Arterial Gas Embolism

Other Names

• Air embolism
• Gas Embolism
• Diving gas embolism

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Background

• This page refers to Arterial Gas Embolism (AGE), a potential catastrophic phenomenon in which compressed gases enters the arterial circulation during ascent causing end organ dysfunction

History

• First reported by Pol in 1854

Epidemiology

• DCS is far more common than AGE in the available literature
  • In two case series of 3018 cases, only 6.5% were diagnosed as AGE

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Pathophysiology

• General
  • Classically presents with loss of consciousness within minutes of surfacing, leading to stroke-like symptoms
  • Should be considered the most severe form of decompression sickness, but can be difficult to distinguish clinically
• Terminology
  • Decompression Illness (DCI): broad term encompassing all disease processes related to decompression
  • Decompression Sickness (DCS): intra- or extravascular bubbles formed as a result of decompression
  • Arterial Gas Embolism (AGE): severe form of DCI in which gas bubbles are introduced into the arterial circulation
  • Decompression Stress: undefined term, need update

Etiology

• General
  • Most commonly occurs from pulmonary barotrauma vis-a-vis ruptured alveoli
  • Less commonly from severe decompression sickness
  • Migration from the venous vasculature via a right-to-left shunt (i.e. patent foramen ovale, atrial septal defect)
• Gas
  • Usually nitrogen
  • Expanding compressed gas trapped in the lungs as pressure falls during ascent
  • Leads to rupture of alveolar-capillary membranes, gas enters pulmonary vasculature
  • May follow breath holding, hyperinflation of the lung
  • May be associated with local lung disease (e.g. bronchial obstruction, bullae)
• Depth
  • Can be seen after ascent from the surface from a depth as shallow as 1 m (pressure change, 0.1 atm)
• End organ dysfunction
  • Occurs due to large intra-artial bubbles
  • Cerebral embolism considered the most serious manifestation
  • Can cause ischemia to other organs (eg, spinal cord, heart, skin, kidneys, spleen, gastrointestinal tract).
• Non-diving causes
  • Non-diving accidents involving compressed air
  • Examples include cardiopulmonary bypass, lung biopsy, neurosurgical procedures

Associated Conditions

• Pulmonary Barotrauma
• Decompression Sickness

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Risk Factors

• Sports
  • Diving
• Occupational
  • Spaceflight
  • Aviation

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Differential Diagnosis

Differential Diagnosis Dive Medicine

• Barotrauma of descent
  • Otic Barotrauma: "ear squeeze"
  • Sinus Barotrauma: "sinus squeeze"
  • Mask Squeeze: air in the mask decreases in volume during a dive, creating negative pressure
  • Barodentalgia: trapped dental air causing squeeze
• At depth injuries
  • Oxygen Toxicity: harmful effects of breathing oxygen at higher partial pressures than normal
  • Nitrogen Narcosis: toxic effects of breathing nitrogen-containing gases while at depth
  • Hypothermia: decrease core temperature with prolonged exposure to cold water
  • Carbon Monoxide Toxicity: CO toxicity typically results from a faulty air compressor
  • Caustic Cocktail: Inhalation of absorbent material used to scrub CO2 mixes with water
• Barotrauma of ascent
  • Pulmonary Barotrauma: occurs when diver breathing compressed air ascends too rapidly
  • Decompression Sickness: Dissolved nitrogen comes out of solution, forms bubbles in blood and tissue ("the bends")
  • Arterial Gas Embolism
  • Alternobaric vertigo
  • Facial baroparesis (Bells Palsy)
• Other
  • Immersion Pulmonary Edema: also termed swimming induced pulmonary edema
  • Salt water aspiration
  • Submersion Injury: includes drowning, near drowning

