This is a foundational yet high-stakes topic, especially in cardiothoracic anaesthesia and ICU, where even “routine” intubations often involve physiologically fragile patients (poor LV/RV function, fixed cardiac output lesions, pulmonary hypertension, etc.).
Let’s go step-by-step — from principles, anatomy, equipment, procedure, verification, complications, and extubation, all framed with evidence from DAS (UK Difficult Airway Society), ASA, NICE, AHA, and EACTA/EACTS guidelines.
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๐ซ Endotracheal Intubation (ETI): Principles, Technique, and Clinical Implications
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## ๐น 1. What Is Endotracheal Intubation?
Endotracheal intubation is the insertion of a **cuffed tube** into the **trachea via the mouth or nose** to:
* Secure the **airway**
* Provide **ventilation and oxygenation**
* Prevent **aspiration**
* Allow delivery of **volatile anaesthetics** or **positive pressure ventilation**
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## ๐น 2. Relevant Anatomy (Quick Recall)
* **Upper airway:** mouth → oropharynx → larynx
* **Laryngeal landmarks:**
* Epiglottis
* Arytenoids
* Vocal cords (target landmark)
* **Trachea:** ~10–12 cm in adults; carina at ~25 cm from lips (average adult male)
* **Right main bronchus:** wider, shorter, more vertical → more common for accidental endobronchial placement.
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## ๐น 3. Indications
### A. **In Operating Theatre**
* General anaesthesia with risk of aspiration
* Need for controlled ventilation (thoracic/cardiac surgery)
* Long or complex surgery
* Need for **lung isolation** (double-lumen tube [DLT] or bronchial blocker)
### B. **In ICU**
* Respiratory failure (PaO₂ < 8 kPa on FiO₂ > 0.6, PaCO₂ > 8 kPa, exhaustion)
* Airway protection (GCS ≤ 8, absent reflexes)
* Cardiac arrest
* Postoperative mechanical ventilation
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## ๐น 4. Equipment Checklist (“SOAP-ME” mnemonic)
| Component | Items | Notes |
| ------------------------ | ------------------------------------------------------ | --------------------------------------------------------------- |
| **S – Suction** | Yankauer suction | Ready and working |
| **O – Oxygen** | High-flow source / bag-mask / circuit | Preoxygenate |
| **A – Airway** | ETT (2 sizes), stylet, bougie, VL blade, LMA, FONA kit | Size 7.0–8.0 (adult female/male) |
| **P – Pharmacology** | Induction + paralytic + emergency drugs | Etomidate / propofol / ketamine / thiopentone; sux / rocuronium |
| **M – Monitoring** | ECG, SpO₂, NIBP, capnography | Must confirm waveform CO₂ |
| **E – Equipment backup** | Difficult airway trolley, FONA setup | Follows DAS Plan A–D |
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## ๐น 5. Pre-Intubation Assessment
### Airway evaluation
* Mallampati, mouth opening, thyromental distance, neck mobility, dentition, jaw protrusion.
* History of **previous difficult airway**.
* In CT patients → consider **sternotomy scars, cervical stiffness, goitre, tracheostomy scars**.
### Physiological assessment
* Haemodynamic stability: induction agents may cause severe hypotension in low EF or critical AS.
* Oxygenation: preoxygenate 3–5 minutes (tight mask, PEEP 5, head-elevated).
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## ๐น 6. Technique of Orotracheal Intubation (Standard)
1️⃣ **Positioning:**
* *Sniffing position* (neck flexed, head extended)
* For obese → *ramped position* (external auditory meatus level with sternal notch)
2️⃣ **Preoxygenation:**
* 100 % O₂ for 3–5 min (or EtO₂ ≥ 90 %)
* Use CPAP 5 cmH₂O if hypoxic or morbidly obese.
3️⃣ **Induction & muscle relaxation:**
* **Drugs tailored to physiology:**
* *Stable*: Propofol 1.5–2.5 mg/kg
* *Poor LV*: Etomidate 0.2–0.3 mg/kg or ketamine 1–2 mg/kg
* *Bradycardia*: Glycopyrrolate/atropine ready
* *RSI*: Suxamethonium 1–1.5 mg/kg or rocuronium 1.2 mg/kg
4️⃣ **Laryngoscopy:**
* Direct (Macintosh) or Video (C-MAC, McGrath, GlideScope)
* Advance ETT between cords under direct vision.
* Stop if cannot visualise → call for help, oxygenate, change device or operator.
5️⃣ **Confirm placement:**
* Continuous **waveform capnography (gold standard)** (NICE, DAS, ASA)
* Bilateral chest rise
* Equal air entry, no gastric sounds
* Condensation in tube
* Secure tube at **21 cm (female), 23 cm (male)** at lips
6️⃣ **Cuff inflation:**
* Inflate until minimal leak (~20–30 cmH₂O cuff pressure)
7️⃣ **Secure tube:**
* Tape firmly; avoid pressure on lips or teeth.
