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Capnography’s Role in Traumatic Airway Intubation

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Does your system have specific protocols on managing ventilation of head-injured patients? Photo Courtesy Christopher T. Stephens, MD


Greetings colleagues,

To begin this last article in the three-part series on managing the traumatic airway, let’s review briefly what has been done at this point. Either you have successfully or unsuccessfully intubated your trauma patient, have gone for a supraglottic airway device or have chosen to hand ventilate the patient during transport with an oral/nasal airway and bag-valve mask (BVM).

The only other option is a surgical airway. We will briefly review these techniques but I warn that you MUST practice these on suitable mannequins or cadavers in a laboratory setting. Another alternative is to purchase some pig tracheas or similar and practice your surgical skills on these.

The point is that practice allows you to appreciate the anatomy and understand the skill. Most EMS protocols use a needle cricothyroidotomy technique in which the cricothyroid membrane is identified between the thyroid and cricoid cartilages. (I encourage you to identify this important landmark on yourself, then your family and friends, followed by practicing on your patients as part of your physical exam.) Once you’re comfortable finding this landmark on many people, it will come second nature in an emergency. Be certain that you’re familiar with the needle cric device/supplies that your system uses; once the needle is in place, either a wire is placed through it to allow for a trochar tracheostomy tube to be placed over the wire or the large bore catheter remains in place for ventilating with a BVM.

Again, however your service trains and uses this technique, be sure to cover it regularly with training. An alternate technique is the open surgical cricothyroidotomy, where a scalpel is used to make a vertical incision over the cricothyroid membrane to identify the membrane. Once identified, make a horizontal stab with the scalpel, followed by flipping the scalpel and placing the handle end in the incision and twisting 90 degrees to enlarge the opening.

At this point, there’s likely a fair amount of blood to deal with so make certain that your partner has suction and 4X4s to blot away the blood. Now you can do one of two things. You can go straight for a smaller endotracheal tube (ETT), such as a 6.0 or 6.5, and place it in the surgical opening. Or you can place a bougie intubating stylet into the opening so that you have something in the airway to guide your ETT over and into the trachea. This is a nice technique to use so that you don’t lose your surgical opening while trying to place the ETT into the hole. Try this on the cadaver, animal tracheas or appropriate mannequin. There are many ways to accomplish a surgical airway and these are some of the ways that we have found useful for teaching our local medics.

So now you have an airway to manage en route to the hospital. We will assume that you have an intubated patient from the case introduced in the first article of the series, “Managing the Traumatic Airway.” Once the tube is secured and you are ready for transport, be certain to re-assess the tube placement once packaged in the ambulance or aircraft. I still find many right mainstem intubations once delivered to me at the trauma center.

Once you’ve determined that the patient has bilateral breath sounds and equal chest expansion, take a quick look at your capnography monitor and pulse oximeter. Are you happy with the waveforms and numbers? These numbers can guide your therapy and airway management throughout transport. Is the patient on 100% FiO2? Be certain that oxygen is reaching the patient! Do you need to suction out the ETT? Make sure that you are able to adequately exchange gases via the ETT for your patient throughout transport.

This is where capnography is so valuable. If your patient still has a blood pressure and pulses, you should pay very close attention to your capnograph waveform. It will let you know if there’s an obstruction between your patient and the end of the ETT by the slope of the waveform. In addition, it will give you insight into your patient’s perfusion status. If a nice, normal waveform is present, then your patient is perfusing adequately enough for cellular respiration to take place.

Note: Your patient may still be in the early stages of shock, and you should always be vigilant for signs of continued blood loss. If your patient is in profound shock, in extremis or arresting, then your capnograph waveform will be distorted with low numbers. Again, this monitor is important for you to use and understand for your intubated patient management in the field. Please take the time to read about, practice and understand waveform capnography. Spend some time in the emergency department looking at ventilated patients who have capnography waveforms on the monitor. This will help you begin to understand the concepts of using this important monitor for sick patients.

