ARDS
at the bedside
Think ARDS whenever a patient with a plausible trigger develops new or worsening bilateral hypoxemia within about a week of the insult.
- common triggers → pneumonia, sepsis, aspiration, pancreatitis, major trauma, transfusion, inhalation injury.
- first actions → increase FiO2 to hold saturation; chest x-ray; arterial blood gas; treat the trigger in parallel. Once intubated, start lung-protective settings immediately; do not wait for a full workup.
- non-invasive support → HFNC or NIV trial in mild hypoxemia with close monitoring (HFNC / NIV); do not delay intubation if oxygenation is not maintained or work of breathing escalates.
early recognition, do not wait for the label
- bilateral opacities not fully explained by fluid overload or cardiac failure, a plausible cause, onset within a week; the 2023/2024 update extends recognition to non-intubated patients on HFNC (define & classify below).
escalate now if
- any moderate to severe ARDS, P/F < 150, this is an ICU patient by definition → prone positioning
- refractory hypoxemia despite lung-protective ventilation, high PEEP, and proning → troubleshooting
- ECMO referral criteria (12), any one of: P/F < 50 for > 3 hr, P/F < 80 for > 6 hr, or pH ≤ 7.25 with PaCO2 ≥ 60 mmHg for > 6 hr despite optimized settings
- hemodynamic instability requiring escalating vasopressor support alongside high ventilatory pressures
- new pneumothorax or barotrauma on high-pressure ventilation → ventilator troubleshooting
define & classify
Berlin Definition, 2012, still the working framework, all four criteria required (1):
- timing → new or worsening respiratory symptoms within 1 week of a known clinical insult.
- imaging → bilateral opacities on chest x-ray or CT, not fully explained by effusion, lobar/lung collapse, or nodules.
- origin of edema → respiratory failure not fully explained by cardiac failure or fluid overload; objective assessment (echo) if no clear risk factor.
- oxygenation → P/F ratio measured on PEEP or CPAP ≥ 5 cmH2O.
| 200-300P/F, mild | lung-protective ventilation, treat the trigger, reassess frequently. A large fraction resolve without progressing. |
| 100-200P/F, moderate | higher-PEEP strategy, consider early prone positioning if trending toward severe. |
| < 100P/F, severe | prone positioning, consider neuromuscular blockade, discuss ECMO referral early. This is an ICU patient. |
the 2023/2024 global definition keeps these bands, adds SpO2/FiO2 < 315 and high-flow nasal oxygen ≥ 30 L/min as alternative criteria, and allows lung ultrasound for imaging (2): this extends recognition to non-intubated and resource-limited settings. It does not change how you ventilate an intubated patient.
initial management
lung-protective ventilation, start immediately
- tidal volume 6 mL/kg predicted body weight, calculated by height and sex, not actual weight (3). Full setup detail on mechanical ventilation.
- plateau pressure < 30 cmH2O, driving pressure < 15 cmH2O where achievable (4).
- oxygenation target SpO2 88-95% or PaO2 55-80 mmHg, do not chase normal saturations.
- permissive hypercapnia to protect these limits: pH down to about 7.20-7.25 without correcting it; avoid in raised intracranial pressure or severe pulmonary hypertension.
calculator ideal/predicted body weight · MDCalc ↗︎
fluid strategy
PEEP
- moderate to severe ARDS (P/F < 200): higher-PEEP strategy beats low PEEP (5); use the high-PEEP/FiO2 ladder on mechanical ventilation.
- titrate PEEP against oxygenation and plateau/driving pressure together. More PEEP that pushes plateau pressure over target is not a win.
reassess
- arterial blood gas 30-60 min after intubation and after any major setting change.
- trend the P/F ratio, not a single value, this drives escalation decisions.
- daily assessment for sedation reduction and spontaneous breathing trial readiness once the P/F ratio and driving pressure are improving.
- reassess the trigger: worsening ARDS despite good vent management usually means the underlying process (infection, pancreatitis, aspiration) is not yet controlled.
advanced management
prone positioning
- criteria (6): P/F ratio < 150 on FiO2 > 0.6 and PEEP ≥ 5, within about 36 hours of ARDS onset.
- prone ≥ 16 hours/day: roughly halved mortality in the original trial; needs a trained team and a protocol, not a solo maneuver. ATS 2024: strong recommendation for >12 hours/day in severe ARDS (4); one of the few ARDS interventions with a large mortality benefit, do not skip it in an eligible patient because it is logistically hard.
neuromuscular blockade, early severe ARDS only
- ACURASYS (2010) showed a mortality benefit from early cisatracurium in severe ARDS with deep sedation (7).
- ROSE (2019), larger, same drug and dose, light-sedation comparator: no mortality benefit, more ICU-acquired weakness and serious cardiovascular events with early blockade (8).
- practical → ATS 2024 suggests neuromuscular blockade in early severe ARDS (conditional, low certainty) (4): a short course, 48 hours, with deep sedation running, for refractory hypoxemia or persistent dyssynchrony despite optimized sedation; not routine, not prolonged.
recruitment maneuvers
- brief recruitment maneuvers can transiently improve oxygenation, but the PHARLAP “staircase” high-pressure strategy increased arrhythmias and hemodynamic instability without mortality benefit (9): not routine; if attempted, keep it brief and be ready for hypotension or desaturation. ATS 2024: higher PEEP without recruitment maneuvers, and a strong recommendation against prolonged high-pressure maneuvers (4).
corticosteroids
- DEXA-ARDS (2020) showed a mortality benefit from dexamethasone 20 mg IV daily × 5 days, then 10 mg IV daily × 5 days in moderate to severe ARDS (10).
- SCCM 2024 focused update: conditional recommendation for corticosteroids in critically ill ARDS (11), no mandated agent, dose, or duration; starting late (> 14 days after onset) may harm. Agent, dose and timing are an ICU discussion, not an automatic order. ATS 2024 likewise suggests corticosteroids for ARDS (conditional, moderate certainty) (4).
troubleshooting
- P/F ratio < 150 despite FiO2 1.0 and an optimized high-PEEP strategy → prone position if not already done.
- already proned, still severely hypoxemic → look for a reversible complication (pneumothorax, mucus plug, worsening trigger) before calling it refractory; see ventilator troubleshooting.
- rising plateau or driving pressure on a fixed tidal volume → compliance is worsening: reassess fluid balance and the trigger, not just the vent.
- fighting the vent despite optimized sedation → consider short-course neuromuscular blockade, see advanced management above.
- refractory hypoxemia or hypercapnia despite prone positioning and optimized settings → ECMO referral criteria below.
evidence
Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.
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Last updated · October 2026