Tag Archive | "end-tidal co2"

The Five Ws of Intubation

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Ask yourself “w” questions (i.e., who, what, when, where and why) when starting an intubation. Photo iStockPhoto.com

We learned that airway comes first in the very first class all of us took in EMS. Up until the recent changes in the American Heart Association guidelines, we had the following mantra stuck in our heads: “Annie, Annie, are you OK?” We were to open the airway, then look, listen and feel. So when it comes to managing the airway in the field, this is the first priority and often the most overwhelming to EMS providers.

Airways can be simple or complex depending on the particular patient, the environment and the experience of the provider. The gold standard for a secure airway, however, the ultimate goal is oxygenation with successful first-time insertion of the endotracheal tube (ETT).We reserve the ETT for a particular patient population in the EMS community. Let’s call them the “who.”

Who & When
The “who or “when” would be those patients who are unable to protect their own airways, who are apneic or who require ventilator support—either manually or by ventilator.

In some cases, selecting this group is obvious. If they can’t breathe on their own, then someone or something needs to do it for them. In other patients, it’s a little harder to determine whether we need to intervene with the airway. This is where we providers need to read the signs or look at tea leaves for guidance. We find signs in our assessment with things like rate and quality of respiration, end-tidal CO2, skin color, work of breathing and pulse oximetry. And sometimes, you’ve gotta ask yourself, “What are the voices telling me?”

Sometimes we providers become a bit anxious, regardless of our level of certifications, licensure or experience, about placing an ETT and controlling a patient’s ability to breathe spontaneously. A good example of this is the provider that doesn’t have the correct medications or the experience to perform a rapid sequence intubation (RSI) on a patient, so they attempt to “snow” the patient with narcotics or try to muscle past the patient’s gag reflex. We’re all guilty of this in some form or fashion at some point in our careers. I sometimes hear providers (including physicians) say, “I did the best with what I had.” Is this really our best? Maybe looking at other options and supportive care that is more time consuming, less glorious and in the best interest of the patient would be the better choice.

What
“What” are we really attempting to do when we intubate using direct laryngoscopy? The simple explanation would be to place a tube into the patient’s trachea to allow for ventilation. This is easier said than done. It’s simple enough in concept but requires us to displace the anatomy that stands between the oral opening and the trachea. Part of this challenge is m the largest obstacle in the airway—the tongue. We need to move it out of the visual field to be able to see the laryngeal structures. Usually when you encounter that huge floppy tongue, there’s a big floppy epiglottis attached to the base of it. If you don’t see it right away, look in the pool of pizza, beans and beer oozing out of the airway, lying in the back of the posterior oral pharynx.

What's the structure at the base of the tongue that prevents aspiration?

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Complicating the patient’s own anatomy is the fact that we’re trying to place a large metal stick in this small space and make enough room to guide the ETT through it to the trachea without inadvertently placing it in the esophagus. If we understand the anatomical structures and how they move, we can use that to successfully manipulate the airway.

One of the most common mistakes I see is when providers attempt to pry with the laryngoyscope blade as opposed to lifting the structures. Remember that the structures we’re attempting to displace are still attached to the patient by a large hinge joint known as the jaw, or mandible. If we displace the jaw, the soft structures attached will follow. This holds true for correct manipulation as well as incorrect ones. If we pry back toward the patient’s head, then all the structures we’re attempting to move out of our way are simply coming up in our face. You may hear this referred to as rocking or prying. It’s often associated with contact with the teeth and pulling the oral opening closed.

The most common cause of that is holding high on the laryngoscope handle and using the 90-degree angle of the handle and blade as the fulcrum and rocking back. Remember basic physics from high school? “Every action has an equal and opposite reaction.” If you’re pulling back on the stick, the other end of the stick is going to react as well and pull the structures right into your view. If we lift the stick up and away, say toward the corner of the ceiling, the jaw will lift and the tongue and epiglottis will follow.

