A bag-mask device (BMD), also known as an Ambu bag or bag-valve-mask (BVM), is a handheld tool used to provide manual ventilation to individuals who are not breathing or breathing inadequately. It is a standard component of resuscitation kits in emergency settings. Delivering effective breaths with a BMD is important for patient outcomes. This article provides guidance on how rescuers can deliver these breaths effectively.
Mastering Bag-Mask Device Technique
Effective use of a bag-mask device begins with proper patient positioning to ensure an open airway. Placing the patient in the “sniffing position,” which involves flexing the neck forward and extending the head, helps align the airway passages. This alignment moves the tongue away from the back of the throat, which can otherwise obstruct airflow.
Achieving a tight, leak-proof seal between the mask and the patient’s face is important for effective ventilation. The “E-C clamp technique” is a common method, where the thumb and index finger form a “C” shape over the mask to hold it down, while the remaining three fingers form an “E” shape to lift the patient’s jaw into the mask. This technique helps prevent air from escaping around the mask edges. Avoid applying pressure to the eyes or soft tissues of the neck, as this can impede airway patency.
Airway opening maneuvers help maintain an unobstructed passage for air. The head tilt-chin lift maneuver involves tilting the head back and lifting the chin, suitable when spinal injury is not suspected. If spinal injury is possible, the jaw thrust maneuver, performed by lifting the jaw forward without tilting the head, is the preferred method to open the airway. These maneuvers help move the tongue and other soft tissues that might block the airway.
When delivering breaths, squeeze the bag smoothly over approximately one second, observing for visible chest rise. Provide just enough volume to cause the chest to rise, typically around 500-600 mL for an adult, while avoiding over-ventilation. Over-inflating the lungs can force air into the stomach, which can lead to complications. The recommended ventilation rate for adults is about one breath every 5 to 6 seconds, or 10-12 breaths per minute.
Employing a two-rescuer technique enhances the effectiveness of bag-mask ventilation. One rescuer can use both hands to maintain a secure mask seal and open the airway, while the second rescuer squeezes the bag to deliver breaths. This division of labor improves the mask seal, reduces air leaks, and minimizes rescuer fatigue, resulting in more consistent and effective ventilations.
Confirming Ventilation Effectiveness
Visually confirming effective breaths is a primary method to assess ventilation. Observing symmetrical chest rise and fall indicates that air is successfully entering and leaving the lungs. Minimal or no chest rise suggests that the ventilation is ineffective, requiring immediate reassessment of technique and airway patency.
Auscultation, or listening with a stethoscope, provides additional confirmation. Bilateral breath sounds indicate air movement in both lungs. Palpating for a carotid or femoral pulse during ventilation helps confirm that effective circulation is occurring alongside ventilation.
Capnography, or end-tidal carbon dioxide (ETCO2) monitoring, offers the most reliable real-time feedback on ventilation effectiveness and circulation. It measures the concentration of carbon dioxide in exhaled breath. A normal ETCO2 value typically ranges between 35-45 mmHg in healthy adults, and a normal capnography waveform appears rectangular. This direct measurement confirms effective gas exchange in the lungs and adequate perfusion.
Beyond these direct physiological indicators, observing patient response provides secondary signs of effective ventilation. An improvement in the patient’s skin color or an increased level of consciousness suggests effective ventilation. These changes, while not as immediate or precise as capnography, contribute to the overall assessment of ventilation success.
Addressing Common Obstacles
A poor mask seal is a frequent barrier to effective ventilation, often indicated by audible air leaks or the absence of chest rise despite proper bag squeezing. To correct this, reposition hands, ensuring the E-C clamp technique is applied firmly, or consider using a different size mask to better fit the patient’s face. Adjusting the patient’s head position can also improve the seal and direct air into the lungs.
Airway obstruction manifests as a lack of chest rise even with a good mask seal and proper bag compression. This can occur if the tongue falls back or if a foreign body is present. Corrective actions include repositioning the head using a head tilt-chin lift or jaw thrust maneuver, and visually checking the airway for foreign material. If indicated, suctioning can clear secretions or foreign bodies that are impeding airflow.
Gastric inflation, or stomach distension, can occur if too much air is delivered, if breaths are given too rapidly, or if the airway is partially obstructed. This complication increases the risk of regurgitation and aspiration, and can also elevate the diaphragm, hindering lung expansion. To minimize gastric inflation, breaths should be delivered slowly and gently, just until visible chest rise is achieved.
Equipment malfunction, though less common, can also impede effective ventilation. If issues persist despite addressing technique and airway patency, the bag-mask device itself should be checked. Inspect the oxygen tubing for kinks, ensure the reservoir bag is properly attached and inflating, and verify the one-way valve functions correctly to prevent rebreathing of exhaled air. Addressing these potential issues helps ensure the device is operating as intended.