Paramedics and firefighters respond to a 55-year old male in cardiac arrest. They find the victim supine on the floor between the bed and the wall of a small room. The fire fighters initiate chest compressions and bag-valve mask (BVM) ventilation but are unable to achieve a good mask seal. One of the paramedics prepares for endotracheal intubation (ETI)—his first attempt ever on a real patient. He lies prone with his left elbow resting on the floor but has trouble lifting the jaw with the laryngoscope. He makes five laryngoscopy attempts of 45 seconds each. The paramedic finally places the ET tube in the trachea. There’s fogging in the tube so he assumes it’s correctly placed. Because he can’t find adhesive tape, he instructs one of the firefighters to manually hold the ET tube in place. As the other firefighters lift the patient onto the ambulance stretcher, the unsecured ET tube pulls out of the patient’s mouth.
ETI is one of the most important procedures in EMS care, allowing for controlled oxygenation and ventilation of critically ill patients. Numerous research studies over the last 15 years highlight the pitfalls and dangers of prehospital intubation, such as unrecognized esophageal misplacement, tube dislodgement and multiple unsuccessful attempts.1–5 More recent studies highlight that intubation efforts may interfere with essential resuscitation goals such as maintaining cardiopulmonary resuscitation chest compression continuity.6
Bradycardia and oxygen desaturation are also common risks of intubation in traumatic brain injury (TBI).7 The clinical vignette highlights many of these adverse events.
Patients may be harmed by airway management-related adverse events. A wellexecuted intubation effort uses preparation, technique and strategies to avoid these harms. This article offers pearls for improving the safety of prehospital intubation.
1. RESPECT THE DIFFICULTY OF PREHOSPITAL INTUBATION
When performing intubation, exercise a conservative attitude grounded in familiar techniques and strategies, ample practice and rehearsing of potential situations, and a low threshold for rescue interventions in the face of difficult or unsuccessful intubation efforts.
Many EMS practitioners exercise a cavalier attitude toward prehospital intubation, overestimating their airway management skill and proficiency. This is a dangerous mindset considering the inherent difficulty of intubation in the prehospital setting.
Table 1: Eight pearls for improving prehospital intubation safety
There’s no such thing as a “simple” prehospital airway—all prehospital airways are difficult. Intubation is a complex and difficult procedure encompassing over 100 separate manual and cognitive steps.8 These elements are complicated by the uncontrolled and noisy prehospital environment. Patients requiring intubation in the field are critically ill and often situated in odd and inaccessible positions; for example, collapsed on the floor in a cramped room or entrapped in a mangled car. Visualizing the airway may be complicated by poor ambient light and blood and vomit obscuring the oropharynx. Even the most seasoned emergency physician or anesthesiologist would be challenged by intubation under these conditions.
2. PREPARE, POSITION, PREOXYGENATE
Careful and meticulous preparation is essential for successful and safe intubation.
Preparation starts with ensuring that all necessary equipment is present, functioning and immediately available at the patient’s side. Necessary intubation equipment include not only the ET tube but also the stylet, syringe, lubricant, laryngoscope, BVM, oral and nasal airways, oxygen tank and regulator, capnography and tube confirmation devices, tube securing devices, and spare tubes. In addition, rescue supraglottic airway (SGA) devices (e.g., Combitube, King Laryngeal Tube [King LT], Laryngeal Mask Airway [LMA], i-gel) must be readily available.
Positioning of the patient is important to optimize laryngoscopy. Intubation will be easiest if you’re comfortably positioned. The classic position for laryngoscopy is with the patient supine and at the level of your xiphoid. This position allows the entire left arm to contribute to the lifting force of laryngoscopy while affording a direct view of the patient’s mouth and airway. (See Figure 1,above.) Some operators brace the left elbow against the chest to stabilize and aid lifting force.
Prehospital intubation often occurs with the patient at ground level, which dramatically alters the ergonomics of laryngoscopy. If you assume a prone position, pivoting the elbow on the ground may restrict left arm movement; you may find that the wrist must provide all of the laryngoscopy lifting force. (See Figure 2, below.)
Furthermore, it may be difficult to visualize the airway structures from this angle. Intubating in the kneeling, sitting or lateral position introduces similar ergonomic challenges.
Small adjustments in positioning can dramatically ease laryngoscopy. Ensure the patient is supine and straight; any slight rotation of the neck or torso can alter laryngoscopic view. Intubation may be easiest if the patient is already elevated; for example, on a bed or elevated ambulance stretcher. Using a manikin model of an immobilized trauma patient, one study showed that raising head of the backboard improves the speed of intubation.9 If necessary to intubate in the kneeling or sitting position, some operators find it helpful to brace the left elbow against the thigh to improve arm leverage.