If your patient has signs of a traumatic brain injury, what you do with your ventilation management becomes VERY important. You must maintain your end¬-tidal carbon dioxide numbers between 30–35 mmHG to prevent either hypo- or hyperventilation with subsequent cerebral perfusion abnormalities. Please read up on this and discuss with your medical director. Only patients showing signs of tentorial herniation should be mildly hyperventilated in the field, avoiding end tidals lower than 28 mmHg!

Poll Question: Does your system have specific protocols on managing ventilation of head-injured patients?

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If your system still isn’t using continuous capnography on your monitor, it will be important for you to at least monitor continuous pulse oximetry and end-tidal using a colorometric easy cap device during transport to ensure correct tube placement. We all need to aim for zero misplaced endotracheal tubes in the field. If there is ANY doubt, take the tube out! This is a very important concept. It’s much better to assist an airway with a BVM and oral/nasal airway (or a supraglottic device) than have a misplaced tube on arrival at the trauma center!

I hope that these articles have given you some tools to use in the field when faced with a trauma airway. Remember to read, discuss with colleagues and medical directors, and practice airway maneuvers whenever possible! A great place to start is by attending a cadaver airway lab in your area or sign up for one at a national conference. I wish each of you the best of luck in your EMS career and please feel free to contact me anytime with questions or concerns. I am here for all of you field providers! Work hard and do the very best for your patients.

Part I: Managing the Traumatic Airway
Part II: Trauma Airway Intubation Is a Team Effort

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Christopher T. Stephens, MD, MS, NREMT-P

Completed BS in Biology from Loyola Marymount University. Completed paramedic school at Houston Community College and trained with the Houston Fire Department. Paramedic in Houston, Texas and Galveston, Texas. University of Houston College of Pharmacy (MS in Pharmacology), University of Texas Medical Branch School of Medicine – (MD, Anesthesiology Residency) Trauma Anesthesiology Fellowship – University of Maryland Shock Trauma Center Currently Assistant Professor of Anesthesiology at University of Maryland School of Medicine and Attending Trauma Anesthesiologist - R Adams Cowley Shock Trauma Center, Baltimore, MD. Director of Education, Division of Trauma Anesthesiology, R Adams Cowley Shock Trauma Center. Medical Director, Maryland Fire&Rescue Institute. Instructor for Maryland State Police Aviation Command; Flight Physician, Tactical Physician

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Roadmap to the Glottis

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When we intubate a patient, all we really want to do is place the endotracheal tube in the glottis. Let’s face it, the glottic opening can be a tough feature to locate on a good day, let alone wh

To get two the epiglottis and the posterior cartilages, your two new best intubation buddies, you have to get past the tongue first. Illustration JEMS/Wainwright Media

en things just aren’t going well. Blood, vomit, laryngospasms, edema; you know the drill. If you want to find the glottis, stop looking for the glottis. What? Read on, friends, I’ll show you.

Anatomy of the Larynx
The larynx is made up of three single cartilages and three pairs of cartilages.

The thyroid is the largest of the laryngeal cartilages. It’s within this cartilage that the glottis is located. The anterior ends of the vocal cords are attached to the thyroid cartilage. This feature gives us the ability to directly move the glottis to improve our view. Known by different names, external laryngeal manipulation (ELM), backward upward rightward pressure (BURP), digital physical laryngeal manipulation; the procedure of manipulating the thyroid cartilage to optimize the glottic view has been described for many years.(1–3)

The cricoid cartilage, the most inferior of the laryngeal cartilages, is the only laryngeal cartilage that’s a complete ring. In pediatric airway, the cricoid cartilage is the narrowest part of the airway. Non-cuffed tubes fit snuggly into the ring to prevent air leak. Cricoid pressure has been used to improve glottic view during laryngoscopy, but I think you will find that laryngeal manipulation does a better job of optimizing the glottic view. One of the very best studies I’ve read on the use of cricoid pressure was published in 2007. The authors concluded, “We recommend that the removal of cricoid pressure be an immediate consideration if there is any difficulty either intubating or ventilating the ED patient.”(4) As an airway professional, you owe it to yourself to read the entire study.