Where
“Where” makes a difference—whether it’s on the cot, in the door, on the floor, in the dark on a train and in the rain. (This is starting to sound like a Dr. Seuss book, but it really is true.) We should make our first attempt our best attempt, so we should try to pick a place or modify the conditions to create our best attempt. If we can get the patient to the stretcher and an elevation and position that enhances our ability to obtain direct visualization of the airway, we’re setting ourselves up for success.

One bad habit I see providers have in the field is to slide the patient to the end of the cot and allow their head to hang back or attempting to intubate with the cervical collar in place. Again, think about the anatomy, have you ever tried to talk with a cervical collar on or hang your head over the back of the chair you’re sitting in? Did you notice that your chin was pointing one direction and your airway was going the other? Provide the patient has no cervical injury the ideal position would be to lift the patients head so to bring their ears even with their chest, you may hear this referred to as ear-to-sternal notch or a wedge technique.

Another great trick you might want to think about is a concept that Dr. Richard Levitan introduced in his book, “The Airway Cam Guide to Intubation and Practical Emergency Airway Management”, ELM or bimanual laryngoscopy, where the intubator actually will manipulate the trachea to bring the glottis opening into view. If the patient has a suspected cervical spine injury, hold inline stabilization while another provider secures the airway, allowing the jaw to be manipulated without restriction. We can’t always relocate the patient when we need to control the airway, so try to use gravity and the patient’s own anatomy to assist in locating and securing the airway.

Why & How
That would leave us with two final questions: why and how. The “why” is pretty simple, to oxygenate my patient. However, that is easier said than done because many of the airway adjuncts we use and the oxygen delivery system are subject to human error, failure or misuse result in injury to the patient, hyper- or hypo-oxygenation, so we must constantly reassess to ensure we are providing adequate oxygenation in a safe manner.

Finally comes the “how?” The simple answer is to do things with the easiest, safest and most efficient means possible. Every situation is different; some patients may require a simple oropharyngeal airway (OPA), a few breaths and transport. Another may need RSI, a definitive airway and the use of video laryngoscopy, which uses a camera and a video monitor to visualize the airway and the glottis, enabling faster intubation. A few may even need a surgical airway.

What benefit might video laryngoscope have that traditional direct laryngoscope does not?

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Conclusion
The patient, the situation, the patient’s illness or injury, the provider’s experience, and the resources available will determine the tools and means of airway control. Ultimately you have to have an airway plan tattooed on your brain so it’s right there every time you need to manage an airway. We’ll save that discussion for another day.

I hope the next time you pick up a laryngoscope or an endotracheal tube you ask yourself these simple questions: who, what, where, when, why and how. Hope to see you soon.

Stay safe,
Jim Radcliffe, BS, MBA, EMT-P

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Oxygenation & Ventilation Are Not the Same Thing

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Combine capnography with pulse oximetry when monitoring ventilation and oxygenation in the prehospital environment. Photos Courtesy Jim Brown, Maryland Institute of Emergency Medical Services Systems

I recently observed a paramedic who made one of the most difficult prehospital clinical decisions I have seen during my 16 years of involvement in prehospital care. We were notified that a motor vehicle crash patient was inbound by helicopter, Category A (the highest in Maryland). Details about the crash were scant, and while the patient was swiftly rolled into our trauma resuscitation unit, I nearly stepped on a slippery, blood-laden tubular object that had fallen off the backboard—the endotracheal tube.

The flight paramedic proceeded to tell me that the patient had been intubated in the field and although there had been an appropriate colorimetric change on the CO2 detection device, lung sounds were difficult to appreciate en route and capnographic waveforms were absent. Yet, the patient’s pulse oximeter continued to read 99% the entire time. Nevertheless, the paramedic pulled the tube shortly before arrival, and proceeded to mask ventilate the patient with an oral airway. One might ask, “What on Earth was this paramedic thinking?”

As it turned out, the paramedic made a difficult but supremely commendable and 100% appropriate decision to extubate the patient. The medic later admitted that he struggled with the decision to remove what was thought to be a “perfectly good endotracheal tube.” But in the end, he knew the difference between ventilation and oxygenation, and based on his assessment, he knew that the former was not being accomplished, and that failure of the later would quickly ensue. These two separate—although highly related—processes are often confused and frequently misunderstood, and comprehending the difference is critical in the prehospital arena. Advanced technologies have an important role in monitoring ventilation and oxygenation, and an understanding of the limitations of these devices is a prerequisite for effective use.

