Tag Archives: EMS

FOAMed Resources Part VIII: EMS/Prehospital

Authors: Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC) and Manpreet Singh, MD (@MPrizzleER – emDOCs.net Associate Editor-in-Chief; Assistant Professor in Emergency Medicine / Department of Emergency Medicine – Harbor-UCLA Medical Center) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW Medical Center / Parkland Memorial Hospital)

The Prehospital environment is where emergency medicine begins. These providers are paramount in the initial stages of evaluation and management of critically ill patients. While most providers in the ED have medical or trauma rooms with adequate equipment and space, this is not the case for EMS. The stress, situation, and patient all present significant challenges to care providers.

The following list is comprised of blogs/podcasts with great education pearls, valid content, and major impact on EM, with clear reference citation. If you have found other great resources, please mention them in the comments below!


  1. https://prehospitalmed.com/tag/minh-le-cong/


Prehospital and Retrieval Medicine (PHARM) from Minh Le Cong is a fantastic prehospital resource with podcast and blog. Posts center on transport/retrieval medicine, airway, sedation, and prehospital critical care. This resource is a must for those with interest in airway, sedation, and EMS. Each podcast and blog post is well researched, providing succinct keys to success.


  1. http://emcrit.org/?s=prehospital


Scott Weingart’s blog and podcast contain several posts on cutting edge prehospital topics and procedures. REBOA, amputation care, hemostatic resuscitation, airway, sedation, hypothermia, and many more controversial topics are covered. These posts are well researched, with citations to the primary studies. Many of the prehospital podcasts contain interviews with experts in the field of prehospital medicine.


  1. http://www.fireemsblogs.com


Fire EMS Blogs is a network of sites covering EMS, rescue, hazmat, command, and training from San Diego. A wide variety of blogs are available including discussion of interesting cases, ECG interpretation, life as an EMS provider, and evidence-based medicine.


  1. http://hemscriticalcare.com


HEMS Critical Care from Philip Neuwirth brings together posts from blogs around the FOAMed universe pertaining to EMS/prehospital medicine into one place. If you’re interested in prehospital medicine and don’t have the time to regularly look through multiple online blogs, this resource does it for you.


  1. http://www.tamingthesru.com/hems-and-ems/


Taming the SRU is an all-around great resource concerning emergency medicine. The podcast and blog’s prehospital page covers topics including out-of-hospital cardiac arrest, stroke care, trauma, and STEMI. Posts and podcasts are thorough, and each podcast has a summary in bullet format.


  1. http://emfirstblog.com


EMFirst is dedicated to first responders and prehospital providers. Benjamin Ayd and Pratik Das cover classic and cutting edge EMS topics including TXA, REBOA, trauma, and ketamine. Not many posts are up now, but this site has a ton of potential.


  1. http://www.medicnerd.com


Medic Nerd from founder Mike Stewart seeks to provide enjoyable and effective EMS education through videos and blog posts. Videos explain physical exam findings, IV drip rates, prehospital procedures, interesting cases, and controversial studies. For those studying for a qualifying exam, flashcards are also provided (http://www.medicnerd.com/critical-care-paramedic-review-flashcards/).


  1. http://prehospitalwisdom.blogspot.com


Prehospital wisdom from Denver Paramedics is a blog with posts on EMS runs, interesting cases, and ECGs. Controversies in prehospital medicine are investigated, including C-spine protection, adenosine, distracting injury definition, and many others.


  1. http://resus.me/category/prehospital/


RESUS.ME has a complete prehospital section with EMS procedures, literature, and conferences. Posts provide key prehospital literature updates in a format that illuminates the key takeaways.


  1. http://www.ems12lead.com/


EMS 12-Lead is a leading resource for and by paramedics who are interested in all things EKG. Check out their posts to see EKG and cardiac rhythm analysis for patients in the field, and you can also submit your own case.


  1. http://www.scancrit.com


SCANCRIT is a blog covering anesthesia, critical care, and emergency medicine, with a focus on the critically ill patient. Posts are written by two Scandinavian anesthesiologists, who evaluate in-hospital and out-of-hospital medicine. Recent posts have investigated GCS, VF, hemorrhage evaluation and management, brain bleeds, and ATLS updates.

Thanks for reading our look at EMS resources. Comment below with other helpful sites!

