When should endotracheal intubation be performed in a patient who cannot protect the airway or maintain adequate gas exchange despite maximal non‑invasive ventilation?

When to Decide to Intubate

Endotracheal intubation should be performed immediately when a patient cannot adequately protect their airway or when respiratory failure manifests as refractory hypoxemia (PaO₂ < 60 mmHg despite high-flow oxygen or SpO₂ < 90% despite FiO₂ 1.0), hypercapnia, acidosis, physical exhaustion, or diminished consciousness. 1, 2

Primary Indications for Intubation

The decision to intubate is based on three fundamental criteria that should be assessed systematically:

Inability to Protect the Airway

• Proceed with intubation when the patient cannot adequately protect their airway, which is the most critical indication. 1
• Assess for absent or diminished gag reflex, inability to handle secretions, pooling of secretions in the oropharynx, and ineffective cough. 3
• Diminished consciousness or depressed mental status mandates airway protection regardless of other parameters. 1, 2

Failure of Oxygenation

• Intubate when SpO₂ remains < 90% despite FiO₂ of 1.0 via face mask or other non-invasive means. 2
• Refractory hypoxemia with PaO₂ < 60 mmHg despite maximal oxygen therapy is an absolute indication. 1
• Physical exhaustion from increased work of breathing, even with adequate oxygen saturation, warrants intubation to redirect blood flow to vital organs. 1

Failure of Ventilation

• Intubate when respiratory rate exceeds 35 breaths/min with signs of fatigue or when vital capacity falls below 15 mL/kg. 1
• Hypercapnia and acidosis indicate ventilatory failure requiring mechanical support. 1
• Inability to achieve adequate ventilation despite optimal face mask technique is an indication for intubation. 2

Role of Non-Invasive Ventilation

Non-invasive ventilation (CPAP, NIPPV, or high-flow nasal oxygen) should not delay definitive intubation when airway protection is compromised or when the patient is deteriorating. 1

• In sepsis-related respiratory failure, noninvasive positive-pressure ventilation has not been clearly shown to be effective, and it is critically important not to impede the timing of appropriate respiratory interventions such as mechanical ventilation. 1
• In acute heart failure with pulmonary edema, non-invasive ventilation may relieve dyspnoea but does not reduce mortality or intubation rates when compared to standard therapy. 1
• The key pitfall is delaying intubation while attempting non-invasive ventilation in patients who are already failing to protect their airway or who have severe respiratory distress. 1, 2

Timing Considerations

Do not wait for complete respiratory arrest—intubate when the trajectory is clearly toward failure despite maximal non-invasive support. 1, 2

• The fundamental principle is that patients do not die from failure to intubate, but from failure to oxygenate or from continuing futile attempts at non-invasive management. 2
• In critically ill patients, early intubation before complete decompensation allows for better pre-oxygenation and more controlled conditions. 1, 2
• Contraindications to non-invasive ventilation include hypotension, vomiting, possible pneumothorax, and depressed consciousness—all of which favor early intubation. 1

Special Clinical Scenarios

Sepsis and Respiratory Failure

• Control of the upper airway and consideration of ventilatory assistance is an important first step in sepsis-related respiratory dysfunction. 1
• Once endotracheal tube placement occurs, mechanical ventilation is almost universally indicated due to coincident respiratory failure. 1

Acute Heart Failure

• Primary indications include respiratory failure leading to hypoxaemia, hypercapnia, and acidosis. 1
• Physical exhaustion, diminished consciousness, and inability to maintain or protect the airway are additional reasons to intubate. 1

Anticipated Difficult Airway

• When difficult intubation is anticipated in a critically ill patient, the most experienced available operator must manage the case. 1
• Awake intubation should only be attempted by suitably skilled clinicians with careful positioning, minimal sedation, adequate topical anaesthesia, active pre-oxygenation, and a clear plan for failure. 1
• In most critically ill patients with inadequate cooperation or urgency, intubation after induction of anaesthesia with full neuromuscular blockade is optimal. 1

Critical Pitfalls to Avoid

• Delayed transition to definitive airway management due to over-reliance on non-invasive ventilation causes greater morbidity than early intubation. 2
• Inadequate pre-oxygenation in high-risk patients (obesity, critical illness) increases morbidity and mortality. 2
• Multiple repeated intubation attempts should be avoided—limit to three attempts maximum before moving to rescue strategies. 1, 3, 2
• In patients with borderline respiratory function, moving them to another location may precipitate complete respiratory failure—bring the team to the patient instead. 1