Airway & Respiratory

Prehospital Management of Difficult Airways

Issue 5 and Volume 41.

LEARNING Objectives

  • Understand what makes management of an airway difficult.
  • Learn the different mnemonics and acronyms to help determine when an airway will be difficult.
  • Know which tools to use for different airway difficulties.

KEY Terms

Cricothyrotomy: An emergency incision into the larynx, performed to open the airway of a person who’s unable to be ventilated.

Denitrogenation: The elimination of nitrogen from the lungs and body tissues during a period of ventilation with pure oxygen.

Patent: Open and unblocked.

A difficult airway is one in which the EMS provider identifies potential attributes of the patient that would make it difficult to utilize a bag-valve mask (BVM), insert an extraglottic airway, perform a laryngoscopy, and/or perform surgical airway interventions.1 It’s the ability to appropriately assess the patient’s airway that allows providers to predict which will be difficult, optimize their first attempt and ensure the highest likelihood of success when managing a patient’s airway. Thorough airway assessments help drive your clinical decision-making and help determine the tools you choose to wield when managing a particular airway.

DIFFICULT BVM VENTILATION

The airway literature has identified numerous attributes that are likely to cause some difficulty for the clinician to adequately ventilate a patient with a BVM. Using the mnemonic “MOANS” allows providers to quickly recall potential issues so they can attempt to compensate. (See Table 1.) Successful BVM ventilation is dependent on a patent airway, a good mask seal and appropriate ventilation. Anything that impedes any of these components will cause the provider to have a difficult time ventilating their patient with a BVM.

The current body of evidence suggests that men and patients with a partially or non-visible uvula (Mallampati class 3 or 4) are more difficult to ventilate with a bag-mask device.1,2 Issues that inhibit a mask seal cause air to leak, making ventilations more difficult. Factors such as the presence of a beard and/or debris such as blood, dirt, vomit, etc. around the landmarks that the mask is placed can cause complications, but there are ways providers can improve their ability to deliver effective ventilations. One major improvement, which really should be done anytime the resources are available, is to utilize a second provider during BVM ventilations. By having one provider hold a mask seal and the other squeeze the bag, the providers can more easily ensure the best possible seal, which will minimize air leaks. Beyond the utilization of a second provider, if the crew takes a moment to wipe off any potential debris, the provider holding a mask seal is less likely to slide and will be able to hold a more secure mask seal.

prehospital airway management

With BLS airway adjuncts, EMS providers often limit themselves to an oropharyngeal or nasopharyngeal airway adjunct. These devices aren’t mutually exclusive.3 It’s perfectly reasonable to place two nasopharyngeal airways in along with an oropharyngeal airway to help optimize airway patency. While ventilating obese patients, placing them in a ramped position (stacking blankets behind the patient’s upper body and head until the tragus aligns with the sternal notch) helps reduce the pressure on the diaphragm and makes it easier for the provider to ventilate.Obesity is also associated with difficult BVM ventilations. With obese patients or late-stage pregnant women, the mass of tissue can place pressure on the chest and diaphragm, which inhibits chest rise with the traditional amount of pressure exerted by a provider squeezing a bag (50-100 cmH2O). Providers can improve their ventilation techniques for obese patients by utilizing airway adjuncts, utilizing two providers, and adjusting the patient’s position.

The “O” in MOANS can also stand for “obstructions” such as foreign bodies or pathophysiologic obstructions from specific disorders. Partial or complete obstructions, in the upper or lower airway, can make it difficult and potentially impossible for providers to deliver effective ventilations. This can be identified during your assessment while listening to breath sounds, even without a stethoscope at times in severe cases. Upper airway sounds include sonorous respirations, gurgling and stridor, while lower airway sounds include wheezes, crackles or ronchi.