Ventilation vs. Oxygenation
Ventilation and oxygenation are separate physiological processes. Ventilation is the act or process of inhaling and exhaling. To evaluate the adequacy of ventilation, a provider must exercise eternal vigilance. Chest rise, compliance (as assessed by the feel of the bag-valve mask), and respiratory rate are qualitative clinical signs that should be used to evaluate the adequacy of ventilation. Capnography, long the standard of care in the operating room and intensive care unit, can also be used to assess ventilation. Also, continuous quantitative waveform capnography has become the standard of care for monitoring endotracheal tube placement.(1) Capnography can be used to assess end-tidal carbon dioxide ( EtCO2) concentration or tension. Normal values of EtCO2 are 35-37 mmHg, and in normal lungs, the EtCO2 approximates the arterial CO2 concentration in the blood with a value that is usually lower by 2 to 5 mmHg.(2) Use of capnography is not limited to intubated patients; nasal cannulas and face masks can be modified to detect EtCO2.

Do you regularly use quantitative waveform capnography?

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EtCO2 can be measured by colorimetry and capnography. Colorimetric devices provide continuous, semi-quantitative EtCO2 monitoring. A typical device has the following three color ranges:

Purple—EtCO2 is less than 0.5%
Tan—EtCO2 is 0.5–2%
Yellow—EtCO2 is greater than 2%

Normal EtCO2 is greater than 4%; hence, the device should turn yellow when the endotracheal tube is inserted in patients with intact circulation.(2) False positives may occur when the device is contaminated with acidic substances, such as gastric acid, lidocaine or epinephrine. The device will not provide an accurate reading it is expired or if the tube is clogged with secretions. Causes of increased or decreased EtCO2 are listed in Table 1.(2) One of the most common causes of increased EtCO2 is hypoventilation, since CO2 cannot be removed from the body when air exchange is impaired.

Capnography provides both a waveform and digital reading (mmHg of CO2 in exhaled gas). Capnography is no longer merely a standard for the operating rooms; it is a standard for ensuring ventilation after intubation anywhere, and it is now a fundamental objective means for assessing the adequacy of CPR.(1) For example, if the EtCO2 is less than 10 mmHg, the American Heart Association recommends optimizing chest compressions to improve the quality of CPR.(1,3–4) Capnography has prognostic value for trauma and cardiac arrest patients, and it correlates well with such other physiologic parameters as coronary perfusion pressure and cardiac output.(5) For a more in-depth discussion of the physics and use of capnography in the prehospital setting, visit www.capnography.com.

The pulse oximeter is a good way to ensure adequate oxygenation of your patients.

Oxygenation refers to the process of adding oxygen to the body system. There is no way to reliably measure arterial oxygenation via clinical signs alone. Cyanosis, pallor and other physical findings are not reliable. The pulse oximeter, which relies on a spectral analysis of oxygenated and reduced hemoglobin as governed by the Beer-Lambert law, represents the principle means of assuring adequate oxygenation in a patient.(2) Saturation of peripheral oxygen (SpO2) levels measured with a pulse oximeter correlate highly with arterial oxygenation concentrations.(6) An easy way to remember the correlation between SpO2 and approximate partial pressure of oxygen in arterial blood (PaO2) is presented in Table 2.

Despite years of use in a wide variety of settings, even experienced physicians and nurses have significant knowledge deficits regarding the limitations and interpretation of pulse oximetry.(7–9) Pulse oximetry has several limitations. Hypoxia follows hypoventilation, and it may take 30 seconds or more for the pulse oximeter to reflect conditions of life-threatening hypoxia. Relying on the pulse oximeter alone can decrease the margin of safety because corrective actions taken after the pulse oximeter falls may be too late. Hypovolemia, vasoconstriction, peripheral vascular disease or nail polish may cause false readings. It should be noted that pulse oximetry, while a significant technological advance over the past 20 years, has not been reliably shown in all studies to improve outcomes.(10) However, in studies based on closed claims data (i.e., lawsuits), the use of pulse oximetry, at least in the operating room, has been suggested to reduce the serious mishap rate by at least 35%.(11)

Pulse oximetry is superior to physical examination for monitoring ventilation.

