearing, tend to cause greater damage.

A diver who may have sustained ear barotrauma should discontinue diving and seek medical attention.

Decompression Illness

Decompression illness (DCI) is an all-inclusive term that comprises dysbaric injuries, arterial gas embolism (AGE), and decompression sickness (DCS). Because the two diseases are considered to result from separate causes, they are described separately. However, from a clinical and practical standpoint, distinguishing them in the field may be impossible and unnecessary, since the initial treatment is the same for both. DCI can occur even in divers who have carefully followed the standard decompression tables and the principles of safe diving.

Arterial Gas Embolism

Overinflation of the lungs can result as a scuba diver ascends toward the surface without exhaling. 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 the spaces around the lung. Air entering the pleural space causes lung collapse or pneumothorax. Air can also enter the mediastinum (space around the heart, trachea and oesophagus), causing mediastinal emphysema. Air in the mediastinum frequently tracks under the skin (subcutaneous emphysema) or into the tissue around the larynx, precipitating a change in the voice characteristics. While mediastinal or subcutaneous emphysema usually resolves spontaneously, pneumothorax may require specific treatment to remove the air and reinflate the lung.

Air can also enter the arterial blood, where bubbles distribute into the body tissues, including the heart and brain, where they disrupt circulation. AGE may cause minimal neurologic symptoms or symptoms may be dramatic and require immediate attention. These signs and symptoms include numbness, weakness, tingling, dizziness; visual blurring; chest pain; personality change; bloody froth from mouth or nose; paralysis or seizures; loss of consciousness; or death. In general, any scuba diver who surfaces unconscious or loses consciousness within 10 minutes after surfacing should be assumed to have AGE. Institution of basic life support, including the administration of 100% oxygen, is indicated, followed by rapid evacuation to a hyperbaric treatment facility.

Decompression Sickness

Breathing air under pressure causes inert gas (nitrogen) to diffuse into the body's tissues. This diffusion occurs at different rates in various tissues and continues as long as the partial pressure of inspired gas is greater than the absorbed gas in the tissues. Thus, the amount of inert gas absorbed is dependent on the depth and time spent at depth. As the diver ascends to the surface, this process is reversed as the partial pressure of residual gas exceeds that in the circulatory and respiratory systems. Ascent from a dive can cause supersaturation of inert gas (tissue partial pressure exceeding ambient pressure), allowing dissolved gas to form bubbles in tissues and causing signs and symptoms of decompression sickness. These symptoms include joint aches or pain; numbness, tingling, mottling or marbling of skin; coughing spasms, shortness of breath; itching; unusual fatigue; dizziness, weakness; personality changes; loss of bowel or bladder function; staggering, loss of coordination, tremors; or paralysis; and collapse or unconsciousness.

Serious permanent injury may result from both DCS and AGE.

Flying after Diving

There is an increased risk of developing decompression sickness when divers are exposed to altitude too soon following a dive. The cabin pressure of commercial aircraft may be the equivalent of 8,000ft. Thus, divers should avoid flying or altitude exposure >2,000ft. for a minimum of 12 hours after surfacing from a single no-decompression dive. After repetitive dives or multiple days of diving, a diver should wait a minimum of 18 hours before ascending to altitude, to reduce the risk of decompression sickness. These recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will further reduce DCS risk.

Prevention of Diving Disorders

Recreational divers should dive conservatively and well within the safe limits of their dive tables or computers. Risk factors for DCI are primarily dive depth and bottom time; however, factors such as rapid ascent, repetitive dives, strenuous exercise, dives >60 feet, and altitude exposure soon after a dive also increase risk. Divers should be cautioned to stay well hydrated and rested, dive within the limits of their training, and follow established guidelines for dives unique to the travel destination. Diving is a skill that requires training and certification and should be done with a companion.

Treatment of Diving Disorders

Definitive treatment of DCI begins with early symptom recognition, followed by recompression with hyperbaric oxygen. Supplemental oxygen is considered effective first aid in relieving the signs and symptoms of decompression illness and should be administered as soon as possible. Divers are often dehydrated, either because of incidental causes, immersion, or DCI itself, which can cause a capillary leak. Administration of isotonic glucose-free intravenous fluid is recommended in most cases. Oral rehydration fluids may also be helpful, provided they can be safely administered (i.e., if the diver is conscious).The definitive treatment of DCI is recompression and oxygen administration in a hyperbaric chamber.

The Divers Alert Network (DAN) can be contacted by telephone at (919) 684-2948, ext. 222, or by accessing the website www.diversalertnetwork.org. DAN maintains a 24-hour emergency consultation and evacuation service at (919) 684-8111 or (919) 684-4326. (Collect calls are accepted.) DAN will provide assistance with management of the injured diver, help in deciding if recompression is needed, the location of the closest appropriate recompression facility, and assistance in arranging patient transport.

Bibliography
  • Bennett PB, Elliott DH. The Physiology and Medicine of Diving, 4th Edition. Saunders, London. 1993.
  • Moon RE. Treatment of Decompression Illness. In: Diving Medicine, 4th Edition. Bove AA, ed. Saunders, London: 2004. pp. 195-223.
  • Sheffield PJ, Vann RD. Flying after Recreational Diving Workshop Proceedings. Durham, NC, Divers Alert Network. 2004 ISBN: 0-9673066-4-7
  • Thalmann ED. DAN Dive and Travel Medical Guide. Rev. Ed. 2003. Divers Alert Network, Durham, NC.

- Dan Nord

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