What are the guidelines for using a Servo-u (servo ventilator) small circuit for pediatric patients weighing less than 10 kg?

Servo-u Small Circuit for Pediatric Patients <10 kg

Yes, the Servo-u small circuit is specifically designed for pediatric patients weighing less than 10 kg, and you must measure ventilator parameters near the Y-piece of the patient circuit in these small children to ensure accurate monitoring and minimize dead space. 1

Critical Monitoring Requirements for Children <10 kg

The Paediatric Mechanical Ventilation Consensus Conference explicitly recommends:

• Measure all ventilator parameters near the Y-piece of the patient circuit in children <10 kg to obtain accurate readings and account for circuit compliance effects 1
• This measurement location is essential because the small tidal volumes in these patients make circuit compliance and dead space proportionally more significant 1

Circuit Configuration Recommendations

Essential Circuit Setup

• Use double-limb circuits for invasive ventilation in all pediatric patients 1
• Minimize dead space by limiting added components to the circuit 1
• The small circuit is necessary because apparatus dead space becomes critically important in patients with small tidal volumes 2

Dead Space Considerations

• In infants and small children, apparatus dead space (devices between the endotracheal tube and Y-piece) represents a much larger proportion of tidal volume 2
• Even with tidal volumes at or below calculated dead space, effective alveolar ventilation can occur due to high flow rates and short inspiratory times in small patients 3
• The fixed instrumental dead space has a proportionally greater impact on smaller patients, requiring higher tidal volumes per kilogram to achieve normocapnia 3

Ventilator Settings for Patients <10 kg

Initial Settings

• Tidal volume: ≤10 mL/kg ideal body weight (for a 10 kg child, approximately 100 mL) 4, 5
• PEEP: 5-8 cmH2O as baseline, adjusting based on disease severity 4, 5
• Peak inspiratory pressure: ≤30 cmH2O for obstructive disease, ≤28 cmH2O for restrictive disease 4, 5

Monitoring Parameters

• Measure peak inspiratory pressure, plateau pressure, mean airway pressure, and PEEP at the Y-piece 4
• Monitor pressure-time and flow-time scalars continuously to assess for air trapping and patient-ventilator synchrony 4
• Measure SpO2 continuously in all ventilated children 4
• Measure PCO2 in arterial or capillary blood samples 4

Common Pitfalls to Avoid

Measurement Errors

• Do not rely on ventilator-displayed tidal volume measured at the expiratory valve in small children, as this overestimates or underestimates true-delivered tidal volume depending on circuit compensation settings 6
• The error in tidal volume measurement is relatively greater in infants and small children 6
• Without circuit compensation, displayed tidal volume generally overestimates true-delivered volume; with compensation, it generally underestimates 6

Circuit Management

• Avoid adding unnecessary components between the endotracheal tube and Y-piece, as each addition increases dead space 1, 2
• Do not use home ventilators during the acute phase in the intensive care unit 1
• Avoid hand ventilation unless specific conditions dictate otherwise 1

Ventilator Settings

• For patients <500 g, initial tidal volumes of 5-6 mL/kg may be needed for normocapnia due to the proportionally larger dead space effect 3
• Target patient-ventilator synchrony to reduce work of breathing 4, 5

Additional Supportive Measures

• Use humidification in all ventilated patients 1, 4
• Maintain head of bed elevated 30-45° 1, 4
• Use cuffed endotracheal tubes with cuff pressure ≤20 cmH2O 1, 4