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Airway • Critical Care • Educational

Indications for Intubation (When to Secure the Airway)

A concise, modern overview of intubation and mechanical ventilation indicators—covering oxygenation, ventilation, mental status, and other clinical triggers.

Airway Management Basics More Critical Care Guides

Educational content only—always follow local protocols and consult a licensed clinician.

In this guide:
Dynamic Volumes Oxygenation Thresholds Ventilation & Rate Emergency Indicators Other Clinical Triggers Cited Keywords & Referral Links

Dynamic Volumes (Strength & Capacity)

Abnormal mechanics suggest impending failure and need for a definitive airway.

Measure Normal Strong indication for mechanical ventilation
Vital Capacity 65–75 mL/kg normal < 15 mL/kg intubate likely
Inspiratory Force 75–100 cmH2O normal < 25 cmH2O intubate likely

Oxygenation Thresholds

On Room Air (21% FiO2)

  • PaO2 > 70 mmHg is typical; < 55 mmHg is a strong indication
  • Alveolar–arterial (A-a gradient) < 10–15 mmHg is normal; > 55 mmHg suggests failure

On 100% FiO2

  • Expected PaO2 > 400 mmHg; < 200 mmHg despite maximal oxygen is worrisome
  • A-a gradient < 100 mmHg expected; > 450 mmHg indicates severe shunt/VD mismatch

Refractory hypoxemia despite optimized oxygen delivery is a common pathway to mechanical ventilation.

Ventilation & Respiratory Rate

CO₂ Clearance

  • Normal PaCO2: 35–45 mmHg
  • > 60 mmHg indicates significant hypercapnia → consider ventilatory support

Rate & Work of Breathing

  • Normal respiratory rate: 10–25 bpm
  • > 40 bpm or < 6 bpm signals failure to maintain ventilation

Emergency Indicators for Intubation

  1. Cannot protect the airway
  2. Cannot maintain ventilation/oxygenation
  3. Expected rapid decline in clinical status

Outside the operating room, these criteria commonly guide urgent decisions in the setting of respiratory failure.

Other Situations Raising Concern

  • Need for definitive airway in trauma or during ACLS
  • Altered mental status with GCS < 9
  • Compromised airway (burns, edema, facial trauma)

Cited Keywords & Referral Links

Each keyword below links to a page on gyathshammha.com.

Intubation Mechanical ventilation FiO2 PaO2 PaCO2 A-a gradient Vital capacity Inspiratory force Hypoxemia Hypercapnia Respiratory rate Airway protection Oxygenation Ventilation Glasgow Coma Scale (GCS) ACLS Trauma Seizures Pulmonary toilet / Airway clearance

Bottom line

Consider intubation when mechanics are weak (low vital capacity, poor inspiratory force), oxygenation fails on high FiO2 (low PaO2, high A-a gradient), ventilation is inadequate (high PaCO2, extreme rate), or the patient cannot protect the airway.

This guide mirrors classic thresholds for educational purposes. Always integrate values with the clinical picture.

© • Indications for Intubation • gyathshammha.com