What are the initial ventilatory settings for a patient with severe COVID-19 pneumonia requiring mechanical ventilation?

Mechanical Ventilation in Severe COVID-19 Pneumonia: Clinical Case Discussion

Initial Ventilatory Settings

For patients with severe COVID-19 pneumonia requiring mechanical ventilation, initiate lung-protective ventilation with tidal volume 4-8 mL/kg predicted body weight (targeting driving pressure <14 cmH₂O), plateau pressure <30 cmH₂O, and higher PEEP strategy (>10 cmH₂O) for moderate-to-severe ARDS. 1

Clinical Case Presentation

Day 1: Intubation and Initial Settings

Patient Profile:

• 58-year-old male with severe COVID-19 pneumonia
• Progressive hypoxemia despite high-flow nasal oxygen (HFNO) at 60 L/min, FiO₂ 1.0
• Increasing work of breathing with accessory muscle use 1

Day 1 ABG (Pre-intubation on HFNO):

• pH: 7.32
• PaCO₂: 48 mmHg
• PaO₂: 65 mmHg
• HCO₃: 24 mEq/L
• SpO₂: 88%
• PaO₂/FiO₂ ratio: 65 mmHg (severe ARDS) 1

Intubation Decision:

• Intubation indicated based on respiratory distress and fatigue, not hypoxemia alone 1, 2
• Early intubation in controlled setting performed after 1-2 hours of failed HFNO trial 1

Initial Ventilator Settings (Volume Control Mode):

• Mode: Volume Control (VC-CMV)
• Tidal Volume: 6 mL/kg PBW (420 mL for 70 kg PBW) 1
• Respiratory Rate: 20 breaths/min
• FiO₂: 0.8
• PEEP: 12 cmH₂O (higher PEEP strategy for severe ARDS) 1
• Inspiratory:Expiratory ratio: 1:2
• Target SpO₂: 88-95% (not >96%) 1, 3

Day 1 Post-intubation ABG (2 hours):

• pH: 7.35
• PaCO₂: 45 mmHg
• PaO₂: 72 mmHg
• SpO₂: 92%
• PaO₂/FiO₂ ratio: 90 mmHg
• Plateau pressure: 28 cmH₂O
• Driving pressure: 16 cmH₂O (PEEP 12, Pplat 28) 4

Days 2-3: Optimization and Prone Positioning

Day 2 Diagnosis:

• Persistent severe ARDS (PaO₂/FiO₂ <150 mmHg)
• Bilateral ground-glass opacities and consolidation on chest imaging
• Static respiratory system compliance: 32 mL/cmH₂O 5

Day 2 Interventions:

• Initiated prone positioning for 16 hours daily 1
• Deep sedation with propofol and fentanyl
• Intermittent neuromuscular blockade (rocuronium boluses) to facilitate lung-protective ventilation 1

Adjusted Ventilator Settings:

• Tidal Volume: reduced to 5 mL/kg PBW (350 mL) to achieve driving pressure <14 cmH₂O 4
• PEEP: increased to 14 cmH₂O (monitoring for barotrauma) 1
• FiO₂: 0.7
• Respiratory Rate: 22 breaths/min

Day 2 ABG (Prone position):

• pH: 7.38
• PaCO₂: 42 mmHg
• PaO₂: 95 mmHg
• SpO₂: 96%
• PaO₂/FiO₂ ratio: 136 mmHg
• Plateau pressure: 27 cmH₂O
• Driving pressure: 13 cmH₂O 4

Day 3 ABG (Supine after 16h prone):

• pH: 7.40
• PaCO₂: 40 mmHg
• PaO₂: 88 mmHg
• SpO₂: 95%
• PaO₂/FiO₂ ratio: 125 mmHg
• Sustained improvement noted 1

Days 4-5: Continued Improvement

Day 4 Management:

• Conservative fluid strategy implemented (net negative 500 mL/day) 1
• Continued prone positioning for 14 hours
• Systemic corticosteroids: dexamethasone 6 mg IV daily (for ARDS with COVID-19) 1

Ventilator Settings Day 4:

• Mode: Pressure Control (PC-CMV) transitioned for better patient-ventilator synchrony
• Inspiratory Pressure: 18 cmH₂O (above PEEP)
• PEEP: 12 cmH₂O
• FiO₂: 0.5
• Respiratory Rate: 20 breaths/min
• Achieved Tidal Volume: 380 mL (5.4 mL/kg PBW)

Day 4 ABG:

• pH: 7.42
• PaCO₂: 38 mmHg
• PaO₂: 102 mmHg
• SpO₂: 97%
• PaO₂/FiO₂ ratio: 204 mmHg (moderate ARDS) 1
• Plateau pressure: 26 cmH₂O
• Driving pressure: 14 cmH₂O

Day 5 ABG:

• pH: 7.43
• PaCO₂: 37 mmHg
• PaO₂: 115 mmHg
• SpO₂: 98%
• PaO₂/FiO₂ ratio: 255 mmHg (mild ARDS)
• Reduced prone positioning to 12 hours 1

Days 6-7: Weaning Phase

Day 6 Management:

• Transitioned to Pressure Support Ventilation (PSV)
• Pressure Support: 10 cmH₂O
• PEEP: 8 cmH₂O
• FiO₂: 0.4
• Spontaneous respiratory rate: 18 breaths/min
• Discontinued prone positioning 3
• Neuromuscular blockade discontinued 1

Day 6 ABG:

• pH: 7.44
• PaCO₂: 36 mmHg
• PaO₂: 125 mmHg
• SpO₂: 98%
• PaO₂/FiO₂ ratio: 312 mmHg (no longer ARDS criteria)
• Rapid Shallow Breathing Index: 65 (passing weaning parameters) 3

