What is the preferred mode of ventilation, pressure control ventilation (PCV) or volume control ventilation (VCV), for a patient with respiratory distress, particularly those with acute respiratory distress syndrome (ARDS) or heterogeneous lung injury?

Pressure Control vs Volume Control Ventilation in ARDS

Volume control ventilation (VCV) is recommended in the early stage of ARDS because it facilitates measurement of respiratory mechanics and driving pressure, with no outcome difference between VCV and PCV when the same tidal volume is delivered. 1

Primary Recommendation: Start with Volume Control

Use volume-controlled ventilation during passive inflation in the early phase of ARDS because it enables precise monitoring of plateau pressure and driving pressure—the two most critical parameters for preventing ventilator-induced lung injury. 1 The American Thoracic Society and European Society of Intensive Care Medicine both emphasize that for the same tidal volume, there is no mortality or morbidity advantage of pressure-controlled versus volume-controlled ventilation in terms of stress and strain generated in the lung. 1

Why Volume Control First?

• VCV guarantees delivery of the target tidal volume of 4-8 mL/kg predicted body weight, which is the cornerstone of lung-protective ventilation with proven mortality reduction (31.0% vs 39.8%, P=0.007). 2

• VCV allows accurate measurement of plateau pressure, which must be maintained ≤30 cmH₂O as an absolute ceiling to prevent alveolar overdistension and barotrauma. 3, 2

• VCV enables calculation of driving pressure (ΔP = plateau pressure - PEEP), the single best predictor of mortality in ARDS, which should be kept ≤15 cmH₂O. 4

• VCV provides consistent minute ventilation despite changing lung compliance, which is critical in the unstable early phase of ARDS. 5

When to Consider Pressure Control

Transition to pressure-controlled ventilation may be appropriate later in the disease course during assisted breathing modes when patient comfort becomes a priority. 1

Specific Indications for PCV:

• Patient-ventilator dyssynchrony during assisted ventilation where the decelerating flow pattern of PCV may reduce work of breathing (0.59 ± 0.42 J/L vs 0.70 ± 0.58 J/L with VCV, p<0.05). 6

• Improved respiratory comfort in spontaneously breathing patients because PCV does not limit inspiratory flow and provides higher peak flows (103.2 ± 22.8 L/min vs 43.8 L/min with VCV). 6

• Transition to weaning phase when sedation is being reduced and partial ventilator support is introduced. 1

Critical Caveat with PCV:

Pressure-controlled ventilation does not guarantee a fixed tidal volume, which can lead to inadvertent delivery of excessive volumes if lung compliance improves, or inadequate volumes if compliance worsens. 1 This requires vigilant monitoring of delivered tidal volumes to ensure they remain within the 4-8 mL/kg predicted body weight range. 2

Practical Implementation Algorithm

Early Phase (First 24-72 hours):

1. Use volume control mode (assist-control) with tidal volume 6 mL/kg predicted body weight. 2, 7

2. Measure plateau pressure with inspiratory hold maneuver (0.5-1.0 seconds) and maintain ≤30 cmH₂O. 3

3. Calculate driving pressure (plateau pressure - PEEP) and target ≤15 cmH₂O. 4

4. If plateau pressure >30 cmH₂O, reduce tidal volume below 6 mL/kg as needed. 2

5. Increase respiratory rate as tidal volume is reduced to maintain minute ventilation and prevent acute hypercapnia. 7

Later Phase (After stabilization):

1. Consider switching to PCV if patient develops dyssynchrony or increased work of breathing during assisted modes. 1

2. Monitor delivered tidal volumes continuously to ensure they remain 4-8 mL/kg predicted body weight. 2

3. Continue measuring plateau pressure even in PCV by performing inspiratory holds. 3

4. Titrate inspiratory pressure to achieve target tidal volume while maintaining plateau pressure ≤30 cmH₂O. 5

Common Pitfalls to Avoid

• Do not assume PCV is "safer" because it limits pressure—the delivered tidal volume can still cause overdistension if compliance improves unexpectedly. 1

• Do not use traditional high tidal volumes (12 mL/kg) in either mode—this increases mortality regardless of control variable. 2

• Do not neglect driving pressure monitoring—it predicts mortality better than plateau pressure or tidal volume alone. 4

• Do not forget to optimize PEEP—higher PEEP strategies reduce mortality in moderate-severe ARDS (PaO₂/FiO₂ ≤200 mmHg) and can lower driving pressure. 1, 4