Airway Management in Obese Patients

Airway management in surgery requires specific training on the part of the professional. There are various factors that exist in obese patients that can complicate this.
Airway Management in Obese Patients

Last update: 13 January, 2020

Airway management is one of the fundamental areas in patient care. It requires continuous training, knowledge of maneuvers, and the use of devices that allow adequate and safe ventilation during surgery.

A thorough knowledge of the airway includes anatomy, causes of structural abnormalities, and various techniques to clear the airway. Currently, some difficulties persist with this procedure, such as some causes of death associated with anesthesia.

Obesity and excess weight consist are an accumulation of excessive fat in the body. This can be damaging to health for various reasons. Obesity is a risk factor in numerous chronic diseases, such as diabetes, cardiovascular diseases, and cancer.

Frequently, the difficulty of maintaining a clear airway in obese persons during surgery is underestimated. Studies on abnormal airways divide the causes into two groups: congenital (from birth) and acquired disorders. In this second area, morbid obesity is included.

The accumulation of fat in a morbidly obese patient can be a cause of difficulties in both a laryngoscopy and with intubation. That’s why it’s necessary for the professional to evaluate the level of excessive fatty tissue present in the body. This includes both internally (mouth, pharynx, abdomen) and externally (breasts, neck, chest wall and stomach).

We’ll now detail a series of characteristics present in morbidly obese people to take into account in airway management. The key is to anticipate possible difficulties and to formulate an action plan before surgery.

Anatomy of obese patients

In an obese patient, fat distribution (the location of the fat in the body), as well as the patient’s weight, are influencing factors. However, when considering airway management in these patients, the distribution of fat is actually more important than the patient’s weight.

Researchers have undertaken certain studies on morbidly obese patients by means of nuclear magnetic resonance. They have studied subjects both with and without Obstructive Sleep Apnea Syndrome (OSAS).

Their studies demonstrate that patients with OSAS have a greater amount of fatty tissue accumulating in specific areas in the body. These include more fatty tissue in the neck and throat, such as the areas surrounding the moving parts of the pharynx.

Thanks to these results, it’s possible to explain why airway management in some obese patients is simpler and in others it’s more complicated. The accumulation of fat in the neck can decrease neck extension, making a laryngoscopy more difficult.

How physiology of obese patients affects airway management

A patient under sedation.

Different studies demonstrate that obese patients have increased muscle tone. During anesthesia, muscle tone decreases. When this happens, the airway can be obstructed, making it difficult to ventilate the patient correctly.

In addition, obese persons have decreased lung capacity. As a consequence, oxygen consumption increases. This means that they are predisposed to the desaturation of oxygen (a drop in oxygen levels) after anesthesia starts.

Drug use in airway management for obese patients

What’s one of the main keys to safety during airway management in obese patients? Achieving an adequate level of anesthetic depth (the degree of anesthesia) prior to ventilation with an oxygen mask.

What happens if a patient only receives a superficial level of anesthesia? During ventilation, it may mean a false diagnosis of ventilation failure.

Most of the drugs used in anesthesia are fat-soluble. For this reason, the initial effect of the anesthesia may be lower in obese patients.

What can medics do when planning surgery on an obese patient? The use of adapted doses is recommended instead of the doses established for those with an ideal body weight.

Difficult Airway or DA

Surgery with intubation.

Currently, the percentage of obese patients with DA (Difficult Airway) is at 15.8%, compared with 5.8% in the rest of the population. A difficult airway is the situation where an anesthesiologist experiences difficulty ventilating a patient.

What factors contribute to a difficult airway? A BMI (Body Mass Index) greater than 30, as well as OSAS (sleep apnea) can contribute. However, these factors normally don’t hinder intubation.

There are other studies that use more specific markers for airway management in patients, such as the Intubation Difficulty Scale. These studies support the theory that obese patients have more likelihood of DA occurring.

Aspiration and preoperative fasting

Obese patients usually take longer than other patients to empty their stomachs. However, they don’t normally have a higher incidence of aspiration (reflux of stomach contents during anesthesia).

Therefore, when obese patients are going to have surgery, it’s not recommended that they undertake additional fasting measures or treatments for the prevention of aspiration.

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