By Donnie Vinson, MD
Management of the airway is anything but routine in the setting of propofol-mediated deep sedation for upper GI endoscopic procedures. Challenges exist in maintaining adequate oxygenation and ventilation in these “shared airway” procedures. These challenges include the limitation of our supplemental oxygen delivery systems in our procedure rooms (as nasal cannulas are most commonly used), reduced airway access due to patient positioning as well as the presence of the endoscope, and the reduction in muscle tone of the upper airway that results from our level of sedation.
Many of you may have seen the article “Hypoxia During Upper GI Endoscopy: There Is Still Room for Improvement,” which appeared in the Anesthesia Patient Safety Foundation (APSF) Newsletter in June 2019. This article is a great editorial review and a quick read at only 12 paragraphs long.
Given the issues of airway encroachment and the potential for limited oxygen delivery, let us be reminded of our approach to patients in the hospital setting before the induction of general anesthesia. In this setting, we all use the practice of preoxygenation as early as possible, and I encourage prioritizing this approach for patients undergoing upper GI procedures. “Safe apneic time” is the delay from the onset of apnea until O2 saturation drops below 90% (into the steep portion of the hemoglobin-O2 dissociation curve). The simple “maximal preoxygenation” technique can greatly increase the patient’s apneic time. We face patients daily who have decreased capacity for oxygen loading (anemia, lung disease, obesity, and decreased FRC) and, therefore, desaturate much more quickly. Targeting these patients with early oxygenation and even using other forms of high-flow O2 delivery should be prioritized. While some centers do not carry masks such as the Procedural Oxygen Mask (POM), there are alternative ways of increasing the FiO2 beyond those provided by nasal cannula. These include the use of a non-rebreather mask. However, this mask will not be a closed delivery system when maneuvered to provide an access route for the endoscope (it is helpful to roll up the reservoir bag to the base of the mask and tape the bag to prevent it from unrolling, as this allows you easy access to the chin if you need to provide a chin-lift maneuver). Also, some morbidly obese patients may benefit from preoxygenation that begins in the pre-procedure area.
Remember to increase your “safe apneic time” with “maximal preoxygenation.”
