Tag Archive | "ETCO2"

Four Reasons Why Intubation During Cardiac Arrest Doesn’t Always Work


In “Intubation for Cardiac Arrest Patients,” author Samuel M. Galvagno Jr., DO, PhD, identifies several reasons why intubation has not been shown to positively impact outcomes for cardiac arrest patients.

First, intubation during cardiac arrest is not always straightforward, and in at least one study, 30% of patients required more than one attempt.(1)

Second, the learning curve to attain competence is steep—one study suggests up to 60 intubations are required to become proficient—and in some systems, EMS providers do not have opportunities maintain this skill.(2) As Nable et al write, “maintaining proficiency in endotracheal intubation is a significant barrier for many prehospital providers.”(3) In Wang et al, intubation success by medics was only 78%.(1)

Third, intubation is followed by positive pressure ventilation (PPV), and PPV has been shown to decrease preload, lower cardiac output, and negatively impact the effectiveness of chest compressions.(3)

Fourth, intubation may require interruption of chest compressions, and this has clearly been linked with worse outcomes.(4) For the abovementioned reasons, in some countries, such as the U.K., a case has been made for abandoning intubation altogether in cardiac arrest.(5)

References
1. Wang HE, Yealy DM. How many attempts are required to accomplish out-of-hospital endotracheal intubation? AcadEmerg Med. 2006;13:373–377.

2. West MR, Jonas MM, Adams AP, et al. A new tracheal tube for difficult intubation. Br J Anaesth. 1996;76:673–679.

3. Nable JV, Lawner BJ, Stephens CT. Airway management in cardiac arrest. Emerg Med Clin N Am. 2012;30:77–90.

4. Kellum MJ, Kennedy KW, Ewy GA. Cardiocerebral resuscitation improves survival of patients with out-of-hospital cardiac arrest. Am J Med. 2006;119:335–340.

5. Deakin CD, Clarke T, Nolan J. A critical reassessment of ambulance service airway management in prehospital care: Joint Royal Colleges Ambulance Liaison Committee Airway Working Group. Emerg Med J. 2008;27:226–233.

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Color Ranges of a Typical Colorimetric Device


End-tidal carbon dioxide (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%

Tip from Oxygenation & Ventilation Are Not the Same Thing.

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Oxygenation & Ventilation Are Not the Same Thing


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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Ways to Confirm Proper Endotracheal Tube Placement


In “Trauma Airway Intubation Is a Team Effort,” author Christopher T. Stephens, MD, MS, NREMT-P, stresses the importance of confirming proper endotracheal tube placement. He lists several ways this is done:

Chest rise;
Bilateral breath sounds;
Tube fogging;
Calorimetric end-tidal carbon dioxide; and
Continuous waveform capnography.

Continuous waveform capnography ideally should be used by every paramedic unit that’s intubating patients in the field. This will be discussed further in the next article, due out Feb. 8. Stay tuned for more!

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Trauma Airway Intubation Is a Team Effort


Field intubation of trauma patients should be a team effort.

Have a checklist for intubation of trauma patients, and assign your assisting colleagues a role to ensure success on the first attempt. Photo Courtesy Christopher T. Stephens, MD, MS, NREMPT-P


Greetings colleagues!

As the second part of this three-part series on the traumatic airway, we will now focus on intubating the trauma patient case that was introduced in the previous article, “Managing the Traumatic Airway.”

(Missed the first part of this three-part series? Click here to read Part I.)

Why is intubation of trauma patients being scrutinized across the nation, you ask? As an instructor of trauma airway management, I can assure you that it isn’t because you as field providers don’t know how to effectively intubate! In short, there are studies (whether sound or not) that are suggesting worse outcomes in patients who are intubated in the field.

So what, you ask? Sicker patients are sicker and need an endotracheal tube, right? Everyone agrees that there are some patients out there who just need to be intubated. Obstructed airways, vomit, blood and poor anatomy make traumatic airways challenging to manage in the field. In fact, these airways can be challenging in the trauma centers as well. Many patients simply can’t be oxygenated and ventilated effectively with a supraglottic airway—a or bag-valve mask (BVM) and oral airway for that matter, right? These are the cases that get our sympathetic nervous system going and put us in that position where “critical decision making” becomes extremely important.

The Intubation
So you have decided to intubate this trauma patient—who is 110 kg and looks like a small linebacker for your local professional football team. Here are some questions for you:

1. What help do you have?
2. What environment are you in (i.e., street, ditch or ambulance)?
3. Are you able to effectively oxygenate/ventilate this patient with basic tools as discussed previously?
4. Will you plan to do a blind nasal intubation or drug-facilitated oral intubation (rapid sequence intubation/RSI)?

These are some of the questions that must be thought about ahead of time, and a plan must have already been made so that the EMS team can be successful.

I like to teach EMTs and paramedics to think like pilots. Have a checklist and start at the top and work your way down. You will never miss anything this way. Assign your assisting colleagues a role to get the patient intubated successfully on the first attempt.

Ideally, you should have four EMS providers to intubate a trauma patient. The team leader is the one intubating. At this point, the team leader should be assisting the patient’s airway and pre-oxygenating with 100% oxygen via a BVM. Pre-oxygenation is VERY important. It will buy you more time to get that tube in the right hole. You should do this for blind nasal intubations as well. Trauma patients tend to desaturate at an alarming rate because most have been hypoventilating to this point due to pain, semiconsciousness, pneumo- or hemothoraces, etc. And remember, all trauma patients are full stomachs. Some have already aspirated prior to your arrival, which also works against you. All of these conditions make your intubation attempts less forgiving, and you must be prepared to act quickly if the patient becomes challenging and/or desaturates.

