AMBU Bag (Bag-Valve-Mask) in Neonates

Parts of a Neonatal AMBU Bag (Labeled Diagram)

Parts Explained

1. Self-Inflating Bag

• The main compressible chamber (240 mL for neonates - this is the correct size for newborn resuscitation)
• Re-inflates automatically after each squeeze by drawing in air/oxygen
• Do NOT need a pressurized gas source to function - it works on room air alone
• In neonates: use a 240 mL bag (never adult 1600 mL bags)

2. Face Mask

• Sits over the baby's nose and mouth, creating an airtight seal
• Neonatal masks come in size 0 (premature) and size 1 (term newborn)
• Correct size: covers from the bridge of the nose down to just below the lower lip - must not cover the eyes or overlap the chin
• Typically made of soft, transparent silicone for visualization of lip color and secretions

3. Patient Valve (Non-Rebreathing / One-Way Valve)

• Sits between the bag and the mask
• Directs gas flow one way - from bag to patient during inspiration
• During expiration, opens the expiratory valve so exhaled air exits to atmosphere (not back into the bag)
• Prevents rebreathing of CO2

4. Pop-Off Valve (Pressure Relief Valve / Pressure-Limiting Valve)

• Critical safety feature for neonates
• Factory-set at 35-45 cmH2O - automatically releases excess pressure above this threshold
• Protects delicate neonatal lungs from barotrauma and pneumothorax
• Can be occluded manually with a finger when higher pressure is needed (e.g., in meconium cases) - but use with caution

5. Oxygen Inlet (O2 Inlet Tube + Tubing)

• Located at the tail end of the bag
• Connects to an oxygen source via standard green tubing
• Flow rate for neonates: minimum 5 L/min to deliver 40-60% O2 (without reservoir)

6. Reservoir Bag (O2 Reservoir)

• Attached to the oxygen inlet at the distal end of the bag
• Stores 100% O2 between squeezes
• With reservoir bag + ≥5 L/min flow: delivers 90-100% O2
• Without reservoir: delivers only ~40% O2
• Per MSF guidelines: connect O2 reservoir after 2 minutes of ventilation if oxygen is available - start with room air first

7. Air-Inlet One-Way Valve (Fish-Mouth / Inlet Valve)

• At the base of the bag near the O2 inlet
• Allows ambient air to rush into the bag as it re-expands after a squeeze
• Ensures bag re-inflates quickly between breaths

8. PEEP Valve (optional add-on)

• Some neonatal bags include an attachable PEEP (Positive End-Expiratory Pressure) valve
• Typically set at 5 cmH2O in neonates to maintain FRC (functional residual capacity)

How to Use - Step-by-Step (Neonatal)

Pre-Use Preparation

Positioning the Baby

• Place the neonate on a firm, flat, warm surface
• Neck in neutral "sniffing" position - a small shoulder roll (~2 cm folded cloth) under the shoulders helps
• Avoid hyperextension or flexion of the neck - both obstruct the airway
• Head positioned at the edge of the resuscitation table/radiant warmer

Mask Placement (The "2-Point Top Hold" Technique)

1. Stand at the baby's head (position yourself at the top of the baby)
2. Hold the mask with your non-dominant hand:
   • Place the apex of the mask over the bridge of the nose first
   • Lower the mask onto the chin
   • Use thumb and index finger in a "C" shape on the mask body
   • Use middle, ring, and little finger to support the jaw (jaw thrust) - avoid pressing on soft tissues of the neck
3. Verify the seal - no visible air leak at the mask edges

Ventilation Technique

• Rate: 40-60 breaths per minute ("breathe-two-three, breathe-two-three...")
• Pressure: Start at 20-25 cmH2O for the first breath; ongoing breaths at 15-20 cmH2O
• Inspiratory time: ~1 second per breath
• Squeeze the bag with 2-3 fingers only (not the whole hand) - neonatal tidal volume is only 5-8 mL/kg
• Signs of effective ventilation:
  • Visible chest rise (slight, not exaggerated)
  • Improving heart rate (most important sign)
  • Improving SpO2 and color
  • Breath sounds bilaterally on auscultation

Oxygen Protocol (NRP/WHO)

• Start with room air (21% O2) for term neonates ≥35 weeks
• Add O2 if SpO2 remains below target after 90 seconds:
  • 1 min: 60-65%
  • 2 min: 65-70%
  • 3 min: 70-75%
  • 4 min: 75-80%
  • 5 min: 80-85%
  • 10 min: 85-95%
• For preterm (<35 weeks): start with 21-30% O2 via blender if available

Common Mistakes to Avoid

Quick Reference Card

Bag size:       240 mL (neonatal)
Mask size:      0 = preterm | 1 = term
Rate:           40-60 breaths/min
Pressure:       20-25 cmH2O (initial) / 15-20 cmH2O (ongoing)
Pop-off valve:  35-45 cmH2O
O2 without res: ~40% FiO2
O2 with res:    90-100% FiO2
O2 flow rate:   ≥5 L/min
Start O2:       Room air first (term) / 21-30% (preterm)