Scuba-Diving Medical Cause and Response

By Domenic A. Sammarco, R.Ph., EMT

Scuba diving is one of the fastest-growing sports in the nation. Refinements in diving equipment and lower airfares have opened up the sport to thousands who might never have otherwise enjoyed the activity. Thousands fly to exotic Caribbean islands for scuba-diving vacations. The Florida panhandle has great diving, and scuba-diving clubs or individuals frequent the Great Lakes and other smaller lakes. In some areas, local lakes and rock quarries are active training sites for the diving population. There is a thriving industry based on harvesting freshwater mussels, and many lakes and rivers are frequented by divers in search of bounty. So, even if you don't live in a diving "mecca" divers may need your service.

As with any sport, there are associated risks. To become a certified scuba diver, the participant completes a rather involved class, where safe diving practices are taught to help minimize the risks. The certified diver is authorized to dive virtually anywhere in the world. Although certified divers should follow recommended guidelines to make the activity more safe, these are not hard-and-fast rules, and divers are under no legal obligation to follow them. Even if the person adheres to conservative dive plans, there is the risk of injury. A student diver learns the following:

  • How long he/she can stay underwater
  • How deep he can go
  • How slowly he should return to the surface
  • How long he should stay on the surface before the next dive
  • How long he should stay on the surface before boarding and aircraft.

Failure to follow the guidelines can set the diver up for serious injury. Some injuries occur acutely, while others present with delayed signs and symptoms. Potentially life-threatening injuries include: decompression illness (DCI), nitrogen narcosis, air embolism, pneumothoracies, emphysemas and "bad air" injuries. Following is a discussion about the physiology and symptoms of various dive-related maladies.

Decompression Illness (DCI)

Also known as "the bends" or Caisson disease, DCI is caused by too much nitrogen in the bloodstream. Although divers usually breathe compressed air, some are breathing newer "enriched" gas mixes, which have different proportions of gases, but either enriched gas or regular compressed air can have the same result. Underwater, the inhaled gas is under much higher atmospheric pressure than when inhaled on the surface. The inhaled oxygen and nitrogen (air) is essentially dissolved into solution and transported in the blood vessels. When DCI occurs, the dissolved gas within the blood comes out of solution and returns to its gaseous state. This can happen for a variety of reasons, including diving too deep, returning to the surface too rapidly or not waiting long enough between dives. If the nitrogen (normally an inert gas) comes out of solution within the arteries, it can cause a blockage or embolism. The tissue distal to the embolism can be damaged with much the same mechanism as a cerebral vascular accident (CVA), myocardial infarction (MI) or pulmonary embolism (PE). The diver is ideally "weightless" as he floats effortlessly below the surface, but getting into the water or out of the boat with cumbersome equipment requires a significant amount of bending, twisting, turning and physical activity. Muscle strains are always a possibility. Unfortunately, DCI can mimic a simple muscle strain. Many divers have taken decompression "hits" and assumed it was simply muscle fatigue. Some types of decompression injuries may be self-limiting and often subside with minimal side effects. More serious (and perhaps deadly) injuries occur when the affected muscle is the brain or spinal cord.

Decompression illness may present with trembling, impaired vision, dyspnea, numbness, vertigo, hearing loss, unconsciousness and other stroke-like or medical symptoms. Dyspnea, hemoptysis or respiratory failure may indicate lung/alveoli involvement. DCI usually occurs soon after a dive, but manifest itself hours later.

Nitrogen Narcosis

Nitrogen narcosis is a phenomenon that occurs as divers descend to deeper waters. While at depth, the diver with nitrogen narcosis might notice an alteration in mental status or change in cognitive ability. "Narc-ed" divers relate feeling somewhat intoxicated while underwater, with loss of inhibition, giddiness or an unexplained peaceful feeling. Others may feel opposite effects, such as thoughts of impending doom or fear. These unpleasant sensations are the reason nitrogen narcosis is sometimes called "rapture of the deep."

Nitrogen narcosis is an acute problem that can happen to any diver and cannot be predicted. Narcosis usually occurs at deeper depths but may occur anywhere along the water column. Divers are not able to build up any tolerance or immunity to its effects. Fortunately, as the diver returns to shallower water, the intoxicating feeling dissipates and resolves. There are no residual effects, and no treatment is needed.

While nitrogen narcosis sounds like a minimal occurrence, it can have devastating consequences. Diving while under any form of intoxication can be deadly. The "narc-ed" diver can lose his sense of responsibility and fail to heed the precautions that are necessary for safe diving.

