Portable ventilation devices are essential for patients who require continuous mechanical ventilation during transport to and from the operating room. They are also important tools for providing face mask ventilation during emergency airway management, such as a patient in cardiac arrest. Though the flow of oxygen is usually necessary, these devices do not require electricity or a source of pressurized gas for their function. There are two types of portable manual resuscitators: self-inflating and flow-inflating systems.
Self-inflating manual resuscitators are used both in hospital and out-of-hospital scenarios. The primary advantages are the self-inflating nature, portability, and ability to provide room air in the event that oxygen is not available. These systems, however, require an oxygen source to deliver inspired oxygen levels higher than that of room air. They also lack the tactile feel of airway resistance and compliance that can be more easily determined from the anesthesia circle system. Use of these resuscitators may increase the risk of barotraumas due to excessive delivered airway pressure.
There are several self-inflating manual resuscitators on the market. The first product was introduced in 1956 and continues to be the leader even today: the “Ambu bag.” Designed by anesthesiologist Henning Ruben, the device received its name based on its components: air-mask-bag unit (AMBU). Although several different manufacturers produce these breathing systems, each of the system shares the following fundamental components (Figure 16-1).
Basic components of self-inflating resuscitator bags. (Reproduced with permission from Butterworth JF, Mackey DC, Wasnick JD. Morgan and Mikhail’s Clinical Anesthesiology, 5th ed. McGraw-Hill; 2013.)
Self-refilling bag—The self-refilling bag acts as a reservoir for the gas (oxygen and/or air) that is delivered to the patient when manually compressed. Its material has memory- like capability. During expiration, the bag automatically re-expands to its inspiratory position by drawing in gas for the next delivered breath. Because of the semi-rigid nature of these bags, it can be impossible to detect spontaneous breathing. Bag is made of materials such as rubber (silicone, chloroprene, butyl) or polyvinyl chloride (PVC). Most are latex free. Unlike the rubber versions, PVC resuscitators cannot be steam autoclaved. The typical bag volumes are 1500 mL (for an adult), 500 mL (for a child), and 250 mL (for an infant).
Nonrebreathing valve—The nonrebreathing valve is designed to release expired gas to the atmosphere and to prevent it from mixing with fresh inspired gas from the self-refilling bag. During inspiration, the valve ensures that the patient will only receive fresh gas from the self-refilling bag.
The nonrebreathing valve is T shaped and consists of an inspiratory port (directs gas from bag to patient), an expiratory port (directs gas from patient to atmosphere), and a patient port that connects with the artificial airway device. It is a unidirectional valve ...
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