Air Embolism



  • Increasing Incidence of Air Embolism (Due to Increasing Prevalence of Risk Factors)


Cardiothoracic Surgery/Procedures

  • Cardiopulmonary Bypass (see Cardiopulmonary Bypass): venous air embolism
  • Fine Needle Aspiration (FNA) of Lung
  • Lung Resection: venous air embolism
  • Rigid Bronchoscopic Neodymium-Yttrium-Aluminum-Garnet (Nd:YAG) Laser Resection of Endobronchial Lesion: venous air embolism may occur due to coolant gas from the bronchoscope entering the systemic circulation through pulmonary venules
  • Lung Transplantation (see Lung Transplant)

General Surgery/Gastrointestinal Procedures


  • General Comments: common surgical precipitant of venous air embolism (as the surgical incision is usually superior to the heart at a distance that is greater than the central venous pressure)
    • Patients are especially at risk of air embolism in the sitting position (Fowler’s position)
    • Incidence of venous air embolism during neurosurgical procedures in the prone position: 10%
    • Incidence of venous air embolism during neurosurgical repair of cranial synostosis in Fowler’s Position: 80%
  • Craniotomy (see Craniotomy)
  • Shunt Placement

Orthopedic Surgery

  • Arthrography
  • Arthroscopy (see Arthroscopy): venous air embolism
  • Endoprosthesis Placement
  • Total Joint Arthroplasty: venous air embolism

Otolaryngologic Surgery

  • General Comments: common surgical precipitant of venous air embolism (as the surgical incision is usually superior to the heart at a distance that is greater than the central venous pressure)


  • Abortion (by Suction or D+C)
  • Cesarean Section (see Cesarean Section): venous air embolism
  • Douching
  • Hysteroscopy (see Hysteroscopy): venous air embolism
  • Laparoscopy (see Laparoscopy): venous air embolism
  • Normal Labor
  • Oral Sex
  • Placenta Previa (see Placenta Previa)
  • Vaginal Insufflation

Intravascular Access-Related

  • General Comments
    • Venous Air Embolism Can Occur During Central Venous Catheter (CVC) Placement, During Use, or at Time of Catheter Removal (see Central Venous Catheter)
    • Risk Factors for Catheter-Related Air Embolism
      • Fracture or Detachment of Catheter Connections: accounts for 60-90% of episodes
      • Deep Inspiration During Catheter Insertion or Removal: increases the magnitude of negative pressure within the thorax
      • Dysfunction of Self-Sealing Valves in Cordis/Introducer Sheath
      • Failure to Occlude the Needle Nub and/or Catheter During Insertion or Removal
      • Hypovolemia: decreases central venous pressure
      • Presence of Persistent Catheter Tract After Central Venous Catheter Removal
      • Upright Positioning of Patient: decreases central venous pressure to below atmospheric pressure, increasing risk for entraining air rapidly into venous circulation
  • Arterial Line (see Arterial Line)
    • Epidemiology
      • XXXXX
  • Cardiac Pacemaker/Automatic Implantable Cardioverter-Defibrillator (AICD) Placement (see Cardiac Pacemaker and Automatic Implantable Cardioverter-Defibrillator)
    • Epidemiology
      • XXXX
  • Central Venous Catheter (CVC) Placement (see Central Venous Catheter): especially in internal jugular and subclavian veins
    • Epidemiology
      • Air embolism most often occurs with catheter hub fractures or disconnections rather than during the insertion of the catheter
    • Clinical
      • Antegrade Venous Air Embolism
      • Retrograde Cerebral Venous Air Embolism Has Been Reported in Association with Central Venous Catheter Placement (Am J Emerg Med, 2014) [MEDLINE]
        • Air Enters the Right Atrium and Travels to the Brain, Resulting in Retrograde Pneumocephalus (see Pneumocephalus)
  • Hemodialysis (see Hemodialysis)
    • Epidemiology
      • XXX
  • Intravenous Radiographic Contrast Injection (see Radiographic Contrast)
    • Epidemiology
      • XXXX
  • Percutaneous Coronary Intervention (PCI) (see Percutaneous Coronary Intervention)
    • Epidemiology
      • XXXX
  • Radiofrequency Catheter Ablation (see xxxxx)
    • Epidemiology
      • XXXX
  • Ruptured Swan-Ganz Catheter Balloon (see Swan-Ganz Catheter)


