A 9-1-1 call is placed at 1900 hrs. The caller reports that her roommate, a 28-year-old male, is unconscious and face down on his bedroom floor. She_s unsure how long he has beenlying there. She last saw him acting normal at 0800. EMS personnelarrive to find a male, approximately 270 lb., 6' 2", lying prone.
Initial assessment reveals poorly palpable pulses with a heart rate of 40 bpm. Blood pressure is 60 mmHg systolic by palpation. He doesn_t appear to be breathing, and oxygen saturation is undetectable. The man is cyanotic. Three unsuccessful attempts at endotracheal intubation via direct laryngoscopy are made by the senior paramedic. Intubation is abandoned, and the patient is transported to a nearby emergency department (ED). The paramedic attempts to maintain oxygenation with bag-mask ventilation (BMV); oxygen saturation is never determined.
On arrival in the ED, the patient suffers a pulseless electrical activity arrest, and a full ACLS protocol is initiated. The receiving emergency physician inserts a Laryngeal Mask Airway (LMA) and continues with the resuscitation. A rapid review of old records reveal that the man was known to be a chronic opioid abuser and was treated in a hospital across town for respiratory arrest secondary to narcotic overdose approximately one year prior. At that time, he was noted to be an impossible intubation by the emergency physician, and an anaesthesiologist was asked to assist. His airway was secured via crash surgical cricothyroidotomy in the ED. Further physical exam reveals a well-healed cricothyroidotomy scar.
Could this case have been handled differently?
EMS providers, whether basic or advanced, face significant challenges with regard to airway management, oxygenation and ventilation in critically ill or traumatized patients. Studies have shown a wide variation among EMS providers in training and skill level relatedto advanced airway management.
For many decades, BMV and endotracheal intubation (ETI) have been the mainstays of airway management in the prehospital setting. This paradigm persists despite growing concerns that BMV is difficult to teach, learn and perform, even for those who do it regularly (e.g., anesthesia providers). Further, there_s no proof that prehospital ETIƒoften considered the "gold standard" of airway managementƒimproves patient outcomes. In fact, it may even cause significant harm when performed by inexperienced practitioners in challenging situations. Perhaps it_s time for a "seismic shift" in how we think about prehospital airway management.
What the Guidelines Say
The American Heart Association (AHA) 2005 Guidelines for BLS and ACLS are vague and, at times, conflicting in terms of a preferred method of airway management in cardiac arrest situations. However, they do state: "When prehospital providers are trained in the use of advanced airways, such as the Combitube and LMA, they appear to be able to use these devices safely, and they can provide ventilation that is as effective as that provided with a bag and mask ... It is important to remember that there is no evidence that advanced
airway measures improve survival rates in the setting of prehospital cardiac arrest."
In general, patients requiring BLS and ACLS airway management present along a continuum of unresponsive, unconscious or pulseless. In the event the EMS provider is not permitted or able to undertake advanced airway management, it_s reasonable to assume that simple airway maneuvers, such as mouth-to-mask ventilation, will be employed in the majority of situations.
Pitfalls of BMV
BMV is a complex skill that is often performed poorly by health-care providers who don_t employ the skill on a regular (sometimes not even daily) basis. It_s also difficult to teach and learn if not practiced or performed regularly in a controlled setting on real people. Despite these pitfalls, BMV remains an essential tool in the arsenal of any EMS provider in an effort to provide oxygenation and gas exchange to an apneic or hypoventilating patient.
Unfortunately, the adequacy of ventilation provided by a BMV unit is surprisingly difficult to assess. Further, sustained and aggressive attempts at BMV in an unconscious patient with a partially or completely obstructed airway not only result in inadequate oxygenation and ventilation, but they may increase the risk of gastric insufflation, leading to regurgitation and pulmonary aspiration.
Using manikins, Kurola and colleagues compared the efficacy of BMV, ETI and insertion of an extraglottic device (EGD) when inserted by inexperienced EMT students. (Editor_s note: Extraglottic is the generic term for non-tracheal devices. LMA-type devices are often referred to as "supraglottic devices." Esophageal-tracheal Combitube and Laryngeal Tube devices are sometimes referred to as infra- or retroglottic devices.) The researchers reported that ETI and the Combitube provided superior ventilation to BMV: "Wefound that the use of BMV in this testsituation resulted in inadequate minute ventilation." Further, manikins are obviously less apt to develop upper airway obstruction in the supine position as compared with real, unconscious people. And with manikins, upper airway obstruction caused by the tongue is largely eliminated, which results in overestimation of the utility of the technique.
