Compare techniques for exhaled gas ventilation.
Compare self-inflating and flow-inflating manual ventilators.
Discuss issues related to mechanical ventilation and disaster preparedness.
Describe ventilators that can be used for mass casualty respiratory failure (MCRF).
Techniques available for emergency ventilation include exhaled gas ventilation techniques, manual ventilation devices, and oxygen-powered demand valves. Some of these methods (eg, exhaled-gas techniques) may be used by nonprofessional laypersons. Others (eg, manual ventilators) are used during emergency ventilation (eg, cardiopulmonary resuscitation). In recent years, concern has been raised regarding ventilation in the setting of a disaster.
Exhaled Gas Ventilation Techniques
Advantages of mouth-to-mouth ventilation are ease-of-use, availability, universal application, no equipment requirement, and a large reservoir volume (the delivered volume is limited only by the rescuer's vital capacity). However, there are important problems related to mouth-to-mouth ventilation. Gastric insufflation occurs with the high pharyngeal pressures associated with high airway resistance (eg, obstructed airway), low lung compliance, short inspiratory times (which produce high inspiratory flows), and rapid respiratory rates (which does not allow adequate time for lung deflation between breaths and the development of auto-PEEP). With mouth-to-mouth ventilation, the delivered oxygen concentration is about 16% and the delivered carbon dioxide concentration is about 5%. A major concern related to the use of mouth-to-mouth ventilation is the potential for disease transmission. It is therefore prudent to use a protective barrier device during emergency ventilation. Mouth-to-mouth ventilation is discouraged, and alternative ventilation devices (eg, bag-valve-mask) should be used whenever possible.
Face Shield Barrier Devices
Face shield devices use a flexible plastic sheet that contains a valve and/or filter to separate the rescuer from the patient. These devices make the task of exhaled gas ventilation more pleasant for the rescuer. Their ability to prevent disease transmission is unclear. Many of the limitations of mouth-to-mouth ventilation (eg, difficulty using the device effectively, gastric insufflation, low inspired oxygen) also apply to these devices.
These devices provide a barrier between the rescuer and the patient to prevent infectious disease transmission during emergency ventilation. The mask should provide an adequate seal using an air-filled resilient cuff on the mask and should have a port for administration of supplemental oxygen. It should be constructed of a transparent material to allow visual detection of regurgitation. A one-way valve or filter should be attached to the mask to protect the rescuer from contamination with the patient's exhaled gas or vomitus. An extension tube may also be used as an additional barrier between the rescuer and the patient, and the exhaled gas of the patient should be vented away from the rescuer. The valve or filter should not jam in the presence of vomitus or humidity, and it should have minimal airflow resistance. The dead space of the mask should be as small as possible.