What are the indications for using Pressure-Regulated Volume Control (PRVC) mode in mechanically ventilated patients?

Indications for PRVC Mode

PRVC (Pressure-Regulated Volume Control) is NOT specifically recommended by major guidelines and should generally be avoided as a primary ventilation mode in critically ill patients, particularly those with ARDS or severe airway obstruction. Instead, start with volume-cycled assist-control ventilation for most mechanically ventilated patients requiring full support 1, 2, 3.

Why PRVC Is Not Recommended

Failure to Deliver Target Volumes in High-Resistance States

• In patients with severe airway obstruction, PRVC consistently fails to deliver programmed tidal volumes, potentially causing dangerous hypoventilation 4.
• Experimental data shows that with high airway resistance at 200 mL tidal volume, PRVC delivered only 120 mL (Evita XL) and 104 mL (Servo-i)—representing 40-48% volume deficits 4.
• This volume delivery failure occurs because PRVC prioritizes pressure limitation over volume guarantee, making it unsuitable for patients with high resistance or poor compliance 4.

No Advantage in Work of Breathing

• PRVC offers no reduction in work of breathing compared to volume control ventilation with high flow rates (75 L/min) during lung-protective ventilation 5.
• In 40% of patients with acute lung injury/ARDS, PRVC allowed tidal volumes to markedly exceed lung-protective targets (>6.4 mL/kg), increasing risk of ventilator-induced lung injury 5.
• Work of breathing was actually higher with PRVC (1.35 ± 0.60 J/L) compared to volume control (1.09 ± 0.59 J/L), though not statistically significant 5.

Lack of Outcome Benefits

• While PRVC reduces peak inspiratory pressures by approximately 4 cmH₂O compared to volume control, this has not translated to improved clinical outcomes including mortality, ventilator days, or mode failure rates 6.
• The theoretical advantage of lower peak pressures is clinically irrelevant since plateau pressure, not peak pressure, determines ventilator-induced lung injury risk 7.

What to Use Instead

Primary Recommendation: Volume-Cycled Assist-Control

Start with volume-cycled assist-control (AC) ventilation when initiating mechanical ventilation 1, 2, 3. This mode:

• Provides complete ventilatory support immediately after intubation 2, 3
• Guarantees a backup respiratory rate that prevents central apneas, which commonly occur with pressure support modes 7, 2
• Allows precise control of tidal volume to achieve lung-protective targets 3

Critical Initial Settings

• Set tidal volume at 6 mL/kg predicted body weight (NOT actual body weight) to reduce mortality in ARDS and sepsis-induced respiratory failure 1, 2, 3
• Calculate predicted body weight: Men = 50 + 2.3 × (height in inches - 60); Women = 45.5 + 2.3 × (height in inches - 60) 1, 3
• Maintain plateau pressure ≤30 cmH₂O to prevent alveolar overdistension 7, 2, 3
• Use high inspiratory flow rates (75 L/min) with decelerating flow waveform if available 5, 8

Rare Situations Where PRVC Might Be Considered

Stable Patients Without Severe Lung Disease

• PRVC may be acceptable in hemodynamically stable patients without ARDS, severe obstruction, or high ventilatory demands 6, 9
• Even then, it offers no proven advantage over properly configured volume control with decelerating flow 8, 9

Specific Contraindications to PRVC

• Never use in severe airway obstruction (asthma, COPD exacerbations) due to volume delivery failure 4
• Avoid in ARDS where precise tidal volume control is essential for lung protection 5
• Do not use in patients with high or variable respiratory drive where excessive tidal volumes may occur 5
• Contraindicated when permissive hypercapnia is needed, as volume underdosing will worsen CO₂ retention 4

Common Pitfalls to Avoid

• Do not assume PRVC provides lung protection—it can deliver excessive tidal volumes in spontaneously breathing patients 5
• Do not rely on peak pressure reduction as a surrogate for safety—only plateau pressure matters for ventilator-induced lung injury 7, 8
• Monitor delivered tidal volumes continuously with PRVC—the mode may silently hypoventilate patients with changing lung mechanics 4, 6
• Avoid PRVC in tachypneic patients where patient-ventilator dyssynchrony and variable volumes increase VILI risk 3