What is the role of mechanical ventilation in managing respiratory failure in adult and pediatric patients, including those with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS)?

Role of Mechanical Ventilation in Respiratory Failure

Mechanical ventilation serves as essential life support in respiratory failure, not as a therapeutic intervention itself, but as a bridge to recovery while the underlying cause is treated with medical therapy. 1

Primary Indications for Mechanical Ventilation

Mechanical ventilation should be instituted when patients meet any of the following criteria:

• Refractory hypoxemia (PaO2 < 60 mmHg despite high-flow oxygen) 1
• Severe tachypnea (respiratory rate > 35 breaths/min) 1
• Reduced vital capacity (< 15 ml/kg) 1
• Inability to protect the airway 1
• Severe acidosis (pH < 7.25) with hypercapnia (PaCO2 > 60 mmHg) 1
• Increased work of breathing that cannot be sustained 1

Ventilation Strategy in ARDS

Strong Recommendations

For all patients with ARDS, use lung-protective ventilation with low tidal volumes (4-8 ml/kg predicted body weight) and maintain plateau pressures ≤ 30 cmH2O. 1, 2 This represents the cornerstone of ARDS management with moderate confidence in mortality reduction.

For severe ARDS (PaO2/FiO2 < 100), implement prone positioning for more than 12 hours per day. 1, 2 This strong recommendation is based on moderate confidence in improved survival outcomes.

Avoid routine use of high-frequency oscillatory ventilation in moderate or severe ARDS. 1, 3 Recent large trials demonstrated potential harm rather than benefit.

Conditional Recommendations

• Apply higher PEEP (≥ 15 cmH2O) in moderate to severe ARDS 1, 2, 3
• Consider recruitment maneuvers in moderate to severe ARDS, though evidence quality is lower 1, 2, 3

Oxygenation Targets

Target arterial oxygen saturation of approximately 90% (PaO2 ~60 mmHg) 1. PEEP application can provide dramatic improvements in oxygenation by preventing alveolar collapse and lung derecruitment 1.

Ventilation Strategy in COPD Exacerbations

Noninvasive Positive Pressure Ventilation (NIPPV)

NIPPV should be the first-line approach for COPD exacerbations with acute respiratory failure when acidosis (pH < 7.35) and hypercapnia (PaCO2 > 45-60 mmHg) are present. 1 One-year mortality is lower with NIPPV compared to conventional mechanical ventilation or medical therapy alone 1.

Contraindications to NIPPV

Do not use NIPPV in patients with:

• Respiratory arrest 1
• Cardiovascular instability 1
• Impaired mental status or inability to cooperate 1
• Copious/viscous secretions with high aspiration risk 1
• Recent facial or gastroesophageal surgery 1

Invasive Ventilation Indications in COPD

Proceed to endotracheal intubation when:

• NIPPV fails (worsening ABGs/pH in 1-2 hours or lack of improvement after 4 hours) 1
• Severe acidosis (pH < 7.25) with hypercapnia (PaCO2 > 60 mmHg) 1
• Life-threatening hypoxemia (PaO2/FiO2 < 200 mmHg) 1
• Severe tachypnea (> 35 breaths/min) 1

Special Considerations for ARDS with COPD

In ARDS patients with comorbid COPD, lower PEEP levels are appropriate compared to ARDS patients without COPD. 4 Electrical impedance tomography-guided PEEP titration results in lower PEEP requirements (approximately 7 cmH2O vs 10 cmH2O by ARDSnet protocol) with improved ventilation ratio, mechanical power, and hemodynamics 4.

Intubation Route and Airway Management

Use orotracheal intubation as the preferred route due to increased rates of nosocomial sinusitis with nasotracheal tubes 1. Nosocomial sinusitis significantly contributes to ventilator-associated pneumonia, which independently increases mortality 1.

Initial Ventilator Settings

Upon intubation, initiate:

• Volume-cycled ventilation using assist-control mode 1
• Tidal volume: 4-8 ml/kg predicted body weight (calculate using: men = 50 + 2.3 × [height in inches - 60]; women = 45.5 + 2.3 × [height in inches - 60]) 1
• Plateau pressure target: ≤ 30 cmH2O 1, 2

Key Benefits of Mechanical Ventilation

The primary benefit in ARDS is reducing work of breathing, allowing blood flow redistribution to other vital organs 1. This is particularly critical as the respiratory muscles can consume significant cardiac output during severe respiratory distress.

Critical Pitfalls to Avoid

• Never delay intubation when NIPPV is inadequate or contraindicated 1
• Do not use actual body weight for tidal volume calculations—always use predicted body weight 3
• Avoid noninvasive ventilation in moderate-to-severe ARDS, as delayed intubation increases mortality 3
• Do not prioritize normocapnia over lung-protective ventilation 2
• Never use high tidal volumes to normalize blood gases, as this increases mortality 1

Weaning and Liberation

Implement daily spontaneous breathing trials as the central component of weaning protocols, as this consistently reduces mechanical ventilation duration 1. For patients at high risk for extubation failure, use NIV after extubation to reduce ICU length of stay and mortality 1.