Cervical Collars for C-Spine Trauma: The Facts

Authors: Joshua Bucher, MD (@JBucherMD – EMS Fellow and Attending Physician, Morristown Medical Center) and Joslyn Joseph, DO (@EMDocJos – EM Resident Physician, Morristown Medical Center) // Edited by: Alex Koyfman, MD (@EMHighAK – emDOCs.net Editor-in-Chief; EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Manpreet Singh, MD (@MPrizzleER – emDOCs.net Associate Editor-in-Chief; Assistant Professor in Emergency Medicine / Department of Emergency Medicine – Harbor-UCLA Medical Center)

Case: A 42-year-old male comes in complaining of neck pain and difficulty moving his upper extremities after trauma. The patient was involved in a motor vehicle collision where he was in the front passenger seat and was hit from that side. The patient had a loss of consciousness and complains of nausea, headache, vomiting, and trouble with motor function of his arms. He also complains of decreased sensation.

On exam, the patient has decreased sensation of bilateral upper extremities as well as 3 out of 5 strength in his upper extremities. What is the best method to immobilize the patient’s spine?

Introduction: A few months ago we covered an article considering the evidence and myths surrounding the pre-hospital use of the long backboard for spinal immobilization in trauma patients with suspected spinal cord injuries (http://www.emdocs.net/pre-hospital-management-of-spinal-injuries-debunking-the-myths-of-the-long-backboard/).  This time, we will consider the utility of another device reflexively applied to these patients – the rigid cervical collar.  From the NAEMT to PHTLS and ATLS, c-spine stabilization is considered a major priority after the ABCs.  Pre-hospital EMS protocols dictate that whenever a patient admits to neck pain or any neurological symptoms following trauma, applying a rigid plastic, often ill-fitting, uncomfortable cervical collar is mandatory.   The purpose of these devices is to prevent further motion of the cervical spine by maintaining in-line stabilization that could theoretically worsen a c-spine injury, convert a partially unstable fracture into an unstable fracture or a convert a partial spinal cord injury into a complete spinal cord transection.  This bears us to ask the question – what evidence exists to support the use of these devices?

  1. Can small voluntary spinal movements cause harm?
    • There is a fear that any movement of the cervical spine will cause further injury or worsen already existing spinal fractures or injury; however, there is no evidence that slight movement of the cervical spine will cause worsening injury. Maiman et al performed a study on cadavers involving applying forces to their necks vertically, forward and rearward to attempt to cause ligamentous injury and fracture. The loads required to cause an injury ranged from 645 to 7,439 Newtons of force.1 This study sets precedent that it may not be movement of the spine, but the force from a strong impact that causes injury. Therefore, the fear of movement, such as minimal head turning, flexion and extension of the cervical spine, or movement during airway management causing worsening injury appears to be somewhat unfounded.
  1. Do cervical collars truly immobilize the cervical spine?
    • Again, we can turn to cadaver studies as well as biomechanical analysis of live patients during extrications to answer this question. Horodyski et al tested axes of cervical motion in all planes in lightly embalmed cadavers both with an intact c-spine and induced global instability at C5-C6.  Motion was tested in five cadavers using EMG sensors applied to the C5-C6 vertebral bodies, comparing no collar, to a one-piece extrication collar (Ambu), and two-piece (Aspen) collar in repeated measures.  The results of this study indicated that though significantly more motion occurred in the unstable cadaver c-spine, no significant difference in motion occurred with the application of either cervical collar compared to the no intervention group.  Even more surprising, a similar cadaver study with induced unstable C-spine fractures by Lador et al documented increased intervertebral motion in both the axial and cranial-caudal planes in the one-piece rigid collar group compared to no intervention as well as the creation of a “pivot point” of enhanced motion where the collar contacts the TMJ and shoulder areas (we will mention this later).2 Finally, a study by Dixon et al extricating healthy volunteers from a simulated motor vehicle crash in a RCT comparing conventional equipment and manual aided techniques including the cervical collar showed four times as much motion using equipment as opposed to controlled self-extrication with no collar.3
  1. Does the cervical collar positively affect the neurological outcomes of patients with spinal cord injuries?
    • There are no prospective, randomized patient studies that look at the use of cervical collars versus placebo. Hauswald et al. performed a retrospective cohort study comparing blunt trauma patients in two different systems, the United States (which routinely immobilizes patients) and Malaysia (which does not routinely immobilize patients). They compared patients with and without spinal immobilization and performed multivariate logistic regression analyses. They found that there was less neurologic disability in the unimmobilized patients from Malaysia (OR 2.03, 95% CI 1.03-3.99; p=0.04).4 This supports the possibility that immobilization may actually be harmful.
  1. Can cervical collars cause further harm to the trauma patient?
  • C-collars can potentially increase intracranial pressure. Stone et al. took healthy volunteers and placed them in cervical collars. Their internal jugular vein cross-sectional area was measured before and after cervical collar application, and showed a mean percentage increase of 37% with the collar applied.5 Theoretically, the decreased venous return may increase intracranial pressure, which is something we want to avoid in patients with intracranial injury.
  • The neck pivot-shift phenomenon was demonstrated by Lador et al. in a study performed on cadavers. Intervertebral movements were measured based on CT imaging after application of cervical collars. It was found that “pivot points” shifted the center of rotation lateral to the spine and worsened motion between vertebrae. These points can cause stress on the c-spine due to the use of the collar.
  • The cervical collar can lead to increased intracranial pressure. A prospective study found that CSF pressure increased by approximately 25 mm H20 in a group pre- and post c-collar application in patients undergoing lumbar puncture.6