Let me now introduce to you, straight from the back of the tongue—the most important airway landmark, the intubator’s very best airway friend, the gateway to the glottis—THE EPIGLOTTIS!

Remember when I told you to stop looking for the glottis? I want you to start looking for the epiglottis. Remember from our last lesson that the inferior (extrinsic) tongue muscles are connected to the mandible, hyoid and epiglottis. We can use that connection to locate the epiglottis. I’ve found the epiglottis to be easier to locate on a more reliable basis for both novice and experienced providers. Sounds like a study in the making.

Try this: Insert the laryngoscope blade into the patient’s mouth and just follow the tongue posteriorly until you locate the epiglottis. Lift the epiglottis and there’s the glottic opening. Most of the time, it’s just that easy.

Posterior Cartilages
The second best friend of the intubator is the group of three pairs of cartilages, which lie along the posterior border of the glottic opening; the corniculate, cunneiform and aryetnoid cartilages. The arytenoids sit on top of the posterior portion of the cricoid cartilage. The posterior end of each vocal cord is attached to an arytenoid cartilage. The length and medial-lateral positioning of the vocal cords are accomplished by movements of the arytenoids. The arytenoids can’t be seen in the standard laryngospic view because they’re buried in tissue.

The corniculates sit on top of the arytenoids and are seen during laryngoscopy immediately lateral to the interarytenoid notch. The cureiform are embedded in the aryepiglottic folds. They give support to these membranes, which connect the arytenoids to the epiglottis. In the standard laryngoscopic view, the cuneiform can be seen immediately lateral to each of the corniculates.

Collectively these cartilages go by a variety of names: the arytenoids, posterior cartilages, nodes. Regardless of which term you use, know that they are the posterior border of the opening to the glottis and are identified by a notch in the middle and two pairs of bumps on either side.

Conclusion
So there you are. Your new best intubation buddy is the epiglottis, and your second best buddy, the posterior cartilages. I find it ironic that these most helpful features lay right behind our nemesis, the tongue. A good knowledge of the airway anatomy is really a roadmap to success. Bust open that A&P book that you’ve got shoved up there on the shelf. It will make you a better provider.

Take care and be safe.
Charlie

References
1. Benumof JL & Cooper SD. Qualitative improvement in laryngoscopic view by optimal external laryngeal manipulation. J Clin Anesth. 1996;8(2):136–140.
2. Knill RL. Difficult laryngoscopy made easy with a “BURP.” Can J Anaesth.1993;40(3):279–282.
3. Levitan RM, Mickler & Hollander JE. Bimanual laryngoscopy: A videographic study of external laryngeal manipulation by novice intubators. Ann Emerg Med. 2002;40(1):30–37.
4. Ellis DY, Harris T & Zideman D. Cricoid pressure in emergency department rapid sequence tracheal intubations: a risk-benefit analysis. Ann of Emer Med. 2007;50(6): 653–665

Watch a video of Charlie explaining how to visualize the glottis.

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Charlie Eisele, BS, NREMT-P

Charlie Eisele, BS, NREMT-P has been active in EMS since 1975. After 22 years of service, he recently retired from the Maryland State Police, Aviation Command where he served as a State Trooper, flight paramedic, instructor, flight operations supervisor, director of training, and tactical paramedic. For over 25 years, Charlie has been a collegiate level educator and curriculum developer. He has served numerous programs including the University of Maryland, and its R Adams Cowley Shock Trauma Center, College of Southern Maryland, Grand Canyon National Park, Marine Corps Base Quantico, Virginia Department of Fire Programs, and Maryland State Police. Charlie is the co-developer of the internationally delivered advanced airway program at the R Adams Cowley Shock Trauma Center. He is the Airway and Cadaver Lab Course manager for the University of Maryland critical care emergency medical transport program. He’s the co-developer of the EMS Today airway and cadaver lab program. Charlie has been recruited nationally to provide airway management curriculum and education for a variety of private, federal, state and local organization. Charlie is an Eagle Scout and a published author. He serves on the Journal of Emergency Medical Services Editorial Board and is a member of the program board for the EMS Today Conference & Exposition.

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