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Hand-squeezed, self-inflating resuscitators are easy to use and 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
Ngày đăng: 22/10/2022, 10:55
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