Scuba Diving: Decompression Illness & Other Dive-Related Injuries

CDC Yellow Book 2024

Environmental Hazards & Risks

Author(s): Daniel Nord, Gregory Raczniak, James Chimiak

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 generally are rare, few clinicians are trained to prevent, diagnose, or treat them.Recreational divers should assess potential risks before diving, be prepared to recognize signs of injury, and seek qualified dive medicine help promptly when needed.

Preparing for Dive Travel

When assisting patients who are planning dive-related travel, take into consideration chronic health conditions, any recent changes in health (e.g., injuries, pregnancy, surgeries), and medication use. Underlying respiratory conditions (e.g.,asthma, chronic obstructive pulmonary disease, infections, history of spontaneous pneumothorax) can challenge the breathing capacity required of divers. Mental health disorders (e.g., anxiety, claustrophobia, substance abuse) and disorders affecting central nervous system higher function and consciousness (e.g., seizures) raise special concerns about diving fitness. While it is important to review patient medications for their compatibility with diving, usually the primary concern is the underlying condition for which the patient takes medication.

People with known risk factors for coronary artery disease, including but not limited to diabetes, elevated blood pressure, family history, an abnormal lipid profile, 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 examination might include an electrocardiogram, exercise treadmill test, or echocardiogram. 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 and subsequent diving.

During the travel medicine examination, remind divers (and would-be divers) of actions they can take in advance to reduce or eliminate risks. Identifying and assessing potential hazards (e.g., environment, water and weather conditions, planned depth and bottom time) can help divers 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 divers can implement. A diver should never feel compelled to make a dive, especially if feeling unwell.

Of special note, many dive operators routinely screen clients by requiring a medical statement signed by the diver’s physician with approval to dive. Divers should communicate with their dive operator ahead of travel to acquire the necessary form to share with their personal physician. By being prepared with properly signed documentation upon arrival at their dive destination, the traveling diver can forestall denial of dive privileges.

Diving Disorders


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 & Sinus

The most common injury in divers is ear barotrauma (Box 4-07). 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. Health care providers 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 (e.g., the Valsalva maneuver). Additional risk factors for ear and sinus barotrauma include:

  • Use of solid earplugs.
  • Medication (e.g., 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 have ear or sinus barotrauma should discontinue diving and seek medical attention.

Box 4-07 Symptoms of ear barotrauma

  • Decreased hearing
  • Pain
  • Sensation of fullness
  • Sensation of “water in the ear” (serous fluid/blood accumulation in the middle ear)
  • Tinnitus (ringing in the ears)
  • Vertigo (dizziness or sensation of spinning)


Scuba divers reduce the risk for 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 exhaling, which can happen, for example, when a novice diver panics and kicks back toward the surface. 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: the pleural space, mediastinum, or pulmonary vasculature. Gas entering the pleural space can cause lung collapse or pneumothorax. Gas entering the mediastinum (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. 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).

Mediastinal or subcutaneous emphysema might resolve spontaneously, but 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

Decompression illness (DCI) describes bubble-related dysbaric injuries, including AGE and decompression sickness (DCS). Because scientists consider these 2 conditions to result from separate causes, they are described here separately. From a clinical and practical standpoint, however, distinguishing between them in the field might be impossible and unnecessary, because the initial treatment is the same for both (Table 4-03). 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 can result from AGE or DCS.

Table 4-03 Decompression illness syndromes: clinical findings

  • Ataxia
  • Blurred vision
  • Chest pain or bloody sputum
  • Loss of consciousness
  • Convulsions
  • Dizziness
  • Muscular weakness
  • Numbness or paresthesia Paralysis
  • Personality change, difficulty thinking, or confusion
  • Loss of bowel or bladder function
  • Collapse or unconsciousness
  • Coughing spasms or shortness of breath
  • Dizziness
  • Unusual fatigue
  • Itching
  • Joint aches or pain
  • Mottling or marbling of skin
  • Numbness or tingling
  • Paralysis
  • Personality changes
  • Staggering, loss of coordination, or tremors
  • Weakness


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 clinical presentation of arterial gas embolism (AGE) ranges from minimal neurologic findings to dramatic symptoms requiring urgent and aggressive treatment.

In general, 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. Because relapses can and do occur, divers suffering AGE should be rapidly evacuated to a hyperbaric oxygen treatment facility even if they appear to have recovered fully.

Decompression Sickness (“The Bends”)

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 gas can supersaturate tissues, where it separates from solution to form bubbles, interfering with blood flow and tissue oxygenation.

