A 30-year-old man has just arrived at the emergency department (ED). He was driven in by friends with a chief complaint of difficulty breathing with a history of asthma. Your initial assessment of the 300-pound, 5-foot-tall male shows impending respiratory failure. He is cyanotic with agonal respirations. While examining his airway, you see a beard and a large overbite. How will you manage this patient’s airway? Will this be an uncomplicated intubation? This patient presents with many factors that can make traditional endotracheal intubation difficult or even impossible.
Many patients challenge our airway-management skills. The increased incidence of obesity, anatomical structure, and disease processes all contribute to our inability to provide effective airway management for our patients.1 In its Practice Guidelines for Management of the Difficult Airway,2 the American Society of Anesthesiologists (ASA) defines a difficult airway “as the clinical situation in which a conventionally trained anesthesiologist experiences difficulty with face mask ventilation of the upper airway, difficulty with tracheal intubation, or both.” In addition, the ASA outlines a systematic approach to management of patients with difficult airways, including a portable kit containing multiple devices in order to provide effective airway management. Finally, the American Heart Association3 states that no one method or device can provide effective airway management for all patients.
One way to envision difficult-airway management is as a difficult-airway toolbox. This toolbox contains skills and techniques as well as devices. It is not necessarily a kit as described in the ASA guidelines, although many EDs and anesthesia departments have such physical kits and carts. The toolbox is much more than that: It also includes a wealth of knowledge and skills that can be utilized when one is presented with a challenging case. What is in your toolbox? This article will discuss some of the most common techniques and devices that you may consider for your difficult-airway toolbox.
The toolbox starts with effective bag-mask ventilations. This represents the foundation of all advanced airway management. All caregivers should be proficient in the delivery of effective ventilations with a bag-mask device.3 Bag-mask ventilations, used with an oral pharyngeal or nasal pharyngeal airway, may be the only mechanism available for effective airway control. In addition, endotracheal intubation has been shown to have an unacceptably high incidence of complications when provider experience level is low or monitoring of tube placement is inadequate.3
Once bag-mask ventilations have been initiated and proven to be effective, it is time to decide if an advanced airway is required and what type of device will provide an effective airway with minimal risk to the patient. Airway assessment is the key to making the right decision. The Mallampati score has been the traditional tool used to evaluate a patient’s airway and probability of successful intubation. Recent studies have questioned the effectiveness of Mallampati to predict difficult airways. Thus, rather than using one tool, a multiple point assessment has been recommended.4
The US National Emergency Airway Management Course has developed a method of evaluating multiple factors that influence the difficulty of a patient’s airway. The LEMON method (Look–Evaluate–Mallampati–Obstruction–Neck Mobility) encourages a systematic evaluation during the initial assessment of a patient. Look represents the evaluation of external characteristics. Items such as obesity, short neck, prominent upper incisors (overbite/buck teeth), receding jaw, burns, facial trauma, anaphylaxis, etc are included in this evaluation. Evaluate uses a three-three-two rule. This is a measurement of thyroid to floor-of-mouth distance (greater than three fingers), hyoid mental distance (greater than three fingers), and interincisor distance (greater than two fingers). Measurements of less than these distances represent a difficult airway. Mallampati classification is included in the evaluation, but, as stated previously, may have limited use in the emergency airway setting. Obstructions can create a difficult airway. Obstructions include blood, vomitus, teeth, epiglottis, tumors, and foreign bodies. Neck mobility is the last assessment point in the method. Preexisting medical conditions such as scoliosis, kyphosis, and spinal abnormalities limit neck mobility and prevent proper placement of the patient for some advanced airway procedures. In addition, spinal precautions due to trauma, impaled objects, and immobilization can limit neck mobility.5
One modification of LEMON suggests adding an “S” (LEMONS) for oxygen saturations and the time/oxygen component. A saturation of 100% following preoxygenation has an “adequate reserve,” above 90% but less than 100% has a “limited reserve,” and less than 90% has “no reserve.”6 The latter presents with a high risk of complications during intubation and might suggest the use of alternative methods and devices.
