Key Terms
BURP maneuver: A maneuver in which pressure is applied to the larynx in a backward (i.e., posteriorly against the cervical vertebrae), upward (i.e., superiorly as possible) and rightward (i.e., slightly laterally to the right) manner.
Epiglottis: A leaf-shaped structure located posterior to the base of the tongue.
Faucial pillars: The vertical folds of tissue formed by the muscles that create the fauces or the aperature of the mouth into the pharynx.
Glottis: The space between the vocal cords where the endotracheal tube is inserted.
Sellick’s maneuver: A method of reducing the risk of the aspiration of stomach contents during endotracheal intubation by rapid sequence intubation by applying pressure to the cricoid cartilage and pushing it against the sixth cervical vertebra.
Soft palate: The structure composed of mucous membrane, muscular fibers and mucous glands forming the posterior portion of the roof of the mouth.
Uvula: The round piece of flesh hanging from the posterior soft palate.
Learning Objectives
>> Identify four steps that have been shown to consistently improve clinicians’ ability to visualize
the glottis.
>> Adapt three techniques to improve clinicians’ ability to visualize the glottis for field use.
It’s a cold, dark January evening. After a long day of running calls, you and your partner are looking forward to finally sitting down to a hot dinner when your meal preparations are interrupted by a familiar request: “Medic Five, respond to an unconscious subject on the ocean bike path, south of the fairgrounds.”
On arrival, you and your partner find an engine company on scene. They’re in the process of opening a large, barricade-style gate, providing access to an unlighted area of a bike path frequented by your city’s large homeless population. After a brief hike, you find three male transients gathered around a collapsed, apparently unconscious man. They state that the man, a transient who’s well known to you, had been drinking heavily when he suddenly and without warning lost consciousness. You assess the patient, who weighs approximately 300 lbs., and find him to be unconscious and unresponsive to all stimuli. No spontaneous respirations are present, and peripheral pulses are absent.
The physical examination reveals no indications of trauma, and both dependent lividity and rigor mortis are absent. The ECG shows narrow complex pulseless electrical activity (PEA). Based on these findings, it’s determined the patient is a viable candidate for resuscitation. The absence of apparent trauma allows for the airway to be opened through head extension. After an oropharyngeal airway (OPA) is sized and placed, bag-valve-mask (BVM) ventilations are initiated with supplemental oxygen. Your partner prepares for endotracheal intubation (ETI) by checking his laryngoscope, ensuring the integrity of the ET tube and readying suction equipment. Magill forceps are on hand for relief of a possible airway obstruction.
Lying supine on the ground at the patient’s head and using a #4 Macintosh laryngoscope blade, your partner indicates he’s having trouble visualizing the glottic opening. After anterior laryngeal pressure fails to improve visualization, your partner elects to resume BVM ventilations with an OPA in place.
Taking the laryngoscope from your partner, you ask the engine company, which has already placed the patient on a long backboard, to move the patient to the waiting stretcher. You have the stretcher raised to the level of your mid abdomen, which allows you to move freely and comfortably above the patient. You have your partner place three folded blankets under the patient’s head and shoulders to achieve head and neck extension beyond sniffing position. After swapping out the Macintosh blade for a #4 Miller blade, you have your partner apply backward, upward, rightward pressure to the patient’s larynx while you attempt visualization. With the glottic opening clearly visible, you pass an 8.0 internal diameter ET tube between the vocal cords and advance the tube to 24 cm at the patient’s teeth.
The patient is then ventilated with oxygen titrated to 94% pulse oximetry (SpO2), in accordance with American Heart Association guidelines, and capnography confirms a successful placement with ongoing end-tidal carbon dioxide (EtCO2) measured at 34 ppm for the duration of the transport to the hospital. On your arrival at the hospital, the emergency department physician confirms successful placement via an X-ray.
