What is the role of mechanical power in pediatric mechanical ventilation?

Mechanical Power in Pediatric Mechanical Ventilation

Mechanical power should be considered when setting ventilation parameters in pediatric patients to minimize ventilator-induced lung injury, though specific power targets have not been established for the pediatric population. 1

Understanding Mechanical Power in Pediatric Ventilation

Mechanical power represents the energy transferred from the ventilator to the respiratory system per unit of time, combining multiple ventilation parameters:

• Pressure
• Volume
• Flow
• Respiratory rate

This concept is particularly important as it contributes to ventilator-induced lung injury (VILI) in mechanically ventilated children 1.

Clinical Application in Different Pediatric Conditions

Restrictive Lung Disease

• Limit plateau pressure ≤28 cmH₂O (≤29-32 cmH₂O if chest wall elastance is increased) 2
• Use higher respiratory rates with lower tidal volumes to maintain minute ventilation 2
• Consider PEEP titration to improve oxygenation, though no specific method is defined 2

Obstructive Airway Disease

• Limit plateau pressure ≤30 cmH₂O 2
• Allow for longer expiratory times to prevent air trapping
• Assess intrinsic PEEP to guide external PEEP settings 2

Pediatric ARDS

• Target physiologic tidal volumes and avoid Vt >10 mL/kg ideal body weight 2
• For PARDS, follow PALICC guidelines for SpO₂ targets (92-97% when PEEP <10 cmH₂O and 88-92% when PEEP ≥10 cmH₂O) 2

Components of Mechanical Power to Monitor

Tidal Volume

• Target physiologic tidal volumes 2
• Avoid Vt >10 mL/kg ideal body weight 2
• In lung hypoplasia syndromes, optimal Vt may be smaller than physiologic due to lower lung volumes 2

Respiratory Rate

• Set respiratory rate based on respiratory system mechanics and disease trajectory 2
• Higher rates may be needed in restrictive disease to maintain minute ventilation 2

Pressure Settings

• Monitor and limit plateau pressure according to disease type 2
• Balance PEEP settings with hemodynamics and oxygenation 2

Inspiratory Time/I:E Ratio

• Set based on respiratory system mechanics and time constants 2
• Avoid flow end-inspiratory or expiratory flow interruption 2

Special Considerations

Spontaneous Breathing

• Maintain spontaneous breathing when possible 2
• Consider controlled mechanical ventilation for severely ill children requiring high ventilator settings 2

Cardiac Children

• Positive pressure ventilation may reduce work of breathing and afterload in LV failure but increase afterload in RV failure 2
• Titrate ventilator settings more carefully in cardiac children 2

Chronically Ventilated Children

• Apply same principles as for acute respiratory conditions during exacerbations 2
• Preserve spontaneous breathing when possible 2

Pitfalls and Challenges

1. Limited Pediatric-Specific Data: Most mechanical ventilation practices in pediatrics have been adapted from adult protocols, neglecting differences in lung pathophysiology and response to injury 3

2. Variability in Practice: Substantial variation exists in ventilator management for children with ARDS, with clinicians often not following protocol recommendations 4

3. Monitoring Challenges: Unlike in adults, there are no established mechanical power thresholds for children that correlate with outcomes

4. Balancing Components: Focusing on individual parameters (like tidal volume) without considering their combined effect as mechanical power may lead to suboptimal ventilation strategies

5. Developmental Considerations: The impact of mechanical power likely varies with age and developmental stage of the child's respiratory system

Clinical Implications

While the concept of mechanical power is important in pediatric mechanical ventilation, current guidelines do not provide specific targets. Instead, clinicians should focus on:

1. Limiting plateau pressures according to disease type 2
2. Using appropriate tidal volumes (avoiding >10 mL/kg) 2
3. Setting respiratory rates based on disease and mechanics 2
4. Titrating PEEP to optimize oxygenation while monitoring hemodynamics 2
5. Maintaining spontaneous breathing when appropriate 2

By considering these components collectively as contributors to mechanical power, clinicians can work to minimize ventilator-induced lung injury in pediatric patients.