A bag valve mask (BVM) is a device equipped with a face mask and a self-refilling compartment or bag that a healthcare provider uses to provide artificial ventilation. This hand-held emergency medical device is designed to deliver air directly from the atmosphere or pure oxygen from a supplemental system that supplies oxygen. The bag valve mask is sometimes called a resuscitator or an "Ambu® bag" and can be used not only on patients who are in respiratory arrest, but also on those who are suffering respiratory failure. Respiratory arrest is the complete cessation of spontaneous breathing; respiratory failure refers to breathing that are not adequate to continue supporting life. These makes are made in sizes for infants, children, and adults.
While there are different types of masks that aid breathing, they must all consist of a set of basic parts to be considered a bag valve mask. Those parts include a self-refilling bag and a jam-proof valve that allows up to 15 liters of oxygen to flow per minute and that also is non-rebreathing. This feature is what keeps a patient from breathing the air he or she exhales back in. The equipment should not freeze even in temperatures below 32° F (0° C) and the bag should be easy to clean and sterilize unless the unit is disposable. While the bag might come in more than one color, the mask is a soft, clear plastic.
Other respiratory equipment, such as an endotracheal or breathing tube, can be used in conjunction with the bag valve mask, which is why almost all units are equipped with a standard 15/22 respiratory fitting. If supplemental oxygen is delivered to a patient during use, also known as bagging, it is attached to the device and enters a reservoir. When the rescuer compresses the bag, the air inlet closes and oxygen from the reservoir is delivered to the patient. Passive exhalation by the patient happens when the rescuer releases the bag. During the patient's exhalation, the air inlet to the reservoir is open to allow oxygen to enter so it can be delivered with the next squeeze of the bag.
It is possible to use a bag valve mask with or without supplemental oxygen. The device can pull air directly from the atmosphere when oxygen is not attached. Use of supplemental oxygen, however, is almost always the preferred option, particularly in cases of respiratory arrest.
Obtaining a good seal over a patient's mouth and nose is the most difficult part of using a bag valve mask, and bagging is not always successful if attempted by a single rescuer. It is for this reason that it is very strongly recommended that two rescuers work together so that one can maintain a good seal while the other bags. Bag valve mask units are not only employed to provide artificial respiration, they also are one of the most effective infection barriers between the patient and the healthcare provider.