Monitoring Breathing in the Sedated Patient

By Rose Dodson    

Monitoring Ventilation with a Bluetooth Stethoscope

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.

image on white paper

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. Headset-SR068 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.

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What type of CO2 sampling line?

You’ve finally decided on a monitor. Good for you. That was a feat in itself. Now it’s time to decide on the method you will use to sample the CO2.

The first thing to consider when choosing the type of sampling line or “sampling” cannula for monitoring CO2 is the type of monitor that you have.  Monitors such as Criticare, Mindray and Datascope,  require a male luer lock on the monitor side of the tubing.   On the other hand, brands such as EDAN and Welch Allyn  require a female luer on the monitor side of the sampling line or cannula.

CO2 Sampling Lines

Male and Female Luer Locks

The next consideration would be the patient side of the equation. With that comes the question:

Do you deliver supplemental oxygen and how?   Through an oxygen cannula or with a nitrous hood?

1. We occasionally deliver supplemental oxygen, but not always.

One effective way of monitoring CO2 in a non intubated patient, is through a nasal sampling cannula.

Nasal Sampling Cannula

Permits EtCO2 sampling during spontaneous breathing.

It is a specific  “sampling cannula” designed for CO2 monitoring.  It is not your standard 50 cent oxygen cannula….more like a $4 cannula. With this sampling cannula you will sample CO2 through both nostrils. Therefore the CO2 value will be more stable as you are obtaining a greater amount of data with no additional gases being introduced other than room air.

Now, when you are ready to  deliver supplemental oxygen  you can set the nitrous hood on top of the sampling cannula or you could “piggyback” your oxygen cannula on top of the sampling cannula.   Obviously this can be a cumbersome method, but it is doeable. This would be considered a “stacked” or “piggyback” method of monitoring CO2.

2. We deliver supplemental oxygen through a cannula.

There  are specifically designed cannulas just for this purpose.  Each manufacturer has a slight variation in their design, as you can see from the diagram below.  

ETCO2 Cannula

A recent study at the Medical College of Wisconsin  shows that a “divided” cannula, such as, the one manufactured by Salter Labs is the only one that shows efficacy with respect to BOTH O2 delivery and CO2 measurement.  Some are more effective at delivering oxygen and others more effective at monitoring CO2.

Divided Cannula

Salter Divided Cannula

3. We use a nitrous hood to deliver oxygen.

Lastly,  if you use a nitrous hood to deliver your supplemental oxygen, you have a couple of options.

1.   Modify your nitrous hood and use a straight sampling line to connect directly to the nitrous hood (as shown in our previous post).

2.  Use a disposable custom designed nitrous hood and  connect to it using a straight sampling line.  Here’s an example of one by Accutron:

Nitrous hood with CO2

Accutron clear view hood with CO2

This should clear things up for you a bit.  If you have questions, don’t hesitate to ask.

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Water Trap–What’s That?

Every CO2 monitor has some form of collecting moisture. This is commonly referred to as a water trap or a moisture trap. In some cases, in lieu of a moisture trap a dehumidification tubing is used.

Patient Monitor Water Traps

Patient Monitor Water Traps

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How to Modify a Nitrous Hood to Monitor CO2

By Rose Dodson

nitrous hood CO2

It may sound complicated; however it’s actually quite simple. The same nitrous hood you use everyday can be adapted to monitor CO2. We’ll show you how.

 You will need only three items:

1. Nitrous Hood 


2. 1/8″ Hole Punch Pliers (commonly used for crafts)


3. Nitrous Hood Adapter 

nitrous hood adapter

First, use the hole punch or other cylindrical object to make a rounded hole in the nitrous hood near the top.  If you are using a hood with a liner,  then you will need to puncture through both the liner and the hood, as shown here.

porter nasal hood

You are now ready to attach your CO2 sampling line.  Attach the male luer lock end to the nasal hood adapter and the opposite end to the monitor.

Co2 LIne Nitrous Hood

Yep, it’s just that simple.

Good Luck and let us know if we can help.

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Understanding CO2 Monitor Options for Capnography

By Rose Dodson 

Stand Alone CO2 MonitorIf your practice needs to add capnography, you’ll need to understand the options for monitoring CO2.  Where should you begin?

In this blog post, we’ll help you with the initial considerations, then, we’ll explore the types of capnography units that are available.