Based on the available data, it does not appear that cervical collars have any appreciable positive effect on patient care. However, at this point in time, they are the recommended treatment option. Hopefully this knowledge will help your daily practice by understanding the effects of cervical immobilization.

Case Resolution: The patient is carefully placed into a rigid, padded collar and asked not to move his neck in any direction. He undergoes appropriate imaging and management per the trauma and spinal surgery teams.

References / Further Reading

  1. Maiman DJ, Sances A, Jr., Myklebust JB, et al. Compression injuries of the cervical spine: a biomechanical analysis. Neurosurgery. 1983;13(3):254-260.
  2. Lador R, Ben-Galim P, Hipp JA. Motion within the unstable cervical spine during patient maneuvering: the neck pivot-shift phenomenon. The Journal of trauma. 2011;70(1):247-250; discussion 250-241.
  3. Dixon M, O’Halloran J, Cummins NM. Biomechanical analysis of spinal immobilisation during prehospital extrication: a proof of concept study. Emergency medicine journal: EMJ. 2014;31(9):745-749.
  4. Hauswald M, Ong G, Tandberg D, Omar Z. Out-of-hospital spinal immobilization: its effect on neurologic injury. Academic emergency medicine: official journal of the Society for Academic Emergency Medicine. 1998;5(3):214-219.
  5. Stone MB, Tubridy CM, Curran R. The effect of rigid cervical collars on internal jugular vein dimensions. Academic emergency medicine: official journal of the Society for Academic Emergency Medicine. 2010;17(1):100-102.
  6. Kolb JC, Summers RL, Galli RL. Cervical collar-induced changes in intracranial pressure. The American journal of emergency medicine. 1999;17(2):135-137.

Interpreting Waveform Capnography: Pearls and Pitfalls

Author: Brit Long, MD (@long_brit – EM Chief Resident at SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK – EM Attending Physician, UTSW / Parkland Memorial Hospital) and Manpreet Singh, MD (@MPrizzleER – Clinical Instructor & Ultrasound/Med-Ed Fellow / Harbor-UCLA Medical Center)

It’s been a busy day in the ED, full of sick patients requiring resuscitation. You just intubated a patient in respiratory distress with COPD who failed a trial of noninvasive positive pressure ventilation. The intubation went well, and you are now securing your ETT and connecting end-tidal waveform capnography to evaluate the tracing. The chest X-ray shows optimal position of the ETT, you have the post-procedural analgesia and sedative agents on board, and you’re feeling good as you exit the resuscitation bay.

The next patient is an 8 year-old male with a fall and forearm deformity. X-ray reveals an angulated, mid-shaft radial fracture that will need reduction. You evaluate the patient for the necessary procedural sedation, gather your equipment and airway supplies, and prepare for the sedation. You plan on using ketamine. Before you push the ketamine, you have the patient on monitors, including waveform capnography.


Capnography has shown great potential in several conditions and procedures in emergency medicine. Literature exists for its use in cardiopulmonary resuscitation, intubation for confirmation of ETT placement, resuscitation of critically ill patients with sepsis, monitoring response to treatment in patients with respiratory distress (specifically COPD, CHF, and asthma), pulmonary embolism, and procedural sedation. For more details, go HERE.

However, how do you interpret quantitative capnography waveforms? We own the resuscitation of critically ill patients, and with boarding increasing in EDs, we need to know how to interpret waveforms. This instrument can provide a great deal of important information if properly understood.