  • Blunt Abdominal Trauma: venous or arterial air embolism
  • Head/Neck Injuries (see Traumatic Brain Injury): venous or arterial air embolism
  • Penetrating/Blunt Chest Trauma: venous or arterial air embolism

Positive Pressure Ventilation

  • Positive Pressure Ventilation, Especially with High Levels of PEEP (see Invasive Mechanical Ventilation-General): gas may enter the circulation if the pulmonary vascular integrity is disrupted concomitantly with alveolar rupture from airspace overdistention
    • Occurs most commonly in adults with acute respiratory distress syndrome (ARDS) (see Acute Respiratory Distress Syndrome) or premature neonates with respiratory distress syndrome (hyaline membrane disease)

Decompression Sickness

  • Diving Ascent: breath hold (with closed glottis) with ascent leads to gas expansion within lungs, with rupture of alveoli into capillaries -> if the pulmonary veins tear as the alveoli rupture, air can return to the left heart with the oxygenated blood and then embolize through the arterial system (alternatively, air bubbles may form in the venous system during ascent and embolize to the systemic circulation via a patent foramen ovale)
    • Air embolism occurs in 7 out of every 100k dives


Venous Air Embolism to Right Ventricle/Pulmonary Circulation

  • Venous Air Embolism Results in Right Ventricular Obstruction: leading to right ventricular failure and increased central venous pressure and hypotension
  • Venous Air Embolism Results in Obstruction to Pulmonary Artery Outflow: results in “air lock”
  • Venous Air Embolism Results in Abrupt Rise in Pulmonary Pressures: due to air bubble emboli to the pulmonary vasculature
  • Air Bubbles Occlude Pulmonary Capillaries and Induce Vasoconstriction and Formation of Platelet Microthrombi: results in local endothelial damage and accumulation of neutrophils, platelets, fibrin, and lipid droplets at the gas-fluid interface
    • Localized pulmonary hypoperfusion: may result in hypercapnia
    • Noncardiogenic pulmonary edema
    • Bronchoconstriction
    • Hypoxemia: due to alveolar flooding and ventilation-perfusion mismatching
    • Increased physiologic dead space: with a rise in PaCO2 if ventilation is held constant
    • Decreased lung compliance: due to pulmonary edema
    • Increased airway resistance: due to bronchoconstricting mediators (serotonin, histamine) released from damaged endothelium
  • Rate/Volume of Air Introduced into the Venous Circulation Determine the Clinical Effect of Venous Air Embolization: due to the fact that the capacity of the lung to filter microbubbles of air from the venous circulation can be exceeded
    • It is estimated that 300-500 mL of gas introduced at a rate of 100 mL/sec is a fatal dose for humans (his flow rate can be achieved through a 14-gauge catheter with a pressure gradient of only 5 cm H2O)

Arterial Air Embolism to Systemic Circulation

  • Mechanisms of Arterial Air Embolism
    • Direct Introduction of Air into Arterial System
    • Incomplete Filtration of Air by Pulmonary Capillary Bed: the capacity of the lung to filter microbubbles of air from the venous circulation can be exceeded (as noted above)
    • Paradoxical Air Embolization From Right->Left Side of Heart Via Intracardiac Shunt: in patients with a left-to-right shunt, venous air embolization into the pulmonary circulation can raise right heart pressures and reverse the direction of the shunt, allowing paradoxical embolism to occur
    • Air Traversal of Pulmonary Circulation Via Pulmonary Arteriovenous Malformation (AVM)
  • Destination of Arterial Air Emboli
    • Coronary Artery
    • Brain
    • Spinal Cord
    • Skin
  • Occlusion of Systemic Vessels: bubbles occlude systemic vessels and allow formation of associated platelet microthrombi, inducing the release of mediators and oxygen free radicals

