An air embolism is a serious medical complication that occurs when a bubble of air or gas enters the bloodstream and obstructs blood flow. This event is most frequently associated with procedures involving intravenous (IV) access. Medical professionals take precautions to prevent air from entering the circulatory system during the insertion, use, and removal of these devices. The severity of the complication is determined by the volume and speed of air introduced into the veins.
Defining Air Embolism and Entry Via IV Access
An air embolism is the mechanical blockage of a blood vessel by a gas bubble. This occurs when a direct connection exists between an air source and the vascular system, and a pressure gradient favors the movement of air into the bloodstream. The risk varies depending on the type of IV access used.
Central venous catheters (CVCs), including PICC lines and implanted ports, pose a higher risk than standard peripheral IVs. CVCs route directly into the large central veins near the heart. In these large veins, pressure is often negative relative to the atmosphere, especially during inhalation, which can actively suck air into the body.
Air can enter the central circulation if meticulous technique is not maintained during several common procedures. These include the insertion or removal of the catheter, exposing the open lumen to air. Improper line management, such as a loose connection, a cracked catheter, or an open, unclamped port, also provides a pathway for air ingress. Furthermore, failure to completely remove air from IV tubing, syringes, or infusion bags before connecting them to the patient can introduce air into the vein.
How Air Embolism Affects the Body
Once air enters the venous system, it travels to the right side of the heart. If a large volume of air enters rapidly, it can accumulate in the right ventricle and the pulmonary artery, creating a mechanical obstruction known as an “air lock.”
This air lock prevents the right ventricle from effectively pushing blood into the pulmonary circulation, leading to a sudden drop in cardiac output and acute right-sided heart failure. Consequences include sudden shortness of breath, chest pain, and a rapid heart rate. Low blood pressure and confusion follow as the body’s tissues are starved of oxygenated blood.
A specific finding is the “mill-wheel murmur,” a churning sound heard over the heart as the air and blood mix. Smaller air bubbles that pass into the lungs can cause pulmonary artery hypertension. Air can also pass from the right to the left side of the heart through an existing opening, such as a Patent Foramen Ovale, leading to an arterial air embolism that can cause a stroke or heart attack.
Safety Measures for Preventing Air Embolism
Preventing air embolism relies on established protocols for IV access devices. Before any infusion, all air must be removed from the IV tubing and syringes through priming. Specialized equipment, like infusion pumps with air-in-line detectors, provides an additional technological safeguard.
Patient positioning is important when manipulating central lines. During insertion or removal of a central venous catheter, the patient is often placed in the Trendelenburg position (lying on the back with the head lower than the feet). This positioning increases central venous pressure, counteracting the negative pressure gradient that could draw air into the vein.
Healthcare providers instruct patients to perform a Valsalva maneuver (bearing down or holding their breath during exhalation) as the catheter is being pulled. This action increases intrathoracic pressure, preventing air from being sucked into the open vein. After removal, an air-occlusive dressing must be applied immediately to seal the insertion site.
Emergency Treatment Steps
If an air embolism is suspected, medical staff must prevent further air entry by clamping the line or securing the connection. The patient is given 100% oxygen to breathe, which helps reduce the size of the air bubble. This high-flow oxygen promotes the diffusion of nitrogen out of the bubble and into the bloodstream for removal.
Repositioning the patient is done using the left lateral decubitus Trendelenburg position, also known as Durant’s maneuver. The patient is placed on their left side with the head tilted down. This helps shift the air bubble away from the pulmonary artery opening and trap it in the apex of the right ventricle, relieving the air lock.
Further measures include supportive care for blood pressure and circulation, often with intravenous fluids or medications. If a central line is present, aspiration of the air directly from the right atrium via the catheter may be attempted. Hyperbaric oxygen therapy (HBOT) may be considered for neurological symptoms or cardiovascular instability. HBOT involves breathing 100% oxygen at high pressure, which compresses the air bubble and accelerates its dissolution.