Delayed Sequence Intubation: Sedate to Preoxygenate, Then Intubate

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Updated July 2026  |  More ICU clinical guides →

Every experienced ICU nurse has seen it: a hypoxic patient who desperately needs to be preoxygenated before intubation, but who is so agitated, delirious, or air-hungry that they claw the mask off their face. Rush them to intubation without preoxygenating and they desaturate to dangerous levels the moment the paralytic takes effect. Delayed sequence intubation, or DSI, is the answer to this specific bind. It is, in the simplest terms, procedural sedation performed for the procedure of preoxygenation — you give a sedative that calms the patient without stopping their breathing, use the resulting cooperation to fill their lungs with oxygen, and only then proceed to intubation. This guide explains how DSI works, how it differs from standard RSI, and what the nurse watches for.

The problem DSI solves

Preoxygenation is what buys you a safe apnea window during intubation — a well-preoxygenated patient can tolerate the seconds to minutes of not breathing while the tube goes in without their saturation crashing. But preoxygenation only works if the patient tolerates the mask or high-flow device long enough to denitrogenate their lungs. The agitated, encephalopathic, or severely dyspneic patient fights the mask, so they arrive at intubation with a low starting saturation and almost no reserve. The instant the RSI drugs stop their breathing, they desaturate into a danger zone, and the operator is now rushing under pressure. DSI breaks this loop by making the patient tolerate preoxygenation first.

How it differs from RSI

The essential difference is the preserved respiratory drive during the sedation phase. In RSI you accept apnea and race it; in DSI you protect breathing precisely so you can improve the oxygen reserve before you ever accept apnea. This is why the choice of sedative matters so much.

Why ketamine

DSI depends on a sedative that produces a calm, dissociated patient while leaving airway reflexes and respiratory drive largely intact — and ketamine is the prototype for exactly this. It lets you dissociate an agitated patient so they tolerate a tight mask, high-flow nasal oxygen, or even noninvasive ventilation, without the apnea that a standard induction dose of other agents would cause. The patient keeps breathing and keeps protecting their airway while their lungs fill with oxygen. Dosing and agent selection are provider decisions and vary by patient and hemodynamics.

The oxygenation happens during the pause

The whole point of the deliberate delay is oxygen delivery, so the preoxygenation must be maximized during those minutes. That means a high-fraction oxygen source (a flush-rate non-rebreather, high-flow nasal cannula, or noninvasive ventilation for the shunt patient), often layered with nasal cannula oxygen that stays on through the eventual apneic period to provide apneic oxygenation. Head-up positioning improves the efficiency of preoxygenation. The nurse watches the saturation climb and holds during this window rather than rushing — the improvement in reserve is the entire return on the technique.

The nurse's role

DSI asks the nurse to manage two mindsets at once: procedural sedation vigilance during the delay, and full intubation readiness the whole time. Practically, that means having the airway cart and paralytic ready before anything is pushed, applying complete monitoring, delivering the sedative on order, then supporting and optimizing preoxygenation (device fit, positioning, apneic-oxygenation cannula). Throughout, you watch respiratory rate and effort, the oxygen saturation trend, and the depth of dissociation — and you are ready to move immediately to paralysis and tube placement when the team calls it, or to support the airway if the patient obstructs. As with any sedation, you keep continuous eyes on breathing.

Where to go from here

Pair this with the preoxygenation and apneic oxygenation guide, the rapid sequence intubation nurse-role guide, the peri-intubation hemodynamics guide, and the awake intubation guide for the other end of the difficult-airway spectrum.