Once you have pre-oxygenated your patient for at least 60 seconds, attempt your intubation. If it’s a blind nasal intubation, you may have more time because the patient is still breathing. You also have the luxury to just assist them to the hospital if it fails. If you’re planning a drug-facilitated intubation, then all bets are off. Once you have decided to push drugs, you had better have your skills, colleagues and equipment ready for action.

During pre-oxygenation of the patient, the team leader must assign roles. The second medic will draw up and be responsible for pushing drugs, then handing supplies to the intubating team leader (i.e., endotracheal tube, suction, bougie, another blade, video laryngoscope, etc).

The third provider is responsible for removing the front of the cervical collar (yes, the front of the c-collar MUST be removed PRIOR to laryngoscopy) and holding cricoid pressure correctly. Note: Cricoid pressure needs to be learned correctly and practiced. Some protocols have done away with cricoid pressure; I feel that it’s still an important tool to be used in traumatic airways with full stomachs.

The fourth provider will hold in-line manual stabilization of the cervical spine throughout the intubation. When the team leader states that they’re ready, the second medic should push the appropriate drugs and appropriate doses. This is a decision that has to be made correctly and using expert paramedic critical decision techniques. Understanding the physiology/pharmacology of rapid sequence intubation (RSI) is as important as the skill itself. How sick is the patient? What are their vital signs prior to pushing drugs? Do they have pulses (central or peripheral?) Are they in shock? Do they have signs of a head injury?

Which of roles below do you most often play during the field intubation of a trauma patient?

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These are questions that must be answered during a rapid primary and secondary survey while preparing to intubate the patient. Is the patient combative due to shock, head injury, alcohol/drugs, or all of the above? If able, try and get a baseline set of vital signs prior to pushing drugs. This will help guide your drug choice and dosing. Drug selection and dosing is an EXTREMELY important topic for trauma patients and should be discussed at length with your medical director and training supervisors. Anesthetic agents are powerful and can make patients worse if used incorrectly.

There are many issues to think about when dealing with a traumatic airway, and hopefully you will have some time to work through a good plan of action so if things start to go wrong, your checklist and plan will be there for you to fall back on.

Once the patient has been relaxed with succinylcholine or an alternative paralytic agent, the team leader should perform their laryngoscopy with the blade they’re most comfortable using. Remember, your first shot is always your best shot! I teach trauma airways with a Macintosh 3 blade for most adults because I find it easier for medics and trainees to keep the tongue out of the way with the wider Macintosh blade.

As an alternative, you may also use a video laryngoscope, such as the Glidescope Ranger, for your intubation. The Glidescope Ranger has been useful for managing traumatic airways. It allows everyone assisting to see what the team leader is seeing, which can therefore help them anticipate what the team leader may need to get the job done, such as suction, bougie or a smaller endotracheal tube. As with any piece of airway equipment, there’s a learning curve with video laryngoscopy. You must practice it on mannequins, cadavers in airway labs and on live patients in the operating room, if possible.

I want to say a few words about the intubating stylet or bougie. Since I manage traumatic airways for a living, in my opinion, the bougie is the single most important piece of intubating equipment. This little flexible styllete has been my savior during many a difficult airway in the trauma center. That being said, a bougie and video laryngoscope is a VERY effective combination of equipment to intubate the trauma patient. I encourage each of you to grab an airway mannequin, a bougie and a demo Glidescope Ranger and practice this technique. This is going to be the wave of the future for airway management, especially in the uncontrolled field environment, where help can be lacking.

If you can’t see a view of the vocal cords or confirm the tube to be in the esophagus, you must go to Plan B. This may include changing blades, switching to a video laryngoscope, or perhaps allowing another, more-experienced airway operator to assist. Do NOT forget to attempt oxygenating and ventilating the patient with an oral/nasal airway and BVM between intubation attempts. Do your best to get the patient as close to 100% oxygen saturation as possible prior to your next intubation attempt.

If the second attempt fails, consider either placing a supraglottic airway device or simply performing BVM assisted ventilations with an oral/nasal airway throughout transport. Remember, this technique sometimes requires two rescuers to perform adequately. If you can’t intubate and can’t ventilate the patient, you must proceed to a surgical airway—either a needle or open surgical cricothyroidotomy. We will discuss this in the next article.

The Confirmation
Once the endotracheal tube is placed, it’s important for tube confirmation to be established. This can be done in many ways. Chest rise and bilateral breath sounds are important but can sometimes be misleading. If the patient is warm and still perfusing, tube fogging should be noted, as well as end-tidal carbon dioxide (ETCO2). Either an easy cap (calorimetric) ETCO2 or continuous waveform capnography should be employed as the gold standard for tube confirmation. Continuous waveform capnography ideally should be used by every medic unit that’s intubating patients in the field. This will be discussed further in the next article.

Once the correct tube location is confirmed, be certain that the tube is secured well, the cervical collar is replaced, and the tube location is reassessed after securing because tubes sometimes migrate into the right mainstem bronchus when being secured. At this point, you’re still not out of the woods! Now that you have successfully intubated the patient, you must worry about their physiology while transporting. This is a point that many field providers dismiss when managing airways in the field and a topic that may prevent medical directors from removing intubation from protocols around the nation. So there you have it—four providers ideally to get the task done correctly!

Stay tuned for the final article in this series of managing the traumatic airway.

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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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