February 1, 2013
by Andrew C. Adams, DDS
During conscious sedation, the primary goal of any anaesthesia provider is to protect the airway. In dentistry this is a double-edged sword, since we work in the mouth. It affords us the ability to constantly monitor the airway, but it also means we are often moving the head and neck into a position that might cause or increase the likelihood of airway obstruction. As a patient becomes more sedated, the muscles of their airway become more relaxed. This loss of muscle tone allows the soft tissue of the airway to collapse and cause obstruction. It will manifest as snoring, laboured breathing with use of accessory muscles, or apnea. It is amazing how some individuals can become apneic with even minimal sedation. On the other hand, perhaps it is not surprising considering how many individuals are diagnosed with either central or obstructive sleep apnea.
During treatment under sedation the most simple and effective maneuver one can employ when any soft tissue airway obstruction occurs is the head-tilt, chin-lift. This position is very effective at opening the airway. A key concept in anaesthesia is that the head-tilt, chin-lift maneuver should be employed at the first sign of obstruction and then maintained throughout the case if necessary. A bite-block or mouth prop can help accomplish this with minimal operator fatigue. We must always remember, however, that for the patients’ safety, airway-breathing-and-circulation (“the ABCs”) come first. Positioning the patient for dentistry during sedation is something of an art form. Sometimes the positions that we would like may impair ergonomics. Here, the practitioner must sacrifice optimal operator comfort for a patent airway.
When the head-tilt, chin-lift is not sufficient on its own, a jaw thrust can be added. This can be accomplished by the provider placing their thumbs at both angles of the mandible and protruding the jaw forward. A jaw thrust can be combined with a head-tilt, chin-lift. While it is a very effective method at opening the airway, it is also very stimulating (painful) and a patient with moderate sedation will wake up from this maneuver. Under normal circumstances, a jaw thrust should not be routinely needed for moderate sedation.
In an emergency, bag-valve-mask (BVM) ventilation may be necessary in order to ventilate a patient. If one hasn’t “bagged” a real person before, it’s an acquired skill but there are some steps one can employ to make it easier and more effective. First, consider placing an oral-pharyngeal airway or a nasal-pharyngeal airway in order to maximize airway patency. These will make a big difference in increasing one’s ability to provide positive pressure ventilation. Many BVMs allow supplemental oxygen to be added, however never delay emergency treatment while waiting for an oxygen tank to arrive. Traditionally, it was taught to hold the face-mask of a BVM to a patient’s face using a modified “C-E” clamp, referring to the shape the provider’s finger’s make on the mask and jaw, allowing for simultaneous mask placement and head-tilt, chin-lift, jaw-thrust. This allows the provider’s second hand to remain free to squeeze the bag and deliver positive pressure. A recent article in Anesthesiology suggests that a two-provider method, where one provider holds the mask with both hands and the second squeezes the bag is more effective. These authors found that that compared to the one-handed technique, the two-provider method resulted in greater airway patency, as well as greater tidal volumes and minute ventilation. These results were obtained in apneic and unconscious patients with an oral pharyngeal airway inserted.1 At your next CPR recertification give both methods a try, and allow other staff members to practice as the second provider.
As with all aspects of dentistry, case-selection for sedation dentistry is key. It is useful to have predictors regarding who will have a difficult airway and thus who will be challenging to manually ventilate if necessary. Many studies have evaluated criteria that predict difficult or impossible mask ventilation, and they have largely agreed on the criteria that make an airway difficult to manage. Predictors of challenging airways include: patients with a body mass index (BMI) greater than 30 kg/m2, age greater than 57 years, limited jaw protrusion ability, snoring, a history of sleep apnea, thick or obese neck anatomy, and those with missing teeth.2,3
A thick neck or a BMI indicative of obesity suggests extra soft tissue in the airway that can easily cause obstruction when the patient is relaxed. A history of snoring or sleep apnea also suggests an airway that has collapsible soft tissue. Research has shown that males have difficult airways more often than females. Limited jaw protrusion is defined as someone who cannot advance their lower incisors more anterior than an end-to-end relationship. This concept relates to retrognathism in that a retruded mandible will predispose one to a more-easily collapsed airway. Finally, missing teeth can lead to a loss of vertical dimension, and this over-closing can lead to an airway that will collapse more readily.
These are valuable predictors that dentists are able to assess and should be considered for inclusion on your office’s medical history forms. Airway assessment should be contemplated for every sedation case as it helps to determine who appropriate candidates for sedation are.OH
Dr. Adams is a first-year resident in the Dental Anaesthesia program at the University of Toronto.
Oral Health welcomes this original article.
1. Joffe, A., Hetzel S., Liew, E. A Two-handed Jaw-thrust Technique Is Superior to the One-handed “EC-clamp” Technique for Mask Ventilation in the Apneic Unconscious Person. 2010. Anesthesiology. 113:873-9
2. Kheterpal et al. Incidence and Predictors of Difficult and Impossible Mask Ventilation. 2006. Anesthesiology. 105:885-91
3. Langeron et al. Prediction of Difficult Mask Ventilation. 2000. Anesthesiology 92:1229-36