The Bag-Valve-Mask (BVM) is a manual ventilation tool used in emergency medical settings to provide immediate respiratory support to a patient unable to breathe adequately. This handheld device functions as a temporary, positive-pressure ventilator, manually pushing air into the patient’s lungs. Often referred to by the proprietary name “Ambu bag,” the BVM is a standard component of resuscitation kits in both pre-hospital and hospital environments.
Core Components and Function
The BVM system is composed of three main parts: a self-inflating bag, a one-way valve mechanism, and a face mask interface. The self-inflating bag, which typically has a capacity of 1,000 to 1,600 milliliters for adults, acts as the air reservoir and manual pump for ventilation. Squeezing this bag forces the gas through a one-way valve system and into the patient’s airway.
The non-rebreathing valve directs forced air into the patient while simultaneously preventing the patient’s exhaled breath from returning to the bag. When the rescuer releases the bag, it automatically expands, drawing in either ambient air or supplemental oxygen through a separate inlet. An oxygen reservoir bag is attached to the BVM’s air inlet, allowing the device to deliver a high concentration of oxygen, potentially close to 100%, with each breath.
Primary Scenarios for Use
The BVM provides positive pressure ventilation to patients who have insufficient or absent spontaneous breathing. This includes respiratory arrest, where the patient has stopped breathing entirely, or severe respiratory failure, where breathing is too shallow or slow. The device is used during cardiopulmonary resuscitation (CPR) following a cardiac arrest to deliver rescue breaths between chest compressions.
The BVM also prepares a patient for advanced airway procedures, such as endotracheal intubation. Clinicians use the device for pre-oxygenation, giving the patient a high concentration of oxygen before the procedure begins. It can also maintain temporary ventilation for patients dependent on a mechanical ventilator who need to be moved within the hospital. The BVM is an immediate, portable solution for managing a compromised airway until a more definitive method can be established.
Key Operational Considerations
Effective BVM use requires trained personnel to achieve a proper seal and deliver breaths correctly. A significant challenge is ensuring a tight, leak-free seal between the face mask and the patient’s face. Clinicians often use a technique involving their hand to form a “C” shape over the mask and an “E” shape under the jaw to lift it, ensuring the airway remains open and the mask is secure.
The effectiveness of the BVM is directly tied to the use of supplemental oxygen. While the device can function using ambient air, connecting it to an oxygen source at a high flow rate, typically 15 liters per minute, ensures the patient receives the highest possible oxygen concentration. If ventilation is performed too forcefully or with excessive volume, it can lead to gastric insufflation. This occurs when air is pushed into the esophagus and stomach, increasing the risk of regurgitation and aspiration of stomach contents into the lungs.
To mitigate these risks and improve the mask seal, the two-person technique is often preferred, particularly in pre-hospital settings. One rescuer maintains the firm, two-handed seal and lifts the patient’s jaw to open the airway. The second rescuer focuses on squeezing the bag with slow, controlled breaths, ensuring only enough volume is delivered to produce visible chest rise.