Prospective Study to Evaluate Mapleson Circuit With Monitored Anesthesia Care During Endobronchial Ultrasound (EBUS) Bronchoscopy

Monitored anesthesia Care (MAC) is a type of conscious sedation delivered by an anesthesiologist, during which different medications are given, usually via the intravenous route, to obtain varying levels of sedation depending on the surgery or procedure. This is routinely done for all EBUS procedures at Cooper University Hospital. Since MAC anesthesia does not include having a secure airway, occasionally the patient may develop episodes in which their oxygen level drops. During these episodes, the anesthesiologist will stop the procedure temporarily until the oxygen level returns to a normal range.

Often, changes in sedation amount is also required during this time. In traditional MAC anesthesia, the patient is receiving oxygen via a nasal cannula or a mask capable of measuring capnography. If oxygen is delivered via a capnography mask, the routine is to create a hole with scissors in the side of the mask in order to allow the bronchoscope into the patient's mouth. The Mapleson Circuit is a breathing system used to deliver oxygen and remove carbon dioxide during anesthesia. It consists of fresh oxygen flow, a reservoir bag, an expiratory valve, tubing, and a connection to the patient. There are different types of Mapleson circuits depending on the different arrangements of its components. The investigators plan to use a Mapleson D circuit attached to a nasal trumpet via a connector.

Endobronchial Ultrasound is a technique that uses ultrasound along with bronchoscopy to visualize the airway wall and structures adjacent to it. The clinical application and diagnostic benefits of EBUS have been well established, including diagnosis and staging of lung cancer. EBUS is usually performed under conscious sedation for patient comfort.

The route of entry for the EBUS scope requires passage through the vocal cords and into the airways. The procedure tends to be very stimulating for this reason, which is the reason for the necessity for anesthesia. Due to the amount of anesthesia required to subdue the airway reflexes for a smooth procedure, occasionally, the patient may become apneic or obstruct and not take adequate tidal volume breaths, leading to hypoxia. During these instances, the procedure is halted until the patient's oxygen levels return to baseline. The investigators have noticed that anesthesiologists who prefer to use the mapleson circuit with a nasal trumpet in place tend to less often interrupt the procedure due to hypoxia.

Placing a nasal trumpet in one nare allows access to the oropharynx, bypassing soft tissue that may relax under anesthesia and cause obstruction. Connecting that nasal trumpet to a device that can not only deliver oxygen efficiently when the subject is spontaneously breathing, but can also be used as an assist device to deliver assisted breaths in the event that the patient becomes hypoxic or apneic provides a method to oxygenate into the oropharynx without having to interrupt the procedure. It also helps maintain an airway from the nares into the oropharynx and prevent episodes of obstruction, which are commonly seen under MAC anesthesia. All anesthesiologists are familiar with the mapleson circuits as well as nasal trumpets.

No research has been done in this field specifically regarding EBUS. There is no anesthetic standard of care that is specific for an EBUS procedure. The anesthesia can be local anesthesia alone, with just topicalization of the airways, or MAC, or even general anesthesia with an endotracheal tube or a laryngeal mask airway. The choice is practitioner dependent.

Our experience has been that MAC with a mapleson circuit leads to less procedural interruptions, less hypoxic episodes and shorter procedural duration.