What are the optimal settings for Volume-Controlled Ventilation (VCV) during sleep?

Optimal Settings for Volume-Controlled Ventilation During Sleep

For optimal volume-controlled ventilation (VCV) during sleep, use a tidal volume of 6-8 mL/kg of predicted body weight with a backup rate of 10-15 breaths per minute and an inspiratory time set to 30-40% of the respiratory cycle. 1

Initial VCV Settings

• Start with IPAP minimum of 8 cm H₂O and EPAP minimum of 4 cm H₂O 1
• Set maximum IPAP at 30 cm H₂O for adults (≥12 years) and 20 cm H₂O for children (<12 years) 1
• Target tidal volume of 6-8 mL/kg of predicted body weight 1, 2
• Set initial backup respiratory rate equal to or slightly less than the patient's spontaneous sleeping respiratory rate, with a minimum of 10 breaths per minute 1
• Use an inspiratory time (IPAP time) of 30-40% of the total respiratory cycle time 1

Adjusting VCV Parameters

Pressure Settings

• Increase IPAP if tidal volume is low (<6-8 mL/kg) 1
• Increase pressure support if arterial PCO₂ remains 10 mm Hg or more above goal for 10+ minutes 1
• Increase pressure support if SpO₂ remains below 90% for 5+ minutes with low tidal volume 1
• If patient awakens complaining of excessive pressure, lower to a comfortable level to allow return to sleep 1

Respiratory Rate and Timing

• Adjust backup rate in 1-2 bpm increments every 10 minutes if ventilation goals aren't met 1
• For patients with obstructive airways disease, use shorter inspiratory time (approximately 30% of cycle time) to allow adequate exhalation 1
• For patients with restrictive disease, use longer inspiratory time (approximately 40% of cycle time) 1
• Calculate appropriate inspiratory time based on respiratory rate to maintain proper I:E ratio 1

Volume-Targeted Pressure Support Considerations

• Volume-targeted BPAP (VT-BPAP) automatically adjusts IPAP between set limits to deliver targeted tidal volume 1
• Initial settings for volume-targeted pressure support: EPAP = 4 cm H₂O, IPAP min = EPAP + 4 cm H₂O, IPAP max = 25-30 cm H₂O 1
• Set initial target tidal volume at approximately 8 mL/kg ideal body weight 1
• This approach combines benefits of both volume and pressure control 3, 4

Addressing Central Apneas and Asynchrony

• Use spontaneous-timed (ST) mode with backup rate for all patients with central hypoventilation, central apneas, or muscle weakness 1
• Consider switching from spontaneous to ST mode if adequate ventilation or respiratory muscle rest isn't achieved with maximum pressure support 1
• Excessive pressure support during sleep can cause central apneas by lowering PaCO₂ below the apneic threshold 1
• Adjust pressure relief, rise time, and IPAP duration to optimize patient comfort and synchrony 1

Supplemental Oxygen

• Add supplemental oxygen if awake SpO₂ <88% or when pressure support and respiratory rate have been optimized but SpO₂ remains <90% for 5+ minutes 1
• Start at 1 L/minute and increase in 1 L/minute increments every 5 minutes until SpO₂ >90% 1

Monitoring and Adjustments

• Monitor for signs of patient-ventilator asynchrony, which can significantly disrupt sleep 1
• Adjust mask fit or change mask type if significant unintentional leak is observed 1
• Consider heated humidification if the patient complains of dryness or nasal congestion 1
• For patients with concurrent obstructive sleep apnea, follow AASM guidelines for titrating PAP to eliminate obstructive events 1

Common Pitfalls to Avoid

• Setting tidal volumes too high (>8 mL/kg) can increase risk of ventilator-induced lung injury 2, 5, 6
• Insufficient backup rate can lead to central apneas and sleep fragmentation 1
• Improper inspiratory time settings can cause patient-ventilator asynchrony 1
• Failure to adjust for underlying lung disease (obstructive vs. restrictive) can lead to suboptimal ventilation 1
• Inadequate humidification can cause upper airway dryness and poor sleep quality 1