When and how should pressure‑regulated volume control (PRVC) mode be used on a ventilator?

PRVC Mode Ventilator: When and How to Use

Pressure-Regulated Volume Control (PRVC) should be used selectively in mechanically ventilated patients, primarily during the recovery/assisted breathing phase rather than initial acute management, as it provides lower peak inspiratory pressures while maintaining target tidal volumes—but carries significant risk of delivering excessive tidal volumes in ARDS and severely obstructed patients.

Initial Ventilation Strategy: Avoid PRVC

During the acute phase of respiratory failure, volume-controlled ventilation is recommended over PRVC 1. Volume control facilitates accurate measurement of respiratory mechanics and driving pressure, which are critical for lung-protective ventilation strategies. For ARDS specifically, maintain:

• Tidal volumes: 6-8 mL/kg ideal body weight
• Plateau pressure ≤30 cmH₂O 2
• Permissive hypercapnia with pH >7.2 2

Critical Pitfall: PRVC Delivers Excessive Tidal Volumes

The most important caveat is that PRVC consistently delivers higher tidal volumes than programmed settings 3. In a 2020 study of 272 septic patients, over 90% ventilated with PRVC received delivered tidal volumes significantly exceeding set tidal volumes at all time points, even after ARDS recognition (p<0.001) 3. This directly contradicts lung-protective ventilation principles and increases ventilator-induced lung injury risk.

Specific Contraindications

Severe Airflow Obstruction

PRVC should be avoided in severely obstructed patients 4. In high-resistance simulations:

• Evita XL delivered only 120 mL when 200 mL was programmed (40% deficit)
• Servo-i delivered only 104 mL when 200 mL was programmed (48% deficit)
• This leads to hypoventilation and respiratory acidosis 4

ARDS Patients

Given the consistent over-delivery of tidal volumes 3 and the established mortality benefit of low tidal volume ventilation in ARDS 2, PRVC undermines lung-protective strategies and should not be used in this population.

Potential Appropriate Uses

Traumatic Brain Injury

PRVC may offer advantages in TBI patients requiring ICP control:

• Produces less fluctuation in ICP and PaCO₂ compared to pressure control (p=0.02 and p=0.05 respectively) 5
• Mean ICP and PaCO₂ were similar between modes
• More stable PaCO₂ theoretically provides better ICP management through consistent cerebral vasomotor tone

COPD Exacerbations (With Caution)

In elderly COPD patients with respiratory failure, PRVC showed:

• Significantly lower peak inspiratory pressure after 2-4 hours and 48 hours (p<0.05) 6
• Reduced pulmonary barotrauma risk
• Rapid improvement in blood gas parameters

However, this must be balanced against the risk of hypoventilation in severe obstruction 4.

Transition to Assisted Breathing

PRVC may be considered during the recovery phase when transitioning from controlled to assisted ventilation 1. Pressure-controlled modes (including PRVC) can provide better respiratory comfort during assisted breathing because they don't limit inspiratory flow. However, this requires:

• Close monitoring of delivered vs. set tidal volumes
• Regular adjustment of settings
• Confirmation that peak pressures remain acceptable

Monitoring Requirements When Using PRVC

If PRVC is used, mandatory monitoring includes:

• Actual delivered tidal volume (not just set volume)
• Peak and plateau airway pressures
• Driving pressure (Pplat - PEEP)
• Arterial blood gases
• Patient-ventilator synchrony
• Respiratory rate and work of breathing

Algorithm for Mode Selection

Initial acute phase (first 48 hours):

• Use volume control ventilation
• Enables accurate respiratory mechanics assessment
• Facilitates lung-protective ventilation

Recovery/assisted breathing phase:

• Consider PRVC if peak pressures are problematic
• Only if close monitoring of delivered volumes is feasible
• Avoid in ARDS or severe obstruction

Special populations:

• TBI with ICP monitoring: PRVC may reduce ICP fluctuations 5
• Mild-moderate COPD: PRVC may reduce peak pressures 6
• Severe obstruction: Use volume control to prevent hypoventilation 4

Key Takeaway

The theoretical advantage of PRVC (lower peak pressures while maintaining volume) is undermined by its tendency to deliver excessive tidal volumes 3, making it inappropriate for ARDS and potentially dangerous in severe obstruction 4. When lung-protective ventilation is the priority—which it should be in most critically ill patients 2—volume control remains the safer choice.