What is the recommended critical‑care management for a patient currently on invasive mechanical ventilation, including lung‑protective ventilation, sedation and weaning protocols, prophylaxis, and adjunctive measures for moderate to severe ARDS?

Critical Care Management for Mechanically Ventilated Patients

All mechanically ventilated patients must receive lung-protective ventilation with tidal volumes of 4-8 ml/kg predicted body weight and plateau pressure ≤30 cmH₂O, as this is the single most important intervention to reduce mortality and ventilator-induced lung injury. 1, 2, 3

Mandatory Lung-Protective Ventilation Settings

Core Ventilator Parameters

• Set tidal volume at 6 ml/kg predicted body weight (acceptable range 4-8 ml/kg PBW), calculated as: males = 50 + 0.91[height (cm) - 152.4] kg; females = 45.5 + 0.91[height (cm) - 152.4] kg 1, 3
• Maintain plateau pressure ≤30 cmH₂O at all times by performing end-inspiratory hold maneuvers during volume-controlled ventilation—this takes priority over all other pressure measurements 1, 3, 4
• Apply PEEP ≥5 cmH₂O minimum, titrating to ≥10 cmH₂O for moderate-severe ARDS based on gas exchange, hemodynamic status, and lung recruitability 1, 2, 3
• Monitor and minimize driving pressure (plateau pressure minus PEEP), as this correlates directly with mortality 3, 4
• Target PaO₂ 70-90 mmHg or SpO₂ 88-97% to avoid oxygen toxicity while ensuring adequate tissue oxygenation 2, 3

The evidence strongly supports these parameters: meta-regression demonstrates that larger tidal volume gradients (greater difference between low and traditional volumes) show significantly lower mortality risk, with trials combining low tidal volume and higher PEEP showing the greatest mortality benefit (RR 0.58,95% CI 0.41-0.82) 1.

ARDS Severity-Based Escalation Protocol

For Moderate ARDS (PaO₂/FiO₂ 100-200 mmHg)

• Continue lung-protective ventilation with optimized PEEP 3
• Consider recruitment maneuvers before PEEP selection 1
• Implement conservative fluid management once shock resolves to avoid worsening pulmonary edema 3

For Severe ARDS (PaO₂/FiO₂ <150 mmHg)

Implement prone positioning immediately—do not delay waiting for other interventions to fail:

• Apply prone positioning for >12 hours daily as this reduces mortality and should be implemented early, not as a last resort 1, 2, 3, 4
• Consider neuromuscular blockade with cisatracurium infusion for 48 hours when plateau pressures exceed 30-35 cmH₂O or in early severe ARDS to improve ventilator synchrony 1, 2, 3
• Consider corticosteroids when initiated early in the disease course, as this may reduce mortality in moderate-to-severe ARDS 3

For Refractory Severe ARDS

Consider venovenous ECMO as rescue therapy if PaO₂/FiO₂ remains <70 mmHg for ≥3 hours or <100 mmHg for ≥6 hours despite optimized ventilation, prone positioning, and neuromuscular blockade 1, 3

Essential Monitoring Parameters

Continuous Assessment

• Monitor plateau pressure with serial end-inspiratory pauses (0.3-0.5 seconds) to confirm lung-protective ventilation 3, 4
• Calculate mechanical power if available, targeting <20 J/min normalized to body weight, as this integrates all ventilator parameters into a single injury metric 4
• Use continuous end-tidal CO₂ monitoring to detect circuit disconnection, confirm tube placement, and track dead space ventilation 4
• Accept permissive hypercapnia (pH ≥7.20) when necessary to maintain lung-protective ventilation 4
• Monitor right ventricular function with echocardiography to detect acute cor pulmonale, which occurs in 20-25% of ARDS patients 3

Sedation and Ventilator Synchrony Management

• Titrate sedation according to protocols with regular drug interruption to promote respiratory muscle activity when gas exchange and hemodynamics improve 1, 3
• Perform daily sedation interruptions and spontaneous breathing trials to assess neurological status and readiness for weaning, which reduces time to extubation by 81% and ventilator mortality by 49% 2
• Ensure patient-ventilator synchrony, as even assisted ventilation can induce lung injury through high tidal volumes and transpulmonary pressures 3

Weaning Protocol

Readiness Assessment

Assess weaning readiness daily when clinical parameters improve:

• Improved gas exchange (PaO₂/FiO₂ ratio trending upward) 3
• Reduced PEEP requirement (can tolerate ≤8 cmH₂O) 3
• Hemodynamic stability without escalating vasopressor support 1, 3
• Improved respiratory mechanics (lower plateau pressure, better compliance) 1, 3

Spontaneous Breathing Trial Execution

• Perform daily spontaneous breathing trials using T-piece, CPAP, or low-level pressure support as the central component of weaning protocol 3
• Reduce sedation and transition to partial ventilator support to promote respiratory muscle activity in conjunction with lower patient ventilatory drive 1

Essential Prophylaxis Bundle

• Elevate head of bed ≥30 degrees to reduce aspiration risk 3
• Administer pharmacological or mechanical DVT prophylaxis to reduce venous thromboembolism risk 2, 3
• Provide stress ulcer prophylaxis for high-risk patients 3
• Initiate early enteral nutrition with antioxidants and anti-inflammatory amino acids, which may improve gas exchange 3

Critical Pitfalls to Avoid

• Never delay prone positioning in severe ARDS (PaO₂/FiO₂ <150 mmHg)—implement early as it reduces mortality 2, 3, 4
• Avoid inducing hypervolemia, which can harm patients with excess morbidity; maintain euvolemia instead 2
• Do not use absolute mechanical power without normalization to body weight, as this provides misleading risk assessment 4
• Never allow plateau pressure to exceed 30 cmH₂O—reduce tidal volume further if necessary, even below 4 ml/kg PBW 1, 3, 4