Downsides of ETI
As indicated earlier, ETI is a key step in the ACLS protocol in the resuscitation of cardiopulmonary arrest victims. However, studies have shown that ETI performed in challenging settings by personnel who may have limited training and experience with the procedure may result in unrecognized complications, failures and unnecessary delays in transfer to definitive care centers. (Editor_s note: For more on this, readThe Disappearing ET Tube" in March 2009JEMSat jems.com/journal.)
Cudnik and colleagues published an analysis of 570 trauma patients intubated in the field by EMS providers. They reported a significant delay in time for transfer to a trauma care center among patients intubated in the field. It was unclear if this resulted in clinically significant negative outcomes. The authors argued that, "Injured patients may benefit from airway management techniques that require less time for execution."
Another concerning aspect of prehospital airway management is the continued emphasis on BMV as a rescue technique for difficult or failed ETI. Although BMV is a vital skill and a long-standing pillar of oxygenation and ventilation, there are inherent pitfalls associated with its performance in ensuring adequate gas exchange. Using a flawed technique as a backup to another flawed technique is not good practice.
It_s important to note that the body of evidence on this subject focuses on the situation of an unconscious or unresponsive patient. These findings imply severe physiologic compromise. In many cases, paramedics are faced with those who have succumbed to cardiopulmonary arrest. In these circumstances, airway reflexes and oropharyngeal muscular tone is lost, and oxygenation is predicted to be severely compromised as well.
Exploring the Options
The science of airway management is a rapidly growing area of interest. More devices designed to facilitate oxygenation and ventilation are available now than ever before. Many health-care professionals charged with airway management are gaining widespread familiarity with a myriad of alternate approaches to gas exchangeƒoften using novel devices in operating rooms, EDs, critical care units and the field. In many cases, they are simpler to use, are more effective and waste less time.
There are a broad spectrum of EGD devices designed to deliver oxygen to a patient_s lungs. These devices are generally designed to be inserted blindly and seated in a position outside of the patient_s trachea. Certain devices considered to be EGDs may be used successfully when inadvertently placed in the trachea.
In the operating room, the most commonly used EGDs are the LMA and its derivatives (e.g., LMA-Fastrach, LMA-Supreme, LMA-Unique). Additionally, the Combitube and the Laryngeal Tube (i.e., the King LT) have enjoyed widespread popularity among EMS providers and emergency physicians.
At present, EGDs are widely employed by ALS providers as first-level rescue devices when endotracheal intubation fails. This practice is in keeping with the American Society of Anesthesiologists (ASA) algorithm for management of a difficult airway. The ASA guidelines recommend the immediate insertion of an LMA as a rescue device when intubation has failed (after three attempts if BMV delivers adequate oxygen and one attempt if not able to BMV). Although the application of this algorithm to prehospital airway situations is questionable, it positions EGDs as first-line rescue devices, even in the hands of experts in airway management.
As previously mentioned, the effectiveness of BMV is difficult to judge, and that_s just one problem. We believe patients are better off if BLS providers attain proficiency in the rapid placement of an EGD as a first-line airway management technique. And the use of an EGD may also be ideal as a first-line technique for ALS providers or at least as an immediate backup to ETI before turning to BMV.
Indeed, several studies have investigated the efficacy of EGDs in terms of a learning curve and effectiveness when used by paramedics. Kurola and colleagues reported that clinically inexperienced EMT students were able to successfully place a Laryngeal Tube faster than they were able to perform ETI in a simulated cardiac arrest. Additionally, they compared LT, ETI and BMV in terms of efficacy and reported that ETI and EGD placement resulted in more effective ventilation.
The 2008 Scandinavian Society for Anaesthesiology and Intensive Care Medicine Guidelines for prehospital airway management state: "When performing advanced cardiopulmonary resuscitation, we recommend that non-anesthesiologists primarily use a supraglottic airway device."
Several newer additions have been made to the EGD class. Notably, this includes the iGel, Cook ILA, Air-Q and EasyTube. These devices are associated with variable levels of familiarity and scientific data to support their efficacy. Further research is needed to assess the utility of these devices in the prehospital setting.
The use of EGDs in unresponsive patients is clearly supported by expert opinion, as well as clinical research. Familiarity with the rapid placement and confirmation of EGDs should be a mandatory skill for all EMS providers. Hopefully, the increasing use of these devices will make BMV and ETI subordinate in the tier of airway management protocols.JEMS
Steven Petrar,MD, works in the Department of Anesthesia, Dalhousie University, Halifax, Nova Scotia, Canada.
Michael Murphy,MD, FRCPC, is professor and chair of the Department of Anesthesia, Dalhousie University. He is a founding faculty member of The Difficult Airway Course: EMS. Contact him email@example.com.
Orlando Hung,MD, FRCPC, works in the Department of Anesthesia, Dalhousie University.
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