Sonorous respirations usually imply that the tongue is blocking the airway, necessitating the provider to reposition the patient’s airway and utilize some basic airway adjuncts. Gurgling is the result of fluid in the upper airway of a spontaneously breathing patient that the provider can attempt to control with suction. Stridor is caused from a narrowing of the upper airway. If it’s a foreign body, the provider can try manual thrusts to remove it or attempt to manually remove it with Magill forceps if it’s visible. However, if it’s a pathophysiological obstruction along the lines of laryngeal edema, the provider should try to treat any potential causes of the edema in hopes of reversing it as well as prepare for an intubation along with the possibility of a surgical cricothyrotomy.

Wheezes are caused by bronchoconstriction and may benefit from the introduction of bronchodilators into the ventilation circuit. Crackles occur when fluid fills the bases of the lower airway, whereas ronchi occurs when thick, viscous secretions block a part of the lower airway. Although best ventilation practices include the use of a positive end expiratory pressure (PEEP) valve on the exhalation port of the BVM, patients with crackles or ronchi present would benefit from higher levels of PEEP to help keep the alveoli open and push fluid out.

The “A” and the “N” in the mnemonic stand for “age” and “no teeth.” Older patients are typically more difficult to ventilate due to physiological changes with the aging process. As patients age they lose muscle tone and tissue elasticity, making it difficult to form a mask seal. Utilizing two-provider BVM ventilation can mitigate this along with evaluating the mask size. Since the maxillary and mandibular structures may reduce in size with the aging process, a standard adult mask may be too large for some older patients.4 Using a pediatric mask may help to achieve an appropriate seal.

Another issue with mask seal comes from the absence of teeth. If dentures are in place and secure, their presence will help the provider form a better seal. However, if they’re loose, they can become an airway obstruction. Providers must use their clinical judgment to evaluate the risks of leaving dentures in compared to the risks of ventilating the edentulous patient with a BVM.

The last portion of the MOANS mnemonic refers to “stiff and snoring,” which have been discussed briefly. Snoring can usually be rectified with an airway adjunct along with repositioning the patient. It’s beneficial to know if they have a history of sleep apnea before ventilations are attempted, but the information may not be available.

“Stiff” refers to patients with a condition that’s likely to reduce airway compliance such as acute respiratory distress syndrome, pneumonia, pulmonary edema, etc. Providers can utilize mainstream capnography between the mask and the bag to evaluate inhaled and exhaled carbon dioxide as long as they’re able to maintain a secure mask seal.

Capnography may help in your clinical decision-making, but you’ll likely feel the compliance issues as soon as you attempt to ventilate the patient. Stiff lungs may necessitate higher PEEP and are at a higher risk of pneumothorax.

prehospital airway management

The LEMONS mnemonic is utilized in the Difficult Airway Course and in Advanced Trauma Life Support as a tool to help providers anticipate potentially difficult airways. This assessment is crucial in helping the intubator determine what tools to use as well as what backup options they should have ready and available.DIFFICULT LARYNGOSCOPY

“Looking externally” is something that’s done innately as providers walk to the patient. Although this assessment is often done in seconds, there’s an abundance of information to process, none of which should be ignored. This portion of the assessment is what formulates a provider’s gestalt, or general impression, about an airway. If something feels off because of the presence of blood, a goiter or other anatomic abnormality, or a variety of issues, it may be picked up while you’re looking externally. Don’t limit yourself to just looking-
palpate the airway as well.

“Evaluating” the intubating geometry of the patient is done using the 3-3-2 rule. The first “3” assesses the mouth opening by measuring the patient’s index, middle and ring finger between the upper and lower incisors. If the patient fails this portion, another provider can help improve the intubator’s view by gently pulling on the right-hand corner of the patient’s mouth.5 The second “3” refers to the distance between the mental protuberance and the hyoid bone in comparison to the width of the patient’s index, middle and ring finger. This assessment determines if the patient’s mandible is long enough to adequately displace the patient’s tongue into the submandibular space. If the patient fails this assessment then there’s a high likelihood the patient’s tongue may be difficult to displace and obstruct the provider’s view.