Other multifaceted evaluations exist, but their goals are the same: to complete a systematic assessment of every patient’s airway during the initial examination. By identifying patients with difficult airways early, you can plan for your interventions and choose the best method and device for your patients. Further research might prove that some methods are better at predicting the degree of difficulty of a patient’s airway.
When endotracheal intubation is used to control a difficult airway, external manipulation of soft tissues of the anterior neck may assist in visualization and placement of the endotracheal tube. The three primary methods are the Sellick maneuver, backward-upward-rightward pressure (BURP), and bimanual laryngeal manipulation. The Sellick maneuver is backward pressure on the crichoid cartilage. It is used as a method to prevent regurgitation of stomach contents. BURP is used by exerting pressure on the thyroid cartilage. Positioning the thyroid cartilage backward, upward, and rightward is believed to improve laryngeal view with a laryngoscope. Both of these maneuvers are done by an assistant during intubation. To utilize bimanual laryngeal manipulation, the laryngoscope operators use their right hands for laryngeal manipulation while conducting laryngoscopy. Once proper visualization is obtained, the laryngeal position is maintained by an assistant while the operator passes the endotracheal tube. A recent study demonstrates that the latter method provided the best visualization.7 As are the previous assessment methods, multiple methods of manipulation to assist with placement of an advanced airway are part of a difficult-airway toolbox.
Advanced Airways and Devices
Endotracheal intubation is a common technique for airway management but, as discussed previously, may not be appropriate for all patients. There are two devices that may improve the success rate of intubation with difficult airways: the gum elastic bougie and the lighted stylet.
Gum bougie. The elastic gum bougie is a widely used tool in Europe. It is a 60-cm-long tracheal tube introducer with a 36-degree angled distal tip (2 cm from its end). It is available in its classic form (reusable, with a braided core) or as a less expensive, single-use endotracheal tube introducer (ETTI). Both devices are used the same way. The gum bougie is passed through the glottic opening under direct laryngoscopy. Unlike classic endotracheal intubation, the glottic opening does not need to be visualized. The design of the gum bougie allows it to be passed posterior of the epiglottis. Two methods are utilized to confirm placement through the glottic opening. One is a washboard sensation of clicks as the tip slides over tracheal rings as it is advanced. The second is to use the length of the gum bougie to pass it to the carina. Failing to meet resistance for the full length of the gum bougie indicates placement in the esophagus. Once placement is confirmed, an endotracheal tube is slid over the gum bougie, using the Seldinger technique, into the trachea. Some maneuvering and lifting of the pharyngeal soft tissue with a laryngoscope may be required to advance the endotracheal tube. Some studies have shown an increase in successful intubation with the use of the gum bougie over traditional stylets. The gum bougie is suggested for patients with limited neck mobility or facial trauma, or when visualization of the glottic opening is not possible.8
Lighted stylet. Multiple forms of the lighted stylet have been in existence since 1957. Regardless of the specific device, the techniques are very similar. The stylet (with a light source at its tip) is placed in a standard endotracheal tube. The tube is shaped into the classic hockey stick form. The endotracheal tube/stylet combination is passed through the mouth and guided anteriorly through the glottic opening. While passing the endotracheal tube, a glow will be visible on the anterior neck. It will start just below the hyoid bone and, as the tube is advanced, will move to just above the thyroid cartilage. At this point, the endotracheal tube is slid off the stylet and into the trachea. The exaggerated sniffing position utilized for classic endotracheal intubation is not required. A slight extension has been shown to facilitate passage of the lighted stylet/endotracheal tube.9 Like the gum bougie, the lighted stylet does not require direct visualization of the glottic opening. A low light environment will increase the visibility of the stylet. One caveat, though: Slight extension of the neck may be contraindicated in trauma patients, limiting the effective use of the lighted stylet.
