What are the indications for intubation in patients with severe respiratory distress or failure, including those with acute respiratory distress syndrome (ARDS), severe pneumonia, or acute exacerbations of chronic obstructive pulmonary disease (COPD) or asthma?

Indications for Intubation in Severe Respiratory Distress

Intubate immediately for apnea, impending respiratory arrest, severe hypoxemia despite supplemental oxygen (SpO2 <90% on high-flow oxygen), severe tachypnea (respiratory rate >40 breaths/min), muscular respiratory failure with accessory muscle use, altered mental status preventing airway protection, or inability to clear secretions. 1

Primary Clinical Indications

Absolute Indications

• Apnea or impending respiratory arrest - these have compelling face validity and require immediate intubation 2
• Severe hypoxemia - SpO2 <90% despite supplemental oxygen and noninvasive support 1
• Altered mental status - inability to maintain or protect the airway 1
• Respiratory muscle failure - use of accessory muscles, physical exhaustion 1
• Severe tachypnea - respiratory rate >40 breaths/min 1

Physiological Thresholds

• Respiratory failure with hypoxemia, hypercapnia, and acidosis - the triad indicating ventilatory failure 1
• Cardiovascular instability - hemodynamic compromise requiring airway control 2
• Physical exhaustion - inability to sustain work of breathing 1

Condition-Specific Considerations

ARDS Patients

• Intubate when noninvasive support fails within 2-4 hours - delayed intubation increases mortality 1
• Monitor for tidal volumes persistently >9.5 ml/kg predicted body weight during NIV - this suggests need for intubation 1
• Rapid shallow breathing index (RSBI) >105 breaths/min/L during NIV predicts intubation need 1
• Avoid delayed intubation - failure to recognize lack of improvement during noninvasive support may result in cardiac arrest with devastating consequences 1

COPD Exacerbations

• Try noninvasive ventilation (NIV) first for COPD with respiratory acidosis - it reduces intubation rates and mortality 3, 2
• Intubate if NIV fails - indicated by persistent or worsening acidosis, hemodynamic instability, inability to tolerate mask, or excessive secretions 2
• Contraindications to NIV include cardiovascular instability, vomiting, depressed consciousness, or inability to protect airway 1

Severe Asthma

• Use NIV cautiously - only in HDU/ICU where immediate intubation is available 3
• Intubate for cardiovascular instability or failure to respond to NIV within 1-2 hours 2

Pneumonia and Sepsis

• Early intubation is appropriate based on standard clinical criteria to avoid complications of respiratory failure 1
• In sepsis-related ARDS, avoid routine NIPPV - these patients are more likely to fail noninvasive therapy 1

Noninvasive Support Trial Parameters

When to Attempt NIV Before Intubation

• Cognizant younger patients with moderate ARDS 1
• SAPS II score <34 1
• ARDS not caused by pneumonia 1
• Normal or near-normal mental status without significant secretions 1
• Expected resolution within 72 hours 1

Monitoring During NIV Trial

• Close monitoring is mandatory - deterioration can occur abruptly 1
• Positive responses should be evident within 2-4 hours - if no substantial improvement in gas exchange and respiratory rate, start invasive ventilation without delay 1
• High respiratory drive during NIV may encourage excessive transpulmonary pressure swings, increasing risk of patient self-inflicted lung injury 1

Critical Pitfalls to Avoid

Delayed Intubation

• Delayed intubation is associated with increased mortality in acute respiratory failure 1, 4
• Intubation ≥15 days after symptom onset carries significantly higher mortality (OR 2.13) despite similar oxygenation levels 4
• Do not persist with failing NIV - recognize lack of improvement early 1

Premature Intubation

• Premature intubation exposes patients to unnecessary risks of invasive mechanical ventilation including ventilator-associated pneumonia 1
• Balance is key - intubate early enough to prevent deterioration but not so early as to bypass potentially successful noninvasive support 1

Technical Errors

• Ensure adequate sedation and anesthesia during intubation procedure to minimize risks 1
• Orotracheal intubation is preferred over nasotracheal to reduce VAP risk 1
• Pre-oxygenation is essential before intubation attempts 1

Post-Intubation Targets

Once intubated for ARDS or severe respiratory failure:

• Target SpO2 88-92% to avoid oxygen toxicity while maintaining adequate oxygenation 3
• Use low tidal volumes (4-8 ml/kg predicted body weight) 1, 3
• Maintain plateau pressure ≤30 cmH2O 1, 3
• Apply adequate PEEP (10-15 cmH2O for moderate-severe ARDS) 3