What is the best approach for managing acute lung injury in a patient with severe respiratory distress, possibly due to sepsis or pneumonia, requiring mechanical ventilation and supplemental oxygen?

Management of Acute Lung Injury

Implement lung-protective mechanical ventilation with tidal volumes of 6 mL/kg predicted body weight and plateau pressures ≤30 cmH₂O as the cornerstone of management, combined with higher PEEP strategies and prone positioning for severe cases. 1

Initial Respiratory Support Strategy

High-Flow Nasal Oxygen (HFNO) and Non-Invasive Ventilation (NIV)

• Consider HFNO or NIV only in patients with mild-to-moderate hypoxemia who are hemodynamically stable, alert, and cooperative 1
• If FiO₂ >70% and gas flow >50 L/min are required for >1 hour on HFNO, or if respiratory distress worsens, proceed immediately to invasive mechanical ventilation 1
• Do not use NIV in patients with hemodynamic instability, multiple organ failure, or altered mental status 1
• Monitor closely for signs of patient self-inflicted lung injury (P-SILI), particularly in moderate-to-severe ARDS (PaO₂/FiO₂ <200 mmHg) where excessive respiratory effort can worsen lung injury 2
• Early intubation is critical when respiratory distress persists or worsens on non-invasive support—delayed intubation significantly worsens outcomes 2

Indications for Invasive Mechanical Ventilation

Proceed to intubation when any of the following are present:

• Refractory hypoxemia (PaO₂ <60 mmHg despite high-flow oxygen) 1
• Respiratory rate >35 breaths/min 1
• Vital capacity <15 mL/kg 1
• Inability to protect airway 1
• Failure to improve or acute deterioration on HFNO/NIV within 1 hour 1

Mechanical Ventilation Strategy

Core Lung-Protective Settings

The Surviving Sepsis Campaign provides the most authoritative guidance for ventilator management:

• Tidal volume: 6 mL/kg predicted body weight (strong recommendation) 1
• Plateau pressure: maintain ≤30 cmH₂O (strong recommendation) 1
• PEEP: use higher PEEP strategies (8-15 cmH₂O) in moderate-to-severe ARDS rather than lower PEEP (weak recommendation) 1
• Apply PEEP to prevent end-expiratory alveolar collapse (atelectotrauma) 1
• Target oxygen saturation 88-92% in patients at risk for hypercapnic respiratory failure; otherwise 94-98% 3

Predicted Body Weight Calculation

• Men: 50 + 2.3 × (height in inches - 60) 1
• Women: 45.5 + 2.3 × (height in inches - 60) 1

Permissive Hypercapnia

• Allow PaCO₂ to rise while maintaining protective ventilation parameters to prevent ventilator-induced lung injury 1
• This strategy is safe and effective without adverse consequences in most patients 1

Advanced Ventilatory Interventions for Severe ARDS

Prone Positioning

For patients with PaO₂/FiO₂ <150 mmHg (severe ARDS), implement prone positioning for >12 hours daily (strong recommendation) 1

• This intervention improves oxygenation in approximately 65% of patients and reduces mortality 1
• Requires experienced staff due to risks of endotracheal tube dislodgement and line complications 1
• Patients who respond (>10% improvement in PaO₂) often maintain benefits for up to 18 hours after returning supine 1

Recruitment Maneuvers

• Consider in patients with severe refractory hypoxemia in conjunction with higher PEEP (weak recommendation) 1
• Monitor blood pressure and oxygenation closely; discontinue if deterioration occurs 1
• Effects may be transient, and routine use is not supported 1

Neuromuscular Blockade

Use neuromuscular blocking agents for ≤48 hours in patients with PaO₂/FiO₂ <150 mmHg when signs of injurious respiratory effort persist despite optimized ventilator settings and sedation (weak recommendation) 1, 2

• Improves oxygen supply and patient-ventilator synchrony 1
• Avoid routine use in all ARDS patients; reserve for severe cases 1
• Monitor depth of blockade with train-of-four monitoring 1

Fluid Management

Adopt a conservative fluid strategy in patients with established ARDS who do not have tissue hypoperfusion (strong recommendation) 1

• Judicious fluid resuscitation and/or fluid restriction improves physiology and outcomes 1
• Patients who lose weight or have decreased microvascular pressures through diuresis show improved oxygenation and reduced mechanical ventilation duration 1
• In hypo-oncotic patients with established lung injury, albumin combined with furosemide may improve physiology and reduce ventilation duration 1

Adjunctive Therapies and Rescue Strategies

Extracorporeal Membrane Oxygenation (ECMO)

• Consider VV-ECMO for severe refractory hypoxemia (PaCO₂ >60 mmHg despite optimal ventilation, excluding ventilation dysfunction) after muscle relaxation and prone positioning have failed 1
• ECMO should only be performed in specialized centers with expertise 1
• Can be used in severe ARDS patients with lung injury score >3 or pH <7.2 due to uncompensated hypercapnia, but not recommended for all ARDS patients 1

Therapies NOT Recommended

Inhaled nitric oxide does not improve mortality in ARDS and should not be routinely used 1, 4

• Despite acute improvements in oxygenation, no effect on days alive and off ventilator support 4
• FDA labeling explicitly states INOmax is not indicated for use in ARDS 4

High-frequency oscillatory ventilation is not beneficial and may be harmful in moderate-to-severe ARDS (strong recommendation) 1

• May be considered as rescue therapy only in severe ARDS with refractory hypoxemia 1
• Risk of worsening hemodynamics and right ventricular failure 2

β-2 agonists should not be used for ARDS treatment without bronchospasm (strong recommendation) 1

Supportive Care Measures

Head of Bed Elevation

Maintain head of bed elevated 30-45 degrees to prevent ventilator-associated pneumonia (strong recommendation) 1

• Semi-recumbent position decreases VAP incidence from 50% to 9% in enterally fed patients 1
• Patients may be laid flat temporarily for procedures and hemodynamic measurements 1

Airway Management

• Orotracheal intubation is preferred over nasotracheal due to lower sinusitis rates 1
• Nosocomial sinusitis contributes significantly to ventilator-associated pneumonia development 1

Antimicrobial Therapy

• Use empirical antibiotics targeting suspected infection as soon as possible 1
• Avoid blind or improper combination of broad-spectrum antibiotics 1

Corticosteroids

Routine use of corticosteroids should be avoided unless specific indications exist 1

• May be beneficial in patients with evidence of fibroproliferation 5

Monitoring and Weaning

Key Monitoring Parameters

• Plateau pressure (maintain ≤30 cmH₂O) 1, 5
• Driving pressure (≥18 cmH₂O indicates increased risk of derecruitment) 2
• PaO₂/FiO₂ ratio (changes predict outcomes) 1
• Respiratory system compliance 3

Weaning Strategy

Use spontaneous breathing trials in patients ready for weaning (strong recommendation) 1 Implement a standardized weaning protocol (strong recommendation) 1

• Establish spontaneous breathing as soon as possible to reduce positive pressure requirements 3
• Minimize continuous or intermittent sedation, targeting specific endpoints 1

Critical Pitfalls to Avoid

• Never delay intubation in worsening respiratory distress on non-invasive support—this significantly worsens outcomes 2
• Avoid tidal volumes >8 mL/kg predicted body weight, which increases barotrauma risk 3
• Do not use zero PEEP, which leads to atelectasis and worsens oxygenation 3
• Monitor for right ventricular dysfunction, which can be exacerbated by lung derecruitment and increased afterload 2
• Do not overlook fluid management—fluid overload worsens respiratory mechanics 3