AMBU: the impact of mechanical ventilation on the effectiveness of CPR

By Cristiano Antonino On Mar 10, 2022

The AMBU is a ‘self-expanding balloon’ used by healthcare professionals and rescuers to support breathing, and is one of the devices used in first aid during cardiopulmonary resuscitation

AMBU stands for “Auxiliary Manual Breathing Unit”

It was designed and marketed in 1956.

The AMBU is made of self-expanding plastic material which connects at its ends to two one-way valves.

The proximal valve has a 15 mm universal connector which is used to connect it to various airway management devices.

The AMBU is most commonly used with face masks, which are available in various sizes and shapes to ensure a perfect fit on the patient’s face.

The face mask must be positioned on the patient’s face using the “CE” manoeuvre: 3 fingers under the chin to obtain a hyperextended position of the head and 2 fingers above the mask to keep it applied and avoid air leaks during insufflation.

The AMBU face mask must be placed over the patient’s mouth. The operator can then perform insufflations at a ratio of 30:2 during CPR manoeuvres, i.e. 2 ventilations for every 30 compressions (in adults).

By pressing down on the balloon in the swollen, self-expanding part, the air inside is forced through the valve and into the lungs.

During exhalation, the valve blocks the return of carbon dioxide-rich air.

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The AMBU is available in paediatric and adult versions

The paediatric version generally has a capacity of about 500ml, while the adult version has a capacity of 1,300-1600ml.

However, it is important to bear in mind that the compression carried out (usually with one hand) gives the adult patient the necessary 500-800ml.

The AMBU can be made of various materials, the most common being: silicone, PVC, SEBS

At the bottom of the balloon there is a connection to connect the reservoir and to an oxygen source.

The reservoir is a bag (approx. 1,600 ml capacity) whose purpose is to increase the percentage of oxygen in the mixture delivered to the patient by the oxygen supplied by the cylinder, so that ventilation is more effective.

The reservoir is only used in the presence of an oxygen source, without whose pressure it would not be able to expand and perform its function.