DAS25: From Footnote to Phenotype

In the 2015 Difficult Airway Society (DAS) guidelines, obesity appeared as a footnote, tucked into a long list of “risk factors” for difficult mask ventilation and intubation. It was something to note, not something to plan around.

DAS 2025 flips that script. In line with the broader shift from “rescuing failure” to “engineering success,” patients living with obesity are finally recognized as a distinct high-risk airway phenotype. They get their own section, their own rationale, and a clear directive: mitigating risk in this group requires a package of measures, not a minor adjustment to standard technique.

Just as important, DAS explicitly aligns itself with the Society for Obesity and Bariatric Anaesthesia (SOBA) 2025 best-practice recommendations. If the old approach was medicine by tarot card — laryngoscope in one hand, vibes in the other, SOBA replaces divination with actual strategy.

SOBA calls out the problem directly:

“In all existing guidelines, recommendations relating specifically to airway management in patients living with obesity are an addendum or subsection… To our knowledge, there are no other recommendations specific to the airway management of patients living with obesity.”
— McKechnie et al., 2025

And the motivation is equally clear:

“Whilst generic airway guidelines offer assistance, there are no evidence-based guidelines specific to this group of patients… It is hoped the recommendations made will improve the safety and efficacy of airway management in patients living with obesity.”
— McKechnie et al., 2025

Taken together, SOBA 2025 and the new DAS obesity section signal a fundamental shift: obesity isn’t a footnote anymore. It’s a physiologic airway phenotype with its own risk profile — and its own set of expectations for how we should manage it.

This raises three essential questions:

• How should we define patients living with obesity in a way that’s clinically useful?
• What actually makes their physiology so unforgiving when the airway goes wrong?
• And now that DAS 2025 has weighed in, what do they want us to do differently?

Let’s take a closer look.

1. Defining Patients Living with Obesity in a Clinically Useful Way

Obesity alone isn’t a perfect predictor of difficult laryngoscopy, but patients living with obesity are consistently over-represented in airway complications and poor outcomes (NAP7, NAP4).

Traditional definitions stop at BMI > 30 kg/m². Still, newer thinking (including the Lancet Commission’s framing) treats obesity as a chronic, systemic disease driven by excess adiposity that alters the function of tissues, organs, and entire physiology.

The airway population is also evolving:

• Obesity prevalence is rising.
• Use of GLP-1 agonists is increasing, thereby increasing the risk of aspiration via delayed gastric emptying (Dhatariya et al., 2024).

SOBA 2025 takes a pragmatic stance:

A BMI ≥ 40 kg/m² is the operational threshold (the point at which significant excess adiposity can be assumed), and airway management should be managed as physiologically high-risk from the outset. 

But what actually makes this group high-risk isn’t the number alone — it’s the physiology that comes with it.

2. Why Physiology Makes These Airway Events So Unforgiving

When anatomical and physiological burdens stack, the airway becomes exponentially more dangerous. The same features that make mechanics more difficult also make recovery from errors far less forgiving.

Respiratory Physiology

• ↑ Oxygen consumption and ↑ CO₂ production → rapid desaturation and short safe apnea times.
• ↓ FRC an elevated diaphragm, reduced compliance, and abdominal load (worse when supine).
• ↑ Airway resistance → rapid, shallow breathing and impaired preoxygenation.

Upper Airway Anatomy

• Pharyngeal fat deposition → increased collapsibility under sedation or paralysis.
• Visualization is harder, and mask ventilation is more likely to fail.

Cardiopulmonary Risk

• Comorbidities include atherosclerosis, hypertension, diabetes, cardiomyopathy, and arrhythmias.
• ↑ Aspiration risk is increased by higher gastric volume and increased intra-abdominal pressure.

Hemodynamics

• Noninvasive BP readings often overestimate stability.
• In higher-risk patients, consider an arterial line and use the shock index to detect deterioration early.

Pharmacokinetics & Pharmacodynamics

• Obesity alters nearly every step of drug handling — absorption, distribution, metabolism, and elimination.

General rules of thumb:

• Lipophilic agents (propofol) → dose to Total Body Weight (TBW)
• Hydrophilic agents (ketamine) → Ideal Body Weight (IBW)
• Neuromuscular blockers (succinylcholine, rocuronium) → TBW

Clinical Pearl: This cohort is consistently under-represented in trials. Clinical judgment overrides formulas. Titrate to effect and monitor closely.

3. So What Does DAS 2025 Actually Want Us to Do Differently?

Below are the five practical takeaways distilled from DAS 2025’s obesity section.

1. Manage the airway in the OR when possible.

• Better lighting, equipment, monitoring, staffing, and fail-safe pathways. Complication rates are measurably lower than in non-OR environments.

2. Preoxygenate in a ≥30° head-up position.

It’s physiology. Head-up:

• increases FRC
• improves preoxygenation
• prolongs safe apnea time
• makes mask ventilation and laryngoscopy easier

Align the external auditory meatus with the sternal notch. Keep the patient head-up through induction.

3. Use high-flow nasal oxygen (HFNO) for preoxygenation and apneic oxygenation

• HFNO provides:
  • Mild PEEP
  • High FiO₂
  • Extended safe apnea time

If HFNO isn’t available, use CPAP/NIV or standard nasal cannula at 15 L/min during attempts.

4. Move early to a second-generation supraglottic airway if mask ventilation struggles.

Obesity increases the risk of difficult mask ventilation. A second-generation SAD gives a better seal and can serve as an intubation conduit. Insert it early when the mask isn’t giving you the oxygenation you need.

5. Consider awake tracheal intubation (ATI).

Awake techniques preserve spontaneous ventilation and airway reflexes — the things you can’t afford to lose in this phenotype.

DAS 2020 made ATI structured.
DAS 2025 makes ATI a physiologic priority.

• sTOP Checklist (DAS 2020):
• s – Sedation: optional and light
• T – Topicalisation: lidocaine ≤ 9 mg/kg (lean body weight)
• O – Oxygenation: HFNO, head-up
• P – Performance: limit to 3+1 attempts, use capnography

Mark the cricothyroid membrane before you start. Ultrasound if landmarks are obscured.

Conclusion

There’s still no universal algorithm for airway management in patients living with obesity — and that’s fine. The point isn’t to simplify the physiology; it’s to stop ignoring it.

DAS 2025 moves obesity where it belongs: From a footnote to a phenotype.

If the patient in front of you is living with obesity, that’s your pre-event cue, not your post-event excuse. It should shape your plan before anything goes wrong.

What’s Coming Next On This Topic @PAC

The Protected Airway Collaborative is taking this new emphasis seriously. Over the coming months in 2026, our team is developing a comprehensive PAC Learning Space dedicated to the management of patients with obesity.

This new space will include:

• Evidence-based frameworks distilled from DAS 2025, SOBA 2025, and contemporary research
• Digital learning modules that translate physiology into practical, repeatable strategies
• Interactive simulations tailored to the obese airway phenotype
• Deliberate practice resources for skill-building in positioning, oxygenation, airway setup, and crisis management
• Printable PACscapes and equipment guides for pop-up training anywhere

Our goal is simple: translate updated guidance into real-world performance and help clinicians develop the cognitive and technical skills needed to manage this high-risk airway phenotype from the outset.

Under Construction

This is where the next evolution of airway education begins.