The Ambu has a squeezable bag, a one-way valve, and a face mask. Compressing the bag opens a valve, forcing air through a mask or artificial airway into the lungs, according to the journal "Critical Care Nurse." Releasing the bag closes the valve and exhalation occurs passively through the exhalation port. During exhalation, the bag automatically refills with room air or oxygen. The cycle continues until spontaneous breathing occurs or breathing is mechanically supported by a breathing machine.
In a medical emergency, rescue workers can help a patient breathe using a squeezable bag with a face mask called the Ambu bag. Before its invention, rescue breathing attempts were often futile. Those efforts, including mouth-to-mouth resuscitation, caused more problems than they solved. The problems of abdominal distention, vomiting, aspiration, and poor ventilation carried a poor prognosis. The success of the Ambu bag in rescue breathing improved emergency services in rural and urban communities.