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Clinical Features

• History
  • Symptoms develop quickly and dramatically following ascent
    • One study found symptoms occurred at ascent to the surface or within 5 minutes after arrival in 92% of cases
    • Latency greater than 10 minutes is rare should broaden the differential
  • Ascent is often rapid
    • For example, panic induced breath holding after an underwater mishap
    • However, AGE can occur during a normal ascent
  • Causes variety of stroke-like syndromes upon ascent
    • Loss of consciousness (39%)
    • Confusion (37%)
    • Dizziness and presyncope (30%)
    • Hemiplegia (27%)
    • Visual changes (21%)
    • Headache (20%)
    • Dysphasia (11%)
    • Seizures (11%)
  • Sudden death can occur
  • Type II decompression sickness may also be present
    • About half of cases of symptoms of pulmonary barotrauma (chest pain, hemoptysis, etc)
    • Coronary: arrhythmias, myocardial infarction, cardiac arrest
    • Skin: cyanotic marbling of skin, focal pallor of tongue
    • Kidneys: hematuria, proteinuria, renal failure
• Physical Exam
  • Thorough neurological exam
  • Thorough cardiopulmonary exam

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Evaluation

• The diagnosis is primarily clinical
  • There are no specific biomarkers or imaging signs
  • MRI and CT are not sensitive enough to exclude
  • Diagnostic testing often does not contribute and should not delay treatment
  • However in patients with a broader differential, relevant investigations may be appropriate

Imaging

• May be helpful to confirm suspected diagnosis
  • Echocardiography (showing air in the cardiac chambers)
  • Chest CT (showing local lung injury or hemorrhage)
  • Head CT (showing intravascular gas and diffuse edema), although visible arterial gas is inconsistently present and its absence does not rule out arterial gas embolism
  • Abdominal CT (showing gas within mesenteric vessels or the portal vein)

Radiographs

• Standard Chest Radiograph
  • May show pneumothorax, pneumomediastinum, etc

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Classification

• Not applicable

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Management

• First Aid/ Prehospital
  • Standard resuscitation efforts should be performed if necessary
  • Place diver in supine position
  • Administer the highest oxygen fraction of inspired O2 possible
• Positioning
  • Keep patient supine
  • Placement in lateral decubitus position or Trendelenburg is no longer recommended
• Oxygen Therapy
  • Patients seen with suspected AGE should be placed on 100% oxygen as soon as possible
  • This should be continued until HBOT is initiated
  • Of 1045 divers who received Oxygen as first aid, 14% had complete relief of symptoms, 51% had reduced symptoms
    • The cohort also had lower odds of requiring multiple recompression treatments compared to divers who did not get oxygen
• IV Fluids/ hydration
  • Divers are often relatively dehydrated due to multiple factors, including immersion diuresis
  • Active hydration strategy has been show to reduce post dive venous gas emboli
  • If awake, divers should drink noncarbonated, noncaffeinated, nonalcoholic fluid containing sodium and glucose
• Hyperbaric Oxygen Therapy (HBOT)
  • Goals: reduce bubble volume (thus reducing symptoms caused by mechanical disruption of tissue and relieving ischemia)
  • Patient should be immediately recompressed
  • Patient should be flown in compressed airplane if necessary
  • Response to recompression deteriorates with increasing time from injury to compression
• Hemodynamic instability
  • Can make HBOT very tricky
  • Maintain in supine position
  • Endotracheal intubation often required
  • Mechanical ventilation, vasopressors
• Medications
  • Tenoxicam (an NSAID), reduced he number of recompressions required to reach full recovery or a plateau
  • Lidocaine is thought to be neuroprotective; its role in AGE is currently not known

Prevention

• See: Dive Medicine Prevention
• Preventing AGE
  • Slow, controlled ascent
  • Careful exhalation during the last 10 m so that the lungs do not over pressurize

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Rehab and Return to Play

Rehabilitation

• Needs to be updated

Return to Play/ Work

• Needs to be updated

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Complications and Prognosis

Prognosis

• Needs to be updated

Complications

• Death
• Permanent neurological injury

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See Also

• Internal
  • Dive Medicine Main
  • Environmental Main

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