The normal capnography waveform

The main determinants of ETCO2 include alveolar ventilation, pulmonary perfusion, and CO2 production. A normal waveform has four different phases:

  1. Phase I is the inspiratory baseline, which is due to inspired gas with low levels of CO2.
  2. Phase II is the beginning of expiration which occurs when the anatomic dead space and alveolar gas from the alveoli/bronchioles transition.
    a. The transition from phase II to III is the alpha angle.
    b. The alpha angle can be used to assess the ventilation/perfusion of the lung. V/Q mismatches will have an alpha angle greater than 90 degrees.
  3. Phase III is the alveolar plateau, where the last of the alveolar gas is sampled. This is normally the PETCO2.
    a. The transition from phase III to 0 is the beta angle.
    b. The beta angle can be used to assess rebreathing. If rebreathing occurs, the angle is greater than 90 degrees.
  4. This is actually phase 0, reflecting the inspiratory downstroke and the beginning of inspiration.

Of note, an additional phase IV is often seen in pregnancy, which is a quick upstroke before phase 0 begins.

Image 2

Image One
Picture from http://what-when-how.com/wp-content/uploads/2012/04/tmp2A92_thumb221.jpg

How do you analyze the waveform?

Just like you evaluate an ECG or chest Xray, I recommend using an algorithm or systematic process for analysis. This can be divided into several steps:

  1. Look for presence of exhaled CO2 (Is a waveform present?)
  2. Inspiratory baseline (Is there rebreathing?)
  3. Expiratory upstroke (What is the shape i.e. steep, sloping, or prolonged?)
  4. Expiratory/alveolar plateau (Is it sloping, steep, or prolonged?)
  5. Inspiratory downstroke (Is it sloping, steep, or prolonged)

Ensure you evaluate the height, frequency, rhythm, baseline, and shape. With these thoughts in mind, let’s discuss some clinical scenarios.


Before you can reassess your other two patients, you receive an EMS radio call. They were called to the scene of a patient in PEA, and they have started compressions and will be at your doorstep in 3 minutes. The patient arrives, with the crew doing high quality CPR. The patient continues with no pulse, leads and ETCO2 are connected, one amp of epinephrine is given, and US shows a heart rate of 40 bpm. Your waveform capnography shows 10 mm Hg, and the person completing CPR is tiring. As the team leader, you ask another team member to take over.

Image 3
Picture from http://www.slideshare.net/larryide/capnography?next_slideshow=1

This waveform with a dip shows the time to transition to a different provider, with improved perfusion with the new provider doing compressions, as the CO2 has increased indicating better tissue perfusion.

After another minute of CPR, the ETCO2 jumps to 40. A sudden increase in ETCO2 is seen in ROSC during arrest or correction of an ETT obstruction.

Image 4
Picture from http://www.slideshare.net/larryide/capnography?next_slideshow=1

You now have return of pulses and are preparing to intubate the patient. Unfortunately, the resident completing it is not confident in his view and is unsure of tube placement. Your waveform shows the following:

Image 5

This waveform shows a tapering of the ETCO2, suggestive of esophageal intubation. You ask the resident to remove the ETT. He obtains an improved view with videoscope and passes the ETT without difficulty. The waveform looks normal, and the patient is now stable.

Finally you have time to go reassess your COPD patient. Just as you enter the resuscitation bay, he has a desaturation to 88% while on FiO2 of 100%, and your waveform is flat.

Image 6
Picture from http://www.slideshare.net/larryide/capnography?next_slideshow=1

You are now pretty tired of these flat waveforms, and you immediately curb your sphincter response while running to the bedside. Your mind quickly goes through the DOPES mnemonic (displacement, obstruction, PTX, equipment failure, breath stacking) and you see that while moving the patient, the ETT became disconnected from the circuit. You reconnect, with increase in saturation and good waveform.

What are other causes of a sudden flat EtCO2 tracing?

Extubation, capnography not connected to circuit, cardiorespiratory arrest, apnea test in brain dead patient, obstruction of capnography, ventilator disconnection, and esophageal intubation.

After caring for an ankle sprain and beginning the workup of a patient with chest pain, you again reassess the patient with COPD. You notice a steadily increasing EtCO2 baseline in your COPD patient. The waveform looks like this…

Image 7
Picture from http://www.slideshare.net/larryide/capnography?next_slideshow=1

The waveform reflects an elevation of baseline, as well as the plateau, indicating incomplete exhalation. The CO2 is not being appropriately removed. This is often due to insufficient expiratory time, inadequate inspiratory flow, or faulty expiratory valve.

