When paramedics were first introduced in the 1970s, one of the most controversial aspects of their training program was endotracheal intubation (ETI). Prior to that, the skill of intubating the trachea was purely the domain of physicians and nurse anesthetists. Thus, it was difficult to secure time when paramedic students could practice their intubations skills on live patients. In actuality, many paramedics of that era were graduated without ever having the opportunity to perform an ETI on a living patient.
Eventually, paramedic programs gained access to operating rooms (ORs) and clinical areas where paramedic students could practice their ETI skills on patients under the instruction of a physician or nurse anesthetist. As a rule, the vast majority of prehospital ETIs in the field were performed in cardiac arrest victims. Even in the best systems, cardiac arrest resuscitation rates were dismal, and a misplaced endotracheal tube was often written off as not being a factor in a patient_s demise.”ž
In the 1980s, with the introduction of standardized courses in prehospital trauma and medical care, there came a push to intubate patients earlier in the disease/injury continuum. Recommendations came forward to intubate trauma patients with a Glasgow Coma Scale (GCS) of 8 or less.
Likewise, the standardized medical courses and textbooks encouraged early intubation and aggressive ventilatory management in patients with respiratory failure and acute pulmonary edema. Thus, a subtle, often unrecognized transition occurred in paramedic practice. Paramedics were now intubating patients who had a good chance of survival. This subsequently put the practice of ETI in a whole new light.
With the transition to intubating living patients, there followed an increased scrutiny of this procedure. When it was recognized that prehospital ETI success rates were poor, various strategies were identified to improve accuracy. This primarily consisted of techniques to verify endotracheal tube placement, including end-tidal carbon dioxide detection and esophageal detector devices (EDDs). More recently, scrutiny has moved beyond analysis of simple skills performance and is now focused on patient outcomes.
In this article, we’ll review the controversies and status of prehospital intubation. Interestingly, it won_t be the volume and magnitude of the research that ultimately determines whether paramedics will continue to perform ETI.
Is ETI the Gold Standard?
As EMS education has evolved, the role of ETI as a primary paramedic skill has been ingrained in prehospital literature. Nancy Caroline, MD, in the first edition of her book Emergency Care in the Streets, published in 1979, wrote, “Endotracheal intubation is the most definitive means to achieve complete control of the airway.”
This same assertion appeared in textbooks decades later. In the first edition of Paramedic Emergency Care, I wrote, “This [ETI] is the preferred technique for managing a patient’s airway in the field setting.” Ronald Stewart, MD, in the second edition of Basic Trauma Life Support, wrote, “The gold standard of airway care in patients who cannot protect their airway or those needing assistance in breathing is the endotracheal tube.”
This stress on endotracheal intubation may have deemphasized the role of ventilation. Many paramedics were graduated with the idea that failure to intubate a patient was substandard care. In reality, failure to ventilate a patient is substandard care -- not failure to place an endotracheal tube. The difference is significant.
What Are the Success Rates?
Paramedic courses have always been rather brief when compared with education in the other allied health disciplines. In the 1980s and '90s, many paramedic classes were less than 600 clock hours in length. The 1998 National Standard Curriculum for Emergency Medical Technician -- Paramedic recommended that the course be planned for approximately 1,000 - 1,200 total hours of instruction (500 - 600 classroom/practical laboratory hours, 250 - 300 clinical hours and 250 - 300 field internship hours.)
With such time constraints, mastery of advanced airway skills, particularly ETI, was virtually impossible. In contrast, other health care professionals who perform ETI have significantly more education and practice. Emergency medicine residents, for example, are required to perform between 35 - 200 ETIs prior to graduation."ž
Research has demonstrated that paramedic students require at least 15 - 20 intubations to attain basic skills proficiency. The"žNational Standard Curriculum for Emergency Medical Technician -- Paramedic requires only five intubations prior to graduation."ž
Initial studies of prehospital ETI success rates indicated that the incidence of misplaced endotracheal tubes ranged from 0.4% - 5.1%. These initial studies were reassuring in that the success rate was acceptable given that the majority of patients who received prehospital ETI were dead or would soon die. However, researchers in Orange County, Fla., found the ETI success rate to be much worse than initially thought -- for 108 patients it was 25%. This number was higher in trauma patients (37%), but much lower in medical patients (14%). They determined that the incidence of prehospital unrecognized esophageal intubation (UEI) was "alarming." In a 2003 Maine study, researchers found the prehospital ETI success rate to be 81%.