Figure 2: Alternate intubation positionsThe ergonomics of laryngoscopy may dramatically change when you attempt intubation in the sitting (left) or prone (right) position. Some practitioners brace the left elbow against the thigh to improve lift during laryngoscopy.
Preoxygenation is important for safe intubation. Oxygen desaturation may lead to brain injury or cardiac arrest and must be avoided during intubation efforts. Preoxygenation forces nitrogen out of the dead space of the lungs, increasing the duration of “safe apnea,” which is the elapsed time from cessation of ventilation to oxygen desaturation of < 90%.
With proper preoxygenation, a healthy adult may endure up to eight minutes of apnea without oxygen desaturation.10 The theoretical period of safe apnea drops to five minutes for moderately ill adults and 2.7 minutes for obese patients.
Preoxygenation requires delivery of 100% fractional inspired oxygen (FiO2). Spontaneously breathing patients should be preoxygenated for at least three minutes using a non-rebreather mask with the oxygen flow set above 15 Lpm (15 Lpm achieves only 60–70% FiO2 with conventional non-rebreather masks).11 If the patient is able to take vital-capacity breaths (full exhalation followed by full inhalation), preoxygenation may require as little as eight full breaths. In apneic or hypoventilating patients, preoxygenation must be accomplished by a BVM device. Note that with most BVM devices, delivery of oxygen requires either 1) a spontaneous patient breath; or 2) squeezing of the bag. “Blow-by” oxygen through a BVM won’t work.
Even with proper preoxygenation, critically ill prehospital patients have poor pulmonary reserve and will exhibit shorter safe apnea periods than healthy individuals. For example, a trauma patient with a hemothorax will have less available lung dead space for preoxygenation, yet will have increased oxygen demands because of shock; these patients may desaturate very quickly.
3. LIMIT THE NUMBER & DURATION OF INTUBATION ATTEMPTS
Minimize the number and duration of laryngoscopy attempts (i.e., insertion of blade), striving to achieve rapid first-pass intubation success. Each laryngoscopy attempt exposes the patient to apnea and potential hypoxia, which may lead to peri-intubation cardiac arrest. In inhospital series, multiple intubation attempts increase the risk of adverse events, including cardiac arrest.12,13
In the cardiac arrest patient, intubation attempts often cause prolonged CPR chest compression interruptions. In a series of 100 prehospital intubations, intubation efforts resulted in a median of 100 seconds of chest compression interruption.6 Given that even brief chest compression interruptions can reduce cardiac arrest survival, laryngoscopy attempts should be limited to 20 seconds.14
The likelihood of intubation success diminishes with each successive laryngoscopy attempt.4 In the face of multiple unsuccessful laryngoscopy attempts, immediately proceed to rescue SGA insertion. To curtail futile intubation attempts, some EMS agencies have adopted protocols that specify “three attempts and out,” immediately moving to rescue SGA insertion after three total unsuccessful laryngoscopy attempts. Some EMS agencies have adopted stricter “two attempts and out” and even “one attempt and out” policies.
Ergonomics also change when in the kneeling or lateral position.Positioning the left elbow on the ground may limit the available lifting force for laryngoscopy and interfere with your line of vision.
4. CONFIRM & RECONFIRM
One of the most important and catastrophic airway adverse events is unrecognized esophageal intubation. This phenomenon was first highlighted in a study published in 1999, describing a 25% tube misplacement rate among 108 EMS intubations.1 Despite widespread attention to this adverse event, today, anecdotal reports of ET tube misplacements persist.
There’s no single infallible method for confirming ET tube placement—every strategy may falsely miss an esophageal intubation. National consensus guidelines recommend that multiple methods be used to confirm prehospital ET tube placement.15 Furthermore, because movement of the patient occurs extensively in the prehospital setting, reconfirmation of ET tube placement must occur at least every five minutes. If possible, continuous tube placement confirmation is preferable.
Auscultation of the chest and abdomen are the most common tube placement confirmation techniques, but may be inaccurate in the noisy prehospital environment. While useful for verifying initial placement, esophageal detector devices and Toomey syringes require interrupting ventilation. While commonly used, colorimetric carbon dioxide detectors may be difficult to interpret under dark ambient light and in cardiac arrests, where carbon dioxide exhalation depends upon quality chest compressions.
Experts believe that digital and waveform capnography are the best tube placement confirmation technologies, offering high accuracy and the ability to continuously verify tube placement. In fact, one study suggests that tube misplacements can be eliminated with the systematic use of waveform capnography.16
Tube fogging shouldn’t be used to verify ET tube placement as the accuracy of this approach has been disproved.17 Oxygen saturation also shouldn’t be used to verify ET tube placement; even with a misplaced ET tube, a patient may not desaturate for several minutes.
