Avoid Common Airway and Ventilation Errors in Morbidly Obese Patients

Avoid Common Airway and Ventilation Errors in Morbidly Obese Patients

Francis X. Whalen Jr MD

Juraj Sprung MD, PhD

Over the past 20 years, the incidence of obesity has increased significantly in both adults and children. Obesity is defined as a body mass index (BMI) of 30 kg/m2 or greater. The latest data from the U.S. National Center for Health Statistics show that 32% of adults aged 20 years and older—more than 60 million people—are obese, up from 22% in the 1988-1994 data. This increase is not limited to adults; the percentage of young people who are overweight has more than tripled since 1980.

For the anesthesiologist, this means that greater numbers of morbidly obese patients will require care. Concerns with regard to morbid obesity include:

  • Airway and ventilatory management

  • Drug dosing

  • Injuries related to positioning

  • Coronary artery disease, hypertension, pulmonary hypertension, and cor pulmonale

  • Glucose control, hyperlipidemia

  • Increased incidence of various postoperative complications

  • Sleep-disordered breathing (central or obstructive sleep apnea).

This chapter focuses on airway management and ventilatory issues in morbidly obese patients, although morbid obesity affects virtually every organ system.

Several studies have compared the difficulties in intubating the trachea in morbidly obese and normal-weight patients. Intubation is more difficult in morbidly obese persons, although BMI alone has not been shown to be an independent predictor of difficult intubation. Neck circumference and Mallampati score have been shown to be more accurate indicators of a difficult airway: neck circumference of 40 cm was associated with a 5% incidence of a difficult airway, and a 60-cm circumference was associated with a 35% incidence of difficulty.

Morbidly obese patients have a lower functional residual capacity, larger alveolar-to-arterial oxygen gradient, and a higher tendency for hypoventilation during sedation; all these factors make them more prone to oxyhemoglobin desaturation during tracheal intubation. Positioning of morbidly obese patients in the reverse Trendelenburg position has been shown to
allow a longer period of apnea without oxyhemoglobin desaturation, as well as lower respiratory system compliance once mechanical ventilation has resumed. Therefore, the reverse Trendelenburg position may give the operator more time for airway management and also may reduce the incidence of pulmonary aspiration.


In morbidly obese patients with a high Mallampati score or large neck circumference, awake fiber-optic intubation should be considered a first-choice technique for tracheal intubation. Other possibilities include performing the tracheal intubation with rigid intubating devices designed for a “difficult airway,” such as a Glidescope, Bullard laryngoscope, or Wuscope. After being sedated, morbidly obese patients, especially those with sleep apnea, are prone to upper-airway collapse, which thus contributes to increased resistance and obstructive apnea. This situation may convert an elective airway to an emergency procedure. Spontaneous breathing will provide oxygenation and the airway will open to a greater degree, thus providing a better view. Therefore, all attempts should be made to preserve spontaneous ventilation during management of a difficult airway. Alternative airway management, such as translaryngeal illumination with a lighted stylette (e.g., Lightwand), may not be effective in these patients because of increased soft tissue over the anterior neck or redundant tissue in the posterior pharynx.

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Jul 1, 2016 | Posted by in ANESTHESIA | Comments Off on Avoid Common Airway and Ventilation Errors in Morbidly Obese Patients
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