A Bag-Mask Device (BMD), often referred to as a Bag-Valve Mask (BVM), provides positive pressure ventilation to a person unable to breathe adequately on their own. This device is a temporary, life-saving measure, forcing air into the lungs to maintain oxygenation until advanced medical support is available. While the BVM is a simple concept, ineffective ventilation is a common issue in emergency situations, mainly due to the difficulty of creating a proper seal and maintaining an open airway simultaneously. Mastering the correct sequence of steps is necessary for successful oxygen delivery.
Establishing an Open Airway Path
The first requirement for effective ventilation is ensuring the airway is clear and open, as the tongue frequently falls backward in an unconscious person, obstructing the pharynx. The method used depends on whether a spinal injury is suspected.
If there is no indication of trauma, the rescuer should perform the Head-Tilt/Chin-Lift maneuver. This involves placing one hand on the forehead to gently tilt the head back and using the fingers of the other hand to lift the chin forward, moving the tongue away from the back of the throat.
If the patient may have a neck or spinal injury, the Jaw Thrust maneuver is the preferred technique, as it opens the airway with minimal movement of the cervical spine. This requires the rescuer to place their fingers under the angles of the patient’s lower jaw and push the jaw upward and forward. Basic airway adjuncts, such as an Oropharyngeal Airway (OPA) or a Nasopharyngeal Airway (NPA), can help maintain the patency achieved by these positioning maneuvers.
Mastering the Mask Seal Technique
The most frequent cause of air leakage and failed ventilation is an inadequate seal between the face and the mask. To counteract this, rescuers must use a specialized hand placement technique known as the C-E clamp or grip. This technique uses one hand to secure the mask and open the airway, leaving the other hand free to squeeze the bag.
The rescuer’s thumb and index finger form the “C” shape, applying downward pressure onto the rim of the mask to create a tight seal over the nose and mouth. The remaining three fingers form the “E” shape, lifting the jaw upward against the mask to maintain the open airway path. The mask used must be the correct size to cover both the mouth and nose without extending over the chin or eyes.
This single-rescuer technique is challenging, which is why the two-rescuer approach is preferred. This allows one person to focus on maintaining a superior seal with both hands while the second person manages the bag.
Delivering the Correct Ventilation
Once a secure mask seal and open airway are established, the focus shifts to delivering the correct rate and volume of air. The goal is to provide “just enough” volume to cause a visible chest rise, rather than fully compressing the bag. Over-ventilation, or administering too much air, can increase pressure in the chest, reducing blood flow to the heart and brain. It can also force air into the stomach, risking regurgitation and aspiration.
For an average adult, the appropriate volume, or tidal volume, is around 500 to 600 milliliters, which is often only about one-third of a standard adult bag’s capacity. This breath should be delivered slowly over approximately one second.
The recommended rate for adults is one breath every five to six seconds, or 10 to 12 breaths per minute. Children and infants require a slightly faster rate of one breath every three to five seconds.
Confirming Effective Breaths
The final step is verifying that the delivered breath was successful and reached the patient’s lungs. The primary confirmation is the visual sign of the patient’s chest rising and falling symmetrically with each squeeze of the bag. This visible expansion confirms that air is entering the lungs and that the seal and airway maneuvers were effective.
Rescuers should also pay attention to the tactile feedback, noting the compliance of the bag, which is the ease with which it is squeezed. Resistance suggests a persistent airway obstruction or a poor seal. If the chest does not visibly rise, the rescuer must immediately troubleshoot by repositioning the patient’s head or re-adjusting the mask seal. Observing for clinical changes, such as improved skin color, can serve as a secondary sign of successful oxygenation.