If available, the provider should also consider the use of a hyper-angulated blade on a video laryngoscope, which are designed to go around the airway anatomy, eliminating the need to displace the tongue. If the patient fails this test due to their baseline anatomy, the provider can consider utilizing a straight blade inserted it into the right paraglossal space, which provides a view to the right of the blade without the tongue present. If the patient failed due to an underlying pathology (e.g., infection, Ludwig’s angina, etc.), then the intubation should be attempted by the most experienced provider and a cricothyrotomy kit should be available prior to attempting the intubation.

The final “2” of this section measures the distance of the glottis opening by comparing the width of the patient’s index and middle finger to the distance between the hyoid bone and the thyroid notch. If the patient fails this assessment then the provider should anticipate the patient’s glottis opening to be anterior.

“Mallampati” classifications can be a useful tool for providers who have rapid sequence intubation (RSI) capabilities, it’s unreasonable to obtain in the unconscious patient. The Mallampati classifications require the patient to open their mouth and stick out their tongue. The system is classified from the anticipated least difficult intubation, labeled as a class 1, where the provider can see the patient’s soft palate, fauces, complete uvula and pillars, through the anticipated most difficult intubation, labeled a class 4, where none of the traditional landmarks are visible and the provider can only see hard palate. Essentially, the less uvula that the provider sees, the more difficult the intubation will be.

In unconscious patients, providers should utilize the Cormack-Lehane grading system during laryngoscopy. (See Figure 1.) In this system, a grade 1 has a full glottis view, a grade 2 has a partial glottis view, a grade 3 only has a view of the epiglottis, and a grade 4 lacks a view of the glottis or epiglottis. The use of a gumelastic bougie is extremely beneficial for grade 3 views because the coude tip can get under the epiglottis and advance into the trachea. Grade 4 views shouldn’t be attempted unless the view can be improved.

Figure 1: The Cormack-Lehane grading scale

prehospital airway management

One method for improving the view is through the use of external laryngeal manipulation. With external laryngeal manipulation, the intubator has their laryngoscope in their right hand, an additional provider has their index and thumb grasping the larynx, and then the intubator places their right hand on the hand of their assistant. This allows the intubator to manipulate their assistance hand and the patient’s larynx towards the direction that they feel would be most likely bring the glottis into the intubator’s view. Once the optimal view is obtained, the assistant holds the position while the intubator grabs an endotracheal tube and passes it through the glottis opening.

prehospital airway management

The coude tip of the bougie can go underneath the epiglottis while angling itself to go toward the glottic opening.

The issues of “obstruction” don’t vary much from the issues discussed with ventilation. Ultimately, if they weren’t resolved with the BVM, the provider must plan to accommodate for them. If gurgling is heard during ventilations then the provider may consider attempting to obtain a glottis view with their laryngoscope in their left hand while inserting a hard suction with the right hand and having an endotracheal tube within reach to switch out with the suction. If stridor is heard, the most experienced intubator should attempt to perform the laryngoscopy. If the cause is from a foreign body, attempts should be made to visualize and remove the obstruction with Magills. If an injury or illness is causing laryngeal edema, then the intubator can consider attempting to pass a gumelastic bougie through the vocal cords in hopes that they may be able to pass an endotracheal tube, even a small one, through the swollen cords. Regardless of the provider’s experience, the equipment needed for a surgical cricothyrotomy should be out and ready for use.

“Neck mobility” may be from an acute injury or a chronic disorder. Although the underlying cause may change the provider’s capabilities, the optimal management will likely be the same. When providers are attempting to intubate a patient who requires cervical spine immobilization, the provider must be cautious and avoid unnecessarily manipulating the patient’s neck.

In patients with underlying chronic disorders, such as rheumatoid arthritis, providers may not have the physical capability of manipulating the patient’s neck. The use of a hyper-angulated blade on a video laryngoscope is the optimal device for either subset of patients with neck mobility issues. Because the blade is designed to go around the airway anatomy, the provider doesn’t have to manipulate the neck much at all while intubating.

