Bag-valve-mask (BVM) ventilation, often recognized as an Ambu bag, is a manual resuscitation technique that delivers artificial breaths and positive pressure ventilation to individuals experiencing inadequate or absent spontaneous breathing in medical emergencies. It is a common and immediate intervention used in various settings, from pre-hospital environments to hospital critical care units.
Understanding the Bag-Valve-Mask Device
A BVM device comprises a self-inflating bag, a one-way valve system, and a face mask. The self-inflating bag is compressed to deliver air or oxygen-enriched air, automatically re-expanding after each compression by drawing in air from the environment or a connected oxygen source.
A one-way valve system directs gas flow towards the patient during compression and away from the bag during exhalation, preventing rebreathing. A face mask creates a tight seal over the patient’s nose and mouth, available in various sizes for different patient demographics.
Many BVMs also feature an oxygen reservoir (collapsible bag or tubing) and an oxygen inlet port, allowing connection to an external oxygen source for delivery of higher oxygen concentrations, sometimes approaching 100%.
The Mechanics of BVM Ventilation
Delivering controlled breaths with a BVM involves a manual process. First, position the patient and ensure an open airway, often with a head-tilt chin-lift or jaw-thrust maneuver. Airway adjuncts (oropharyngeal or nasopharyngeal devices) may be inserted to maintain patency, especially in unresponsive patients.
Once the airway is clear, the rescuer places the mask firmly over the patient’s nose and mouth, aiming for a complete seal to prevent air leakage. A tight mask seal is crucial for effective ventilation and often requires two hands, making a two-person technique more effective: one person focuses on the mask seal while the other compresses the bag.
The rescuer rhythmically compresses the self-inflating bag, forcing air or oxygen-enriched gas through the one-way valve and into the patient’s lungs. For adults, deliver approximately 500 to 600 milliliters of air with each squeeze, aiming for visible chest rise. When the bag is released, the one-way valve allows the patient to exhale as the bag re-inflates. This cyclical action mimics natural breathing, providing positive pressure ventilation for oxygenation and carbon dioxide removal.
Critical Situations for BVM Use
BVM ventilation is used when a person’s natural breathing is compromised. It addresses respiratory arrest (complete cessation of breathing), providing immediate artificial breaths to maintain oxygen supply to vital organs.
Another situation is inadequate breathing (severe hypoventilation), where breaths are too slow, shallow, or labored to sustain life. Causes include drug overdose, neurological conditions, or severe respiratory distress. The BVM augments these efforts, ensuring adequate oxygen and carbon dioxide removal.
During cardiopulmonary resuscitation (CPR), BVMs are integral for delivering rescue breaths to patients in cardiac arrest. Alongside chest compressions, effective BVM ventilation helps oxygenate the blood and improve outcomes. The device offers a more efficient and hygienic alternative to mouth-to-mouth ventilation.
The Role of BVM in Emergency Care
BVM ventilation is an immediate life-sustaining measure within emergency medical services. Trained healthcare professionals (paramedics, EMTs, nurses, physicians) routinely employ BVMs. It is a foundational skill taught in basic and advanced life support courses.
The BVM serves as a bridge, providing oxygenation and ventilation until more advanced airway management (e.g., endotracheal intubation) can be performed, or until the patient’s spontaneous breathing improves. Its portability and independence from external power sources make it valuable in pre-hospital settings and during patient transport. This rapid, effective respiratory support mitigates immediate threats to life and prevents further patient deterioration.