Rebreathing can also appear with the following waveform with baseline elevation, which is due to inadequate exchange of CO2.

Image 8
Picture from http://www.paramedicine.com/pmc/End_Tidal_CO2.html.

Increased EtCO2 can be due to four components:

  1. Increased CO2 production (fever, NaHCO3 administration, tourniquet release, and overfeeding syndrome).
  2. Pulmonary perfusion increase (increased cardiac output, increased blood pressure).
  3. Alveolar ventilation decrease (hypoventilation, bronchial intubation (remember that victory shove?), partial airway obstruction, rebreathing).
  4. Equipment malfunction (exhausted CO2 absorber, inadequate fresh gas flow, ventilator tubing leak, ventilator malfunction).

Once you slow down his respiratory rate and increase the flow rate, his saturations and waveform improve. Suddenly, the alarm alerts you to high pressures in the circuit, and his waveform shows:

Image 9
Picture from http://www.paramedicine.com/pmc/End_Tidal_CO2.html

This waveform is due to obstruction of the ETT, either through ETT kink, foreign body in airway, bronchospasm, or mucous plug. You see high peak pressures and suction the tube, while ordering an in-line duoneb. Five minutes later the patient again improves. You wipe the sweat from your brow, as this patient is keeping you busy.

After all this excitement, you prepare for the sedation of the 8 year-old male with forearm fracture requiring reduction. The sedation and reduction go smoothly with ketamine. He is starting to wake from his dissociative state, and you see this:

Image 10
Picture from http://www.slideshare.net/larryide/capnography?next_slideshow=1

This waveform demonstrates hyperventilation. Notice the baseline is unchanged. This waveform shows steadily decreasing plateau, reflecting tachypnea, increase in tidal volume, decreased metabolic rate, or fall in body temperature.

A decreasing EtCO2 has several etiologies:

  1. Decreased CO2 production (hypothermia)
  2. Pulmonary perfusion decrease (reduced cardiac output, hypotension, pulmonary embolism, cardiac arrest)
  3. Alveolar ventilation increase (hyperventilation, apnea, total airway obstruction, extubation)
  4. Apparatus malfunction (circuit disconnection, leak in sampling, ventilator malfunction)
Recap of Factors Affecting EtCO2 – Table from EMSWorld

What if his respiratory rate had started to decrease?

The alveolar plateau will begin to steadily increase, which is due to decrease in respiratory rate, decreased tidal volume, increased metabolic rate, and hyperthermia. Notice the baseline is still close to 0, so CO2 is appropriately exchanged.

Image 11
Picture from http://www.paramedicine.com/pmc/End_Tidal_CO2.html

Just before you send the COPD patient to the ICU, the nurse grabs you, as the waveform has now changed.

Image 12
Picture from http://www.paramedicine.com/pmc/End_Tidal_CO2.html

This small dip in the alveolar plateau is known as a “curare cleft.” This waveform appears when the paralytic begins to subside and the patient tries to breathe during partial paralysis. You increase the analgesic drip, and the patient is transferred to the ICU.


Use an algorithm for waveform capnography analysis.

  1. Look for presence of exhaled CO2 (Is a waveform present?)
  2. Inspiratory baseline (Is there rebreathing?)
  3. Expiratory upstroke (What is the shape i.e. steep, sloping, or prolonged?)
  4. Expiratory/alveolar plateau (Is it sloping, steep, or prolonged?)
  5. Inspiratory downstroke (Is it sloping, steep, or prolonged)

Ensure you evaluate the height, frequency, rhythm, baseline, and shape.

Understanding waveforms and how to interpret them can provide a great deal of information. We are the masters of resuscitation, and this is a vital component of caring for critical patients.

Pocket Guide: Left – Intubated Patient, Right – Non-intubated Patient Available at: http://www.emsworld.com/article/10287447/capnography-as-a-clinical-tool

References/Further Reading

-Kodali BS. Capnography outside the operating rooms. Anesthesiology. 2013 Jan;118(1):192-201.
-Thompson JE, Jaffe MB. Capnographic waveforms in the mechanically ventilated patient. Respir Care. 2005 Jan;50(1):100-8; discussion 108-9.
-Blanch L, Romero PV, Lucangelo U. Volumetric capnography in the mechanically ventilated patient. Minerva Anestesiol. 2006 Jun;72(6):577-85.

Online Resources