Tag Archive | "capnography"

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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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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Capnography’s Role in Traumatic Airway Intubation


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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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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