What if the patient’s airway prevents effective endotracheal intubation? There are two devices in prominent use as an alternative to endotracheal intubation: the laryngeal mask airway (LMA) and the double-lumen tube with one blind end that functions as an esophageal obturator airway and the other as a standard cuffed endotracheal tube. Both devices are inserted blindly, without the need for direct laryngoscopy, and offer airway management for patients for whom endotracheal intubation is unsuccessful or not an option. Another advantage of both devices is the reduction in training needed to obtain and maintain competency. This allows more widespread use of the devices over endotracheal intubation. Patients must be unconscious and without a gag reflex for their use. Both the LMA and the double-lumen tube have been proven to be as effective as endotracheal intubation for ventilation and are superior to bag-mask ventilations.3
Laryngeal mask airway. The LMA is available in multiple sizes and is sized based on the patient’s weight. It can be inserted without manipulation of the patient’s cervical spine. It does not provide the aspiration prevention level of an endotracheal tube, but it can be used with less training. Care should be taken to follow the manufacturer’s recommendations for inserting and securing the LMA. Misplacement or migration of the LMA may lead to inadequate ventilations. Once a patient regains consciousness or becomes agitated, the LMA should be removed.10
Double-lumen tube. Unlike the LMA, the double-lumen tube has two possible correct placements. The device may be placed in the esophagus or the trachea during blind insertion. The tube is available in two sizes and is sized by the patient’s height. Since the device has two possible locations after insertion, proper assessment postinsertion is crucial. Furthermore, ventilation of the correct lumen to produce lung inflation is required. If the tube is placed in the esophagus, tracheal suctioning cannot be done through the device. As with the LMA, the double-lumen tube should be removed if a patient regains consciousness or becomes agitated. The device is contraindicated for patients with caustic ingestion and esophageal disease or trauma.10
A well-stocked difficult-airway toolbox can provide a clinician with many methods for effective airway management. Remember, the goal of difficult-airway management is to provide effective oxygenation and ventilation while limiting complications. A supplemental technique may shorten the length of the intubation and, with the use of the LMA and double-lumen tube, can provide an interim airway that will limit hypoxia during a difficult intubation. No one technique or device will work for all patients; but a difficult-airway toolbox can provide a broad spectrum of solutions for the safe and effective management of patients with difficult airways.
Alan W. Henschke, EMT-P, is clinical educator at Norwalk Hospital, Norwalk, Conn. For further information, contact [email protected]
- State specific prevalence of obesity among adults. MMWR Morb Mortality Wkly Rep. 2006;55:985-8.
- Practice guidelines for management of the difficult airway. an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology. 2003;98:1269–77.
- 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Part 7.1: Adjuncts for airway control and ventilation. Circulation. 2005;112(suppl 1);IV-51-57.
- Lee A, Fan LT, Gin T, Karmakar MK, Ngan Kee WD. A systematic review (meta-analysis) of the accuracy of the Mallampati tests to predict the difficult airway. Anesth Analg. 2006;102:1867-78.
- Reed MJ, Rennie LM, Dunn MJ, Gray AJ, Robertson CE, McKeown DW. Is the ‘LEMON’ method an easily applied emergency airway assessment tool? Eur J Emerg Med. 2004;11:154-7.
- Braude D. Difficult airways are “LEMONS”: updating the LEMON mnemonic to account for time and oxygen reserve. Ann Emerg Med. 2006;47:581.
- Levitan RÂ, Kinkle WC, Levin WJ, Everett WW. Laryngeal view during laryngoscopy: a randomized trial comparing cricoid pressure, backward-upward-rightward pressure, and bimanual laryngoscopy. Ann Emerg Med. 2006;47:548-55.
- Moscati R, Jehle D, Christiansen G, et al. Endotracheal tube introducer for failed intubations: a variant of the gum elastic bougie. Ann Emerg Med. 2006;36:52-6.
- Lionel D, Cook-Sather S, Schreiner M. Lighted stylet tracheal intubation: a review. Anesth Analg. 2000;90:745-56.
- Sanders MJ. Mosby’s Paramedic Textbook. Rev 3rd ed. St Louis: Mosby Lifeline; 2007