As a starting point for this discussion, let’s consider a very common scenario:

Dr. Smith utilizes conscious sedation in his practice.  Last year he added two new operatories to his existing three-treatment room facility and purchased two multi parameter monitors.   He currently has three older Criticare Ngenuity monitors without CO2 monitoring and expects them to last a few more years before needing replacement.  The state board just passed a new regulation requiring that anyone who uses moderate sedation must monitor CO2.

What are the C02 monitoring options for Dr. Smith in this scenario?

1.      Was purchasing new monitors already on the agenda?

Dr. Smith had in fact talked to his office manager a few months ago about buying new monitors to replace the three older units. One of them has been having trouble and they were going to evaluate them again at the end of the year.

With the mandate, it seems to make sense to move forward with the purchase of three new multi parameter monitors. (Approximate cost $4500-$6000 each)

2.      Can existing monitors be upgraded to include a capnograph ?

Two of Dr. Smith’s monitors are still in warranty and it would be nice if they could be retrofitted to add the capnography.  Is that possible?

There is only one way to find out:  call the monitor’s manufacturer  and ask them. You will need the model number and serial number of the units when you call.  As a general rule, if the monitors are over five years old, the chances of an upgrade are not that good.

Dr. Smith called in to find out that his newer units are upgradeable, however the cost of adding a capnograph would be over $3000, which would be almost as much as purchasing a new unit.

3.      What about purchasing a unit that only monitors CO2 to go with the existing monitors?

Remember when an electrocardiogram became a requirement, and there was not a good option for purchasing a simple ECG monitor?  It was necessary to purchase a complete multi parameter patient monitor with an electrocardiogram built in.   Fortunately, the CO2 monitoring situation is different!

Simple, reliable CO2 monitors ARE available.  They are completely separate monitors that are relatively easy to use and cost less than half of a multi parameter monitor that includes CO2.  (Approximate cost $1800-$2000 each)

So, in light of these facts, what are the options for adding capnography to Dr. Smith’s office?

  •  Option 1: Purchase 5 NEW multi parameter monitors at an approximate total cost  of $22,500 – $30,000.
  •  Option 2:  Add stand alone capnographs to all 5 monitors at an approximate total cost of  $9000 – $10,000.
  •  Option 3: A hybrid approach—move forward with replacing the 3 older units with monitors that include capnography and add stand alone CO2 units to work with the 2 newer monitors at an approximate total cost of $17,100 – $22,000.

An added benefit of options #2 and #3 is that a stand alone CO2 monitor can serve as a backup.

Your practice situation will vary from this scenario, but this example should give you a framework for making a good decision about adding capnography to your practice.

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5 Tips To Keep Your Crash Cart Current

By: Rose Dodson
1.  Two Key Symbols to look for on the packaging.
 manufacture date symbolThis image tells you when it was manufactured .
symbol for expired drug
This tells you the date it expires.
For the most part you will be more concerned about the latter.


2. Checking expiration dates. Expiration dates on certain consumable crash cart items, such as emergency drugs, is a given. However, there are other disposable items that could be questionable.  For example airway devices such as I-Gels, LMAs, and ET tubes all have a specific shelf life and you should be able to find an expiration date on the packaging.

bag-valve-mask-all3. Consider shelf life and update accordingly. On the other hand a bag valve mask resuscitator (Ambu Bag) doesn’t have a specific shelf life and while you do want to consider updating them every few years, you probably won’t find an expiration date. In this case the manufactured date might be of value.  I would say after 5+ years, it’s probably time to consider updating your BVM.


4. Check the dates on your IO Device. For example if you have the EZ IO intraosseous drill, the needles expire about every 4 years.

5. Your AED.
Your AED has two separate components to consider when getting it up to date–The electrodes/pads and the battery. 
The electrodes have a conductive gel that will dry out over time, so it’s important that you keep these current. The standard shelf life is about 2 years, however there are certain companies such as Zoll that will not expire for about 5 years.Then there is the AED battery to consider. The expiration date or usefulness of the battery can vary quite a bit depending on the manufacturer. The standard would be 4-5 years. In some cases there will be an expiration date on the battery and in others you will only see the date of manufacture.
Keeping your crash cart up to date can seem like a daunting task. Hopefully this will clear up a few questions.
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