Development of an Airway Management Plan

Key Points

• Decision bias can be reduced by considering each aspect of airway management separately.

• The utility of any airway device is dependent on prior experience and availability; two different practitioners may justifiably come to widely opposing management decisions.

• The Cormack and Lehane (CL) laryngeal view score has not been validated as indicating the ease or difficulty of tracheal intubation.

• The vast majority of difficult airways (DAs) are not predicted.

• The degree of lingual tonsil hyperplasia and its effect on ease of laryngoscopy may vary with seasonal allergies and patient conditions.

• A prior history of no difficulty with ventilation or intubation is an indicator, but not a guarantee, of ease of management east.

• Airway evaluation indices have poor sensitivity and specificity.

• Preoperative endoscopic airway evaluation (PEAE) provides improved information about the invisible airway.

• An examination of neck surface landmarks should be part of the routine airway evaluation in every patient.

Introduction

A multitude of algorithms, techniques, and opinions focused on management of both the routine and difficult airway (DA) patient can be found in the anesthetic literature. Airway management practitioners study the mechanics of airway evaluation and history taking and can apply devices and procedures once a course of action is chosen. Less distinctly described are the “hows” and “whys” of arriving at this plan. Perhaps this lack of attention occurs because too many algorithms, techniques, opinions, and devices exist, and because the availability of tools and our experience with them vary greatly among practitioners.

The patient with an anticipated DA is often, therefore, an enigma. The large database of the Danish Society of Anesthesiology highlights the gap between the anesthesiologist’s prediction and outcome of a DA. ^, In this collection of nearly 200,000 anesthetic cases, 93% and 94% of difficult intubation (DI) and difficult mask ventilation (DMV) cases, respectively, were unanticipated, whereas predictions of difficulty were correct only 25% of the time.

Similarly, confounding the issue is the condition of the patient and the experience of the operator. For example, a patient presenting for elective abdominal surgery in the operating room may be easy to manage (in terms of his or her airway) with a videolaryngoscope (VL). That same patient presenting emergently a week later with ileus, hypoxemia, and a depressed level of consciousness to a junior physician in a community-based emergency department where a standard direct laryngoscope is the device of choice must be treated differently and may result in a different outcome.

Indeed, making decisions regarding one’s ability to intubate the trachea or ventilate via face mask or supraglottic airway (SGA) and what other risks the patient faces (e.g., pulmonary aspiration of gastric contents, tolerance of oxyhemoglobin desaturation) must be individualized not only to the patient but also to the practitioner, context, and time.

Decision-Making

Decision-making can be flawed. A variety of cognitive models have been described, and all are influenced by biases that result in a preference for including or excluding evidentiary factors in the process of making a decision and formulating a plan. In airway management, several biases can affect the course of the clinician’s cognitive processes. Confirmation bias is the act of seeking information that confirms ones predetermined opinion. Fixation bias or “tunnel vision” causes the clinician to focus on a single aspect of the patient to the detriment of other (possibly more important) pieces of information. Visceral bias is the VIP phenomena—someone “important” or to whom the operator has an attachment is treated out of the norm. Retrospective bias refers to applying a prior positive or negative outcome as proof for or against a correct decision. Omission bias may be one of the strongest in the field of airway management: inaction out of fear of causing harm or damaging one’s reputation, especially in the presence of an “authority.” The Fourth National Audit Project (NAP4) of the Royal College of Anaesthetists and the Difficult Airway Society (DAS) demonstrated these phenomena in instances where clinicians seemingly avoided awake intubation in favor of inappropriately using SGAs or regional anesthetics or ignored physical examination findings and historic evidence suggestive of a DA because of skill and confidence-related issues.

A component-by-component approach to the airway management decision-making process can encourage the isolation of biases and empower the clinician to arrive at a rational plan. Although the derived plan may be outside the operator’s comfort level or rejected by another invested clinician (e.g., the surgeon), knowledge that a logical, step-by-step approach was employed should fortify the conclusion. In some cases, this may lead to the seeking of help from skilled personnel, delaying of procedures, or a change in the care plan. For example, in the case of a patient with COVID-19 infection who requires tracheal intubation for intensive care, advice might be given to the primary care team that airway management is too hazardous and non-invasive repiratory support might be sought.