Oxygen saturation levels can drastically reduce the amount of time that providers have to intubate a patient. Patients who are already ill may start at a lower saturation and their percentages will drop quickly. Two things that can help patients maintain oxygen saturations during intubation and quickly improve oxygen saturations if they’ve dropped are the use of “nasal oxygen during efforts securing a tube,” known as NO DESAT,6 and a thorough nitrogen washout. With NO DESAT, the provider initiates oxygen via a nasal cannula at 15 Lpm during the preoxygenation phase. The same nasal cannula is left on at 15 Lpm throughout the intubation. The concept of a nitrogen washout, or denitrogenation, is that the patient has been breathing ambient air, which is 79% nitrogen, prior to the provider’s interventions. By ventilating the patient with high-flow oxygen, the provider is displacing the nitrogen in the lungs and maximizing the amount of available oxygen. Utilizing these two techniques together ensures providers have an adequate amount of time to successfully intubate the patient without putting them at a substantial risk.

The last component of the LEMONS mnemonic is “situation.” Truth be told, paramedics rarely, arguably never, have to intubate a patient on the floor, in the back seat of a car, in between the toilet and the wall of a bathroom, or in any other complex position. The fact is that the likelihood of successful intubation decreases in these settings. Providers must maintain situational awareness and evaluate the resources available on scene, the current location and position of the patient, the length of time the patient must stay in that area (e.g., prolonged extrication, additional resources required to safely move the patient, etc.) and any other potential complications that may exist regarding the patient’s airway before attempting the intubation.

Providers often attempt to work around a scene instead of making the scene work for them. Move furniture out of the way so providers are as comfortable as possible while managing an airway. If providers become uncomfortable, grips will be lost and seals will be broken. Move the patient to an area and position that’s optimal for the intubator. It’s not unreasonable for EMS providers to place the patient onto the stretcher and adjust it to a comfortable height for the intubator.

On scenes where it isn’t possible to move the patient or adjust the environment, like an extrication, the provider should evaluate if it’s reasonable to manage the patient’s airway with BLS maneuvers until the patient can be moved. Otherwise, it may be the most clinically appropriate not to attempt an intubation and go straight to an extraglottic device. Remember, the only bad airway is the one that isn’t oxygenating the patient.

CONCLUSION

Assessment and planning are crucial in airway management. Providers must use every available tool to optimize their first attempt. The decision not to intubate is often a more difficult and nobler decision then the decision to intubate. Every case is different and providers must utilize good clinical decision making to perform the best airway: The one that oxygenates the patient.

REFERENCES

1. Walls RM, Murphy MF: Manual of emergency airway management, fourth edition. Lippincott Williams & Wilkins: Philadelphia, 2012.

2. Yildiz TS, Sloak M, Toker K. (2005) The incidence and risk factors of difficult mask ventilation. J Anesth. 2005;19(1):7-11.

3. Perris T, Brudney S, editors: Top tips in anaesthesia. Greenwich Medical Media: Cambridge, U.K., 2005.

4. Sveikata K, Balciuniene I, Tutkuviene J. Factors influencing face aging. Stomatologija. 2011;13(4):113-116.

5. Nutbeam T, Daniels R, editors: ABCs of practical procedures. Wiley-Blackwell: West Sussex, U.K., 2010.

6. Levitan R. (2010.) No DESAT. Emergency Physicians Monthly. Retrieved March 28, 2016, from www.epmonthly.com/article/no-desat/.

7. Chrimes N, Fritz P. (2013.) The vortex approach: Management of the unanticipated difficult airway. Rollcage Medic. Retrieved March 28, 2016, from http://rollcagemedic.yolasite.com/resources/Archived_newsletters/the-vortex-approach-management-of-the-unanticipated-difficult-airway.pdf.