A Bag-Mask Device (BMV) is a manual resuscitation tool used to provide positive pressure ventilation to a patient who is not breathing or whose breathing is inadequate. This equipment consists of a self-inflating bag, a one-way valve, and a face mask. The ability to deliver oxygen and ventilate the lungs effectively is directly linked to patient survival and preventing hypoxic brain injury. Achieving effectiveness requires the operator to master preparing the patient’s airway and maintaining a tight seal.
Establishing Airway Patency and Mask Seal
Effective ventilation requires ensuring the airway is open, as the tongue and soft tissues often obstruct the throat in an unconscious patient. Proper positioning is achieved by placing the patient in the “sniffing position,” involving slight neck flexion and head extension to align the ear canal with the sternal notch. This alignment helps pull the tongue away from the posterior pharyngeal wall, creating an unobstructed path for air movement.
For patients without a suspected spinal injury, the head tilt-chin lift maneuver further opens the airway by gently tilting the head back and lifting the bony part of the chin. If a spinal injury is suspected, the jaw thrust maneuver is employed instead, as it minimizes neck movement while lifting the lower jaw forward.
Once the airway is positioned, the mask must be seated correctly over the patient’s face, covering both the nose and mouth. Choosing the correct mask size is important, as a mask that is too small prevents a proper seal, while one that is too large can be difficult to manage. A tight, leak-free seal directs air into the lungs.
The single-person technique utilizes the E-C grip, where the thumb and index finger form a “C” shape to press the mask down, while the remaining three fingers form an “E” shape to lift the jaw. The two-person technique, where one rescuer uses both hands to hold the mask and lift the jaw, is generally more effective at maintaining a secure seal. Pressure must be maintained on the bony parts of the jaw, rather than the soft tissue, to prevent inadvertent airway obstruction.
Optimizing Ventilation Delivery
With the airway open and the mask seal secured, the focus shifts to the mechanics of delivering the breath. The amount of air delivered, known as the tidal volume, must be sufficient to oxygenate the blood but not so large that it causes harm. For an adult patient, the recommended volume is typically between 500 and 600 milliliters. Squeeze the bag only until a gentle, visible rise of the patient’s chest is observed, avoiding forceful compression.
Delivering too much air, or hyperventilation, carries several risks. Excessive pressure can lead to barotrauma, a pressure-related injury to the lungs. It can also increase the pressure inside the chest cavity, which decreases blood return to the heart, reducing blood flow to the brain and other organs. Furthermore, forceful breaths increase the likelihood of gastric insufflation, which can cause vomiting and subsequent aspiration.
The rate and duration of the breath must be controlled for optimal gas exchange. For an adult who has a pulse but is breathing inadequately, a smooth squeeze should be delivered over approximately one second, with a breath provided every five to six seconds. When performing ventilation during CPR, the rate is adjusted to one breath every six seconds (about 10 breaths per minute). This slow, deliberate rhythm ensures the lungs have time to fill and fully exhale the carbon dioxide before the next breath.
Confirming Effective Ventilation
Effective ventilation requires real-time feedback to confirm that the steps taken were successful. The most immediate feedback is visual confirmation of chest rise and fall. The chest should lift with the delivery of the breath and then fall naturally as the patient exhales, indicating that air successfully reached the lungs. An absence of this movement suggests a problem with the airway, the seal, or the volume delivered.
Rescuers can use other sensory feedback mechanisms. Auditory confirmation involves listening for bilateral breath sounds over both sides of the chest to ensure air is entering both lungs equally. Tactile feedback is available by feeling the compliance of the bag during the squeeze; a stiff bag may indicate an obstruction, while a bag that is too easy to squeeze often indicates a leak in the mask seal.
The most objective measure is waveform capnography, which monitors the amount of carbon dioxide (CO2) in the patient’s exhaled breath (EtCO2). A normal EtCO2 level is typically between 35 and 45 mmHg, and the presence of a square-shaped waveform indicates effective ventilation. Capnography provides a continuous assessment of gas exchange, allowing the rescuer to adjust the rate and volume of breaths to maintain the CO2 within the target range.
Immediate Corrective Actions for Ineffective Breaths
If real-time feedback indicates the breath was ineffective, such as the absence of chest rise, the rescuer must immediately engage in systematic troubleshooting. The most common cause of failed ventilation is an airway obstruction or a poor mask seal, making immediate repositioning the first corrective action. The rescuer should adjust the patient’s head position, maximizing the head tilt-chin lift or jaw thrust maneuver to open the airway.
Following repositioning, the next step is to re-establish the mask seal, which may have been compromised. This often involves adjusting the pressure and placement of the E-C grip or transitioning to the two-person technique for a firmer grip on the mask and jaw. If the patient is unconscious, consider inserting an airway adjunct, such as an oropharyngeal or nasopharyngeal airway, to mechanically prevent the tongue from blocking the throat.
The rescuer must also quickly check the equipment for any malfunction, such as a loose connection or a bag that is not re-inflating correctly. If the mouth or pharynx is visibly obstructed by secretions or foreign material, quick suctioning of the airway is necessary to clear the path for air. This sequence of checking position, seal, and equipment ensures effective air delivery is restored quickly.