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Conclusion
Ideally, when monitoring ventilation and oxygenation in the prehospital environment, capnography should be combined with pulse oximetry. With capnography, providers are able detect respiratory insufficiency early and are able to institute early interventions, thereby preventing arterial oxygen desaturation. However, as with any monitoring technology, the best “monitor” is the provider. Pulse oximeters and capnometers do not treat patients. Integrating the information from your monitors and clinical assessment to make sound clinical decisions is the key to successful airway management. As evidenced by the astute assessment and action of a paramedic, knowing the difference between ventilation and oxygenation is a critical concept that must be understood.

References
1. Neumar RW, Otto CW, Link MS, et al. Part 8: Adult advanced cardiovascular life support, 2010 American Heart Association Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2010;122[Suppl 3]:S729–S767.
2. Galvagno SM, Kodali BS. Critical monitoring issues outside the operating room. Anesthesiology Clin. 2009;27(1):141–156.
3. Lewis LM, Stothert J, Standeven J, et al. Correlation of end-tidal carbon dioxide to cerebral perfusion during CPR. Ann Emerg Med. 1992;21(9):1131–1134.
4. Callaham M, Barton C. Prediction of outcome of CPR from end-tidal carbon dioxide concentration. Crit Care Med. 1990;18(4):358–362.
5. Sanders AB, Atlas M, Wy GA, et al. Expired PCO2 as an index of coronary perfusion pressure. Am J Emerg Med. 1985;3(2):147–149.
6. Galvagno SM. Emergency Pathophysiology. Jackson, Wyo.: Teton NewMedia, 2004.
7. Sinex JE. Pulse oximetry: Principles and limitations. Am J Emerg Med. 1999;17(1):59–67.
8. Elliot M, Tate R, Page K. Do clinicians know how to use pulse oximetry? A literature review and clinical implications. Aust Crit Care. 2006;19(4):139–44.
9. Stoneham M, Saville G, Wilson I. Knowledge about pulse oximetry among medical and nursing staff. Lancet. 1994;344(8933):1339–1342.
10. Pedersen T, Dyrlund Pedersen B, Møller AM. Pulse oximetry for perioperative monitoring. Cochrane Database Syst Rev. 2003;3: CD002013.
11. Tinker J, Dull D, Caplan R, et al. Role of monitoring devices in prevention of anesthetic mishaps: a closed claims analysis. Anesthesiology. 1989;71(4): 541–546.

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Samuel M. Galvagno Jr., DO, PhD

Dr. Galvagno has been involved with prehospital care for more than 19 years. He started his EMS career as a National Ski Patroller in upstate New York, and became an EMT in 1992 in Maryland. Before and while attending medical school at the New York College of Osteopathic Medicine, he was a paramedic in Maryland and New York. He completed his internship at Saint Vincent’s Midtown Hospital in Hell’s Kitchen, New York before working as an emergency physician and flight surgeon in the U.S. Air Force. On leaving active duty, Dr. Galvagno received residency training at Harvard Medical School, Brigham and Woman’s Hospital, followed by a fellowship in Critical Care Medicine at the Johns Hopkins School of Medicine. He also completed a research fellowship and extensive training in epidemiology and biostatistics at the Johns Hopkins Bloomberg School of Public Health; he is due to receive his PhD in 2012 with a thesis focused on helicopter emergency medical services for adults with major trauma. Dr. Galvagno is the author of numerous publications and book chapters, including his own textbook, Emergency Pathophysiology. He is currently an assistant professor in the Divisions of Trauma Anesthesiology and Adult Critical Care Medicine at the R Adams Cowley Shock Trauma Center, Baltimore. He remains active in the U.S. Air Force, and is the director of critical care Air Transport Team (CCATT) operations and assistant chief of professional services at Joint Base Andrews, Maryland. He is board-certified in anesthesiology, adult critical care medicine and public health.

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