More recent studies have shown the incidence of misplaced prehospital endotracheal tubes to be around 5%. A prospective study of 132 patients intubated in the prehospital setting found that 9% were misplaced (11 esophageal and one in the hypopharynx). In 15% of the intubated patients, the ET tube was in the right mainstem bronchus.
Wang and associates examined the reasons for failed prehospital ETI over a one-year period in a county-wide EMS system. During that time, there were ETI attempts on 592 patients, of which 536 (90.5%) were successful. They found various reasons for failure; however, only a small percentage of these patients were judged to have a "difficult airway."
They also found that prehospital intubations often require multiple attempts. In a review of 1,941 cases of prehospital ETI, more than 30% of patients received more than one attempt. The cumulative success rate per attempt for the first three attempts was 69.9%, 84.9% and 89.9%. These success rates were lower for non-arrest patients (57.6%, 69.2% and 72.7% respectively).
Most studies of prehospital pediatric ETI have demonstrated that the success rate is worrisome. In one 1989 study of pediatric medical cardiopulmonary arrests, the overall ETI success rate was just 64%. A study of 63 pediatric patients requiring prehospital ETI in Milwaukee County, Wis., found an intubation success rate of 78%.
Although a great deal of the literature has been critical of the prehospital ETI success rate, other studies have not found significant problems. In a study of 264 pediatric prehospital intubations, researchers found only one UEI, resulting in a success rate of 99%. Bulger and colleagues reported a prehospital ETI success rate of 98.4% in Seattle and King County, Wash. Wayne and Friedland reported a 95.5% ETI success rate in Bellingham, Wash.
What About Patient Outcomes?
Prehospital procedures and methodologies have been more closely scrutinized in the literature during recent years. Some have been found efficacious, some have not. Ultimately, the question medical directors must ask is, "Does this procedure or practice improve patient outcomes?" Prior to recent research, outcome data was unknown or extrapolated from other disciplines. One of the principal areas of study has been prehospital ETI, and the literature is mixed.
Wang and colleagues completed a multi-center evaluation of prehospital ETI. Although they found that the overall ETI success rate was 86.8%, they were unable to associate prehospital success with field or initial emergency department (ED) survival.
Outcome studies of trauma patients who receive ETI generally fail to show any benefit from the procedure. One study found that prehospital ETI was associated with a decrease in survival in patients with moderate to severe traumatic brain injury (TBI) when compared with those intubated in the ED.
In a New Orleans study, prehospital ETI was associated with a similar or greater mortality than bag-valve mask (BVM) ventilation alone. In a Pennsylvania Trauma Registry study of 4,098 trauma patients who received prehospital ETI (43.9%) or in-hospital ETI (56.1%), it was found that the adjusted odds of death were higher for prehospital ETI compared to in-hospital ETI (OR = 3.99 [95% CI=3.21à4.93]). The chances of a poor neurologic outcome were also worse for the patients who received prehospital ETI (OR = 1.61 [95% CI=1.15à2.26]) as well as moderate to severe functional impairment.
Dallas researchers found that prehospital ETI and positive-pressure ventilation were associated with hypotension and decreased survival. In 2006 an Australian study stated, "Overall current paramedic airway practice in most states of Australia is not supported by the evidence and is probably associated with worse patient outcomes after severe head injury. For road-based paramedics, rapid transport to hospital without intubation should be regarded as the standard of care."
In a best-evidence report on prehospital ETI in adults with major head injuries, British researchers wrote, "It is concluded that prehospital intubation is associated with increased mortality in these patients."
Outcome studies of pediatric prehospital ETI patients have failed to demonstrate any improvement in morbidity or mortality. In a controlled clinical trial of 830 consecutive patients less than 12 years old (or who were estimated to weigh less than 40 kg), subjects were randomized to receive either BVM ventilation or BVM ventilation followed by prehospital ETI. They found no significant difference in survival to discharge or neurological status at discharge between the groups. A study of pediatric patients with severe TBI failed to demonstrate any survival advantage or functional advantage for patients who received prehospital ETI when compared with those who received only BVM ventilation.
Less In-Hospital Experience
By far, the best way for a paramedic student to gain ETI experience on living patients is in the OR. However, with the advent of acceptable alternative airways, such as the Laryngeal Mask Airway (LMA), the number of general anesthesia patients undergoing ETI has decreased significantly. This means there's even less opportunity for students"žof all disciplines to practice.
Unfortunately, paramedic students also seem to be at the bottom of the ETI pecking order. Anesthesia residents, nurse anesthetist students, emergency residents, critical care fellows and others generally have priority over paramedic students. This limitation is complicated by the fact that so little clinical time is set aside for ETI practice in most paramedic programs.
