The bag valve mask (BVM) is known by many different names, including manual resuscitator, self-inflating bag, and so on. It is, however, best known as an Ambu bag. Ambu is the company that introduced the BVM in the 1950s. In this discussion, the device will be referred to as a BVM.
The BVM is elegantly simple in its design. There are no parts made from metal (usually), no screws, no washers, and no springs (usually) or anything else of a complicated nature. The main parts are a self-inflating bag, with two valves (one on either end of the football-shaped and -sized bag), an inlet for fresh gas, and an outlet that both ventilates the patient and allows that ventilation to be expired.
The BVM is an unsung hero in medical care. Think of all the patients worldwide who are ventilated by a BVM at some time during the day. BVMs are used by first responders, by critical care personnel, and by anesthesia personnel. Transporting critically ill patients would be much more difficult and cumbersome without BVMs.
Bag valve masks can be used in the field, the battlefield, an ambulance, a helicopter, the emergency department, the intensive care unit, and the operating room. During disasters, BVMs may be the only type of ventilator that can work because they do not require electricity. (To be complete, there are mechanical, pneumatically powered ventilators available that do not use electricity to function, but there probably aren’t that many of them in your facility, so if a disaster struck, most patients needing ventilation would be ventilated with a BVM if electrical power was interrupted.)
For anesthesia providers, the BVM also has one other important purpose: it is your spare anesthesia machine, conveniently located in a bag on your supply cart. You should never start a case, unless it is a dire emergency, without making sure you have your backup anesthesia machine in the room. Ensuring that a BVM is present should be a part of your morning checkout.
Bag Inlet Valve and Oxygen Delivery
At the end that attaches to the oxygen source (which will be called the proximal end), there is a standard clear oxygen tubing that connects to the oxygen source. This tubing is permanently joined to the proximal end of the bag. The oxygen enters the bag through a thin disc valve (bag inlet valve), which is opened by the negative pressure of the expanding self-inflating bag, as well as the pressure and flow of the oxygen from the source (Figure 19-1).
Disc valve at the proximal end of the bag valve mask. Oxygen flows through coaxial inner tubing, and on self-inflation of bag, the disc valve opens, ...