SCUBA Diving Injuries: DCS and AGE

Ovid: 5-Minute Sports Medicine Consult, The

SCUBA Diving Injuries: DCS and AGE
Paul B. McKee
  • Decompression sickness (DCS): Formation of nitrogen gas bubbles in the blood and body tissues caused by inadequate elimination of the nitrogen gas. As a diver descends and breathes air, the tissues can become saturated with nitrogen due to the increased pressure. As the diver ascends, the excess nitrogen must be eliminated. If the nitrogen is not eliminated, it can become trapped in the tissue, thus resulting in the symptoms of DCS. The term DCS is used in a general sense to denote all forms of injury due to bubble formation occurring as a consequence of a sudden reduction in ambient pressure.
    • Type I DCS is characterized by musculoskeletal pain (vague, intense pain), dermal complications (pruritus, rash, blebs), and constitutional symptoms (fatigue, malaise, anorexia). Extreme fatigue may be a sign or forerunner of a more severe decompression illness.
    • Type II DCS is characterized by neurologic symptoms (paresthesias, weakness, poor sphincter control, paralysis), cardiorespiratory symptoms (dyspnea, nonproductive cough, hemoptysis), and vestibular symptoms (tinnitus, dizziness, hearing loss) (1)[C].
  • Arterial gas embolism (AGE): A CNS injury (usually cerebral) or systemic injury (usually cardiac) as a consequence of pulmonary barotrauma. Barotrauma refers to injury produced by mechanical forces caused by a change of pressure in a gas-filled space (the lungs). Air released from an overpressurized alveolus enters the pulmonary circulation and causes occlusion of the organ's blood supply. Venous gas emboli reach the arterial circulation paradoxically via a patent foramen ovale or a right to left shunt (2,3,4)[C]. AGE can be confused with type II DCS.
  • It is sometimes difficult to tell the difference between type II DCS and AGE, because both can cause similar symptoms. The time of onset of symptoms may be more informative. The time course of air embolism symptoms from lung overexpansion is usually short (immediately or within minutes after surfacing), whereas decompression sickness usually develops later after a dive (hours to days).
  • Some clinicians advocate grouping type II DCS and AGE into 1 clinical entity called decompression illness (DCI). The 2 are treated the same (recompression).
  • Synonym(s): The bends; Air embolism; Caisson disease; Decompression illness
  • DCI is estimated to occur in ∼4 in 100,000 sport divers per year (Divers Alert Network statistics).
  • Predominant age is young adulthood (20–29 yrs).
  • Predominant sex is male; however, there is no evidence to suggest that men are more susceptible (5)[C].
Risk Factors
  • Rapid ascent from SCUBA diving
  • Flying too soon after SCUBA diving
  • Inexperienced divers (6)[C]
  • Multiple/repetitive dives
  • Tunnel work (Caisson disease)
  • Inadequate pressurization/denitrogenation when flying
  • Prolonged dive at depth of >33 ft
  • Taking a warm shower after diving
  • Obesity (nitrogen is lipid-soluble)
  • Fatigue
  • Dehydration
  • Poor physical conditioning
  • Acute illnesses (pulmonary or GI)
  • Breath-hold diving
  • Holding breath while ascending
  • Patent foramen ovale
  • Intracardiac septal defects
  • COPD (increases risk for pulmonary barotrauma)
  • Strenuous physical activity while diving (commercial diving)
  • Physical activity before or after diving
  • Panicking while diving
  • Diving in cold water
  • Rough sea conditions
General Prevention
  • Follow the dive profile.
  • Only dive nondecompression dives or perform adequate safety stops.
  • Avoid flying or traveling to higher altitudes for 24 hr after diving.
  • Maintain good hydration.
  • Avoid holding breath while diving.
  • The history should include the dive profile, rate of ascent, time of onset of symptoms, and changes in the type or intensity of symptoms.
  • An independent account from a dive buddy or dive instructor is often useful, especially if the patient's consciousness is impaired.
  • Obtaining information from a dive computer (if the patient was using one) is also very useful.
  • Note any history of previous dives in the past few days, any exposure to altitude (which can precipitate decompression sickness), and any previous health problems.
Physical Exam
  • Gas deposition in joints and soft tissues may manifest as a “pain only” syndrome (limb bends), or simple pruritus (cutis marmorata), blebs (or skin bends), fatigue, or vague soreness.
  • Gas deposition in the cerebral circulation causes strokelike symptoms (cerebral bends).
  • Gas deposition in the spinal cord (or autochthonous bubbles) can cause transverse paresis (spinal cord bends or spinal decompression sickness).
  • Development of bubbles in the inner ear can cause deafness or equilibrium dysfunction, nausea, vomiting, and nystagmus (inner ear bends or “staggers”).
  • Excessive venous bubbles develop and release vasoactive substances causing pulmonary irritation and bronchoconstriction. Symptoms may include chest pain, dyspnea, and cough (lung bends or “chokes”).
  • Other symptoms include headache, ataxia, delirium, coma, convulsions, confusion, patchy numbness, coughing paroxysms (Behnken's sign), arrhythmias, cardiac arrest, tachy- or bradycardia, vertigo, aphasia, blindness, and rapidly ascending paraplegia.
  • Skin lesions: Painful, pruritic, red rash on torso; burning blebs on skin; lymphedema. Also palpate skin for SC emphysema.
  • Joints: Erythema and edema on periarticular surfaces. There is usually pain with movement.
  • Neurologic: Various manifestations of a cerebrovascular accident, including numbness, weakness, aphasia, paresthesias, paralysis, paraplegia, confusion, personality changes, etc.
  • Cardiac: Arrhythmias, tachy- or bradycardia, findings of congestive heart failure
  • Pulmonary: Decreased breath sounds if pneumothorax present
Diagnostic Tests & Interpretation
  • Chest radiography to look for pneumothorax, mediastinal emphysema, heart enlargement
  • CT scan of the brain to look for cerebral abnormalities
  • US to look for gas bubbles in joints, tendons, bursae, muscles
  • Diagnostic repressurization (place the patient in a hyperbaric chamber, descend to 60 ft or 2.8 ATA; symptoms should improve within 15 min if DCS is truly the correct diagnosis)
Differential Diagnosis
  • Traumatic injury to extremity
  • Cerebrovascular accident
  • Acute myocardial infarction
  • Musculoskeletal strains
  • Urticaria/anaphylaxis
  • Malingering
  • Contaminated breathing gas (carbon monoxide)
  • Near drowning and hypoxic brain injury
  • Seafood toxin poisoning (ciguatera, puffer fish, paralytic shellfish, sea snake, cone shell)
  • Migraine
  • Guillain-Barre syndrome
  • Multiple sclerosis
  • Transverse myelitis
  • Spinal cord compression (from disk protrusion, hematoma, or tumor)
  • P.525

  • Middle ear or sinus barotrauma with cranial nerve compression
  • Inner ear barotrauma
  • Unrelated seizure (hypoglycemia, epilepsy) and postictal state from unrelated seizure
  • Cold water immersion pulmonary edema
Ongoing Care
Follow-Up Recommendations
  • Referral to the nearest hyperbaric chamber facility should be done as soon as possible.
  • Follow-up should be made with a physician knowledgeable in dive medicine.
  • The prognosis is excellent for early symptomatic presentation, referral, and treatment.
  • The duration and severity of symptoms prior to presentation and treatment negatively affects outcome.
  • 993.3 Caisson disease
  • 958.0 Air embolism as an early complication of trauma

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