Evaluation of the Airway

The value of a history of difficulty with airway management is limited, unless there is clear and extensive documentation. For example, a history of difficult or failed tracheal intubation by direct laryngoscopy (DL) is a strong predictor (6- and 22-fold, respectively) of difficulty on a future presentation ^, ; yet, multiple studies have demonstrated a 94% to 95% rate of rescue of failed DL by video-assisted laryngoscopy (VAL). The number of available techniques and devices is vast, and the range of experience with a particular device will vary greatly between practitioners. Documentation of the success of laryngoscopy for the purpose of communication most often relies on the Cormack and Lehane (CL) grading scale, which was not developed for VAL, flexible intubation scopes (FISs), or other modern devices. The CL grade has not been validated as an indicator of the ease or difficulty of intubation with DL, but much of the literature assumes that the ability to see the glottis correlates with ease of tracheal intubation. For example, Rose and Cohen, in a prospective study of 18,500 tracheal intubations, described that poor visualization of the glottic structures was associated with a higher rate of DI by DL. Cook, modifying the original CL grading system to more practically describe the findings of a full or partial laryngeal view, a visible and mobile or immobile epiglottis, or no view, was able to correlate CL grade to time to intubation as well as the need for airway adjuncts. Contrary to this, Adnet and colleagues noted that in a study of 331 patients the majority of patients with poor CL grades on DL were intubated on first attempt, and 4 patients with complete views of the larynx were difficult to intubate. Aziz and colleagues noted that 35% of intubation failures during use of the GlideScope VL (Verathon Inc., Bothell, WA) were associated with complete views of laryngeal structures ; similarly, Cooper and colleagues found the rate to be 54%. Because the incidence of an adequate view of the larynx during VAL is high (99.78% in one study), an adequate laryngeal view is likely irrelevant to the success or failure of intubation—other factors influencing tracheal tube delivery being more important.

Invisible and asymptomatic changes in the airway’s anatomy can have profound effects on the ability to manipulate the airway with any one device. Findings such as lingual tonsil hyperplasia may vary with time, season, allergies, or other factors. Therefore, any history of difficulty with airway management should raise the suspicion that more than routine procedures may be required and should be prepared for. Alternatively, a previous history of a DA does not destine the patient to special procedures and concerns in all future events.

Should a history of difficulty be elicited from the patient or medical record, an effort should be made to determine not only the nature of the encounter, but also how each facet of management (e.g., intubation, mask ventilation [MV], SGA ventilation) was performed and affected. Critical information includes the experience of the airway manager, the device(s) used, and contextual issues. This information guides the practitioner’s decision on the individual components of airway management.

The Need to Control the Airway

Although it is one of the most common procedures of the anesthesia practitioner, controlling the airway entails risk to the patient. Not only are intrinsic respiratory drives and reflexes obtunded, but difficulty in airway control via face mask, SGA, or tracheal intubation may ensue or complications in successful management may be encountered even after uneventful management. In the American Society of Anesthesiologists (ASA) Closed Claims Database, 80% of laryngeal trauma claims were associated with cases of routine airway management and no suspicion of injury. The risks and benefits of airway control should always be considered and balanced. A common example of this balance is the preference for regional anesthesia in obstetric anesthesia; a 10-fold increase in airway-related maternal morbidity and mortality is well documented and is in great part responsible for this practice. Patient and surgeon preference, as well as the operator’s skill level, must be considered in this decision, with the latter taking priority. The guidelines of the ASA Task Force for Management of the DA caution similarly and recommend that there be a preformulated strategy for managing the airway, as well as dedicated equipment available, when regional anesthesia is selected for any procedure. This same recommendation is made in the airway management guidelines of other international expert organizations. ^,

Laryngoscopy and Intubation

Definitive airway management has traditionally been understood to mean tracheal intubation by some means (e.g., by DL, VAL, or flexible scope intubation [FSI]). Although it may be argued that face mask or SGA ventilation may constitute as secure an airway as tracheal intubation, this discussion will assume the traditional meaning. This is not to say that all decisions regarding airway management should result in a plan for tracheal intubation; rather, by assuming tracheal intubation as the default plan, the safety of a plan can be incrementally evaluated when the default plan (i.e., tracheal intubation) appears impossible or difficult. Several factors are considered in the assessment of the ease of tracheal intubation: airway evaluation indexes, practitioner experience, and device availability.