How Rapid Sequence Intubation Secures the Airway

Rapid sequence intubation is a method of placing a breathing tube into the windpipe by giving a fast-acting sedative and a muscle relaxant in close succession, with the goal of achieving unconsciousness and full paralysis quickly enough to minimize the window during which a patient could vomit and inhale stomach contents into the lungs.¹ It is the dominant technique for emergency airway control in hospitals and, increasingly, in the field. But the procedure done today barely resembles the one first described decades ago, and several of its longstanding rituals are now openly questioned by the evidence.

Why the Procedure Exists

The core problem RSI solves is aspiration. When someone needs a breathing tube urgently, they often have a full stomach, impaired reflexes, or both. Vomit entering the lungs during intubation can cause severe pneumonia or death. The original idea, developed in the 1960s, was straightforward: knock the patient out and paralyze them so fast that there is almost no gap between consciousness and a secured airway. The patient never reaches a half-awake state where gagging and vomiting are most likely.

Over time, the indications expanded well beyond full-stomach emergencies. RSI is now the go-to approach for trauma patients, people in respiratory failure, those with dangerously low oxygen levels, and many other critically ill patients who need a definitive airway quickly. A contemporary review notes that most key aspects of the original technique, from drugs to equipment to who performs it, have been challenged and changed, yet the underlying principles of rapid airway control and aspiration avoidance remain central.²

The Drugs Behind the Speed

RSI depends on two classes of medication given in rapid succession: an induction agent that renders the patient unconscious and a neuromuscular blocker that paralyzes the muscles so the vocal cords relax and the tube can pass through. Choosing the right combination matters, because each drug carries trade-offs that play out in the minutes after injection.

Induction Agents

The two most commonly used induction agents are etomidate and ketamine. Etomidate has long been favored for its hemodynamic stability; it tends to keep blood pressure relatively steady during and right after injection. Ketamine, on the other hand, can stimulate the cardiovascular system, which sounds like a benefit in a patient who is already in shock. The reality is more nuanced. A meta-analysis of randomized trials found that ketamine probably causes more short-term blood-pressure swings around the time of intubation compared to etomidate, but it appears to reduce the need for starting a continuous blood-pressure-supporting drip afterward and causes markedly less suppression of the adrenal glands.³ A separate systematic review confirmed the adrenal-insufficiency finding, showing ketamine was associated with substantially lower odds of adrenal suppression.⁴ Neither drug appears to have a clear edge in mortality or first-pass intubation success.

Propofol is a third option, widely used in elective operating-room settings. It tends to lower blood pressure more sharply, so it is generally avoided when a patient is already hemodynamically unstable. Current expert guidance favors etomidate or ketamine over propofol for critically ill patients who are already teetering.⁵

Neuromuscular Blockers

For decades, succinylcholine was the default paralytic because it acts within roughly 45 seconds and wears off in just a few minutes. That short duration was considered a safety net: if the tube could not be placed, the patient would start breathing on their own fairly quickly. But succinylcholine carries a list of uncommon but serious side effects, including dangerous rises in potassium, malignant hyperthermia in susceptible individuals, and prolonged paralysis in people who lack the enzyme to break it down.

Rocuronium, a longer-acting agent, has steadily gained ground. A Cochrane review of 50 studies found that succinylcholine still produced somewhat better intubating conditions overall, but that at a higher dose of rocuronium the difference in intubation conditions disappeared. The review noted succinylcholine’s clinical superiority was primarily its shorter duration of action.⁶ A randomized trial in out-of-hospital patients found that at the higher dose, rocuronium matched succinylcholine in onset time and actually had fewer intubation-related complications within fifteen minutes.⁷ The availability of sugammadex, a reversal agent that can rapidly switch off rocuronium’s paralysis, has largely neutralized the concern about its longer duration. Succinylcholine is now increasingly being replaced by rocuronium in many systems worldwide.⁸

Pretreatment Drugs

Older RSI protocols called for pretreatment with drugs like atropine, lidocaine, or fentanyl a few minutes before induction. The idea was to blunt unwanted reflexes such as a spike in heart rate or intracranial pressure during laryngoscopy. In practice, evidence supporting routine use of these agents is thin, and their use has largely fallen out of favor except in select situations.⁹

Pre-oxygenation and Apneic Oxygenation

Before the drugs go in, clinicians spend time flooding the patient’s lungs with oxygen. The goal is to build up a reservoir so that once the patient is paralyzed and stops breathing, oxygen levels stay high long enough to place the tube. In a cooperative patient, this means breathing high-concentration oxygen through a tight-fitting mask for three to five minutes.