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## ๐น 7. Specialized Airway Management in Cardiothoracic Anaesthesia
| Context | Airway Device / Plan | Notes |
| ------------------------------------------- | ----------------------------------------------- | -------------------------------------------------- |
| **CABG / valve surgery** | Standard cuffed ETT (7.0–8.0) | Avoid nasal route; secure firmly for TEE insertion |
| **Thoracic surgery / one-lung ventilation** | Double-lumen tube (DLT) or bronchial blocker | Confirm with fiberoptic bronchoscope |
| **Re-do sternotomy / mediastinal mass** | Awake fiberoptic or VL-assisted intubation | Avoid loss of spontaneous breathing |
| **Severe AS / low EF** | Etomidate / ketamine; minimal haemodynamic drop | Preload before induction |
| **Obese / OSA** | Ramped, high-flow nasal O₂, video-laryngoscopy | Avoid prolonged apnoea |
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## ๐น 8. Confirmation of Tracheal Placement
**Mandatory** according to:
* **NICE NG159 (2021)**
* **DAS Airway Guidelines (2015)**
* **ASA 2022 Difficult Airway update**
✅ **Continuous waveform capnography** – always confirm after 6 breaths.
❌ **Colorimetric detectors or chest rise alone** are unreliable.
If no CO₂:
* Check disconnection, circuit leak, oesophageal intubation, or low CO.
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## ๐น 9. Post-Intubation Management
* Auscultate for equal air entry.
* Confirm **tube depth** on chest X-ray (tip 2–3 cm above carina).
* Secure circuit to avoid tension.
* **Sedation & analgesia**: propofol, midazolam, fentanyl, dexmedetomidine as appropriate.
* **Humidification** and **suction** to prevent secretion plugging.
* **Cuff pressure monitoring** 20–30 cmH₂O to prevent mucosal ischemia.
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## ๐น 10. Complications
| Category | Examples | Prevention / Management |
| --------------------- | ------------------------------------------------------------------------------------------- | --------------------------------------------------- |
| **During intubation** | Dental injury, laryngospasm, aspiration, oesophageal intubation, hypoxia, brady/tachycardia | Gentle technique, preoxygenate, rapid confirmation |
| **Mechanical** | Tube obstruction, cuff leak, accidental extubation | Secure, suction, monitor pressures |
| **Physiological** | Hypotension, arrhythmia (esp. in CAD/low EF) | Titrate induction drugs, fluids, vasoactive support |
| **Late** | Sore throat, tracheal stenosis, VAP | Cuff pressure control, aseptic care |
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## ๐น 11. Difficult Intubation & DAS “Plan A–D” (Summary)
| Plan | Action | Goal |
| ----- | ------------------------------------------ | --------------------- |
| **A** | Direct or video-laryngoscopy (≤3 attempts) | Intubation |
| **B** | 2nd-gen supraglottic airway | Oxygenation |
| **C** | Face-mask ventilation | Oxygenation / wake-up |
| **D** | FONA (scalpel-bougie-tube) | Life-saving access |
**Principles:**
* **Stop and oxygenate** between attempts.
* **Declare difficulty early.**
* **Capnography** after every airway intervention.
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## ๐น 12. Extubation Principles
Extubation = *planned airway management step*, not just tube removal.
### Assess readiness:
* Haemodynamically stable
* Awake, following commands
* Adequate spontaneous effort (VT > 5 mL/kg, NIF < –20 cmH₂O)
* PaO₂/FiO₂ > 200, FiO₂ ≤ 0.4
* Reversal of neuromuscular block (TOF > 0.9)
* Minimal inotropes
* No surgical concern (bleeding, airway oedema)
### DAS Extubation Guidelines:
* Prepare same as intubation
* Oxygenation ready
* Suction before deflation
* Consider **airway exchange catheter** if anticipated reintubation risk
* Observe for **laryngospasm, stridor, bronchospasm, desaturation**
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## ๐น 13. In the ICU (Prolonged Intubation)
* **Cuff pressures:** check every 6–8 h.
* **ETT repositioning:** rotate daily.
* **Suctioning:** as per protocol (closed system).
* **Sedation breaks / weaning trials:** daily to assess readiness for extubation.
* **Prevent VAP:** elevate head 30–45°, oral care, subglottic suction ETTs.
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## ๐น 14. Guidelines & References
* **DAS (UK) 2015:** Unanticipated Difficult Intubation
* **DAS 2019:** Awake Tracheal Intubation
* **ASA 2022:** Difficult Airway Practice Guidelines
* **NICE NG159 (2021):** Critical Care in Adults
* **EACTA/EACTS 2021:** Perioperative Airway and Ventilation in Cardiac Surgery
* **AHA 2021:** Advanced Airway Management in Cardiac Arrest
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## ✅ **Key Summary Table**
| Step | What to Remember | CTICU / Cardiac Focus |
| -------------------- | ------------------------------------------ | ---------------------------------------------------- |
| **Preparation** | SOAP-ME, preoxygenation, drugs ready | Avoid hypotension / desaturation |
| **Technique** | Gentle VL intubation, confirm waveform CO₂ | One attempt, early help |
| **Post-intubation** | Equal air entry, secure ETT, ABG check | Verify DLT with bronchoscope |
| **Difficult airway** | Plan A–D, FONA readiness | Cardiac surgery → early awake approach if predictors |
| **Extubation** | Planned, safe, reversible | Use exchange catheter if risky |
| **ICU care** | Cuff pressure, suction, humidification | Prevent VAP, maintain sedation targets |
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### ⚕️ **Clinical Pearls for You (Cardiac Anaesthesia Context)**
1. **First attempt is the best attempt** — always use VL in high-risk cardiac patients.
2. **Preoxygenation is therapy**, not just preparation — CPAP or HFNO if poor reserve.
3. **Avoid long apnoea times** — maintain spontaneous ventilation if uncertain airway.
4. **Always confirm with waveform CO₂** — no exception.
5. **Anticipate haemodynamic crash after induction** — preload, vasopressors ready.
6. **Document airway grade, tube type, depth, and extubation plan.**
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