The bag-mask device, often called a BVM or Ambu bag, provides manual ventilation to patients who are not breathing adequately or have stopped breathing. Healthcare providers and trained first responders widely use this device in emergencies like cardiac arrest, respiratory failure, and trauma, to maintain oxygen levels.
This manual method delivers positive pressure ventilation, pushing air into a patient’s lungs, ensuring they receive adequate oxygen until more advanced medical care is available. Compared to other techniques like mouth-to-mouth resuscitation, the BVM offers a more hygienic and efficient alternative.
Proper Setup and Patient Preparation
Effective bag-mask ventilation begins with proper setup and patient preparation. Selecting the correct mask size is important to ensure a secure fit over the patient’s nose and mouth. A mask that is too small will not fully cover the nose and mouth, while one that is too large may extend over the eyes or chin, leading to an ineffective seal. The mask should sit on the bridge of the nose, cover the entire mouth, and finish at the cleft of the chin.
Achieving and maintaining an airtight seal between the mask and the patient’s face is crucial to direct air into the lungs. A common and effective technique for this is the E-C clamp method. In this method, the thumb and index finger form a “C” shape around the mask, while the remaining three fingers form an “E” shape along the patient’s jawbone, lifting it towards the mask. The two-person technique, where one rescuer maintains the mask seal and airway while the second squeezes the bag, is generally preferred as it improves the seal and allows for more controlled air delivery.
Optimizing patient positioning is important for opening the airway. The head-tilt/chin-lift maneuver is a standard technique for unconscious patients without suspected spinal injury. This involves placing one hand on the patient’s forehead and gently tilting the head back while using the fingers of the other hand to lift the chin forward, moving the tongue away from the back of the throat and opening the airway. If a spinal injury is suspected, the jaw-thrust maneuver is the preferred method, as it opens the airway by lifting the jaw forward without tilting the head, minimizing neck movement.
Technique for Delivering Breaths
Once proper setup and patient positioning are established, the next step involves the precise technique for delivering breaths. The appropriate rate of ventilation varies depending on the patient’s age. For adults, the recommended rate is one breath every 5 to 6 seconds, equating to 10 to 12 breaths per minute. For children and infants, a faster rate of one breath every 3 to 5 seconds is advised, which translates to 12 to 20 breaths per minute.
When delivering breaths, the goal is to provide enough air to cause a visible, gentle rise of the patient’s chest. Over-inflating the lungs should be avoided. For adults, a tidal volume of approximately 500 to 600 mL per breath is sufficient, which often corresponds to squeezing the bag until it is about one-third full. Each breath should be delivered smoothly over approximately one second, allowing adequate time for exhalation between breaths.
Proper hand placement on the bag involves squeezing it to deliver the breath. If using the two-person technique, one rescuer maintains the mask seal and airway, while the second focuses on squeezing the bag. This coordination helps ensure consistent and effective air delivery.
Recognizing Effective Ventilation
Recognizing effective ventilation is important to ensure the patient receives adequate oxygen. The most observable sign of effective breath delivery is visible and symmetrical chest rise and fall with each breath. This indicates that air is entering the lungs and causing them to expand.
In addition to visual cues, rescuers should listen for breath sounds over both sides of the chest, indicating air entry into the lungs. Feeling for exhaled air from the mask during the patient’s passive exhalation can also confirm airflow. Monitoring the patient’s overall response provides further indication of effective ventilation, including an improvement in skin color or level of consciousness.
For trained rescuers, capnography measures the amount of carbon dioxide in exhaled breath (end-tidal CO2), offering real-time feedback on ventilation effectiveness. This advanced monitoring tool provides a numerical value and waveform that can help confirm adequate air exchange and guide ventilation efforts.
Addressing Challenges During Ventilation
Despite careful preparation and technique, challenges can arise during bag-mask ventilation that may hinder effectiveness. An inadequate mask seal is a common problem, allowing air to leak around the mask rather than entering the patient’s lungs. This can be addressed by re-adjusting the mask position, ensuring the correct mask size is used, applying the E-C clamp method firmly, or switching to a two-person technique for a better seal.
Airway obstruction can impede ventilation, often caused by the tongue falling back in an unconscious patient. Repositioning the patient’s airway using the head-tilt/chin-lift or jaw-thrust maneuvers can alleviate this. Inserting an oropharyngeal or nasopharyngeal airway adjunct can help maintain an open airway by preventing the tongue from obstructing the throat.
Gastric inflation, where air enters the stomach instead of the lungs, is a risk, especially with overly forceful or rapid ventilations. This can lead to vomiting and further complications. Minimizing gastric inflation involves delivering appropriate breath volumes, aiming only for visible chest rise, and avoiding aggressive squeezing of the bag. If gastric inflation occurs, reducing tidal volume while maintaining ventilation frequency can help.
Equipment malfunctions, such as the bag not refilling, are less common but require immediate attention. Checking for kinks in the oxygen tubing or issues with the bag’s one-way valve can help troubleshoot these problems.