Ventilator Settings in Paediatric Conditions

1. General Principles

2. Key Ventilator Parameters

Tidal Volume (VT)

• Target: 5–10 mL/kg body weight; values >10 mL/kg should be avoided
• In Paediatric ARDS (PARDS): PALICC guidelines recommend 5–8 mL/kg predicted body weight for patients with near-normal compliance
• For patients with poor respiratory compliance: restrict to 3–6 mL/kg predicted body weight
• There is no evidence linking tidal volume to mortality in the PICU irrespective of disease severity (meta-analysis data)

Mode of Ventilation

• Pressure-Controlled Ventilation (PCV) is generally favoured over Volume-Controlled Ventilation (VCV) in paediatrics
  • PCV produces a decelerative flow pattern (better distribution, lower peak pressures)
  • Disadvantage: variable tidal volume depending on compliance and resistance
• Volume Guarantee combined with PCV is an advance that addresses the variable VT issue
• No mode has been proven superior by randomised data in paediatrics

PEEP (Positive End-Expiratory Pressure)

• Routinely used to prevent atelectasis and stabilise recruited alveoli
• Optimal PEEP is undetermined in healthy paediatric lungs; typically set at 5 cmH₂O for routine cases
• In PARDS:
  • Moderate PARDS: 10–15 cmH₂O
  • Severe PARDS: may require >15 cmH₂O (monitor haemodynamics closely)
  • Using PEEP lower than ARDS Network Protocol levels is associated with increased mortality in PARDS (Khemani et al.)

Peak Inspiratory Pressure (PIP) / Plateau Pressure

• Data from children with acute lung injury show a direct relationship between peak inspiratory pressure and mortality
• Sustained plateau airway pressures >35 cmH₂O risk barotrauma (pneumothorax, pneumomediastinum, subcutaneous emphysema)
• Driving pressure = PIP − PEEP; minimising driving pressure is associated with improved survival in ARDS

FiO₂

• Wean toward <0.60 when possible to reduce oxygen toxicity
• Permissive hypoxaemia (tolerated relative to systemic O₂ delivery) is an accepted strategy in PARDS

Respiratory Rate (RR)

• Age-appropriate rates; higher rates are physiologically normal in infants and neonates
• Minute ventilation = VT × RR; adjusted based on PaCO₂ targets

I:E Ratio

• Standard ratio: 1:2
• Prolonged expiratory phase may be needed in obstructive conditions (asthma, bronchiolitis) to avoid air trapping

3. Permissive Hypercapnia

• The patient can buffer the acidosis (renal HCO₃⁻ retention)
• No contraindications from co-existing disease (e.g., raised ICP, pulmonary hypertension)

4. Condition-Specific Considerations

Paediatric ARDS (PARDS)

• Restrictive tidal volumes (3–8 mL/kg depending on compliance)
• Higher PEEP (10–15 cmH₂O, up to >15 in severe)
• Permissive hypoxaemia and hypercapnia
• HFOV as rescue therapy only

Asthma / Obstructive Airway Disease

• Use prolonged expiratory time (lower RR, higher I:E ratio toward 1:3 or 1:4) to prevent dynamic hyperinflation
• Extrinsic PEEP during intubated mechanical ventilation may be beneficial (demonstrated in four adult studies and one paediatric study)
• Permissive hypercapnia is especially important — avoid high PIP

Neonates / Infants

• Minimise circuit dead space: bidirectional gas flow in equipment adds to physiological dead space; this is critical in small patients where even small increases in dead space cause exponential rises in PaCO₂
• Use smaller tidal volumes with attention to weight-based calculations
• Cuffed tubes increasingly used to improve end-tidal CO₂ accuracy and reduce OR pollution

Upper Airway Obstruction (Croup, Epiglottitis)

• Spontaneous ventilation should be maintained during induction
• Avoid paralysis and rapid-sequence induction when there is significant obstruction
• Continuous positive airway pressure of 10–15 cmH₂O helps relieve dynamic upper airway collapse during induction

5. High-Frequency Oscillatory Ventilation (HFOV)

• MAP: set ~5 cmH₂O above the last mean airway pressure on conventional ventilation
• Amplitude (ΔP): adjusted to visible "chest wiggle" from clavicles to abdomen/pelvis
• Wean FiO₂ toward <0.60 by titrating MAP upward by 1–2 cmH₂O
• Overdistention on CXR: >9 posterior ribs or flattened hemidiaphragms

1. Inline suction to ensure ETT patency
2. Increase ΔP (amplitude)
3. Decrease frequency (Hz)
4. Deflate ETT cuff

6. Weaning and Extubation

• Daily Spontaneous Breathing Trials (SBTs) are recommended
• In one PICU study (RESTORE trial), 43% of patients passed their first extubation readiness test; of those, 66% were extubated within 10 hours
• Computerised ventilation protocols are being increasingly adopted to reduce variability in weaning decisions

7. Neuromuscular Blockade in PARDS

• Reduces VILI by controlling tidal volumes and allowing higher PEEP tolerance
• Reduces oxygen consumption from respiratory muscles
• A paediatric trial showed improvement in OI and mortality with early vecuronium exposure
• Cisatracurium is an option without increased muscle weakness risk (from adult ACURASYS data)