Recommended Tidal Volume for Mechanical Ventilation
For patients with ARDS, use a target tidal volume of 6 mL/kg predicted body weight (PBW) with an upper limit plateau pressure goal of 30 cm H₂O. 1
Core Ventilation Strategy for ARDS
The 6 mL/kg PBW target is a strong recommendation based on high-quality evidence showing reduced mortality (31.0% vs 39.8%, P=0.007) and increased ventilator-free days compared to traditional 12 mL/kg volumes. 2 This represents the cornerstone of lung-protective ventilation endorsed by the Surviving Sepsis Campaign guidelines. 1
Calculating Predicted Body Weight
- For males: PBW = 50 + 2.3 × (height in inches - 60) 3
- For females: PBW = 45.5 + 2.3 × (height in inches - 60) 3
- Use height-based PBW, not actual body weight, as lung size correlates with height rather than weight—this is particularly critical for women and obese patients who risk receiving excessive volumes if actual weight is used. 4, 5
- Arm demispan can serve as a surrogate for height measurement when direct measurement is impractical. 4
Pressure Targets and Monitoring
Maintain plateau pressure ≤30 cm H₂O as an absolute ceiling, even if this requires further reduction in tidal volume below 6 mL/kg PBW. 1, 6 This pressure limit prevents ventilator-induced lung injury through alveolar overdistension. 6
Target driving pressure (ΔP = plateau pressure - PEEP) ≤15 cm H₂O, as this parameter predicts mortality better than tidal volume or plateau pressure alone. 7, 8 If driving pressure exceeds 15 cm H₂O:
- Decrease tidal volume below 6 mL/kg PBW if necessary 7
- Increase PEEP to recruit collapsed alveoli and improve compliance 7
- Consider prone positioning for severe ARDS (PaO₂/FiO₂ <150) 1
Ventilation Strategy by Clinical Scenario
Sepsis-Induced ARDS (Moderate to Severe)
- Tidal volume: 6 mL/kg PBW (strong recommendation) 1
- Plateau pressure: ≤30 cm H₂O 1
- PEEP: Higher PEEP strategies over lower PEEP (weak recommendation, moderate quality evidence) 1
- Prone positioning: Strongly recommended when PaO₂/FiO₂ <150 mm Hg 1
Respiratory Failure Without ARDS
- Tidal volume: 6-10 mL/kg PBW is acceptable 1
- A recent trial (PREVENT) showed no significant outcome difference between 6 mL/kg and 10 mL/kg PBW in non-ARDS patients, though lung-protective strategies remain advocated. 1
- Plateau pressure: Still maintain ≤30 cm H₂O 6
ACLF/Cirrhosis with ALI
- Tidal volume: 6 mL/kg PBW (lung-protective strategy) 1
- Plateau pressure: <30 cm H₂O 1
- PEEP considerations: Use low PEEP (<10 cm H₂O) for mild ARDS (PaO₂/FiO₂ 200-300) to avoid impeding venous return in vasodilated patients; higher PEEP acceptable for moderate-severe ARDS (PaO₂/FiO₂ <200) with hemodynamic monitoring. 1
Common Pitfalls and How to Avoid Them
Using actual body weight instead of PBW leads to excessive tidal volumes, particularly in women and obese patients—always calculate and use PBW. 4, 5
Accepting plateau pressures >30 cm H₂O significantly increases barotrauma risk (pneumothorax, pneumomediastinum)—if plateau pressure exceeds this threshold despite 6 mL/kg PBW, reduce tidal volume further and accept permissive hypercapnia. 6
Ignoring driving pressure misses a superior mortality predictor—values ≥18 cm H₂O specifically increase right ventricular failure risk in ARDS. 7
Inconsistent PBW equation use creates interstudy variation up to 24% in women and 15% in men—standardize using the NIH ARDS Network equation as it derives from the landmark trial establishing the 6 mL/kg target. 5
Additional Ventilatory Adjustments
- Permissive hypercapnia may be necessary when using lower tidal volumes to prevent alveolar overdistension. 3
- Recruitment maneuvers are suggested for severe ARDS with refractory hypoxemia (weak recommendation). 1
- Neuromuscular blockade for ≤48 hours when PaO₂/FiO₂ <150 mm Hg (weak recommendation). 1
- Conservative fluid strategy for established ARDS without tissue hypoperfusion (strong recommendation). 1