Diving Ascent

  • Ascent with closed glottis or obstructive airways disease (like asthma) can cause alveolar rupture -> results in pneumothorax or arterial air embolism
  • Air bubble embolism to pulmonary vasculature (or coronary arteries or CNS vessels in case of patent foramen ovale)
  • Bubbles occlude vessels and allow formation of associated platelet microthrombi
  • Large amounts of air can traverse pulmonary circulation


Electrocardiogram (EKG) (see Electrocardiogram)

  • Findings
    • Sinus Tachycardia (see Sinus Tachycardia)
    • Right Heart Strain: peaked p-waves
    • Non-Specific ST-Segment and T-Wave Changes
    • Acute Myocardial Ischemia/Infarction

Capnography (see Capnography)

  • Findings
    • Marked Discrepancy Between Arterial pCO2 and End-Tidal (Exhaled) CO2 May Occur in the Setting of Venous Air Embolism [MEDLINE]
      • Decreased End-Tidal CO2 Occurs Due to Increased Physiologic Dead Space and Worsening of Ventilation-Perfusion Matching
  • Intraoperative Echocardiography and End-Tidal CO2 Monitoring May Increase the Sensitivity of Detecting Early Air Emboli in High-Risk Patients During Surgery

Complete Blood Count (CBC) (see Complete Blood Count)

  • Findings
    • Thrombocytopenia (see Thrombocytopenia): due to formation of platelet microthrombi

Serum Creatine Kinase (CK) (see Serum Creatine Kinase)

  • Elevated Creatine Kinase May Occur in Divers with Air Embolism (Unclear if This Also Occurs in Other Patients with Air Embolism) (see Elevated Serum Creatine Kinase)

Chest X-Ray (CXR) (see Chest X-Ray)

  • Findings
    • Pulmonary Edema: may occur in cases who develop acute respiratory distress syndrome (ARDS) (see Acute Respiratory Distress Syndrome)
    • Air in Hepatic Circulation
    • Air in Main Pulmonary Artery
    • Atelectasis (see Atelectasis)
    • Enlargement of Pulmonary Artery
    • Focal Oligemia: predominantly in the upper lobes
    • Intracardiac Air

Chest Computed Tomography (CT) (see Chest Computed Tomography)

  • Findings
    • May detect air in the central venous system (especially the axillary and subclavian veins), right ventricle, or pulmonary artery
    • However, this finding is non-specific, as small (<1 mL), asymptomatic air emboli can be detected in 10-25% of contrast-enhanced CT scans if carefully sought: false positive CT studies may be more common when higher resolution or electron beam CT scanners are used

Head Computed Tomography (CT) (see Head Computed Tomography)

  • Findings
    • May Detect Intraparenchymal Gas and Diffuse Cerebral Edema

Hemodynamics (see Hemodynamics and Swan-Ganz Catheter)

  • Central Venous Pressure (CVP): increased
  • Right Ventricular Pressure: increased
  • Pulmonary Artery (PA) Pressure: increased (sensitivity: 45%)
  • Cardiac Output (CO): decreased
  • Mean Arterial Pressure (MAP): decreased

Pulmonary Function Tests (PFT’s) (see Pulmonary Function Tests)

  • DLCO: decreased

Transthoracic Echocardiogram (see Echocardiogram)

  • Findings
    • Acute Right Ventricular Dilation and Pulmonary Hypertension
    • Air within the Right Ventricle
  • Intraoperative Echocardiography or Transcranial Doppler Monitoring May Increase the Sensitivity of Detecting Early Air Emboli in High-Risk Patients During Surgery

Ventilation/Perfusion (V/Q) Scan (see Ventilation-Perfusion Scan)

  • Massive Air Embolism May Result in Perfusion Defects
    • However, Air Embolism-Related Perfusion Defects Usually are Transient and Resolve within 24 hrs (Chest, 1989) [MEDLINE]

Pulmonary Artery Angiogram (see Pulmonary Artery Angiogram)

  • Findings
    • Variably Positive
      • Negative: in cases where the air emboli are rapidly resorbed
      • Positive: may demonstrate signs of vascular occlusion or vasoconstriction -> corkscrewing, tapering, and/or delayed emptying of vessels (Prog Cardiovasc Dis, 1994) [MEDLINE]