A technique that has gained traction in recent years is leaving a high-flow nasal cannula running during the entire intubation attempt. An integrative review found that keeping nasal oxygen flowing during both pre-oxygenation and the apneic period after paralysis can prevent oxygen desaturation, extend the safe window for tube placement, and improve first-pass success.¹⁰ Because the nasal prongs sit beneath the face mask and do not interfere with the laryngoscope, this is an easy addition to the workflow. Many departments now treat it as standard practice.

The Cricoid Pressure Debate

For most of its history, RSI included a step called cricoid pressure: an assistant presses down on the cartilage ring at the front of the neck to compress the esophagus and, in theory, prevent stomach contents from rising up. This maneuver was introduced in 1961 and was long considered a defining feature of the technique. The evidence behind it has not held up well.

A systematic review of randomized controlled trials found that cricoid pressure failed to show any protection against aspiration and was associated with worse first-attempt success, longer time to intubation, and poorer views of the vocal cords.¹¹ A separate emergency-department-focused review reached a similar conclusion: aspiration occurred regardless of whether cricoid pressure was applied, and first-pass success did not improve with it.¹²

One complicating factor is that most people applying cricoid pressure do not actually push in the right spot. A 2024 review pointed out that correct localization of the cricoid cartilage is inaccurate without ultrasound guidance, which means much of the existing evidence is testing an improperly performed maneuver. Still, the same review concluded that cricoid pressure as currently performed likely provides no benefit but probably does minimal clinically relevant harm, and that its use is increasingly a matter of individual clinician judgment rather than a mandated protocol step.¹³ The shift toward video laryngoscopy also blunts the concern about worsened views, since video devices give a much better look at the vocal cords even under suboptimal conditions.

Video Laryngoscopy and First-Pass Success

Getting the tube in on the first try matters more than clinicians once appreciated. Each additional attempt raises the risk of oxygen desaturation, bleeding, airway swelling, and cardiac arrest. Current estimates put first-pass success during RSI at roughly 84%, and complications climb steeply with every additional attempt.¹⁴

Video laryngoscopes, which project a camera view of the airway onto a screen, have become a major tool for improving that number. A multicenter randomized trial published in the New England Journal of Medicine found that first-attempt success was about 85% with video laryngoscopy compared to about 71% with direct laryngoscopy, an absolute difference of over 14 percentage points.¹⁵ A secondary analysis in cardiac arrest patients found a similarly large advantage, with video producing first-attempt success in about 83% of patients versus roughly 65% for direct technique.¹⁶ Prehospital data tells a consistent story, with one ambulance service study showing a 12.6% higher first-pass rate using video.¹⁷ Many systems have now made video laryngoscopy the default first approach for all emergency intubations.

What Makes RSI Dangerous

The gravest complication is peri-intubation cardiac arrest, where the heart stops during or immediately after tube placement. A meta-analysis identified three dominant risk factors: low blood pressure before the procedure (roughly five times the odds), low oxygen levels before the procedure (roughly four and a half times the odds), and needing two or more attempts at intubation (roughly twice the odds).¹⁸ A second meta-analysis reinforced that pre-intubation hypotension, hypoxemia, and higher body mass index were the most strongly associated risk factors.¹⁹

The practical takeaway is that the minutes before paralysis matter enormously. Aggressively treating low blood pressure with fluids and vasopressors, maximizing pre-oxygenation, and using techniques that boost first-pass success are the most effective ways to prevent the worst outcomes. A patient who arrives with a systolic blood pressure of 70 and an oxygen saturation of 80% is in a fundamentally different risk category than one who is hemodynamically stable, even though both may need intubation just as urgently.

Delayed Sequence Intubation

Some patients who need emergency intubation are too agitated or confused to tolerate pre-oxygenation. They rip off the mask, fight the providers, and cannot cooperate. In those cases, a variation called delayed sequence intubation has emerged. The concept is simple: give a dissociative dose of ketamine first, which sedates the patient enough that they tolerate a face mask or non-invasive ventilation without becoming fully unconscious. Once oxygen levels are optimized, the paralytic is given and intubation proceeds normally.

A prospective study found that oxygen saturations climbed from an average of about 90% before the ketamine dose to about 99% afterward, representing a clinically meaningful safety buffer before the paralytic was administered.²⁰ It has been described as procedural sedation where the procedure is pre-oxygenation. Some prehospital systems have bundled delayed sequence intubation into a broader care protocol alongside patient positioning and apneic oxygenation to reduce hypoxia during out-of-hospital airway management.²¹

RSI Outside the Hospital

RSI was originally a hospital procedure, performed by anesthesiologists and emergency physicians with full backup at their fingertips. Its expansion into prehospital medicine raised legitimate concerns: Could paramedics and flight nurses perform it safely in the back of an ambulance or at a roadside? The accumulated data suggests they can, with the right training and protocols. A large paramedic study covering over 7,500 patients found first-attempt success at 77% and ultimate success at 99%, with RSI-assisted attempts producing better laryngeal views and higher first-pass rates than non-RSI approaches.²²

