Monitoring Breathing in the Sedated Patient

By Rose Dodson    

Not one of you reading this article would disagree with the importance of an open airway. It’s comforting to see the chest rise and fall in the middle of your procedure, or in some cases, the nitrous airbag inflate and deflate. But there’s been more than one case of a patient who stopped breathing while sedated in a dental chair, with no one aware of what was happening until it was too late. You’ve heard the stories.

It’s important to know if your patient—sedated or not—is adequately ventilating. But as you know, at a certain level of sedation, the natural drive to breathe can be inhibited. So it’s critical to pay close attention to a patient’s breathing when he/she is sedated. With a “truly” minimally-sedated patient, there should be no question as to whether he’s maintaining his airway. With conscious sedation, a patient should maintain all of his protective reflexes. Even with a moderately-sedated patient, the ADA states that, “No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate.”

The grey area comes in on the “deep” side of moderate sedation. Keep in mind that sedation functions in a continuum; and its slope gets more slippery as it progresses.  This is especially true with geriatric and pediatric patients. Therefore, if you intend to moderately sedate a patient, you must be capable of recognizing and managing “deep” sedation, should it inadvertently occur. With minimal-to-moderate sedation, one of the key components of managing sedation is knowing how to manage the patient’s airway. (Remember: Airway. Airway. Airway.) The ADA guidelines state that, during moderate sedation, ventilation must be “continually” evaluated.  The rules go on to list three ways in which this can be accomplished:

1. Auscultation of breath sounds
2. Monitoring end tidal CO2, or
3. Verbal communication with your patient

Verbal communication is an obvious monitoring method. Not only does it confirm ventilation, but it also helps determine a patient’s level of sedation.

Monitoring end tidal carbon dioxide (ETCO2) is another way to way to make sure your patient is properly ventilating. For this type of monitoring, you’ll want to consider purchasing an ETCO2 monitor, known as a capnograph.  Every capnograph has some method of capturing moisture buildup from expelled air. Some units have a built-in water trap that require regular emptying. Others have a proprietary CO2 sampling line with a built-in adapter. Per-patient disposables are needed; the type will vary, depending on the manufacturer of the capnograph, and whether you’re using a nasal hood or delivering oxygen through a cannula.

 

Auscultation (listening to breath sounds) can be accomplished through a stethoscope. The familiar monitoring tool helps you recognize subtle changes in breathing and provides information that can alert you if a patient is about to obstruct his airway, allowing you to provide early intervention and prevent respiratory distress.

You may be familiar with the terms “precordial stethoscope” and “pretracheal stethoscope.” Traditionally, a clinician would go to an audiologist and have a mold made of his ear, so a custom earpiece could be made. The earpiece, along with four to five feet of tubing and a weighted bell called a Wenger chest piece, would be used to create a stethoscope for monitoring an anesthetized patient. If placed near the heart, the apparatus would be referred to as a precordial stethoscope; if placed near the trachea, a pretracheal stethoscope. In dentistry,  most doctors place the chest piece over the suprasternal notch, and therefore use a pretracheal stethoscope. For a dentist performing a procedure while tethered by four feet of tubing, this can be a challenge. Further, dental procedures can be noisy making it difficult to hear adequately. Fortunately, with the development of amplified Bluetooth^® stethoscopes that are now readily available, these challenges can be overcome.

 

In one version, the weighted bell, or chest piece, houses the microphone. The housing cuts ambient noise down tremendously, and allows you to hear each breath without having to disturb your sedated patient. Another version utilizes the same Wenger-style chest piece, but has the microphone built in-line with the tubing. Both styles amplify breathing sounds, and have adjustable volume controls that allow you to hear over noise in the procedure area. The only thing a doctor or assistant needs to put on is a Bluetooth^® headset—just like the ones used with cell phones.

The tether traditionally associated with the pretracheal stethoscope is eliminated, enabling you or your assistant to walk to the other side of the room, and still know that your patient is adequately ventilating. Though it may not be a tool you’d use with every sedation, it might be one you’ll take out for your geriatric and pediatric patients. In any case, you’ll find that having a “window” to the airway is an invaluable way to effectively monitor ventilation. Once you experience the comfort of hearing breath-by-breath that your patient is adequately breathing, a pretracheal stethoscope may well be a tool you’ll not want to be without.