Other Conditions Related to Diving


Any incapacitation while underwater can result in drowning (see Sec. 4, Ch. 12, Injury & Trauma).

Hazardous Marine Life

Oceans and waterways are filled with marine animals, most of which are generally harmless unless threatened. Most injuries among divers are the result of chance encounters or defensive maneuvers of marine life. Wounds from marine life have many common characteristics, including bacterial contamination, foreign bodies, bleeding, and occasionally venom. See Sec. 4, Ch. 7, Zoonotic Exposures: Bites, Stings, Scratches & Other Hazards, for prevention and injury management recommendations.

Immersion (Induced) Pulmonary Edema

The normal 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. Cold water can cause peripheral vasoconstriction and augment this central fluid shift. Symptoms and signs of immersion (induced) pulmonary edema (IPE) generally begin on descent or at depth and include chest pain, dyspnea, wheezing, and productive cough with frothy, sometimes pink-tinged 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 work-up to rule out myocardial ischemia, evaluation of left ventricular function, hypertrophy, and valvular integrity.

Nitrogen Narcosis

At increasing depths, generally >100 ft (≈30 m), the partial pressure of nitrogen within the breathing gas increases, causing narcosis in all recreational divers. Nitrogen narcosis can be life threatening when it impairs a diver’s ability to make appropriate and proper decisions while under water. 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 condition is not seen when diving on compressed air within recreational depth limits.

Diving & Air Travel

Flying after Diving

The risk of developing decompression sickness increases when divers go to increased altitude too soon after a dive. Commercial aircraft cabins are generally pressurized to the equivalent of 6,000–8,000 ft (≈1,830–2,440 m) above sea level. Instruct asymptomatic divers to wait before flying at an altitude or cabin pressure >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; or
  • 24–48 hours after a dive that required decompression stops.

These recommended preflight surface intervals reduce, but do not eliminate, risk for 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 to acclimate mentally and physically to their new location 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. When multiple dives are planned, strict guidelines, known as surface intervals, are prescribed to allow adequate time for dissolved inert gas to drop to acceptable levels before the next dive. Tables derived from man-tested algorithms have traditionally been used by divers to manually calculate dive times and surface intervals. Dive computers possess the reliability and computing power to use the same algorithms and compute individual guidance based on real-time depth and time inputs. Dive computers have largely replaced the use of tables for the manual process of dive planning.

Risk factors for DCI are primarily dive depth, dive time, and rates of ascent. Additional factors, such as altitude exposure soon after a dive, difficult diving conditions (e.g., colder water, currents, decreased visibility, wave action), dives to depths >60 ft (18 m), multiple consecutive days of diving or repetitive dives, overhead situations (e.g., diving in underwater caves or wrecks), strenuous exercise, and certain physiologic variables (e.g., dehydration), 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 well-trained, attentive companion (dive buddy).

Treatment of Diving Disorders

Definitive treatment of DCI begins with early recognition of symptoms, followed by recompression with hyperbaric oxygen. Be suspicious of any unusual symptoms occurring soon after a dive, especially neurological symptoms, and evaluate these properly. Provide a high concentration (100%) of supplemental oxygen; surface-level oxygen given for first aid might 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 often are dehydrated. In most cases, treatment includes administering isotonic glucose-free intravenous fluids. Oral rehydration fluids also can be helpful, provided they can be administered safely (i.e., if the diver is conscious and can maintain their airway).

The definitive treatment of DCI is recompression and oxygen administration in a hyperbaric chamber. Stable or remitting symptoms of mild DCI (e.g., constitutional symptoms, some cutaneous sensory changes, limb pain, or rash) in divers reporting from remote locations without a hyperbaric facility might not require recompression. Medical management decisions made with the assistance of a qualified dive medicine physician also should account for the prevailing circumstances, logistics and hazards of evacuation, and the implications of failing to recompress. Serial neurologic exams are essential to the decision-making process.

Divers Alert Network (DAN) maintains 24-hour emergency consultation and evacuation assistance at +1-919-684-9111 (collect calls accepted). DAN can help with the medical management of injured divers by deciding if recompression is needed, providing the location of the closest recompression facility, and arranging patient transport. Divers and health care providers also can contact DAN for routine, nonemergency consultation by telephone at 919-684-2948, extension 6222, or by accessing the DAN.

Travelers who plan to scuba dive might want to ascertain whether recompression facilities are available at their destination before embarking on their trip.

The following authors contributed to the previous version of this chapter: Daniel A. Nord, Gregory A. Raczniak, James M. Chimiak

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