Maximum Tidal Volume for Mechanical Ventilation in COVID-19 ARDS
The maximum permissible tidal volume is 8 mL/kg predicted body weight for this patient with COVID-19-induced ARDS, though targeting 6 mL/kg PBW is the recommended starting point. 1
Primary Guideline Recommendation
The Surviving Sepsis Campaign COVID-19 guidelines provide a strong recommendation to use low tidal volume ventilation (Vt 4–8 mL/kg of predicted body weight) over higher tidal volumes (Vt > 8 mL/kg) in mechanically ventilated adults with COVID-19 and ARDS. 1 This represents the acceptable range, with 8 mL/kg PBW being the upper limit that should not be exceeded.
Target Tidal Volume Strategy
- Start at 6 mL/kg PBW as the initial target, which has strong evidence for mortality reduction in ARDS patients 1, 2
- The landmark ARMA trial demonstrated that ventilation with 6 mL/kg PBW (versus 12 mL/kg) reduced mortality from 39.8% to 31.0% in ARDS patients 2
- This 6 mL/kg target applies equally to sepsis-induced ARDS and COVID-19 ARDS 1
When to Reduce Below 6 mL/kg PBW
If plateau pressure exceeds 30 cm H₂O despite using 6 mL/kg PBW, you must reduce tidal volume further to 4 mL/kg PBW. 3, 4 The American Thoracic Society explicitly recommends this stepwise reduction rather than accepting elevated plateau pressures. 3
- Plateau pressure must remain below 30 cm H₂O as a strong recommendation 1
- Accept permissive hypercapnia (pH >7.15-7.20) when reducing tidal volume to maintain safe plateau pressures 3
- Driving pressure (plateau pressure minus PEEP) should ideally stay below 15 cm H₂O, as values exceeding this threshold predict worse outcomes 3, 4, 5
Critical Calculation Point
Always calculate tidal volume based on predicted body weight, not actual body weight. 3, 4 This is particularly important in elderly patients who may have significant differences between actual and predicted body weight. Using actual body weight risks overventilation and ventilator-induced lung injury.
Addressing the Upper Limit Controversy
While one recent retrospective study suggested tidal volumes of 7-9 mL/kg PBW might be safe in COVID-19 patients 6, this contradicts the strong guideline recommendations from the Surviving Sepsis Campaign. 1 The guideline evidence should take precedence, establishing 8 mL/kg PBW as the absolute maximum, not a target to pursue.
Common Pitfalls to Avoid
- Never exceed 8 mL/kg PBW even if oxygenation appears inadequate—instead optimize PEEP, consider prone positioning, or escalate to rescue therapies 1
- Emergency department physicians frequently set initial tidal volumes 1.5 mL/kg above recommendations, which confers harm 7
- Even small deviations (1 mL/kg above target) increase risk of ventilator-induced lung injury 7
- Do not use traditional tidal volumes of 10-15 mL/kg that were standard before the ARMA trial 2, 8
Monitoring Requirements
- Measure plateau pressure with inspiratory hold maneuvers to ensure accurate assessment 5
- Calculate and track driving pressure as a strong predictor of outcomes 3, 4, 5
- Monitor for adequate oxygenation (SpO₂ maintained no higher than 96%) 1
- Reassess ventilator settings if patient-ventilator dyssynchrony develops 4