Gaining access to the OR for ETI has always been difficult for EMS students. There are several reasons for this: First, EMS education tends to be community-based and not institutional. Second, the length of EMS education tends to be shorter than that of comparable allied health programs. This raises concerns about allowing EMS students into the hospital setting. In addition, in some states, EMS personnel aren't technically licensed. This is more than a matter of semantics. Many insurers and payees limit access to patients to "licensed providers" or students in the process of becoming licensed.
Regardless of the reasons, the problem is real. Researchers at the University of Pittsburgh sent an anonymous survey to 192 paramedic programs accredited by the Commission on Accreditation of Allied Health Programs. Of these, 161 (85%) surveys were returned, and 156 (97%) programs surveyed used OR training, but it was generally limited to a median of 17à32 hours per student.
Half the programs provided fewer than 16 hours of OR training per student. Students attempted a limited number of ETIs (median, 6 - 10). Most (61%) of the programs reported competition from other health-care educational programs and students as a reason for decreasing OR access. Other reasons included increased use of the LMA in the hospital and legal concerns. Of the survey group, 52 (33%) programs reported a recent reduction in OR access and another 56 (36%) anticipated decreased access.
Becoming an Expert
Like any psychomotor skill, it takes instruction and practice to perfect ETI. There are five phases in the process of mastering a psychomotor skill."ž
Imitation: The student repeats what is done by the instructor. In medicine, this is often referred to as, "See one, do one." This level of education is best performed on a manikin or simulator. Some skills are simple enough that they can be learned by observation. Most are not.
Manipulation: The student will use guidelines for skill development, but rely less on the instructor. The student may make mistakes, but correcting mistakes promotes learning. This also allows the student to develop their own style.
Precision: The student has practiced to the point where they don't make mistakes. However, they often can't perform the skill as well in a different setting.
Articulation: The student is able to integrate both cognition and affect into skill performance. They understand why the skill is necessary and when it's indicated. They perform it proficiently and with style. They can perform the skill in multiple settings. This is the phase that students should reach before graduating an initial educational program.
Naturalization: Eventually, the skill is performed without thought. The process has been ingrained into the operator's mind. For example, prior to mastering ETI, a student will reflexively pick up a laryngoscope in their dominant hand (usually right). After mastery, they reflexively pick it up with their left hand regardless of hand dominance.
Repetition is key to perfecting a psychomotor skill, but the amount of repetition needed varies from person to person. It has been shown that complex medical skills can require more than 100 repetitions. It makes sense then that several studies have demonstrated an increased success rate for ETI associated with accumulated live experience.
Perhaps new technology, such as Verathon's GlideScope Ranger (a video laryngoscope), will improve a paramedic's intubation success rate. This device provides enough visualization of the glottis so that a tube can be passed. Devices like these, that decrease the complexity of ETI, should conceivably cut down on the time it takes to truly master the skill.
Less Opportunity in the Field
It was generally assumed that ETI and IV access were the most frequently performed paramedic skills. However, when studied, the number of ETIs per paramedic was found to be quite low. Two factors appear to be involved. First, the number of patients who require prehospital ETI may not be as high as once thought. Second, an increasing number of paramedics and other providers authorized"žto perform prehospital ETI (e.g., EMT-Intermediates, flight nurses) have limited the opportunities for each paramedic to perform ETI.
In a Milwaukee study, researchers found that the average annual number of paramedics was 177, with each paramedic only performing 3.7 ± 3.3 intubations per year.
In a five-year review of 957,836 prehospital patient encounters in Maine (primarily a rural state), the average number of EMS providers eligible to perform ETI annually was 1,352. There were 5,612 total ETI attempts, and only a range of 37% - 42% of eligible providers performed the procedure annually. A mean of 18 providers attempted more than five intubations annually. Only 137 patients requiring prehospital ETI were classified as pediatric. During the study period, the success rate was 84% by providers with less than five annual ETI encounters, and 86% in providers with more than five encounters.
In a one-year study of 11,484 ETIs performed by 5,245 prehospital providers, it was found that most rescuers (> 67%) performed two or fewer ETIs, while 39% did not perform any ETIs.
The American Heart Association recommends that ALS providers perform a minimum of six to 12 intubations a year to remain credentialed in the procedure. EMS systems that have reported a high ETI success rate require a minimum of 15 ETIs per provider per year for credentialing. Only extremely busy EMS systems could ever achieve this level of practice.
