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Hand-squeezed, self-inflating resuscitators are easy to use and do not require a
gas source. The elasticity of a self-inflating bag allows it to refill with oxygen or
room air as the gas intake valve opens. During compression, the gas intake valve
closes, and a second valve opens to allow flow into the patient. A valve between
the mask and the bag allows for patient exhalation into the atmosphere. Most selfinflating bags are equipped with a pressure-limiting pop-off valve that is preset at
35 cm H2 O to prevent barotrauma; if not, an inline manometer should be used (
Fig. 9.7 ). To deliver oxygen concentrations, 60% to 90%, use a flow rate of 10 to
15 L/min. Use a minimum of a 500-mL bag for infants and children.
Anesthesia Bags
Anesthesia breathing circuits (sometimes called a Mapleson circuit) consist of a
source of fresh gas flow attached to a reservoir bag with an adjustable pressurelimiting (APL) valve ( Fig. 9.8 ). These devices are favored by many for several
reasons. When there is no significant leak at the mask-to-patient interface, CPAP
can be provided and the pressure can be adjusted with the APL valve. PPV can
also be provided by squeezing the bag. The respiratory effort can be observed
through changes in the filling and emptying of the reservoir bag. Additionally, if
the fresh gas flow is provided through an oxygen blender, any desired
concentration of oxygen may be provided. However, there are several
disadvantages with this type of bag. First, a high-pressure source of fresh gas
flow is necessary for the system to function. Second, significant experience in
maintaining a complete seal at the mask-to-patient interface is needed to maintain
positive airway pressure so PPV can occur. The operator must adjust the fresh gas
flow rate and the APL valve with the patient ventilation to balance rate of gas
escape from circuit to prevent over- or underfilling. If the bag is removed from a
leak-tight patient application, it promptly deflates and one must wait for the
reservoir to refill. Alternatively, overfilling the bag may result in dangerously
high-pressure transmission to the lung and stomach. Third, exhaled gases return
to the circuit and bag which can lead to hypercarbia unless the fresh gas flow is
great enough (generally twice the patient’s minute ventilation) to “wash out” the
circuit. These disadvantages have prompted many to recommend the primary use
of the self-inflating resuscitator bag as the primary mode of ventilation.