The Uncooperative Patient Who Needs Intubation: A Practical Guide to Delayed Sequence Intubation

When RSI Isn't Enough: The Case for Delayed Sequence Intubation

A 58-year-old male is brought in by ambulance at 0300. GCS 10 (E2V3M5). SpO₂ 88% on a 15L non-rebreather mask. He's agitated, pulling at the mask, swinging at your nursing staff. His wife tells you he has severe COPD and has been worsening over 24 hours. His work of breathing is catastrophic — accessory muscles firing, tracheal tug, intercostal recession. He clearly needs intubation. But every time you bring the mask near his face, he fights it off.

You know the textbook says preoxygenate for 3–5 minutes before RSI. But this patient won't tolerate a mask for 3 seconds. Proceeding straight to rapid sequence intubation without adequate preoxygenation means paralysing a hypoxic patient — and the apnoeic window may be measured in seconds, not minutes. What do you do?

The Problem: Why RSI Alone Isn't Always Enough

Rapid Sequence Intubation (RSI) is the gold standard for emergency airway management — and for good reason. The simultaneous administration of an induction agent and neuromuscular blocker provides optimal intubating conditions while minimising the risk of aspiration. But RSI has a critical assumption baked into its design: that the patient has been adequately preoxygenated before the paralytic is given.

Preoxygenation — the process of denitrogenation, replacing the functional residual capacity's nitrogen store with oxygen — requires 3–5 minutes of tidal breathing on high-flow oxygen, or 8 vital capacity breaths. This creates an oxygen reservoir that buys you time during the apnoeic window after paralysis. In a well-preoxygenated, healthy patient, this window can be 6–8 minutes. In an obese, critically ill COPD patient? It may be less than 60 seconds.

Emergency airway management outside the operating room is associated with significantly increased cardiopulmonary complications and mortality (Karamchandani et al., 2021, Anesthesia & Analgesia, DOI: 10.1213/ANE.0000000000005644). Patients who are agitated, delirious, intoxicated, or have altered mental status from any cause — head trauma, hypoxia, septic encephalopathy, metabolic derangement — often cannot cooperate with preoxygenation. They pull off masks, bite on airways, and fight against non-invasive ventilation. This is not defiance. This is delirium. And it creates a genuinely dangerous situation.

What Is Delayed Sequence Intubation (DSI)?

Delayed Sequence Intubation (DSI) was first described by Scott Weingart in a landmark 2015 paper in the Annals of Emergency Medicine (DOI: 10.1016/j.annemergmed.2014.09.025). The concept is elegant in its simplicity: DSI is procedural sedation where the procedure is preoxygenation.

Instead of the standard RSI approach — induction and paralysis simultaneously, followed by intubation — DSI separates the sequence into two distinct phases. First, a dissociative dose of ketamine is administered. This sedates the uncooperative patient while preserving spontaneous ventilation and protective airway reflexes. With the patient now dissociated but still breathing, you have a 3-minute window to perform effective preoxygenation. Only after adequate preoxygenation do you proceed with the paralytic and intubation.

The key pharmacological advantage is ketamine's unique profile: it provides dissociative anaesthesia without suppressing respiratory drive. Unlike propofol, midazolam, or opioids, ketamine at dissociative doses (1–2 mg/kg IV) maintains spontaneous ventilation, preserves pharyngeal muscle tone, and has a sympathomimetic effect that supports blood pressure — all critical features in the critically ill patient.

The DSI Protocol: Step by Step

Step 1 — Preparation: Assemble all RSI equipment, drugs, suction, and backup airway devices before administering ketamine. Draw up your paralytic (rocuronium 1.2 mg/kg or succinylcholine 1.5 mg/kg) and have it ready at the bedside. Position the patient head-up at 20–30 degrees. Establish monitoring (SpO₂, EtCO₂ if available, ECG). Ensure high-flow nasal cannulae (HFNC) at 15 L/min are in place for apnoeic oxygenation throughout the procedure. Brief your team on the plan.

Step 2 — Ketamine Dissociation: Administer ketamine 1–2 mg/kg IV push. If no IV access is available, use 4–5 mg/kg IM (anticipate a longer onset of 3–5 minutes; have someone establishing IV access simultaneously). Wait 30–60 seconds for dissociation. The patient will become still, with a characteristic dissociative stare. They are now unconscious but breathing spontaneously.

Step 3 — Preoxygenation: With the patient now cooperative (dissociated), apply a non-rebreather mask at 15 L/min OR use non-invasive positive pressure ventilation (NIPPV) with BVM and PEEP valve, OR full NIPPV if available. Preoxygenate for 3 minutes. Monitor SpO₂ and EtO₂ if available (target end-tidal O₂ >85%). The HFNC should remain running under the mask throughout for apnoeic oxygenation during transition to intubation.

Step 4 — Paralysis and Intubation: After adequate preoxygenation, administer your chosen paralytic agent. Wait for full neuromuscular blockade (45–60 seconds for succinylcholine, 60–90 seconds for rocuronium at 1.2 mg/kg). Proceed with laryngoscopy and intubation using your preferred technique. Confirm placement with waveform capnography.

The Evidence: Does DSI Work?

The original Weingart et al. 2015 study enrolled 62 patients across emergency departments and ICUs. Results were striking: oxygen saturations increased from a mean of 89.9% before DSI to 98.8% after preoxygenation — an improvement of 8.9% (95% CI 6.4–10.9%). Among the 32 high-risk patients with pre-DSI saturations ≤93%, all improved their saturations, and 91% achieved SpO₂ >93% before paralysis was administered. Zero complications were observed (Annals of Emergency Medicine, DOI: 10.1016/j.annemergmed.2014.09.025).

