Basics
Description
- Results when air bubbles enter the pulmonary venous return from ruptured alveoli, then propagate through the systemic vasculature:
- Clinical manifestations depend on location of air bubbles in systemic vasculature system.
- Also known as dysbaric air embolism or cerebral air embolism
- Caused by overpressurization of lung tissue, causing pleural tear with air entering the vascular circulation:
- Trapped air (in lungs with closed glottis) expands on diver ascent.
- Boyle law: At a constant temperature, pressure (P) is inversely related to volume (V):
- PV = K (constant) or P1V1 = P2V2
- As pressure increases/decreases, volume decreases/increases.
Etiology
- Pulmonary atrioventricular (AV) shunts, or as paradoxical embolism via a patent foramen ovale
- Breath holding during ascent:
- Symptoms attributable to a shower of bubbles and multiple blood vessel involvement
- Iatrogenically during placement of central venous pressure (CVP) lines, cardiothoracic surgery, or hemodialysis
- Penetrating injuries to heart, with emergent repair of cardiac wound
Diagnosis
Signs and Symptoms
- Cerebral:
- Rapid onset:
- Almost all cases of AGE present within 1st 5 min of surfacing, although most often symptoms are evident in 1st 2 min
- Dive-related stroke
- 2 main presentations:
- Apnea and full cardiopulmonary arrest
- Any combination of neurologic deficits
- Presentation depends on arterial distribution of gas embolism:
- Stupor or confusion (24%)
- Coma without seizure (22%)
- Coma with seizures (18%)
- Unilateral motor deficits (14%)
- Visual disturbances (9%)
- Vertigo (8%)
- Unilateral sensory deficits (8%)
- Bilateral motor deficits (8%)
- Collapse (4%)
- Spontaneous improvement minutes after initial deficits may occur:
- High incidence of relapse
- Improvement may be transiently related to postural changes that affect distribution of bubbles flowing to brain.
- Pulmonary:
- Dyspnea
- Hemoptysis, pleuritic chest pain
- Subcutaneous air
- Cardiac:
- MI owing to air in coronary vessels
- Reduced cardiac output owing to air trapped in ventricle
- Hamman sign: Crepitus on auscultation of heart
- Renal:
- Renal infarction owing to air embolism
History
Elicit time of symptom onset in relation to dive surfacing (almost all symptoms occur within the 1st 10 min).
Physical Exam
Careful neurologic exam owing to the wide variety of neurologic manifestations
Essential Workup
- Clinical diagnosis: Recognize risk factors and various clinical presentations.
- Inquire as to unusual circumstances during ascent:
- Breath holding
- Panic/out-of-air situation
- Thorough neurologic exam must carefully document the extent of the deficits to the motor, sensory, cerebellar, and cranial nerves.
Diagnosis Tests & Interpretation
Lab
- Serum creatinine kinase activity:
- Marker of the severity of cerebral AGE
- CBC
- Electrolytes, BUN, creatinine, glucose
- ABG when respiratory symptoms are present
Imaging
- CXR:
- For evidence of pneumothorax or mediastinal emphysema (both rare)
- Chest CT
- For evidence of local lung injury or hemorrhage
- Ventilation Perfusion Scan
- For evidence consistent with pulmonary emboli
- EKG
- Echo:
- Looking for evidence of patent foramen ovale
- CT head:
- For altered mental status
- Do not delay recompression for CT when AGE almost certain clinically.
Differential Diagnosis
- Cerebrovascular accident (CVA) from causes unrelated to gas embolism
- Neurologic deficits owing to decompression sickness
Treatment
Pre-Hospital
- Cautions:
- Patients who experience sudden neurologic recovery can relapse quickly as bubble positions change.
- Recognize AGE as a potential diagnosis.
- Altered mental status within 10 min of surfacing from compressed air dive
- Sudden neurologic decompensation following placement of central line
- Controversies:
- Trendelenburg positioning patients with suspected AGE is not effective:
- Hypothesized that elevation of legs could cause air bubbles to migrate away from cerebral circulation and that increased hydrostatic pressure in brain will shrink bubbles
- Trendelenburg positioning may in fact increase injury by increasing intracerebral pressure.
Initial Stabilization/Therapy
ABCs:
- 100% oxygen by tight-fitting mask
- Intubation for ventilation/protection of airway required
- IV access with volume augmentation
Ed Treatment/Procedures
- Hyperbaric oxygen recompression therapy (see "Hyperbaric Oxygen Therapy"):
- For all AGE
- Arrange transportation to nearest hyperbaric facility.
- Aircraft capable of cabin pressurization below 1,000 feet barometric pressure best suited for transfers
- Prophylactic chest tube for simple pneumothorax to prevent conversion to tension pneumothorax during recompression
- Fill endotracheal and Foley catheter balloons with water or saline to avoid shrinkage/damage during recompression.
- Divers alert network (DAN):
- Based at Duke University Medical Center
- Provides 24 hr emergency hotline for medical consultation on treatment of dive-related injuries and for referrals to hyperbaric chambers (telephone: [919] 684-8111)
Follow-Up
Disposition
Admission Criteria
Admit all following initial hyperbaric therapy for observation and re-exam.
Discharge Criteria
No AGE patients should be discharged from the ED.
Followup Recommendations
Hyperbaric oxygen referral for patients with arterial gas embolisms
Pearls and Pitfalls
- Symptoms occur during ascent or within 10 min of reaching the surface.
- Patients who experience sudden neurologic recovery can relapse quickly as bubble positions change.
- Fill endotracheal and Foley catheter balloons with water or saline to avoid shrinkage/damage during recompression.
Additional Reading
- Hawes J, Massey EW. Neurologic injuries from scuba diving. Neurol Clin. 2008;26:297-308.
- Levett DZ, Millar IL. Bubble trouble: A review of diving physiology and disease. Postgrad Med J. 2008;84:571-578.
- Lynch JH, Bove AA. Diving medicine: A review of current evidence. J Am Board Fam Med. 2009;22:399-407.
- Tourigny PD, Hall C. Diagnosis and management of environmental thoracic emergencies. Emerg Med Clin North Am. 2012;30:501-528.
- Van Hoesen KB, Bird NH. Diving medicine. In: Auerbach PS, ed. Wilderness Medicine. 6th ed. St. Louis, MO: CV Mosby; 2011.
See Also (Topic, Algorithm, Electronic Media Element)
- Barotrauma
- Decompression Sickness
- Hyperbaric Oxygen Therapy
Codes
ICD9
958.0 Air embolism
ICD10
T79.0XXA Air embolism (traumatic), initial encounter
SNOMED
- 302968001 Arterial air embolus