Flight paramedic programs report even higher numbers. One service documented a first-pass rate of about 89% and an overall success rate above 99%, with transient hypotension or hypoxemia occurring in under 7% of cases. All five patients in whom intubation failed were returned safely to spontaneous breathing without a surgical airway.²³ A two-year study of a ground-based EMS system using RSI for non-cardiac-arrest patients showed first-pass rates over 92% and overall success approaching 99%, with supraglottic backup airways covering nearly all failed cases.²⁴ These numbers are not universal, though. Systems with less rigorous training, lower call volumes, or fewer quality-assurance mechanisms tend to report worse results. Prehospital RSI works when the system around it is built to support it.

Difficult Populations

Pediatric airways present a distinct challenge. Children’s anatomy is different — shorter necks, larger tongues relative to the oral cavity, and a more anterior larynx — and the margin for error in drug dosing and equipment sizing is razor-thin. A video-review study of pediatric emergency RSI found that only about half of children were successfully intubated on the first attempt, and roughly 61% experienced at least one adverse effect during the procedure, with a third developing oxygen desaturation. Trainee providers succeeded on the first attempt only about 45% of the time, while attending physicians managed roughly 89%.²⁵ Those numbers are sobering and underscore that pediatric RSI benefits enormously from experienced hands.

Patients with obesity face a different set of problems. Higher body mass compresses the chest wall, reduces lung capacity, and causes oxygen stores to deplete faster during apnea. Airway anatomy can be distorted by excess soft tissue, making visualization harder. Pharmacokinetics also shift: drug distribution volumes change with body composition, requiring careful weight-based dosing adjustments.²⁶ Pregnant patients share the rapid desaturation problem because pregnancy reduces functional lung capacity, and they face the added urgency of a fetus that depends on maternal oxygenation. Anatomical airway changes during pregnancy, including tissue swelling and weight gain, further complicate intubation.²⁷

When RSI Fails

No matter how skilled the team, some airways cannot be managed from above. When a provider cannot intubate and cannot ventilate by any conventional means, the situation is referred to as “cannot intubate, cannot oxygenate,” and it is a genuine life-or-death emergency. Brain damage from oxygen deprivation begins within minutes. The Difficult Airway Society guidelines identify scalpel cricothyroidotomy — making a small cut through the membrane at the front of the neck to access the windpipe — as the fastest and most reliable rescue technique.²⁸

Institutional protocols for these events vary. One published algorithm pairs a needle-based approach as the first step with a scalpel-and-bougie technique as the backup, emphasizing that having a standardized plan in place before the crisis occurs is what actually saves lives.²⁹ In children, the rescue landscape is even more challenging. Needle cricothyrotomy has traditionally been taught for younger kids, but a recent multidisciplinary review argues that training should shift toward surgical tracheotomy, because needle cricothyrotomy is technically difficult, exceedingly rare, and nearly impossible to maintain competency in.³⁰

Checklists, Teamwork, and Human Factors

RSI is a team procedure. It involves at least two or three people working in tight coordination under time pressure, and small communication failures can cascade into serious harm. Aviation-style checklists have been adopted by many departments to standardize the preparation steps: verifying drug doses, confirming equipment function, assigning roles, and pre-briefing the backup plan if the first attempt fails.³¹

Simulation training that mimics realistic emergency scenarios has also made a measurable difference. One study found that in-situ simulation sessions led to statistically significant improvements in both airway-management performance and human-factors scores like communication and role clarity.³² The gains were not just about technical skill; team members also reported feeling more comfortable using the checklist and understanding their role during the procedure.

What Happens After the Tube Is In

Getting the tube placed is only the beginning. The transition to ongoing mechanical ventilation introduces its own set of risks, particularly around blood pressure. A large multicenter analysis of over 16,000 mechanically ventilated patients found that about 40% of those not already on blood-pressure support required vasopressors within two hours of starting sedation, and propofol-based sedation was associated with a meaningful drop in blood pressure within the first 30 minutes. Sicker patients and older patients experienced larger drops.³³ This means the pharmacological vigilance that characterized the RSI itself does not end when the tube is confirmed in position. Choosing an appropriate post-intubation sedation regimen, anticipating blood-pressure drops, and having vasopressors ready are all extensions of the same careful airway-management mindset.

Ventilator settings also need immediate attention. Tidal volumes, respiratory rates, and positive end-expiratory pressure must be set appropriately for the patient’s body size and underlying condition. In patients with severe lung disease, aggressive ventilation right after intubation can worsen outcomes. Confirming tube position with end-tidal carbon dioxide monitoring, securing the tube properly, and obtaining a chest X-ray are standard verification steps that prevent the delayed disaster of an unrecognized misplaced tube.