What are the management strategies for Acute Respiratory Distress Syndrome (ARDS)?

ARDS Management

Immediately implement lung-protective ventilation with tidal volumes of 4-8 mL/kg predicted body weight and plateau pressure <30 cmH₂O in all mechanically ventilated ARDS patients, as this is the only intervention proven to reduce mortality regardless of ARDS etiology. 1, 2, 3

Severity Classification and Initial Assessment

• Classify ARDS severity using the Berlin Definition based on PaO₂/FiO₂ ratio: mild (200-300 mmHg), moderate (100-200 mmHg), severe (<100 mmHg) 1, 2, 3
• Confirm bilateral pulmonary opacities on chest imaging, acute onset within one week of known insult, and respiratory failure not fully explained by cardiac failure or fluid overload 3, 4

Respiratory Support Strategy by Severity

Mild ARDS (PaO₂/FiO₂ 200-300 mmHg)

• Consider high-flow nasal cannula (HFNC) at 30-40 L/min with FiO₂ 50-60% over conventional oxygen therapy, but only with continuous ICU monitoring 1, 3
• Noninvasive ventilation may be attempted only if SAPS II score <34, patient is hemodynamically stable, alert, cooperative, and ARDS is not caused by pneumonia 3
• Proceed to early intubation in a controlled setting if deterioration occurs within 1 hour, FiO₂ >70%, flow >50 L/min, or Rapid Shallow Breathing Index >105 breaths/min/L 3

Moderate to Severe ARDS (PaO₂/FiO₂ <200 mmHg)

• Proceed directly to mechanical ventilation rather than attempting noninvasive support, as failure rates are high 3

Mechanical Ventilation Protocol

Core Lung-Protective Settings (All Patients)

• Set tidal volume at 4-8 mL/kg predicted body weight (based on sex and height, not actual weight) 1, 2, 3, 5
• Maintain plateau pressure ≤30 cmH₂O 1, 2, 3, 6
• Target SpO₂ no higher than 96% to avoid oxygen toxicity 1, 3

PEEP Strategy

• For moderate to severe ARDS (PaO₂/FiO₂ <200 mmHg): Use higher PEEP strategy without prolonged lung recruitment maneuvers 1, 2, 3
• Higher PEEP reduces mortality and improves oxygenation by preventing cyclic opening and closing of airspaces 2, 7
• Strongly avoid prolonged lung recruitment maneuvers due to high probability of hemodynamic harm 1, 2
• Monitor for barotrauma when using PEEP >10 cmH₂O, particularly in COVID-19 patients 1

Adjunctive Therapies for Severe ARDS (PaO₂/FiO₂ <100 mmHg)

Prone Positioning (Highest Priority)

• Implement prone positioning for >12 hours daily (12-16 hours) in all patients with severe ARDS, as this intervention has demonstrated significant mortality reduction 1, 2, 3
• Apply deep sedation and analgesia during prone positioning 3
• This is a performance measure with proven mortality benefit and should not be delayed 2

Neuromuscular Blocking Agents

• Consider cisatracurium infusion for 48 hours in early severe ARDS to improve ventilator synchrony and reduce oxygen consumption 1, 2, 3
• Particularly beneficial when ventilator-patient dyssynchrony persists despite sedation 3

Corticosteroids

• Administer systemic corticosteroids for ARDS, which has conditional support with moderate certainty of evidence 1, 2
• Particularly recommended for COVID-19 ARDS, which has shown mortality benefit 1

Fluid Management

• Implement conservative fluid management strategy to minimize pulmonary edema while maintaining adequate organ perfusion 1, 2, 3
• Limit total crystalloid to <4000 mL in first 24 hours 2
• Use non-aggressive resuscitation at 1.5 mL/kg/hr after initial 10 mL/kg bolus 2
• Avoid fluid overload, which worsens oxygenation, promotes right ventricular failure, and increases mortality 1, 3

Advanced Rescue Therapies for Refractory Hypoxemia

Venovenous ECMO

• Consider VV-ECMO in selected patients with severe ARDS (PaO₂/FiO₂ <100 mmHg) who fail conventional management, particularly those with reversible disease 1, 2, 3
• Only implement at centers with ECMO expertise 3
• Blood is pumped from femoral vein and returns to right atrium through internal jugular vein after membrane oxygenation 3

Inhaled Pulmonary Vasodilators

• Consider a trial of inhaled pulmonary vasodilator as rescue therapy for severe hypoxemia despite optimized ventilation 1, 3
• Discontinue if no rapid improvement in oxygenation 1, 3
• Avoid routine use of inhaled nitric oxide 1, 6

Monitoring Requirements

• Continuously monitor oxygen saturation, respiratory mechanics, and hemodynamics 1, 2, 3
• Use echocardiography to assess right ventricular function and detect acute cor pulmonale in severe cases 1, 2, 3
• Monitor fluid balance carefully 3
• Assess for ventilator-patient dyssynchrony 3
• Arterial blood gas analysis at 1-2 hours and again at 4-6 hours if initial improvement is minimal 3

Ventilator Weaning

• Perform daily spontaneous breathing trials once the patient's condition improves, as this consistently reduces duration of mechanical ventilation 3
• Use noninvasive ventilation after extubation for patients at high risk for extubation failure to reduce ICU length of stay and mortality 3

Critical Pitfalls to Avoid

• Underutilization of prone positioning in severe ARDS is associated with increased mortality 2
• Delaying intubation in deteriorating patients on noninvasive support 3
• Using prolonged lung recruitment maneuvers with high PEEP 1, 2
• Aggressive fluid resuscitation worsening pulmonary edema 2
• Using tidal volumes >8 mL/kg predicted body weight 2, 5