But There Are Alternatives
The introduction of better alternative airways and non-invasive ventilation is the primary reason prehospital ETI is on the decline. For many years, the alternative airways were unsatisfactory. The esophageal obturator airway (EOA) and esophageal obturator airway with gastric tube (EOA-GT) were introduced in the 1970s. The EOA was easy to insert and didn't require visualization of the airway. However, a subsequent study found it to be no more effective than simple BVM ventilation. Later, complications began to arise, including esophageal rupture and unrecognized tracheal intubation.
Second-generation adjunct airways were introduced in the 1980s and included the pharyngo-tracheal lumen (PtL) airway and esophageal-tracheal combitube (ETC). These devices were better because they didn't rely on obstruction of the esophagus, and they provided a method specifically for ventilating the trachea. Problems later arose when prehospital providers had difficulty discriminating between the esophageal and tracheal modes of the PtL. The ETC was widely used in the prehospital setting. It was also among the first of the adjunct airways to be used in the anesthesia setting.
Supraglottic airways were introduced in the 1980s and represented a significant improvement in adjunct airway effectiveness. The first of these was the laryngeal mask airway (LMA). However, the initial LMAs were non-disposable and required repeated sterilization. Because of this, usage of the LMA in the prehospital setting was limited. Later, disposable versions became available, as well as similar supraglottic airways. Thus, for the first time, paramedics (and EMTs in some systems) had alternative airways that were as good as ETI, and perhaps safer.
Unfortunately, the introduction of alternative airways has been associated with a decrease in ETI success by paramedics. In a study of prehospital intubations before and after introduction of the ETC to an EMS system, the ETI success rate decreased from 93.5% to 91.6%. This is likely related to increased use of the ETC, which resulted in fewer ETI attempts and, thus, less ETI success.
Thus, with the advent of a plethora of adjunctive airway devices that don't require visualization of the airway, and which have been found to be safe and effective, it's hard to continue to justify continued routine ETI usage in prehospital care.
Accepting the Inevitable
Of primary skills, a survey of paramedics ranked ETI as the highest in importance (followed by defibrillation and assessment). Thus, attempts to limit or remove this skill is often met with an emotional response. It isn't an uncommon comment in discussions on various EMS sites that all of the studies critical of prehospital ETI are a priori. In reality, the intent of one of the leading researchers in this area was just the oppositeÆ’to document the effectiveness of prehospital ETI.
This airway procedure is in a tenuous position. Although there's a reluctance to give it up, a preponderance of the literature shows very few patients, if any, benefit from the practice. It can be said almost with certainty that prehospital intubation of all pediatric patients and patients with severe head injury now falls below the standard of care.
Thus, EMS medical directors must first answer the question as to whether prehospital ETI should remain a skill in their system. If they choose to include it, the indications and contraindications must be clearly defined, enforced and audited. There must be a system-wide commitment to education and quality assurance. If there aren't enough intubations"žin a system to support a prehospital ETI program, then the number of paramedics allowed to perform the procedure should be limited.
Recent evidence has shown that increasing paramedic clinical ETI experience results in improved survival for patients intubated in the prehospital setting. It would seem appropriate to rotate paramedics who fail to achieve an adequate number of ETIs through a clinical setting for remediation (if a clinical site is available) or a human simulation lab. But, what will be the accepted incidence of UEI? In the hospital setting, it's 0%.
Eventually, it'll be impossible to educate all paramedics in ETI. The lack of a suitable clinical setting for practice, as well as decreased prehospital usage of ETI, will be the death knell for the procedure.
For most EMS systems, the use of alternate airways will soon replace prehospital ETI. These devices appear effective, safer and require less skills maintenance. Ultimately, however, outcomes will have to be measured.
Ironically, it's not the scientific evidence against prehospital ETI that is driving it out of EMS practice. It's simply the inability to properly educate students in use of the airway. Although mannequin practice and human simulation are improving, there remains a need to learn this skill on human subjects. And if the opportunity for adequate field practice does not occur, then paramedics must be sent to the educational setting for practice. Again, the conundrum is that these settings are limited.
Whether we agree with it or not, or like it or not, the reality is that prehospital ETI for general 9-1-1 care will probably soon be a thing of the past. We must embrace the current adjunct airways and continue the search for that magic device that is better (or as good) as ETIÆ’but without the risks. JEMS
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This article originally appeared in March 2009 JEMS as "The Disappearing Endotracheal Tube: Historic skill threatened by lack of pratice and new devices."