Obesity is a major health problem in the United States. Body mass index (BMI) is used to quantify obesity and is calculated by dividing the weight in kilograms by the height in meters. More than 69% of the US population is considered overweight, and 36% are obese as determined by BMI (Table 58.1) [1].

Obesity has numerous effects on health, and is a risk factor for many diseases and health conditions such as hypertension, dyslipidemia, type 2 diabetes mellitus, coronary artery disease, stroke, gallbladder disease, osteoarthritis, obstructive sleep apnea, pulmonary hypertension, and some cancers (notably endometrial, breast, and colon) [2]. Obesity does not only contribute to medical conditions, but may also affect one’s risk for, and recovery from, trauma. Obese individuals are at increased risk for traumatic injury [3], may have increased risk of chest, pelvis and extremity fractures, and of pulmonary, renal, and thromboembolic posttraumatic complications [4]. Obstructive sleep apnea, being relatively common in the obese, increases seven-fold the risk of motor vehicle accidents [5].

The variety of anatomical and physiological changes that occur with the bariatric patient not only affects their risk for disease, but can dramatically affect their prehospital management. Mask ventilation can be difficult and poor respiratory mechanics can predispose the bariatric patient to rapid desaturation and hypercarbia. Medication administration can be complicated based upon various drug dosing calculations, and high-quality cardiopulmonary resuscitation (CPR) can be hindered by the habitus of the bariatric patient. Increasing numbers of bariatric surgery procedures present the prehospital provider with unique pathologies, while more practically speaking, the bariatric patient can pose significant challenges to patient packaging, lifting, and movement. This chapter reviews the key anatomical and physiological changes and identifies the critical management considerations that the overweight patient poses to our prehospital care systems.

Airway

The bariatric patient can provide significant challenges to airway management as a BMI of greater than 26 kg/m2 is an independent predictor of difficulty in maintaining oxygen saturation with mask ventilation [6]. Redundant soft tissue about the face and neck can complicate both BLS and ALS airway interventions, and positioning of the bariatric patient is critical for successful management of airway and breathing. Whenever practical, the obese patient should be allowed to sit in a Fowler’s or semi-Fowler’s position. This will displace redundant soft tissue around the neck inferiorly, allowing for easier airway management, and will improve the patient’s respiratory dynamics, which is critical as bariatric patients do not tolerate periods of apnea.

Mask ventilation of the bariatric patient requires two-person techniques to be effective, where one provider is assigned to establish and maintain a mask seal with a two-hand grip, while the other provides ventilations. Often this simple but important intervention is not performed either because of a perception of “adequacy” with one-person techniques, or because in some systems there may not be enough personnel to accomplish this. Additionally, the use of a properly sized mask with oral or nasal airway adjuncts is critical to achieving effective mask ventilation in the obese patient. Ramp positioning, where the patient’s external auditory canal is aligned with the sternal notch, has been identified as an important tool to improve laryngoscopic view and also improves mask ventilation and subsequent oxygenation [7]. This positioning can be accomplished by aggressive padding behind the shoulders, neck, and head with towels and blankets. Soft tissue displacement during laryngoscopy may be difficult, thus worsening visualization of the glottic opening, and the ramp placement assists with this.

Interestingly, although increased BMI does predict difficulty with mask ventilation, there is mixed literature to support a similar correlation with tracheal intubation [8]. Regardless, since the obese patient is clearly difficult to effectively mask ventilate, and such a technique is the basis for initial and failed airway management attempts, the bariatric patient must be approached as if any airway intervention will be difficult.

Surgical airway placement may be challenging in the bariatric patient, regardless of the open or percutaneous technique used. Due to the additional soft tissue about the neck, surgical landmarks are often obscured and conventional cuffed tracheostomy tubes may not have adequate length to assure tracheal placement. As a result, a cuffed endotracheal tube is recommended when performing a surgical airway on a bariatric patient. Supraglottic airway devices may be effective in the bariatric prehospital patient based on operating room data [5]; however, there is scant prehospital literature on the topic, and no published experience with the commonly used King airway.

The bariatric patient with respiratory distress or airway compromise can create significant clinical management challenges for higher-risk procedures such as rapid sequence intubation. A patient who is inherently unable to tolerate hypoxia, coupled with predictable difficulty in effective mask ventilation, requires a thoughtful and methodological approach to airway management. Preparation is critical, including adequate preoxygenation with continuous positive airway pressure, two-person mask ventilation techniques, and ramp positioning. Having immediate access to surgical airway equipment and supraglottic airways is also required. Most importantly, developing the critical clinical decision-making skills amongst providers who may perform rapid sequence intubation is imperative to balance the risks and benefits of the procedure in the bariatric patient.

Breathing

The effects of obesity can dramatically affect the acutely ill patient’s respiratory system. The overweight and obese have poor pulmonary reserves as a result of multiple factors. The obese patient demonstrates a restrictive pulmonary physiology as a result of the additional chest wall mass, as well as an increase in resting intraabdominal pressure [9]. Intraabdominal compartment pressure of greater than 12 cmH₂O is often considered a compartment syndrome, and the morbidly obese often have intraabdominal pressures at or exceeding this level [10]. This decreases the effectiveness of the diaphragm for inspiratory effort and decreases venous return. Further, the bariatric patient will have decreased lung volumes, a decrease in functional reserve capacity and expiratory reserve volume, and reduced lung and chest wall compliance. These features impart poor respiratory mechanics and are coupled with an increased ventilation/perfusion mismatch compared to a non-obese patient [5,6]. Thus the bariatric patient has a smaller oxygen reserve, but because of increased metabolic activity has increased oxygen demand and CO₂ production [5]. This constellation of physiological insults results in a rapid onset of hypoxemia in even the “healthy” morbidly obese patient.

To combat this inherently poor baseline physiology, a few important interventions can enhance the oxygenation of the obese patient. Whenever possible, the obese patient should be positioned in either a semi-Fowler’s or ramped position, even during preoxygenation for advanced airway procedures. For the immobilized patient, even slight reverse Trendelenburg positioning can displace body mass to decrease pressure on the diaphragm or the upper chest muscles and therefore improve respiratory muscle mechanics. When considering continuous positive airway pressure (CPAP), bilevel positive airway pressure (BiPAP), or mechanical ventilation, obese patients generally require more positive end-expiratory pressure (PEEP) to maintain alveolar ventilation than their lean counterparts and should generally be started at 10 cmH₂

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