Comparison of Gas Embolism and Decompression Sickness

Symptoms and signs

Common: Unconsciousness, often with seizures (any diver who loses consciousness shortly after surfacing should be assumed to have arterial gas embolism and should be recompressed promptly)

Less common: Milder cerebral manifestations, signs of pulmonary barotrauma (eg, mediastinal or subcutaneous emphysema, pneumothorax)

Extremely variable—the bends (pain, most often in or near a joint), neurologic manifestations of almost any type or degree, and the chokes (respiratory distress followed by circulatory collapse—an extreme emergency), occurring alone or with other symptoms

Onset

Sudden, usually during or within a few minutes after surfacing

Usual: Gradual or sudden, with symptoms developing ≥ 1 hour after surfacing in about 50%; onset up to 24 hours after dives* of > 10 m (> 33 ft) or hyperbaric exposures of > 2 ATA

Rare: Symptoms developing > 24 hours after surfacing is rare although altitude exposure (eg, commercial aircraft flight) can cause delayed onset

Proximate cause

Usual: Breath holding or airway obstruction during ascent (even from a meter [a few feet] of depth, particularly when ascent is rapid); air trapped in the lungs expands during ascent and causes lung tissue injury

Occasional: Severe decompression sickness resulting in arterial bubbles or intrapulmonary gas trapping due to preexisting lung disease (eg, bullae, interstitial lung disease)

Usual: Diving or hyperbaric exposure, especially beyond no-stop limits

Occasional: Diving or hyperbaric exposure to shallow depths (12 m [40 ft] or shallower); low-pressure exposure (eg, flying after diving)

Mechanism

Usual: Overinflation of lungs causing entry of free gas into pulmonary vessels followed by embolization of cerebral vessels

Occasional: Coronary, renal, or cutaneous circulatory obstruction by free gas from any source

Formation of bubbles from excess dissolved gas in blood or tissue when external pressure decreases

Emergency treatment

Essential emergency care as needed (eg, airway patency, hemostasis, CPR or mechanical ventilation)

Prompt transport to nearest recompression chamber

Horizontal position if needed to maintain blood pressure

Unconscious patients with impaired airway reflexes should be kept in the lateral decubitus position to help prevent aspiration, if tracheal intubation is not feasible

100% oxygen by close-fitting mask

Fluids orally if patient is conscious; otherwise, IV

Arterial gas embolism after only a short, shallow dive may not require aggressive fluid administration

Essential emergency care as needed (eg, airway patency, CPR or mechanical ventilation)

Prompt transport to nearest recompression chamber

Horizontal position if needed to maintain blood pressure

Unconscious patients with impaired airway reflexes should be kept in the lateral decubitus position to help prevent aspiration, if tracheal intubation is not feasible

100% oxygen by close-fitting mask

Fluids orally if patient is conscious; otherwise, IV