Discussion
Despite the advent of numerous alternative airway management devices, many in EMS believe ETI should remain the gold standard in advanced airway management. Acknowledged to be a difficult skill to acquire and maintain, ETI requires the practitioner to visualize the space between the vocal cords, known as the glottic opening or glottis, through which the ET tube is passed. Glottic visualization is so fundamental to achieving a successful intubation that if visualization can be achieved and maintained, there’s little risk the tube will be misplaced.1
If, on the other hand, visualization isn’t attained and tube placement is nevertheless attempted, the odds are great that the tube will find its way into the esophagus, which is in natural alignment with the oropharynx.2 If unrecognized and uncorrected, this will produce a catastrophic outcome for the patient. Many studies have been conducted regarding how to best achieve glottic visualization, although almost all have been conducted in well-controlled clinical environments rather than the field. Still, the techniques employed by clinicians to optimize glottic visualization can be replicated by making use of resources commonly available in the field setting.
A review of clinical literature yields the following four steps, which have proved to consistently improve clinicians’ ability to visualize the glottis:
- Place the patient level with the paramedic’s mid abdomen or lower chest;
- Use a straight laryngoscope blade;
- Anticipate difficult intubations; and
- Respond to the predicted difficult intubation with use of the sniffing position, head and neck extension beyond the sniffing position, and the BURP maneuver.
Although such procedures as direct laryngoscopy and ETI may need to be performed by ALS personnel, advanced airway management requires coordinated involvement by all on-scene providers. BLS personnel are an invaluable resource and should be involved in patient positioning and laryngeal manipulation. BLS personnel are also the appropriate level of care for BVM ventilation and SpO2 monitoring.
Let’s examine the techniques and learn how simple modifications allow these procedures to be adapted for field application.
Patient Placement
In the operating room, no patient is ever placed on the floor, with the clinician lying at the patient’s head. In clinical practice, it’s generally accepted that the best position for performing an intubation is standing, with the patient at the level of the clinician’s mid abdomen to lower chest.3—5
In the field setting, EMS providers can achieve this ideal placement by moving the patient to the stretcher and then elevating the stretcher to a position that allows the paramedic the optimum angle for visualization, as well as the ability to move freely and comfortably above the patient. This is far preferable to lying on the ground or floor, with the rescuer’s prone body on the same plane as the patient’s supine body, in which position the rescuer struggles to peer into the patient’s mouth at a fixed angle.
Straight Edges
In our scenario, the first paramedic used a Macintosh blade in his unsuccessful intubation attempt. In the second, successful attempt, the paramedic used a Miller blade. Although curved blades provide better tongue control and may make passing the ET tube easier, straight blades are better than curved blades in achieving glottic visualization.6 The straight blade often produces slightly more crowded conditions than curved blades, but the greater visualization achieved by the straight blade more than makes up for the crowding. In addition, the more crowded conditions of straight blades can be easily overcome by passing the tube in through the corner of the patient’s mouth.
Power of Prediction
The difficulty of an intubation can be predicted by the degree to which the faucial pillars, the soft palate and the uvula are obscured by the base of the tongue.1,7,8 If they’re easily seen, the intubation is anticipated to be easy. If obscured, the intubation will be difficult. There should be three fingerbreadths from jaw to thyroid cartilage, the jaw should be greater than three fingers wide and the jaw/mouth should open greater than two fingers wide. Thus, other predictors of difficult intubations include unusually short or long thyromental distances (the distance from the chin to the thyroid notch); short ramus (jaw bone); obesity; and/or short, thick necks, which limit the ability to extend the head.8,9
In the field, the initial view of the laryngopharyngeal structures usually happens during the first intubation attempt. If the base of the tongue is large, head extension proves difficult. If the vocal cords don’t easily come into view with the elevation of the epiglottis, the patient is a difficult intubation. Determining that a patient will be a difficult intubation allows the paramedic to take certain measures–such as employing the BURP maneuver, putting the patient in the sniffing position and elevating the head and neck beyond the sniffing position–to facilitate intubation in these cases.
