A new review examines the unique challenges of airway management in critically ill adults with obesity and outlines evidence-based strategies to reduce peri-intubation complications. The article emphasises that obesity is increasingly prevalent worldwide and now affects a substantial proportion of patients admitted to ICUs. Between 25% and 40% of ICU admissions involve patients with obesity, many of whom have comorbidities such as hypertension, diabetes and obstructive sleep apnoea syndrome, all of which complicate airway management.
The review explains that obesity creates both anatomically and physiologically difficult airways. Excess adipose tissue in the face, neck, pharynx and hypopharynx narrows the upper airway and increases soft tissue collapsibility. Patients frequently have short necks, reduced mouth opening, larger tongues and higher Mallampati scores, making mask ventilation and laryngoscopy more difficult. Increased fat pads around the shoulders and posterior neck also impair optimal head positioning and alignment of the airway axes during intubation. These factors contribute to a greater incidence of difficult intubation and peri-intubation complications in critically ill patients with obesity.
Respiratory physiology is also profoundly altered. Obesity increases the work of breathing because of the added mass of the chest wall and abdomen and the increased resistance of smaller airways. Functional residual capacity (FRC), which represents the oxygen reserve during apnoea, is markedly reduced as adiposity increases. The diaphragm is displaced cranially by abdominal fat, promoting airway closure and atelectasis, particularly in dependent lung regions. At the same time, oxygen consumption rises because of increased metabolic demands. Together, these changes lead to a severely shortened safe apnoea time, explaining why patients with obesity rapidly desaturate during induction of anaesthesia and intubation.
The article also highlights cardiovascular alterations associated with obesity. Many patients develop left ventricular hypertrophy and elevated filling pressures to maintain cardiac output. Right ventricular strain is particularly important because obesity hypoventilation syndrome, obstructive sleep apnoea and chronic hypoxic vasoconstriction can impair right ventricular function. Transitioning from spontaneous negative-pressure breathing to positive-pressure ventilation during intubation can therefore precipitate haemodynamic instability.
Patient positioning is presented as a critical component of safe airway management. During preoxygenation, positioning the patient in a ramped, reverse Trendelenburg or upright posture improves FRC, ventilation-perfusion matching and oxygenation by reducing diaphragmatic compression. Evidence from operating theatre studies suggests that these positions decrease hypoxaemia compared with the supine position. However, during laryngoscopy and intubation itself, the evidence is less clear. A major ICU trial comparing ramped and sniffing positions found poorer glottic views and lower first-pass success in the ramped group. Consequently, the authors recommend preoxygenating patients in an elevated position but transitioning to a sniffing position for laryngoscopy, aligning the external auditory meatus with the sternal notch.
Hypoxaemia is identified as one of the commonest complications of emergency intubation. The review strongly supports positive-pressure preoxygenation using non-invasive ventilation (NIV). Several major trials demonstrated that NIV significantly reduces severe hypoxaemia and cardiac arrest during emergency intubation. The PREOXI trial, involving over 1,300 patients, showed a particularly marked benefit in patients with obesity, reducing hypoxaemia rates substantially compared with oxygen mask preoxygenation. High-flow nasal oxygen has also been studied, but evidence suggests NIV is superior, particularly in obese and hypoxaemic patients.
The review also discusses ventilation between induction and laryngoscopy. Positive-pressure bag-mask ventilation during this interval reduces hypoxaemia without increasing aspiration risk in most patients. Because obese patients have very limited oxygen reserves, they are likely to benefit even more from this approach. In contrast, apnoeic oxygenation via nasal cannula during laryngoscopy has not consistently demonstrated benefit in critically ill or obese populations.
The authors then examine difficult intubation and first-pass success. Critically ill patients with obesity have approximately double the rate of difficult intubation compared with non-obese patients. Factors such as high Mallampati scores, limited cervical mobility, obstructive sleep apnoea, reduced mouth opening and pre-intubation hypoxaemia are important predictors. Failed or repeated attempts increase the risk of severe hypoxaemia, haemodynamic collapse and cardiac arrest.
Videolaryngoscopy is therefore strongly advocated. Recent large randomised trials demonstrated higher first-attempt success rates with videolaryngoscopy compared with direct laryngoscopy across multiple clinical settings, including in patients with obesity. The authors recommend routine use of videolaryngoscopy in this population. Adjuncts such as stylets or bougies may further improve success, particularly when operators are experienced with their use.
Haemodynamic optimisation is another major focus of the review. Cardiovascular collapse occurs frequently during intubation of critically ill obese patients. Routine fluid boluses before intubation have not reduced this risk in major trials, suggesting fluids should instead be administered selectively based on individual haemodynamic assessment. Ongoing trials are investigating whether pre-emptive vasopressor administration may prevent cardiovascular collapse more effectively.
Regarding induction agents, the review cautions against propofol because it has been associated with increased cardiovascular instability. Ketamine and etomidate are considered more haemodynamically favourable. However, recent evidence suggests ketamine may not improve outcomes compared with etomidate and may even increase cardiovascular collapse in some obese patients. The authors conclude that either drug is acceptable, with the choice guided by patient characteristics, local practice and drug availability. They also discuss the challenges of weight-based dosing in obesity, particularly for sedatives and neuromuscular blocking agents.
Awake tracheal intubation (ATI) is discussed as a valuable option for selected high-risk patients. ATI allows preservation of spontaneous ventilation and may be especially useful when both anatomical and physiological airway difficulty are anticipated. The procedure requires skilled operators, careful topical anaesthesia, cautious sedation and meticulous preparation for failure. Flexible bronchoscopy and videolaryngoscopy are both acceptable techniques, depending on clinician expertise.
Finally, the review outlines several research priorities. These include determining optimal vasopressor strategies, improving sedation approaches during preoxygenation, refining drug dosing in obesity, clarifying the role of cricoid pressure, and assessing artificial intelligence-assisted airway management. The authors acknowledge that much existing evidence derives from operating theatre studies rather than ICU populations, limiting generalisability.
In conclusion, the review argues that airway management in critically ill patients with obesity requires careful attention to both anatomy and physiology. Positive-pressure preoxygenation, optimisation of patient positioning, haemodynamic monitoring and routine videolaryngoscopy are central strategies for reducing complications. Although important uncertainties remain, the article provides a comprehensive framework for safer airway management in this increasingly common and high-risk patient population.
Source: Intensive Care Medicine
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