Bag Valve Mask (BVM) / Ambu Bag 

1. Definition

Bag-Valve-Mask (BVM) is a hand-held manual resuscitation device consisting of a self-inflating bag used to provide positive pressure ventilation to patients with inadequate or absent breathing.

Also called:

• Ambu bag (named after company Ambu A/S)
• Manual resuscitator
• Self-inflating resuscitation bag

2. Historical Background

The Ambu bag was invented in 1953 by:

• Dr. Henning Ruben(Anaesthetist)
• Engineer Holger Hesse

They developed the first self-inflating resuscitator, replacing earlier mouth-to-mouth ventilation and bellows devices.

3. Components of Ambu Bag

 Self-Inflating Bag

Typical volume

Delivered tidal volume is usually ~500–700 mL in adults depending on compression.

 Non-Rebreathing Valve (Patient Valve)

Also called one-way valve.

Function:

• Allows gas flow from bag → patient
• Prevents exhaled gas returning to bag
• Directs expired air to atmosphere

 Face Mask

Mask leak is a major cause of ineffective ventilation.

 Oxygen Inlet Port

Allows connection to oxygen source.

Oxygen flow:Usually 10–15 L/min

 Oxygen Reservoir

Reservoir bag or tubing increases delivered FiO₂.

 PEEP Valve (Optional)

Attaches to exhalation port.most BVM PEEP valves are limited to ~10–20 cmH₂O.

Purpose:

• Maintain positive end-expiratory pressure
• Prevent alveolar collapse
• Improve oxygenation

Typical settings:

• 5–10 cm H₂O

Commonly used in:

• ARDS
• Severe hypoxemia

 Air Intake Valve

Allows bag to refill after compression.

If oxygen supply fails:

• Device still works with room air.

4. Indications in Critical Care

– Apnea

– Cardiac Arrest

During CPR.

Guidelines (AHA):

• 30 compressions : 2 ventilations

Advanced airway present:

• 1 breath every 6 seconds

– Preoxygenation

Used before:

• Rapid sequence intubation (RSI)

Provides:

• Denitrogenation
• Oxygen reserve

– During Intubation Attempts

Maintains oxygenation between attempts.

– Transport Ventilation

When ventilator unavailable.

Example:

• ICU to CT scan
• Ambulance transport

5. Technique of Bag-Valve-Mask Ventilation

Proper technique is critical for effective ventilation.

Two main methods:

1. One-person technique
2. Two-person technique (preferred)

6. One-Person Technique

Rescuer performs both:

• Mask seal
• Bag compression

Hand position:

EC clamp technique

Thumb + index finger → mask seal
Remaining fingers → lift mandible

7. Two-Person Technique (Gold Standard)

Used in ICU and difficult airway.

Person 1:

• Holds mask with two hands
• Performs jaw thrust

Person 2:

• Compresses bag

8. Ventilation Parameters

Proper ventilation avoids barotrauma and gastric insufflation.

Avoid:

• Hyperventilation
• High pressure ventilation

9. Complications of BVM Ventilation

– Gastric Insufflation

Most common complication.

Consequences:

• Vomiting
• Aspiration
• Reduced lung compliance

Risk increases if:

• Pressure > 20 cmH₂O

– Aspiration

Especially in:

• Non-fasted patients
• Trauma

Prevention:

• Cricoid pressure (controversial)
• Early intubation

– Barotrauma

Excessive pressure may cause:

• Pneumothorax
• Pneumomediastinum

– Hypoventilation

Due to:

• Mask leak
• Inadequate bag compression

– Hyperventilation

Very common in CPR.

Consequences:

• ↓ cerebral perfusion
• ↓ cardiac output

10. Troubleshooting BVM Ventilation