In which conditions is pressure control ventilation (PCV) preferred over volume control ventilation?

Pressure Control Ventilation: Clinical Indications and Comparative Advantages

Pressure control ventilation (PCV) is preferred during assisted or spontaneous breathing phases when patient comfort and synchrony are priorities, while volume control ventilation (VCV) should be used during passive ventilation in early ARDS to facilitate measurement of respiratory mechanics and driving pressure. 1

Primary Indication: Assisted Breathing and Patient Comfort

PCV offers superior respiratory comfort during assisted breathing because it does not limit inspiratory flow, allowing the ventilator to match variable patient demand. 1

• PCV significantly reduces patient work of breathing compared to VCV (0.59 ± 0.42 J/L vs 0.70 ± 0.58 J/L, p < 0.05) in patients with acute lung injury and ARDS 2
• The variable decelerating flow pattern in PCV provides higher peak inspiratory flow (103.2 ± 22.8 L/min vs 43.8 L/min with VCV), better matching unstable breathing patterns in acute respiratory failure 2
• When patients transition from passive to assisted ventilation, PCV improves synchrony and reduces sedation requirements 3

Early ARDS Management: Volume Control is Preferred

During the early passive ventilation phase of ARDS, VCV is recommended because it facilitates measurement of respiratory mechanics and driving pressure, which are critical for lung-protective ventilation. 1

• VCV allows automatic collection of plateau pressure and driving pressure during inspiratory pause, essential for titrating PEEP and assessing lung stress 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 1
• VCV guarantees fixed tidal volume delivery, crucial when implementing the 6 mL/kg predicted body weight lung-protective strategy 4

Specific Clinical Scenarios Favoring PCV

High and Variable Respiratory Drive

• PCV accommodates breath-to-breath variability in patient flow demand without increasing work of breathing 5, 2
• The decelerating flow waveform provides immediate high flow at inspiration onset, reducing patient effort 5

Concerns About Peak Airway Pressure

• PCV generates significantly lower peak airway pressures (26 ± 2 cm H₂O vs 31 ± 2 cm H₂O with VCV, p < 0.001) while maintaining similar plateau pressures 6
• This may reduce regional overdistension through more homogeneous gas distribution, particularly at the lung apex 6

Bariatric Surgery and Obesity

• Either PCV or VCV can be used in patients with obesity undergoing surgery, with the choice based on procedural factors 1
• PCV may promote more homogeneous ventilation and improve oxygenation in obese patients 1
• VCV allows better tidal volume control during procedures that intermittently affect chest wall compliance 1

When VCV Remains Superior

Passive Ventilation with Lung-Protective Strategy

• VCV is essential when reducing tidal volume from 6 mL/kg to 4 mL/kg predicted body weight for plateau pressures >30 cm H₂O 4
• VCV ensures consistent minute ventilation when permissive hypercapnia is employed 4

PEEP Titration Using EIT

• The overdistension-collapse method for PEEP titration requires VCV with inspiratory pause >0.5 seconds to measure driving pressure 1
• Alternatively, pressure control with constant support level and sufficient equilibration time can be used, but VCV is more straightforward 1

Difficult-to-Manage Patients

• VCV should be considered when ensuring consistent alveolar ventilation is crucial and patients fail on pressure support 7

Critical Nuances and Common Pitfalls

The Flow Waveform is Key, Not the Mode

• The primary advantage of PCV over traditional VCV stems from the decelerating flow waveform, not the pressure control itself 5, 8
• VCV with decelerating flow provides similar benefits to PCV: better oxygenation (PaO₂ 85 ± 9 mm Hg vs 75 ± 11 mm Hg with square wave, p < 0.05) and lower peak pressures 8
• Modern ventilators offer decelerating flow during VCV, potentially eliminating the need to switch modes 5, 8

PCV Does Not Guarantee Lung Protection

• PCV limits peak airway pressure but does not guarantee fixed tidal volume, which can vary with changes in compliance or resistance 5
• Clinicians must titrate inspiratory pressure to measured tidal volume during PCV to maintain lung-protective targets 5
• Both modes can achieve lung protection when tidal volume, plateau pressure, and driving pressure are appropriately managed 1

Transition Strategy

Begin with VCV during early passive ARDS ventilation, then transition to PCV when weaning sedation and allowing spontaneous breathing efforts. 1

• This approach optimizes respiratory mechanics monitoring early while improving comfort during recovery 1
• A recent trial showed PCV with spontaneous ventilation reduced sedation and adjunctive therapies (33.1% vs 41.3% requiring prone positioning, p = 0.03) without mortality difference 3

Monitoring Requirements Differ by Mode

• During VCV: Monitor plateau pressure, driving pressure, and tidal volume delivery 1, 4
• During PCV: Monitor tidal volume variability, patient-ventilator synchrony, and work of breathing 5, 2
• Driving pressure (plateau pressure minus PEEP) predicts outcomes regardless of mode and should be kept <15 cm H₂O 4