Airway management is an important component of anesthetic care, as well as intensive care and emergency medicine.1 Maintaining a patent airway is critical to achieving adequate ventilation and oxygenation, and failure to do so can be life threatening.2 Consults for emergency airway management can occur throughout the hospital: in intensive care units, emergency departments, general-care floors, and non-patient-care areas.3 There are five main criteria for intubation: 1) inability to maintain airway patency; 2) inability to protect the airway against aspiration; 3) ventilatory compromise; 4) failure to adequately oxygenate pulmonary capillary blood; or 5) the anticipation of a deteriorating course that will eventually lead to the inability to maintain airway patency and protection.4 Practitioners trained in advanced airway management such as anesthesiologists, emergency physicians, intensive/critical care physicians, pulmonologists, neonatologists, nurse practitioners, physician assistants, and respiratory therapists are all able to assess the need for artificial airways, insert artificial airways, and manage them post-insertion.
Mechanical ventilation, sedation, and hemodynamic monitoring associated with endotracheal intubation are standard practice in acute care hospitals throughout the country. Patients of all ages, ranging from premature infants through the elderly, may require intubation. Routine management of these patients has become standardized, and the incidence of complication is rare. But what happens with difficult airways? What happens when no airway can be established? What equipment is needed for difficult airways? It is essential for all health care personnel with advanced skills in airway management to have an effective strategy to prevent and manage these complications when they occur.1
The basics of airway management start with the equipment. If practitioners do not understand what equipment they are using, then they can not expect to have a proper outcome. The most obvious piece of equipment is the endotracheal tube. The size of the tube chosen for intubation is critical to allow for proper tracheal seal, leading to adequate mechanical ventilation (Table 1). The shape of the standard endotracheal tube results in maximum pressure being exerted on the posterior aspect of the larynx, possibly leading to damage.
The next piece of equipment that is essential for airway management is the laryngoscope. The blade is constructed from a polycarbonate compound and comes in two basic styles: Miller and MacIntosh. Miller blades are straight, with a light bulb at the end, and are generally used for neonatal and pediatric intubations. The blade should be inserted distal to the epiglottis and then properly maneuvered to achieve visualization of the vocal cords. MacIntosh blades have a more pronounced curve than does a Miller blade and are generally used for larger pediatric patients and adults. The MacIntosh blade should be placed in the vallecula and then maneuvered properly to achieve visualization of the vocal cords.
Other vital pieces of equipment include a syringe for cuff inflation and a means to secure the endotracheal tube, be it tape or a manufactured airway-securing device. Depending on the facility, the need for adult, pediatric, and neonatal emergency airway equipment may vary. Some facilities use specially prepared airway boxes that have all the essential equipment stored in one place. Other facilities use handheld-sized bags that contain the necessary equipment. Using handheld bags can improve the transport of emergency airway equipment and locating equipment.3
ASSESSING A DIFFICULT AIRWAY
The incidence of difficult intubation has been estimated to be between 3% and 18%.2,3 One of the most difficult situations that can be faced is when bag-mask ventilation proves difficult or impossible. As much as 28% of all anesthesia-related deaths are secondary to the inability to mask ventilate or intubate.2 Being able to identify difficult airways is critical to knowing how to manage them. Difficult airways can be defined by the amount of time taken to achieve intubation or multiple attempts to achieve intubation. Perhaps the most widely used classification is the Cormack and Lehane scale, which describes the best view of the larynx and vocal cords as seen during laryngoscopy2 (Table 2). Another test used to assess the difficulty of an airway was first used by Mallampati and later modified by Samson and Young4 (Table 3). The patients sit facing the medical practitioner and open their mouth widely. The patients’ airways are then given a grade based on which anatomical structures can be seen. The results from this test are influenced by the ability to open the mouth, the size and mobility of the tongue and other intraoral structures, and movement of the craniocervical junction.4 The higher the grade, the more likely the chances of a difficult intubation. Another test to help determine the difficulty of intubation is known as the thyromental distance (Patil’s test). This measurement is taken from the thyroid notch to the lower border of the chin, with the head extended. A normal distance is 6.5 cm. A distance greater than 6.5 cm usually means intubation will be possible. If the distance is less than 6.0 cm, intubation may be impossible.2 One study correlated the Mallampati and thyromental distance and found that if the Mallampati grade is 3 or 4, and the thyromental distance less than 7 cm, then a difficult intubation is likely.2 One way that is used to combine many of these assessment techniques is called the LEMON airway assessment (Table 4). All or any of these tests, along with a thorough physical examination, should be enough to help any advanced airway provider determine the level of severity of the airway they are dealing with.
