Bilateral infiltrates, PaO₂/FiO₂ 110 on PEEP 5, 3 days into pneumonia — this is ARDS; the ventilator itself can injure, so set it like a lung-protective protocol.
ABCDE
Confirm not cardiogenic (echo/BNP); lung-protective ventilation 6 mL/kg PBW; plateau ≤30, driving pressure ≤15; prone ≥16 h/day if P/F <150; conservative fluids once resuscitated.
Diagnose (Berlin): new bilateral infiltrates within 1 week of an insult, not explained by cardiac failure, with PaO₂/FiO₂ ≤300 on PEEP ≥5 — classify: mild 200–300, moderate 100–200, severe <100. 2024 Global Definition also allows diagnosis on HFNO ≥30 L/min, SpO₂/FiO₂ (≤315 with SpO₂ ≤97%), and lung ultrasound — Berlin remains the trial standard
Lung-protective ventilation: tidal volume 6 mL/kg PBW (range 4–8), plateau pressure ≤30 cmH₂O, driving pressure (plateau − PEEP) ≤15
Permissive hypercapnia: accept PaCO₂ rise if pH >7.25; SpO₂ target 88–95%; use PEEP/FiO₂ ladder — higher PEEP for moderate-severe
Prone if P/F <150: prone positioning ≥16 h/day — PROSEVA mortality benefit; check tube, eyes, pressure areas each turn
Fluids conservative: once shock resolves, run a negative balance — diurese to the driest lungs the circulation tolerates
Refractory severe: NMB infusion (cisatracurium) reserved for severe ARDS with patient–ventilator dyssynchrony or refractory hypoxaemia despite proning — not routine (ATS 2023 suggests against routine continuous NMB); consider VV-ECMO if pH <7.25 or P/F <80 despite proning — call ECMO centre early
Order set
- ABG q4–6 h during titration
- VT 6 mL/kg PBW — recalculate PBW now
- Plateau + driving pressure checks
- Daily CXR / lung ultrasound
- Fluid balance — target negative after resuscitation
- Prone positioning schedule if P/F <150
- DVT prophylaxis, enteral nutrition
Monitor
- q4 hPlateau and driving pressure after every vent change
- DailyP/F ratio, fluid balance, sedation minimisation (RASS 0 to −1)
- Each prone cycle16 h prone / 8 h supine with full safety checklist
- WeeklyTracheostomy review if not improving by day 7
Escalate / ICU
- P/F <80 or pH <7.25 despite proning
- Barotrauma (pneumothorax)
- Need for FiO₂ >80% >24 h
- Multi-organ failure — ECMO discussion
Criteria
BerlinBilateral infiltrates, ≤1 wk, non-cardiogenic, P/F ≤300 on PEEP ≥5
VT6 mL/kg PBW (4–8) — the single biggest survival lever
ProneP/F <150 → ≥16 h/day
ECMOP/F <80 or pH <7.25 refractory — refer early
Never
- Increase tidal volume 'to improve oxygenation' — volutrauma kills
- Overhydrate the septic ARDS patient after resuscitation
- Withhold corticosteroids dogmatically — ATS 2023 SUGGESTS corticosteroids (e.g., dexamethasone) for ARDS, particularly early moderate-severe; individualise for infection risk
Key
- Driving pressure (plateau − PEEP) ≤15 correlates with survival better than VT alone
- Proning works only in moderate-severe (P/F <150) — don't prone mild ARDS
- NMB reserved for severe ARDS with dyssynchrony/refractory hypoxaemia despite proning — not routine (ATS 2023)
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- P/F falling despite proning
- New subcutaneous emphysema (barotrauma)
- SpO₂ 88% on FiO₂ 100%
- Right heart strain on echo (PEEP/CO₂ effect)
Differentials
- Cardiogenic pulmonary oedema
- Diffuse alveolar haemorrhage
- Cryptogenic organising pneumonia
- Severe bilateral pneumonia without ARDS
Common mistakes
- Using actual body weight for VT
- PEEP too low in moderate-severe disease
- Deep sedation beyond 48 h paralysis (ICU weakness)
- Late ECMO referral — cannulate before multi-organ failure
Disposition & follow-up
ICU; wean FiO₂ then PEEP as P/F improves; tracheostomy for slow weaners; post-ICU weakness and PTSD follow-up.
💊 Treatment detail — doses & preparation
PropofolIV anaesthetic
DoseSedation 5–50 mcg/kg/min infusion; refractory SE titrate to EEG
Preparation1% (10 mg/mL) lipid emulsion ready vial via syringe pump; change tubing q12 h
MonitorBP (vasodilates), triglycerides, PRIS if prolonged/high dose
Fentanylopioid analgesic
Dose25–100 mcg IV boluses; infusion 0.5–2 mcg/kg/h
Preparation100 mcg/2 mL ampoule undiluted for bolus; infusion 1 mg in 50 mL NS
MonitorRR, sedation score; less hypotension than morphine
Cisatracuriumparalytic infusion
Dose0.15 mg/kg bolus then 1–3 mcg/kg/min ×48 h (severe ARDS)
PreparationInfusion per pump protocol; Hofmann elimination (renal-safe)
MonitorTrain-of-four, avoid ICU-acquired weakness — minimise duration
Conservative fluid strategylung protection
DoseAfter resuscitation: target negative daily balance with diuretics/vasopressor support
PreparationPer FACTT protocol
MonitorFluid balance, oxygenation daily
📖 Berlin definition; 2024 Global Definition; ATS 2023; ARDSNet; PROSEVA; EOLIAReviewed July 2026