ARDS and refractory hypoxaemia

Lung-protective ventilation and PEEP

Reviewed Nov 2026·5 references
New· views rounded down, updated weekly

Tidal volume 6 mL/kg PBW (4-8), plateau ≤ 30 cmH2O, driving pressure ideally ≤ 15, PEEP by table or mechanics (higher PEEP in moderate-severe ARDS), no prolonged recruitment manoeuvres, permissive hypercapnia with pH ≥ 7.20-7.25.

At the bedside

Timed steps
  1. 1

    Vt 6 mL/kg PBW

    Start

    Begin at 8 and reduce to 6 within 1-4 h; 4-5 if Pplat > 30.

  2. 2

    Plateau and driving pressure

    Check

    Pplat ≤ 30 cmH2O (0.5 s inspiratory hold). Driving pressure ≤ 15 cmH2O where possible.

  3. 3

    Choose a strategy

    PEEP

    Mild: lower PEEP/FiO2 table. Moderate-severe: higher PEEP (without prolonged recruitment) suggested by ATS 2024; watch Pplat, BP and compliance response.

  4. 4

    Prolonged recruitment manoeuvres

    Avoid

    Strong recommendation against prolonged/stepwise recruitment (ART trial harm).

  5. 5

    Permissive hypercapnia

    Rate

    Rate up to 35/min to keep pH ≥ 7.20-7.25 (watch auto-PEEP). Avoid hypercapnia in raised ICP and severe RV failure.

  6. 6

    Targets

    Oxygen

    SpO2 88-95% (PaO2 55-80 mmHg) per ARDSNet protocol.

  7. 7

    Escalate

    Refractory

    P/F < 150: prone (next topic); consider NMB; optimise fluids; then ECMO referral.

ARDSNet lower PEEP/FiO2 table

FiO20.30.40.50.60.70.80.91.0
PEEP (cmH2O)55-88-101010-141414-1818-24

ARDSNet higher PEEP/FiO2 table (ALVEOLI)

FiO20.30.40.50.5-0.80.80.91.0
PEEP (cmH2O)5-1414-1616-1820222222-24
Red flag · call your senior now
Pplat > 30 despite Vt 4 mL/kg: severe disease; prone, consider ECMO.
Red flag
Hypotension after PEEP increase: preload, RV failure, overdistension; reduce PEEP and echo.
Pitfall
Using actual body weight for Vt.
Pitfall
Forgetting to measure plateau after every Vt or PEEP change.
Pearl
If compliance improves and driving pressure falls after a PEEP increase, the lung recruited; if Pplat rises with no compliance change, it overdistended.

Calculators for this topic

Predicted (ideal) body weight

ARDSNet predicted body weight from height and sex. Use for tidal volume, not for most drug doses.

Tidal volume from predicted body weight

Lung-protective tidal volume (usually 6 mL/kg PBW; range 4-8).

Driving pressure

Plateau pressure − PEEP (volume control, passive patient).

Static respiratory system compliance

Vt ÷ (Pplat − PEEP).

PaO₂/FiO₂ ratio

Oxygenation ratio with ARDS severity bands (Berlin; PEEP ≥ 5 cmH₂O).

References

  1. 1

    ARDS Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and ARDS. N Engl J Med. 2000;342(18):1301-1308

  2. 2

    Brower RG, Lanken PN, MacIntyre N, et al. Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome (ALVEOLI). N Engl J Med. 2004;351(4):327-336

  3. 3

    Writing Group for the ART Investigators. Effect of lung recruitment and titrated PEEP vs low PEEP on mortality in patients with ARDS. JAMA. 2017;318(14):1335-1345

  4. 4

    Qadir N, Sahetya S, Munshi L, et al. An update on management of adult patients with acute respiratory distress syndrome: an official American Thoracic Society clinical practice guideline. Am J Respir Crit Care Med. 2024;209(1):24-36

  5. 5

    Grasselli G, Calfee CS, Camporota L, et al. ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies. Intensive Care Med. 2023;49(7):727-759

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Prone positioning

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