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For further information, see CMDT Part 37-13: Dysbarism & Decompression Sickness

Key Features

Essentials of Diagnosis

  • Symptoms temporally related to recent altitude or pressure changes (eg, scuba diving and flying)

  • Early recognition and prompt treatment are extremely important

  • Patient must also be assessed for hypothermia, hypoglycemia, concurrent injuries, and medical conditions

  • Consultation with a specialist in diving medicine or in hyperbaric oxygen therapy is indicated

General Considerations

  • Dysbarism and decompression illness result from altitude changes and the environmental pressure effects on gases in the body during underwater descent and ascent, particularly when scuba diving is followed closely by travel to high altitudes (ie, air travel or mountain hiking)

  • Dysbarism results from barotrauma when gas compression or expansion occurs in parts of the body that are noncompressible or have limited compliance

    • Pulmonary overinflation syndrome

      • One of the most serious and potentially fatal results of barotrauma

      • Due to an inappropriately rapid ascent causing alveoli rupture and air bubbles extravasation into tissue planes or even the cerebral circulation

    • Lung barotrauma can result in

      • Pneumomediastinum

      • Pneumothorax

      • Rupture of the pulmonary vein causing arterial gas embolism

    • Overpressurization of the bowels may occur, resulting in

      • Gastric rupture

      • Bowel obstruction or perforation

      • Pneumoperitoneum

    • Less serious conditions include

      • Mask squeeze

      • Ear squeeze

      • Sinus squeeze

      • Headache

      • Tooth squeeze

  • Decompression illness occurs when pressure change is too rapid from higher pressure to lower pressure

    • Symptoms depend on the size and number of gas bubbles released (notably nitrogen)

    • Location (eg, coronary, pulmonary, spinal or cerebral blood vessels, joints, soft tissue) of released gas bubbles also determines symptoms

  • The appearance of symptoms depends on

    • Dive details (depth, duration, number of dives, and interval surface time between dives, water conditions)

    • Degree of physical exertion

    • Age, weight, and physical condition of the diver

    • Rate of ascent

    • The length of time between the low altitude (scuba dive) and high altitude (air travel or ground ascent)

  • Predisposing factors for decompression illness

    • Obesity

    • Injury

    • Hypoxia

    • Lung or cardiac disease, especially right to left cardiac shunt (ie, patent foramen ovale)

    • Dehydration

    • Panic attacks

    • Other comorbidities

    • Alcohol and medication effects

  • Decompression illness also occurs in persons who take hot showers after cold dives

  • Delayed decompression illness

    • May be caused by the cavitation effects of gas trapped in the body, which is described as "vacuum phenomenon" in radiological studies

    • Clinical cases have been reported following post-dive exercise

  • Possible contraindications to diving

    • Asthma

    • Pneumothorax

    • Reduced pulmonary function

    • Lung cysts

    • Thoracic trauma

    • Cardiovascular disease

    • History of bowel obstruction

    • Recent brain or eye surgery

    • Seizures

    • Diabetes mellitus and hypoglycemic episodes

  • Definite contraindications to diving

    • Perforated tympanic membrane

    • Active upper respiratory infection

Clinical Findings

Symptoms and Signs

  • Symptom onset may be immediate, within minutes or hours (in the majority), or up to 36 hours later

  • Symptoms are highly variable

    • Pain in the joints ("the bends")

    • Skin pruritus ...

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