Proper Positioning
Such techniques achieve better visualization in obese patients and those for whom head extension is limited, but they’ve also been found to actually worsen the ability to visualize the glottis in patients without such anatomic challenges.9 In non-difficult airways, simple head extension is the best means of visualization.10
Of the techniques to improve visualization in the difficult airway, the BURP maneuver has been found to be the most effective–even more effective than Sellick’s maneuver.11 To perform the BURP maneuver, the rescuer gently holds the patient’s larynx between their thumb and first two fingers and then pushes the larynx backward, toward the cervical spine, while at the same time pushing the larynx upward and to the patient’s right. If visualization still isn’t achieved, place the patient in “sniffing” position, with the head extended and neck flexed from neutral position approximately 7 cm, which usually requires padding to align the earlobe with the xiphoid process, then perform the BURP maneuver again.10
Elevation of the head and neck beyond sniffing position has also been found to be effective in predicted difficult airways.12 Obviously, these techniques require an assistant, who extends the patient’s head with their right hand while using their left hand to apply the BURP maneuver. Providers may also place padding, such as folded blankets, under the patient’s head and shoulders to achieve the sniffing position or head and neck extension beyond the sniffing position.
Conclusion
The ability to visualize the glottis is fundamental to performing a successful ETI. This doesn’t change because of the less-than-optimum conditions in which EMS providers typically perform patient care. Therefore, the means used to achieve and maintain visualization should be the same irrespective of where the skill is performed.
Although the field is unquestionably a difficult environment in which to perform any complex intervention, minor modifications of proven clinical methods greatly improve the prospects for a successful outcome. Proper positioning of the patient in relationship to the care provider, use of the Miller blade, predicting candidates for difficult intubations and responding to these patients with appropriate interventions to optimize visualization are the keys to ensuring that every patient has the best possible chance of being intubated successfully, and is thereby able to enjoy the lifesaving benefits of definitive airway management. JEMS
References
1. Krobbuaban B, Diregpoke S, Kumkeaw S, et al. The predictive value of height ratio and thyromental distance: Four predictive tests for difficult laryngoscopy. Anesth Analg. 2005;101(5):1542—1545.
2. Caroline N: Airway Management and Ventilation. Nancy Caroline’s Emergency Care in The Streets, sixth ed.; Jones & Bartlett Publishers: Sudbury, Mass., 55—56, 2007.
3. Kusunoki S, Nakatsu K, Kawamoto M, et al. Comparison of emergency medical tracheal intubation performed on a table and on the ground. Masui. 2003;53(4):450—453.
4. King C, Henretig F, King B, (editors) et al. Textbook of Pediatric Emergency Procedures, second ed. Lippincott Williams & Wilkins: Philadelphia, 2008, 227.
5. Stoelting RK & Miller RD. Basics of Anesthesia, fifth ed., Churchill Livingstone: Philadelphia, 216, 2007.
6. Arino JJ, Velasco JM, Gasco C, et al. Straight blades improve visualization of the larynx while curved blades increase ease of visualization. Can J Anesth. 2003;50(5):501—506.
7. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: A prospective study. Can J Anesth. 1985;32(4):429—434.
8. Tse JC, Rimm EB, Hussain A. Predicting difficult intubation in surgical patients scheduled for general anasthesia: A prospective blind study. Anesth Analg.1995;81(2):254—258.
9. Snider DD, Clarke D, Finucane BT. The BURP maneuver worsens the glottic view when applied in combination with cricoid pressure. Can J Anesth. 2005;52(1):100—104.
10. Isono S. Common practice and concepts in anesthesia: time for reassessment: Is the sniffing position a gold standard for laryngoscopy? Anesthesiology. 2001; 95(4):825—827.
11. Takahata O, Kubota M, Mamiya K, et al. The efficacy of the “BURP” maneuver during a difficult laryngoscopy. Anesth Analg. 1997; 84(2):419—421.
12. Schmidt HJ, Mang H. Head and neck elevation beyond the sniffing position improves laryngeal view in cases of difficult direct laryngoscopy. J Clin Anesth. 2002;14(5):335—338.
This article originally appeared in June 2011 JEMS as “Achieving 20/20 Glottic Visualization OR 20/20 Vision: Clinical research provides lessons for achieving perfect glottic visualization.”
4 Steps to Improve Your View
Taking the following four steps will consistently improve your ability to visualize the glottis:
1. Place the patient at the level of the paramedic’s mid abdomen;
2. Use a straight laryngoscope blade;
3. Predict the difficult intubation; and
4. Respond to the predicted difficult intubation with use of the following three techniques: 1) sniffing position, 2) head and neck extension beyond the sniffing position and 3) the BURP maneuver.