Clinical Manifestations

General Comments

  • Minor Cases of Air Embolism: common and may be asymptomatic

Cardiovascular Manifestations

  • Acute Myocardial Infarction (see Coronary Artery Disease)
  • Acute Right Ventricular Failure (see Congestive Heart Failure): may occur when large amount of air is present in right ventricle
    • Elevated Central Venous Pressure (CVP)
  • Chest Pain (see Chest Pain): due to myocardial ischemia
  • Crepitus over Superficial Vessels: observed rarely in setting of massive air embolus
  • Hypotension (see Hypotension)
  • Mill Wheel Murmur: churning sound heard throughout the entire cardiac cycle
  • Pulmonary Hypertension/Cor Pulmonale (see Pulmonary Hypertension)
    • May Occur When Enough Air is Introduced to Obstruct Pulmonary Vasculature
  • Sinus Tachycardia (see Sinus Tachycardia)

Dermatologic Manifestations

Neurologic Manifestations

Ophthalmologic Manifestations

  • Bubbles within Retinal Arteries

Pulmonary Manifestations

  • Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)
    • Epidemiology: may occur even when small smounts of air are introduced
  • Acute Respiratory Failure (see Respiratory Failure)
    • Epidemiology: xxx
    • Clinical
      • Hypoxemia (see Hypoxemia): may be severe
      • Hypercapnia (see Hypercapnia): due to venous air embolism, causing localized pulmonary hypoperfusion and increased dead space
  • Cough/Gasp (see Cough)
    • Epidemiology: may occur when air enters the pulmonary circulation
  • Dyspnea (see Dyspnea)
    • Epidemiology: common (present in 100% of cases)
  • Pleuritic Chest Pain (see Chest Pain)
  • Tachypnea (see Tachypnea)
  • Wheezing (see Wheezing)


Mechanical Ventilation

  • Efforts Should Be Made to Minimize Barotrauma

Central Venous Catheter Removal

  • Catheters Should Be Removed Using a Specified Protocol to Minimize the Risk of Air Embolism


  • Doppler Ultrasound Can Detect Air Embolism During Neurosurgical Procedures


Spontaneous Resolution

  • May Occur in Some Cases, Due to Reabsorption of Air from Pulmonary Vessels

Supportive Care

Prevention of Further Air Embolization

Venous Air Embolism

  • Move Patient to Left Lateral Decubitus Position
    • This Position Places the Right Ventricular Outflow Tract Inferior to Right Ventricular Cavity, Causing Air to Migrate Superiorly into a Position within the Right Ventricle Where the Air is Less Likely to Embolize (and Which Prevents Foramen Ovale Crossover Which Might Result in Embolization to the Brain)
      • Durant’s Manuever: left lateral decubitus position (proven to decrease mortality in animal studies)
      • Left Lateral Decubitus Head Down Position
      • Trendelenburg Position (see Trendelenburg Position)

Arterial Air Embolism

  • Move Patient to Flat Supine Position
    • Due to the Force of Arterial Blood Flow, Air Bubbles Will Be Propelled Forward Even if the Patient is in Head Down Position: consequently, the above maneuvers are unlikely to trap air within the right ventricle
    • However, Head Down Positions Have the Potential to Exacerbate the Cerebral Edema Which is Generally Induced by Cerebral Air Embolism

Restoration of Circulation

  • Move Patient to Left Lateral Decubitus Position to Place the Right Ventricular Outflow Tract Inferior to Right Ventricular Cavity: these maneuvers (described above) may displace large bubbles from the right ventricular outflow tract, relieving the obstruction to blood flow
  • Chest Compressions (see Cardiopulmonary Resuscitation): force air out of the pulmonary outflow tract and into smaller pulmonary vessels, improving forward flow

