A bag mask, also known as a bag-valve-mask (BVM) or manual resuscitator, is a handheld medical device used to provide artificial ventilation to individuals unable to breathe adequately on their own. Its purpose is to move air into the lungs, ensuring oxygen delivery and carbon dioxide removal when natural breathing efforts are insufficient or absent.
Understanding the Bag Mask Components
A standard bag mask device comprises several distinct parts that work in unison to deliver breaths. The self-inflating bag, often made of silicone or rubber, comes in various sizes, such as 240 mL for infants, 500 mL for children, and 1600 mL for adults. This bag automatically re-expands after being squeezed, drawing in air or oxygen.
Connected to the bag is a non-rebreathing valve, which directs delivered air towards the patient and prevents exhaled gases from returning into the bag. It also features an exhalation port, through which the patient’s exhaled breath escapes. A face mask, available in multiple sizes, attaches to the non-rebreathing valve and creates a seal over the patient’s nose and mouth. Some masks are clear with air-inflated cushions for a proper fit.
An oxygen reservoir bag is attached to the opposite end of the bag. This reservoir collects oxygen from an external source, such as an oxygen tank, allowing delivery of high oxygen concentrations to the patient. This ensures that each squeeze of the bag delivers oxygen-enriched air, maximizing oxygenation.
The Process of Delivering Breaths
Delivering breaths with a bag mask involves a coordinated sequence of actions to ensure effective ventilation. The first step involves positioning the patient in a supine position and performing a head-tilt chin-lift or jaw-thrust maneuver to open the airway. Airway adjuncts, such as oropharyngeal or nasopharyngeal airways, may be inserted to prevent tongue obstruction, especially in unconscious patients.
Selecting the correct mask size is also important; the mask should cover the patient’s nose and mouth without extending over the chin, fitting snugly over the bridge of the nose and the two cheekbones. Achieving a proper mask seal is paramount to prevent air leakage. This can be accomplished using a one-handed “E-C” technique, where the thumb and index finger form a “C” around the mask, pressing it onto the face, while the remaining three fingers form an “E” to lift the jaw. A two-person technique, where one person maintains the seal and the other squeezes the bag, is more effective at preventing air leaks and delivering sufficient volume.
If supplemental oxygen is available, connect the oxygen tubing to the bag mask’s oxygen inlet and set the flow rate to 10 to 15 liters per minute. This ensures the reservoir bag remains inflated, providing a high concentration of oxygen with each breath. To deliver a breath, squeeze the bag for about one second, providing enough volume for visible chest rise. For adults, this means delivering a tidal volume of 500 to 600 milliliters.
After delivering the breath, release the bag to allow it to self-inflate, drawing in fresh oxygen or air for the next breath. The rate of ventilation depends on the patient’s age and clinical situation; for adults, a rate is 10 to 12 breaths per minute (one breath every 5 to 6 seconds). For children and infants, a faster rate of 12 to 20 breaths per minute (one breath every 3 to 5 seconds) is appropriate. Observing proper chest rise and fall with each ventilation confirms that air is entering the lungs.
Ensuring Effective Ventilation
Confirming that breaths are being delivered effectively is important. The primary visual cue for effective ventilation is the visible rise and fall of the patient’s chest with each squeeze of the bag. This indicates air is entering the lungs. The absence of chest rise, or minimal movement, suggests an issue with the airway or mask seal.
Preventing gastric inflation is another important assessment. This occurs when air enters the stomach instead of the lungs. This can happen if the bag is squeezed too forcefully or if the airway is not properly opened, leading to air being directed down the esophagus. Gastric inflation can cause complications such as vomiting and reduced lung capacity, so using just enough volume to achieve chest rise is important.
Maintaining an open airway is important. If chest rise is not observed, or if resistance is felt when squeezing the bag, the airway may be obstructed by the tongue, secretions, or a foreign body. Re-adjusting the patient’s head position, re-evaluating the mask seal, or clearing any visible obstructions in the mouth or throat can help resolve these issues.
Troubleshooting common problems involves systematically checking for an inadequate mask seal, which can be caused by facial hair, anatomical variations, or improper hand placement. Re-positioning the mask and ensuring a firm, airtight grip can correct this. If an airway obstruction is suspected, the use of airway adjuncts like oropharyngeal or nasopharyngeal airways can help bypass the obstruction. If a single rescuer struggles to maintain a seal and deliver adequate breaths, a two-person technique is recommended as it provides a better mask seal and more effective ventilation.