Of particular relevance to Australian practice, Latona et al. (2024) published data from LifeFlight Retrieval Medicine in Queensland examining ventilator-assisted preoxygenation (VAPOX) in the aeromedical retrieval setting. Among 40 critically ill patients, 12 agitated patients underwent delayed sequence induction with ketamine. The study demonstrated a statistically significant improvement in SpO₂ after VAPOX application (p<0.001), with a low incidence of critical post-intubation hypoxia (Emergency Medicine Australasia, DOI: 10.1111/1742-6723.14404).

Emerging randomised controlled trial data comparing DSI to RSI in trauma patients suggests hypoxaemia rates of approximately 8% with DSI versus 35% with RSI — a clinically significant difference that reinforces the physiological rationale for optimising preoxygenation before paralysis. A 2026 scoping review published in the Journal of Emergency Medical Services has further examined DSI's expanding role in prehospital emergency medicine, confirming growing adoption across retrieval services internationally.

POCUS: Assessing the Difficult Airway in the Uncooperative Patient

Traditional airway assessment tools — Mallampati classification, thyromental distance, mouth opening, neck mobility — all require patient cooperation. In the agitated, delirious patient who needs intubation, these assessments are impossible. This is where point-of-care ultrasound (POCUS) offers a distinct advantage: it requires no patient cooperation whatsoever.

Pillai et al. (2024) studied 70 emergency department patients requiring intubation and found that ultrasound-based airway parameters could reliably predict difficult laryngoscopy. The pre-epiglottis to epiglottic vocal cord ratio (Pre-E/E-VC) at a cutoff of ≥1.86 predicted difficult laryngoscopy with 83% sensitivity and 94% specificity (AUC 0.835). Tongue thickness at ≥5.98 cm and hyomental distance at ≤6 cm both achieved 83% sensitivity and 88% specificity (International Journal of Emergency Medicine, DOI: 10.1186/s12245-024-00585-6).

Additionally, POCUS can detect unexpected airway pathology — masses, oedema, or anatomical distortion — that may fundamentally alter your airway management plan, as demonstrated in a case report by Adi et al. (2020) where ultrasound identified a laryngeal mass in an uncooperative patient with stridor, guiding the decision for emergency tracheostomy over intubation (American Journal of Emergency Medicine, DOI: 10.1016/j.ajem.2020.09.011).

Clinical Pearls and Pitfalls

Pearl 1: DSI is NOT sedation-only intubation. You must still give a paralytic after preoxygenation. The ketamine buys you time for optimisation — it is not a replacement for neuromuscular blockade. Attempting intubation on a dissociated but non-paralysed patient risks laryngospasm, incomplete relaxation, and a difficult intubation.

Pearl 2: Maintain apnoeic oxygenation throughout. Keep nasal cannulae at 15 L/min running during laryngoscopy. This provides passive oxygen flow to the alveoli during the apnoeic period and can extend your safe apnoea time significantly.

Pearl 3: Ketamine preserves respiratory drive but does NOT protect against aspiration. Position the patient head-up at 20–30 degrees to reduce aspiration risk and improve respiratory mechanics. Have suction immediately available and consider the aspiration risk profile of each patient.

Pearl 4: If using IM ketamine (no IV access), anticipate a longer onset of 3–5 minutes. Use this time productively — establish IV access, complete equipment checks, brief your team. The IM route is especially relevant in the prehospital and retrieval setting.

Pitfall: Do NOT use DSI as a reason to delay definitive airway management. The 3-minute preoxygenation window is for physiological optimisation, not procrastination. If the patient is crashing, you may need to proceed with whatever preoxygenation you can achieve.

References

1. Weingart SD, Trueger NS, Wong N, et al. Delayed sequence intubation: a prospective observational study. Ann Emerg Med. 2015;65(4):349-55. DOI: 10.1016/j.annemergmed.2014.09.025

2. Merelman AH, Perlmutter MC, Strayer RJ. Alternatives to Rapid Sequence Intubation: Contemporary Airway Management with Ketamine. West J Emerg Med. 2019;20(3):466-471. DOI: 10.5811/westjem.2019.4.42753

3. Karamchandani K, et al. Emergency Airway Management Outside the Operating Room: Current Evidence and Management Strategies. Anesth Analg. 2021;133(3):648-662. DOI: 10.1213/ANE.0000000000005644

4. Latona A, Pellatt R, Wedgwood D, Keijzers G, Grant S. Ventilator-assisted preoxygenation in an aeromedical retrieval setting. Emerg Med Australas. 2024;36(4):596-603. DOI: 10.1111/1742-6723.14404

5. Pillai A, Arora P, Kabi A, et al. The diagnostic accuracy of point-of-care ultrasound parameters for airway assessment in patients undergoing intubation in emergency department. Int J Emerg Med. 2024;17(1):12. DOI: 10.1186/s12245-024-00585-6

6. Adi O, Fong CP, Sum KM, Ahmad AH. Usage of airway ultrasound as an assessment and prediction tool of a difficult airway management. Am J Emerg Med. 2021;42:263.e1-263.e4. DOI: 10.1016/j.ajem.2020.09.011

Disclaimer

This content is for educational purposes only and is directed at healthcare professionals. It does not constitute medical advice and should not replace clinical judgement, institutional protocols, or local scope of practice guidelines. The author is a registered medical practitioner in Australia. This content complies with AHPRA advertising guidelines under Section 133 of the Health Practitioner Regulation National Law. All clinical claims are evidence-based and referenced to peer-reviewed literature. Always follow your institution's airway management protocols.