Manual Resuscitator: Working Principle, Core Features and Clinical Applications

1. Working Principle

A manual resuscitator (commonly known as Ambu bag) is a hand-operated positive-pressure ventilation device.

1) When the operator squeezes the self-inflating silicone/rubber bag: the inlet valve closes, the outlet valve opens. Air/oxygen inside the bag is pushed through the mask or endotracheal tube into the patient’s lungs, achieving positive pressure inspiration.

2) When releasing the bag: the bag rebounds elastically. The outlet valve closes to prevent exhaled gas from flowing back; the inlet valve opens. Ambient air or supplemental oxygen flows into the bag to refill it.

3) The patient’s exhaled gas escapes through the separate exhaust valve, avoiding rebreathing. If connected to an oxygen source, higher-concentration oxygen can be delivered to replace room air.

2. Main FeaturesAdvantages

1) Self-inflating design: Works without a continuous gas supply; usable anywhere without power support.

2) Portable & easy to operate: Lightweight, compact, suitable for rapid emergency use.

3) Adjustable ventilation: Operators control tidal volume and respiratory rate manually by squeezing rhythmically.

4) Compatible accessories: Can match face masks, endotracheal tubes, laryngeal masks, oxygen reservoirs. An oxygen reservoir enables delivery of nearly 100% oxygen.

5) Pressure relief valve: Prevents excessive airway pressure to avoid barotrauma (lung injury from overpressure).

6) Disposable/reusable options: Disposable types reduce cross-infection risk; reusable silicone models can be sterilized repeatedly.

3. Clinical ApplicationsEmergency Resuscitation

1) Cardiopulmonary arrest (CPR): Deliver artificial ventilation during cardiopulmonary resuscitation.

Acute respiratory failure, suffocation, choking, drug intoxication, traumatic asphyxia.

2) Perioperative Use

Pre-oxygenation for patients before anesthesia induction.

Temporary ventilation during anesthesia or when disconnecting anesthesia ventilators.

3) Transport & Ward Rescue

Inter-hospital / intra-hospital transfer of critically ill patients who need breathing support.

Temporary ventilation support when mechanical ventilators fail.

4) Special Scenarios

Neonatal, pediatric and adult emergency ventilation (different sizes for various age groups).

First aid at accident scenes, ambulances, emergency departments.