A Bag-Valve-Mask (BVM) is a hand-held device used to provide manual ventilation to individuals who are not breathing adequately or have stopped breathing entirely. Also known as an Ambu bag, it allows a rescuer to deliver breaths by manually compressing a self-inflating bag connected to a face mask. Its purpose is to deliver positive pressure ventilation. Proper BVM operation is important for patient safety and effective oxygenation, making it a standard component in resuscitation kits and healthcare settings.
The Preferred Two-Person Technique
Operating a BVM is most effective when performed by two trained individuals. This two-person approach allows for a better mask seal and consistent ventilation, reducing operator fatigue during prolonged use. One rescuer focuses on maintaining an airtight seal on the patient’s face and ensuring an open airway. The second rescuer concentrates on squeezing the bag to deliver breaths, which improves the delivery of oxygen and ventilation.
The rescuer responsible for the mask seal positions themselves at the patient’s head. They use both hands to hold the mask firmly against the face, employing techniques like the E-C clamp or thenar eminence grip. The E-C clamp uses the thumb and index finger to form a “C” shape around the mask, pressing it down, while other fingers form an “E” to lift the jaw. The thenar eminence grip involves placing both thumbs over the mask to hold it, while fingers lift the jaw. This two-handed technique provides a better mask-to-face seal compared to a one-handed approach.
Once a secure mask seal and open airway are established, the second rescuer attaches the bag to the mask and begins ventilation. They squeeze the bag smoothly, just enough to cause visible chest rise, indicating effective air delivery. For adults, each breath should be delivered over one second. This collaborative method ensures adequate tidal volume is delivered without excessive pressure.
Operating a BVM Solo
While the two-person technique is the preferred method, situations may arise where a single operator must manage BVM ventilation. Operating a BVM alone presents challenges, mainly in simultaneously maintaining a mask seal and compressing the bag. Achieving a tight seal with one hand can be difficult, due to the need for strong hand muscles and precise positioning to prevent air leaks. Poor sealing leads to ineffective ventilation and compromised oxygen delivery.
For solo operation, the E-C clamp technique is used with one hand. The rescuer forms a “C” with their thumb and index finger over the mask to press it onto the face, while other fingers (forming an “E”) lift the patient’s jaw to open the airway. This single-handed grip must provide sufficient pressure to seal the mask while also applying upward traction on the jaw to maintain an open airway. Despite careful technique, solo BVM ventilation is less efficient than the two-person method due to the difficulty in performing both tasks effectively.
Solo BVM operation is reserved for scenarios where limited personnel are available, like initial patient contact in an emergency. In these instances, the single rescuer prioritizes establishing ventilation until additional help arrives. While necessary, this method may not achieve the same ventilatory effectiveness as a two-person effort.
Key Elements for Successful Ventilation
Regardless of the number of operators, several principles ensure effective BVM ventilation. Maintaining an open airway is primary. This involves positioning the patient’s head using maneuvers like the head tilt-chin lift or jaw thrust to move the tongue. Airway adjuncts, such as oropharyngeal or nasopharyngeal airways, can also be inserted to maintain an open airway.
Achieving a proper mask seal is also important, as leakage prevents effective air delivery. The mask must cover both the patient’s nose and mouth without extending past the chin, ensuring a tight fit against facial contours. Selecting the appropriate mask size is important for establishing this seal. Facial hair or lack of teeth can make it challenging to obtain a good seal, sometimes requiring adjustments or airway adjuncts.
Delivering the appropriate tidal volume, the amount of air with each breath, is another factor. For adults, a tidal volume of 500-600 milliliters, or 6-8 mL/kg of body weight, is recommended. For children, the volume is adjusted based on weight; infants need 20-30 mL/kg, and children aged 1-8 years need 10-15 mL/kg. Visible chest rise is the main indicator of adequate volume delivery, and rescuers should avoid over-inflating the lungs to prevent harm.
The correct ventilation rate is also important for patient outcomes. For adults, the recommended rate is 10 to 12 breaths per minute, or one breath every 5-6 seconds. For children, a rate of one breath every 3 to 5 seconds is recommended, while infants require one breath every 2 to 3 seconds. An oxygen flow rate of 10 to 15 liters per minute should be connected to the BVM with a reservoir bag to maximize oxygen concentration. Monitoring for chest rise and fall, and patient response, confirms ventilation effectiveness.