Since the word anesthesia was coined in 1846, the use of pharmacological agents to procure endotracheal intubation has become a standard of care. These medications not only keep the patient comfortable—and in some cases help them to not remember what could be a traumatizing experience—but also can provide the airway team members with maximal physical advantage to achieve proper artificial airway placement. The most effective and commonly used medications can be classified into three categories: pretreatment, induction, and paralysis.5 Pretreatment medications may be used to mitigate the response to the treatment, but the decision is up to the individual clinician.6 The agents that comprise the pretreatment category help to alleviate the physiologic response to laryngoscopy, induction, and paralysis. Pretreatment medications are ideally administered 2 to 3 minutes prior to induction and paralysis.5 A good mnemonic to aid in remembering these medications is LOAD: lidocaine, opioid analgesic, atropine, defasciculating agents.5 Lidocaine may suppress the cough and gag reflex experienced with laryngoscopy and has been considered to have an effect on blunting increases in mean arterial pressure (MAP), heart rate, and intercranial pressure (ICP).5 Opioid analgesics, such as fentanyl, may mitigate the physiologic response increase in sympathetic tone. Atropine can decrease the bradycardic effects of direct laryngoscopy (stimulation of the parasympathetic receptors in the laryngopharynx) and administration of succinylcholine (direct stimulation of cardiac muscarinic receptors).5 Finally, a “defasciculation” dose of a nondepolarizing agent may reduce the duration and/or intensity of muscle fasciculations (twitches) associated with the administration of succinylcholine (due to stimulation of nicotinic acetylcholine receptors).5
Induction agents are rapid acting and provide a prompt loss of consciousness.5,6 The choice of which drug to use is up to the clinician’s preference and prior experiences. Etomidate, ketamine, propofol, and midazolam are some of the more common drugs used. Each has the potential for hemodynamic compromise (hypotension, bradycardia, increased ICP). But as long as the sequelae are treated properly, the administration of a paralytic agent to provide a neuromuscular blockade will provide the patient with the optimum amount of pharmacological support to achieve intubation.
Traditional endotracheal intubation has become commonplace for those clinicians who participate in it on a consistent basis. Grouping together the appropriate team members, having the right equipment, assessing the patient’s airway, and properly medicating the patient should result in successful endotracheal intubation. But what happens when direct laryngoscopy is not adequate or unsuccessful? One piece of equipment that may be useful in that situation is a video laryngoscope that uses digital technology to generate a view of the glottis. Such modified laryngoscopes have a camera lens on the tip of the blade. They provide a real-time view of the airway on an external monitor, allowing for easier vocal cord visualization. Often the lenses have antifog mechanisms to resist lens clouding and secretions.7 Another method to achieve endotracheal intubation is by using a bronchoscope. By inserting the brochoscope through the endotracheal tube and then into the patient’s laryngopharynx, an adequate view of the vocal cords may be achieved and the endotracheal tube can be advanced for proper placement.8
Once endotracheal intubation has been achieved and confirmed, one of the highest priorities is preventing accidental extubation. For as long as the practice of intubating patients has been in place, the potential for unplanned extubation has been a cause for concern.9 One of the best ways to avoid this is to properly secure the endotracheal tube. Depending on the health care facility, this may be done in several different ways. Manufactured endotracheal tube holders and different taping techniques are the main ways to facilitate a secure endotracheal tube. But the prevention of extubation comes not as much from the quality and stability of the securing device, as it does from the knowledge, training, and comfort level of the health care provider in working with these securing devices.9 All unplanned extubations can be recognized as preventable,10 whether it be by adding or adjusting the patient’s sedation level, restraining the patient, or, in the case of neonates, swaddling them. Consistent and effective communication between all team members is the best way to prevent extubation.
Endotracheal intubation is a multidisciplinary team effort that can be easily achieved through proper planning, understanding the equipment, critical thinking, and appropriate adaptation.
Brendan Lillie, BS, RRT-NPS, is a staff respiratory therapist at Newton-Wellesley Hospital in Newton, Mass. For further information, contact [email protected]
- Divatia JV, Bhowmick K. Complications of endotracheal intubation and other airway management procedures. Indian J Anaesth. 2005;49:308-18.
- Gupta S, Sharma R, Jain D. Airway assessment: predictors of difficult airway. Indian J Anaesth. 2005;49:257-62.
- Wilcox S, Bittner E, George E, Buckley VF, Schmidt UH. Improvement in emergency airway equipment transport. Respir Care. 2010;55:852-7.
- Wilson IH, Kopf A. Prediction and management of difficult tracheal intubation. World Federation of Societies of Anesthesiologists. Practical Procedures. 1998;Issue 9:article 9:1-4.
- Laffery KA. Rapid Sequence Intubation. 2011. Available at: emedicine.medscape.com/article/80222-overview. Accessed July 8, 2011.
- Rapid Sequence Intubation: a guide for assistants. Available at: www.scottishintensivecare.org.uk/education/RSI%20brochure.pdf. Accessed July 8, 2011.
- Retrograde Tracheal Intubation. Available at: metrohealthanesthesia.com/edu/airway/fiberoptic.htm. Accessed July 8, 2011.
- Richmond AL, Jarog DL, Hanson VM. Unplanned extubation in adult critical care. Crit Care Nurs. 2004;24:32-7.
- Sessler C, Listello D. Unplanned extubations. Chest. 1995;108:1769-70.
- MHA Fiberoptic Tracheal Intubation. Available at: metrohealthanesthesia.com/edu/airway/fiberoptic.htm. Accessed July 10, 2011.