5. SECURE, SECURE, SECURE
Because of the frequent need to move the patient, ET tube dislodgement is a key concern in the prehospital setting.5 Several strategies can help to prevent tube dislodgement. The ET tube must never be manually held in place and should be secured with adhesive tape, umbilical twill tape or a commercial tube holder. Some practitioners use a C-collar to help minimize head and ET tube movement. When moving the patient onto or off the ambulance stretcher, disconnect the BVM device to avoid pulling upon the ET tube.
SGA devices must also be secured in place using adhesive tape or a commercial tube holder. The minimum vertical dislodgement force is nearly identical for taped ET tubes, LMAs and King LT airways.18 (The minimum dislodgement force is higher for the Combitube.) Note that not all commercial ET tube holders will work with SGAs; the King LT and LMA have tubes that are so large in diameter that they may not be accommodated by a standard ET tube holder.
There’s no such thing as a ‘simple’ prehospital airway—all prehospital airways are difficult.
6. HAVE A LOW THRESHOLD FOR SUPRAGLOTTIC AIRWAY USE
SGAs are excellent for facilitating ventilation when intubation efforts are unsuccessful. (See Figure 3, pp. 36–37.) While usually viewed as a “rescue” for failed intubation, these devices are 1) relatively simple to insert; 2) don’t require confirmation of placement; and 3) seem to ventilate as well as an ET tube. In the face of multiple or difficult intubation efforts, providers should have a low threshold for inserting an SGA. As discussed previously, some EMS agencies have protocols specifying immediate supraglottic airway insertion after three (or two or even one) failed intubation attempts.
Some EMS agencies have embraced a more radical approach, using SGAs instead of intubation in select patient groups such as those in cardiac arrest.19,20 The simplicity of the SGA allows for rapid airway insertion without interrupting CPR chest compressions, while preserving the goal of delivering controlled ventilations.
7. PRACTICE MAKES PERFECT
Intubation is an extremely difficult skill, but the opportunities for EMS professionals to obtain and maintain adequate training are extremely limited. While an ideal setting for learning intubation, U.S. paramedic students typically have access to only 2–4 days of operating room training.21 Some paramedic students graduate without having performed intubation on a live patient. Although some paramedics have frequent intubation opportunities, in many communities paramedics struggle to gain adequate intubation experience. In Pennsylvania in 2003, paramedics performed a median of only one intubation annually.22
Take advantage of all opportunities to refine your intubation and airway management skills. Manikin and human simulators don’t recreate the “mush” feel of live human structures, the range of different airway types encountered in clinical practice, or the presence of blood and secretions. However, manikins are readily available and can provide a platform for daily practice of fundamental airway management and intubation skills.
Scenario training may be useful to rehearse decision-making and airway management algorithms so that actions are automatic when encountered in clinical practice.
Finally, access to the operating room for additional practice on anesthetized patients is an invaluable experience. Be an enthusiastic student and absorb all pearls offered by the anesthesiologist or nurse anesthetist. You may also have the opportunity to practice SGA insertion or to perform BVM ventilation for an extended period of time, which are essential skills.
8. EMBRACE NEW IDEAS
State-of-the-art research is giving birth to new ideas for prehospital airway management. We must maintain an open mind to these cutting-edge ideas because they have strong potential to improve patient safety and outcomes. For example, some EMS practitioners have adopted SGA insertion as the primary airway in cardiac arrest. Extending on this idea, the rapid-sequence airway has been proposed—coupling neuromuscular-blockade administration with SGA insertion, allowing for rapid securing of the airway without the concerns of ET tube misplacement.23–25
Figure 3: Supraglottic airways
Supraglottic airways such as the King Laryngeal Tube (left), Laryngeal Mask Airway (center) and i-gel (right) are important rescue interventions
Some studies suggest that BVM alone may result in higher survival than either ETI or SGA insertion; this controversial idea is plausible because hyperventilation may be less likely with BVM.26 Also, animal studies suggest that all advanced airway devices may compress the carotid arteries, constricting blood flow to the brain in cardiac arrest.27 In Arizona, some paramedics resuscitate cardiac arrests using only a non-rebreather mask for passive ventilation.28
Following these eight pearls for safer prehospital tube placement and management will help you be prepared for adverse airway management events, arm you with the tools you need, and encourage you to keep one eye to the future as you perform this most important—yet difficult—procedure.
Henry E. Wang, MD, MS, is professor and vice chair for research at the Department of Emergency Medicine at the University of Alabama School of Medicine in Birmingham.
Acknowledgments: Thanks to Michael R. Lovelace, RN, CEN, CFRN, CCEMTP, NREMTP, at the University of Alabama School of Medicine; and Dakota Kelly, EMT-P, and Nathan Dunaway, EMT-P, of Birmingham Fire and Rescue Service for assisting with the photographs for this article.
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