Air Embolisms, Pneumothoracies, Mediastinal and Subcutaneous Emphysemas

Air embolisms, pneumothoracies, mediastinal and subcutaneous emphysemas all occur when air escapes the lungs and becomes lodged within various parts of the body. Air embolisms are the obstruction of blood vessels by gas bubbles and are often the result of the diver holding his/her breath on ascent. Atmospheric pressure decreases during the ascent and the air (gas) can expand too quickly, resulting in tissue damage. Especially devastating are the occluded vessels that supply the brain. Lung tissue may also sustain significant injury if air bubbles rupture the delicate alveoli. Air bubbles can enter the bloodstream, causing damage to distal sites within the body, while escaping air bubbles may enter the pleural cavity and cause a pneumothorax. Mediastinal emphysema forces bubbles between the lungs and around the chest. Subcutaneous emphysema means the bubbles are lodged under the skin, generally around the neck.

Symptoms of embolisms, pneumothoracies and emphysemas are largely dependent upon how much air has escaped and into what part of the body the bubbles have traveled. Much like DCI, if the air blocks arteries that supply the brain, stroke-like symptoms may occur. Numbness, tingling, headache, unsteady gait, slurred speech, altered level of consciousness and other neurologic deficits may be noted. A pulmonary embolism may be evident by tachypnea, dyspnea, hemoptysis, and anxious behavior. Pneumonoracies from diving injuries are not usually as massive as those following chest trauma; however, patients may present with chest pain, tachypnea, dyspnea and reduced oxygen saturation. Mediastinal emphysema may be diagnosed by palpating trapped air bubbles under the skin.

Bad Air Injuries

"Bad air" injuries include carbon dioxide excesses, carbon monoxide (CO) poisoning and oil vapor inhalation. These injuries occur if the diver inhales contaminated gases, most commonly carbon monoxide, when faulty air compressors leak harmful CO fumes into the diver's air tank. Hemoglobin is unable to transport the appropriate amount of oxygen to the cells.

Although still rare, oxygen toxicity is more common than it once was. As mentioned earlier, newer "enriched" gases may pump something other than purified air into the diver's tank. Enriched gases usually have an increased percentage of oxygen and reduced nitrogen, which is meant to reduce the dangers from nitrogen. Although unusual, it is possible to have too much oxygen in the tank. While under the pressure of the water column, this high percentage of inhaled oxygen over a prolonged period may be harmful. Diving with this gas mixture requires additional training and equipment. Without it, divers are setting themselves up for a lethal dive. Faulty gas mixtures can be avoided if the compressors are well ventilated, maintained and operated by competent staff.

Because of the wide variety of inappropriate gases that may contaminate the diver's gas, it is difficult to make a blanket statement about symptoms. Carbon monoxide poisoning may present as headache, nausea, vomiting, lethargy or loss of consciousness. Oxygen toxicity (again, this is rare) may present with muscle twitching, nausea and vomiting, dyspnea, mental status changes or seizures.

Treatment of all dive-related injuries includes careful assessment/management of respiratory and hemodynamic status. Aggressive attention to airway, breathing and circulation is paramount. All victims are treated with judicious oxygen delivery, preferably with at least 100% non-rebreather mask. Intubation should be accomplished if respiratory failure is pending or has already occurred. Fluid resuscitation is usually warranted. Unless contraindicated, two large-bore peripheral intravenous lines should be established and normal saline or lactated Ringer's infused. If respiratory or other hemodynamic instability occurs, needle theracentesis and/or chest tubes may be necessary, depending on signs and symptoms. Adhere to local protocols and contact your local medical control for additional support.

Most if the injuries just discussed require transport to a tertiary healthcare facility. Recovery may be dependent upon treatment in a recompression chamber, where additional atmospheric pressure is placed on the diver. The gas returns to solution and can then be metabolized normally. Under no circumstances should the rescuer attempt recompression at the dive site by returning the victim underwater to depth.

If treatment includes air-medical transport, be sure to inform the flight crew of the mechanism of injury. Patients flying at higher altitudes, even in pressurized aircraft, undergo a decrease in atmospheric pressure, which can allow additional gas expansion and exacerbate the injuries. The flight team may be able to transport at lower altitudes.

When possible, the healthcare provider must gain a thorough patient history, as some injuries manifest themselves hours after the dive. Symptoms may mimic those of other devastating injuries. An accurate history may assist in making a definitive diagnosis and subsequent treatment.


As a healthcare provider, you may encounter a patient with dive related injuries, some of which will require additional expense. Divers Alert Network (DAN), a nonprofit organization, can be a great source of advice and assistance. For help with diving emergencies call 919-684-8111 or 919-684-4326. Trained medical staff are available 24 hours a day, 365 days a year.

Even if you work thousands of miles from any Caribbean island, you may find yourself managing dive injuries. Remember, this is emergency medicine. You need to expect the unexpected.