When to use pressure controlled ventilation (PCV) vs volume controlled ventilation (VCV) in patients with respiratory conditions?

Pressure vs. Volume Controlled Ventilation: When to Use Each

For most patients with respiratory conditions, volume-controlled ventilation (VCV) should be used initially, while pressure-controlled ventilation (PCV) may be more beneficial in specific clinical scenarios such as patient-ventilator asynchrony, high peak airway pressures, or when patient comfort is a priority during assisted breathing. 1

General Principles for Ventilation Mode Selection

Volume-Controlled Ventilation (VCV)

• Primary advantages:
  • Guarantees a preset tidal volume and minute ventilation 1, 2
  • Facilitates measurement of respiratory mechanics and driving pressure 3
  • Recommended in early stages of respiratory failure 3
  • Better control of tidal volume during procedures affecting chest wall compliance 3

Pressure-Controlled Ventilation (PCV)

• Primary advantages:
  • Limits maximum airway pressure delivered to the lung 2
  • Provides lower peak airway pressures than VCV 4, 5
  • May result in better respiratory comfort during assisted breathing 3
  • Can promote more homogeneous ventilation within different lung compartments 3

Clinical Decision Algorithm for Ventilation Mode Selection

Use Volume-Controlled Ventilation (VCV) when:

1. Initial ventilation setup is required

   • Facilitates measurement of respiratory mechanics 3
   • Allows for easier assessment of driving pressure 1
   • Provides consistent tidal volumes for initial stabilization

2. Precise control of minute ventilation is critical

   • Ensures delivery of set tidal volumes 2
   • Particularly important in metabolic acidosis requiring specific ventilation targets

3. Monitoring respiratory mechanics is a priority

   • Allows for easier calculation of compliance and resistance
   • Better assessment of driving pressure (plateau pressure - PEEP) 1

4. During procedures affecting chest wall compliance

   • Maintains consistent tidal volumes despite changing thoracic mechanics 3

Use Pressure-Controlled Ventilation (PCV) when:

1. High peak airway pressures are present

   • PCV significantly reduces peak airway pressure compared to VCV 4, 5
   • Helps prevent barotrauma in patients with high airway resistance

2. Patient-ventilator asynchrony is observed

   • Decelerating flow pattern may improve patient comfort 2
   • May reduce work of breathing in spontaneously breathing patients

3. Later stages of respiratory support

   • May result in better respiratory comfort during assisted breathing 3
   • Particularly useful during weaning phases

4. Heterogeneous lung disease is present

   • Promotes more homogeneous ventilation within different lung compartments 3, 4
   • May improve gas distribution in lungs with regional differences in compliance

Special Considerations

ARDS Management

• Both VCV and PCV can be used effectively in ARDS 1
• The key principle is lung-protective ventilation with low tidal volumes (4-8 ml/kg PBW) and plateau pressures <30 cmH2O regardless of mode 1
• For the same tidal volume, there is no outcome advantage between PCV and VCV in terms of stress and strain generated in the lung 3

Obesity

• In patients with obesity, both PCV and VCV can be used with low tidal volumes (6-8 ml/kg PBW) 3
• Individual PEEP settings targeted to physiological goals are more important than ventilation mode 3
• Driving pressure should be monitored closely in obese patients 3

One-Lung Ventilation

• PCV may offer lower peak airway pressures during one-lung ventilation 5
• No significant differences in oxygenation between PCV and VCV during one-lung ventilation in patients with good pulmonary function 5

Common Pitfalls to Avoid

1. Using PCV without monitoring delivered tidal volumes

   • PCV can result in variable tidal volumes that may exceed lung-protective targets 6
   • Regular assessment of actual delivered volumes is essential

2. Focusing solely on peak pressures

   • While PCV reduces peak pressures, plateau and mean pressures are more important for lung protection 5
   • Lower peak pressure in PCV doesn't necessarily translate to reduced lung injury

3. Neglecting patient-ventilator interaction

   • PCV may be more comfortable for spontaneously breathing patients, but can lead to variable minute ventilation 2
   • VCV may increase work of breathing in patients with high respiratory demand

4. Overlooking the importance of flow settings in VCV

   • Many modern ventilators allow decelerating flow patterns in VCV, which can provide similar benefits to PCV 2

Remember that regardless of ventilation mode, the fundamental principles of lung-protective ventilation (appropriate tidal volumes, limiting plateau pressures, and optimizing PEEP) are more important than the choice between PCV and VCV for patient outcomes 1.