Day 7 Management:

• Continued PSV with progressive reduction
• Pressure Support: 8 cmH₂O
• PEEP: 5 cmH₂O
• FiO₂: 0.35
• Daily spontaneous breathing trial performed 3

Day 7 ABG:

• pH: 7.45
• PaCO₂: 35 mmHg
• PaO₂: 135 mmHg
• SpO₂: 99%
• PaO₂/FiO₂ ratio: 386 mmHg
• Patient extubated successfully to HFNO 40 L/min, FiO₂ 0.4

Final Outcome

The patient was successfully extubated on Day 7 with complete resolution of ARDS, transferred to step-down unit on Day 9, and discharged home on Day 18 with supplemental oxygen 2 L/min via nasal cannula. 1

Critical Management Principles

Lung-Protective Ventilation Strategy

The cornerstone of mechanical ventilation in COVID-19 ARDS is strict adherence to lung-protective ventilation with low tidal volumes (4-8 mL/kg PBW, preferably 4-6 mL/kg), plateau pressure <30 cmH₂O, and driving pressure <14 cmH₂O. 1, 4

• Tidal volume should be adjusted based on driving pressure rather than fixed at 6 mL/kg, as COVID-19 patients show heterogeneous respiratory mechanics 4, 5
• Driving pressure is the most important predictor of ventilator-induced lung injury and should be prioritized over absolute tidal volume 4

PEEP Strategy

For moderate-to-severe ARDS (PaO₂/FiO₂ <150 mmHg), use higher PEEP (>10 cmH₂O) with close monitoring for barotrauma, particularly pneumothorax and pneumomediastinum. 1

• COVID-19 patients may have lower recruitability than classical ARDS, so excessive PEEP can cause overdistension 4, 2
• PEEP should be titrated using FiO₂/PEEP tables, targeting adequate oxygenation while minimizing driving pressure 3
• Monitor for barotrauma risk, which appears higher in COVID-19 due to diffuse alveolar injury and high respiratory drive 6

Prone Positioning

Prone ventilation for 12-16 hours daily should be implemented early in moderate-to-severe ARDS (PaO₂/FiO₂ <150 mmHg with FiO₂ ≥0.6 and PEEP ≥10 cmH₂O). 1, 3

• Prone positioning improves oxygenation and reduces mortality in ARDS 1
• Should be initiated within first 48 hours of severe ARDS diagnosis 1
• Requires adequate staffing and monitoring for complications 3

Neuromuscular Blockade

Use intermittent boluses of neuromuscular blocking agents as needed to facilitate lung-protective ventilation, reserving continuous infusion (up to 48 hours) for persistent ventilator dyssynchrony, ongoing deep sedation needs, or persistently high plateau pressures. 1

• Continuous NMBA infusion should be combined with deep sedation in first 48 hours when using prone positioning 1
• Avoid prolonged paralysis beyond 48 hours due to risk of ICU-acquired weakness 1

Fluid Management

Implement conservative fluid strategy targeting net-even to negative fluid balance once hemodynamically stable, as liberal fluid administration worsens oxygenation and prolongs mechanical ventilation. 1

Oxygenation Targets

Target SpO₂ 88-95% (not >96%) to avoid hyperoxia while ensuring adequate tissue oxygenation. 1, 3

• Permissive hypoxemia is acceptable if patient tolerates it without signs of end-organ dysfunction 2, 3
• Avoid excessive FiO₂ due to oxygen toxicity risk 3

Common Pitfalls and Caveats

Intubation Timing

The most critical error is delaying intubation based solely on hypoxemia tolerance—intubate based on respiratory distress, work of breathing, and fatigue rather than PaO₂ alone. 1, 2

• COVID-19 patients often exhibit "silent hypoxemia" with remarkably preserved mental status despite severe hypoxemia 2
• Waiting for profound hypoxemia leads to emergency intubation with higher complication rates 1
• If HFNO or NIV fails to improve within 1-2 hours, proceed to intubation in controlled setting 1

Ventilator-Induced Lung Injury

COVID-19 patients have increased susceptibility to barotrauma due to high respiratory drive and diffuse alveolar damage—strict adherence to plateau pressure <30 cmH₂O and driving pressure <14 cmH₂O is mandatory. 4, 6

• Even on pressure support ventilation, patients can generate excessive transpulmonary pressures leading to pneumothorax 6
• Monitor for subcutaneous emphysema, pneumomediastinum, and pneumothorax, especially with higher PEEP 1, 6

PEEP Titration Errors

Avoid routine use of high PEEP without assessing lung recruitability—COVID-19 ARDS may have lower recruitability than classical ARDS, making excessive PEEP harmful. 4, 2

• Use incremental PEEP trials with assessment of oxygenation, compliance, and hemodynamics 4
• Avoid staircase recruitment maneuvers, which are associated with harm 1

Rescue Therapies

Consider ECMO early (within 7 days) for refractory hypoxemia (PaO₂/FiO₂ <100 mmHg) despite optimized ventilation, neuromuscular blockade, and prone positioning, but only in carefully selected patients at experienced centers. 1

• Inhaled pulmonary vasodilators (inhaled nitric oxide or epoprostenol) can be trialed as rescue therapy, but should be discontinued if no rapid improvement 1
• Recruitment maneuvers may be considered for refractory hypoxemia but avoid aggressive protocols 1, 3

Corticosteroid Use

Administer systemic corticosteroids (dexamethasone 6 mg daily) in mechanically ventilated COVID-19 patients with ARDS, but avoid in those without ARDS. 1