Removal of Air Embolism

  • Percutaneous/Transcatheter Removal of Air from Right Ventricle: these have been used in studies, but the amount of air to be removed is usually small (<20 ml) and removal is generally limited
    • Percutaenous Needle Aspiration of Air
    • Removal of Air Via Central Venous Catheter: aspiration may be attempted in cases where a central venous catheter is already in place
  • High-Flow Supplemental Oxygen (see Oxygen)
    • Supplemental Oxygen Increases the Partial Pressure of Oxygen and Decreases the Partial Pressure of Nitrogen in the Blood, Resulting in a Positive Pressure Gradient for the Diffusion of Nitrogen from the Air Bubbles into the Blood, Accelerating Resorption of Air Emboli
      • High-Flow Supplemental Oxygen Increases the Partial Pressure of Oxygen in the Blood and Decreases the Partial Pressure of Nitrogen in the Blood (Undersea Hyperb Med, 1998) [MEDLINE]
        • This Results in Diffusion of Nitrogen from Inside of the Air Embolism Bubble (Which Has a High Nitrogen Content) into the Blood (Which Will Have a Low Nitrogen Content): decreases the size of the bubble, accelerating bubble resorption
    • In Contrast, Nitrous Oxide (N20) (Sometimes Given During General Anesthesia) Can Diffuse from the Blood into Air Emboli, Causing the Gas Bubbles to Enlarge and the Patient to Deteriorate (Anesth Analg, 1971) [MEDLINE] (Anesthesiology, 2007) [MEDLINE] (see Nitrous Oxide)
      • Therefore, Nitrous Oxide Should Be Discontinued if Air Embolism is Suspected
  • Hyperbaric Oxygen (see Hyperbaric Oxygen)
    • Rationale: decreases air bubble size and increases the arterial oxygen tension, potentially decreasing ischemia
      • May improve outcome even if it is delayed up to 30 hrs later
    • Indications
      • Cardiopulmonary Compromise
      • Neurologic Deficits


  • Corticosteroids (see Corticosteroids): no proven role (in decreasing spinal cord or cerebral edema) in the treatment of air embolism or decompression sickness

Specific Treatment of Diving-Related Air Embolism

  • Left Lateral, Trendelenburg Position (see Trendelenburg Position)
    • This Position Places the Right Ventricular Outflow Tract Inferior to Right Ventricular Cavity, Causing Air to Migrate Superiorly into a Position within the Right Ventricle Where the Air is Less Likely to Embolize (and Which Prevents Foramen Ovale Crossover Which Might Result in Embolization to the Brain)
    • Not clear that this is actually effective though, as blood flow (rather than buoyancy) may be the main determinant of whether air embolizes
  • Supplemental Oxygen (see Oxygen): 100% FIO2
    • Increases the diffusion gradient for nitrogen out of any air bubbles (causing them to shrink)
  • Hyperbaric Recompression: procedure of choice for both decompression sickness and venous/arterial air embolism -> increases nitrogen diffusion from bubbles (causing them to shrink)
    • No randomized trials to establish efficacy though
    • May be useful even in cases where therapy is delayed for 24 hrs or more
  • Correction of Hypothermia: indicated



  • Older studies cite a mortality rate of approximately 30%
  • Prognosis of Air Embolism in Patients Treated with Hyperbaric Oxygen (Intensive Care Med, 2010) [MEDLINE]
    • Intensive Care Unit Mortality Rate: 12%
    • Hospital Mortality Rate: 16%
    • 6-Month Mortality Rate: 18%
    • 1-Year Mortality Rate: 21%
  • Risk Factors for Death in ICU (Intensive Care Med, 2010) [MEDLINE]
    • Cardiac Arrest at Time of Air Embolization
    • Simplified Acute Physiology Score (SAPS II) of At Least 33 on Intensive Care Unit Admission
  • Risk Factors for Death Within 1 Year (Intensive Care Med, 2010) [MEDLINE]
    • Increasing Age
    • Presence of Babinski Sign at Intensive Care Unit Admission
    • Acute Kidney Injury
  • Predictors of Long-Term Neurologic Sequelae (Intensive Care Med, 2010) [MEDLINE]
    • Focal Motor Deficits or Babinski Sign at Intensive Care Unit Admission
    • Need for >5 Days of Mechanical Ventilation