Brian K. Parker, MD, MS; Sara Manning, MD; Michael E. Winters, MD, MBA


Western J Emerg Med. 2019;20(2):323-330. 

In This Article


In critically ill obese patients, intubation is a high-risk procedure that can be fraught with peril. As discussed in the preceding section, obese patients have very little cardiopulmonary reserve and can desaturate rapidly to critical oxygen levels during intubation. Numerous studies have highlighted obesity as a risk factor for difficult intubation.[15–18] De Jong and colleagues reported an increased incidence of difficult intubation in obese patients.[19] They found that an elevated Mallampati score, limited mouth opening, reduced cervical mobility, the presence of obstructive sleep apnea, and severe hypoxemia were associated with difficult intubation.[13,19] Additional factors that have been shown to predict difficult intubation in obese patients include a short neck, a thick neck, diabetes mellitus, and abnormal upper teeth.[1,20,21] Given the challenges of airway management in the obese patient, it is crucial for the EP to optimize intubation conditions to reduce the risk of poor outcome.


Critically ill patients undergoing RSI should be preoxygenated adequately prior to intubation in order to prolong the time to reach critical oxygen saturation thresholds during apnea. The primary goal of preoxygenation is to create an oxygen reservoir by replacing nitrogen within the FRC with oxygen.[1] Common methods of preoxygenation include the use of a face-mask (FM) with 100% fractional inspired oxygen concentration (FiO2), bag-mask ventilation (BMV), noninvasive positive pressure ventilation (NIV), and high-flow nasal cannula (HFNC) devices. Often, the traditional methods of preoxygenation using a FM or BMV are insufficient in the critically ill obese patient.[13] But NIV can be beneficial and is the preoxygenation method preferred by many.[13] The application of continuous positive airway pressure (CPAP) at 10 centimeter (cm) H2O has been shown to reduce atelectasis, improve oxygenation, and increase apnea time without hypoxemia in the obese patient undergoing surgery.[13,22,23] Bilevel positive airway pressure (BPAP) can also be used to preoxygenate obese patients, although it is less well studied than CPAP.[1] Compared with the use of a FM with 100% FiO2, BPAP improves oxygen saturation readings prior to intubation.[1,24] When clinically feasible, CPAP or BPAP should be maintained for at least five minutes during the preoxygenation period.[25] HFNC devices can be considered for the obese patient; however, the minimal positive pressure delivered by HFNC devices can be expected to have little impact on FRC, and evidence supporting their benefit in preoxygenation prior to RSI is limited.[13]

Patient Positioning

Proper positioning is critical for success in both preoxygenation and intubation of the obese patient. Given the alterations in respiratory physiology, obese patients should be placed in either a semirecumbent (head of the bed elevated to 25 degrees) or a sitting position during preoxygenation.[1,13] The upright or semirecumbent position may decrease air trapping, decrease atelectasis, and improve oxygen saturation prior to intubation.[13,26] Similar to the optimal position for preoxygenation, obese patients should be placed in a head up or ramped position to optimize the laryngoscopic view for intubation (Figure).[1,27–29] To ensure proper position, the EP should align the patient's sternal notch with his or her external auditory meatus.[1,28,29]


Patient positioning for intubation

Medication Dosing

Improper dosing of RSI medications can cause significant patient discomfort and may increase the incidence of complications during intubation. Several recent studies demonstrated that obese patients often receive inappropriate doses of sedative and paralytic medications during RSI.[30–32] Bhat and colleagues demonstrated that obese patients were more likely to be underdosed with both etomidate and succinylcholine during RSI.[32] It is therefore important for the EP to be knowledgeable about the proper dosing of medications commonly used during RSI (Table). Medications dosed on total body weight include etomidate and succinylcholine, whereas propofol and the nondepolarizing neuromuscular blocking medications (e.g., rocuronium) are dosed on ideal body weight.[1,21] Ketamine is dosed on lean body mass.[1,21]


It is wise for the EP to consider each intubation of an obese patient as a difficult intubation. As such, adequate preparation is of paramount importance. In addition to the equipment needed for direct laryngoscopy, advanced airway equipment (e.g., supraglottic airway, video laryngoscope, gum elastic bougie, surgical airway equipment) should be placed at the bedside. Video laryngoscopy may be preferred over direct laryngoscopy in the obese patient.[1,33,34] For patients who require BMV during intubation attempts, recall that obesity is a risk factor for difficult BMV.[13,35] The use of an oral or nasal airway, a two-handed jaw thrust, or a two-person technique can improve the efficacy of BMV.[1,21]