Project for Universal Management of Airways

The PUMA Approach to Airway Terminology

Defining universal terminology for airway management is beyond the scope of the Project for Universal Management of Airways. Notwithstanding this, the following glossary of terms used in the PUMA guidelines is provided for clarity. In addition to defining key terminology, the glossary includes a list of other terms commonly used in the literature that the PUMA working group would consider equivalent in meaning. The PUMA approach to terminology has been to use the dominant ‘legacy terms’ from the literature whenever possible, introducing novel terms only when it is considered that the legacy terms were considered unsuitable due to their:

• Potential to compromise clarity of communication and impact the safety or efficacy of patient care.

• Predisposition to divergence of language of the academic literature from that most suited to clinical practice.

Where relevant, comments have been provided on the relative merit of various legacy terms as ‘critical language’, to clarify why particular terms have been selected in preference to the diverse array of other legacy terms in use, particularly when novel terminology has been introduced. While the intention is not to create a universal lexicon of airway terminology, it is hoped that this information will provide valuable insights that will inform future projects to standardise airway terminology.

This glossary will continue to be updated as additional components of the PUMA guidelines are published.

 A

Airway Management Risk Evaluation: the process of assessing patient, team and situation risk factors relating to a particular episode of airway management, with a view to using this information to develop a safe & effective strategy for airway management.

This is typically referred to in the literature as ‘airway assessment’ or ‘airway evaluation’. These terms were felt to be suboptimal due to their exclusive emphasis on patient anatomical factors.

Airway success: the situation in which confirmed alveolar oxygen delivery AND adequate blood oxygen saturation are BOTH present. Airway success indicates successful establishment of an airway via any of facemask, supraglottic airway, tracheal tube or neck rescue.

Legacy terms for this outcome in the literature include ‘(adequate) oxygenation’, ‘(adequate) ventilation’, ‘success’ and ‘Green Zone’. Oxygenation was felt to be an inadequate term as clinicians frequently struggle to identify that oxygenation is not occurring in the circumstance when SpO2 is maintained even when exhaled CO2 cannot be detected (as may occur in the circumstance of upper airway obstruction following pre-oxygenation). Ventilation was felt to be an inaccurate term as in it’s own right it does not convey any index of oxygen delivery and the ‘adequacy’ of ventilation may be judged by some as reflecting also efficacy of CO2 elimination, in addition to oxygen delivery, which is not relevant to the context of emergency airway management. Ventilation also cannot be applied to airway insufflation techniques as might be applied following neck rescue using a cannula technique. The ‘Green Zone’ was felt to be an inappropriate term due to its potential to not be understood by someone not already familiar with it. ‘Success’ was felt to be too imprecise a term with no accepted definition. Simply defining ‘success’ as confirmed alveolar oxygen delivery and adequate blood oxygen saturation was felt to be inadequate as the term ‘success’ is not specific to airway management and is therefore subject to broad individual interpretation without practitioners confirming the definition intended by these guidelines.

Alveolar oxygen delivery can be ‘confirmed’ by return of exhaled carbon dioxide with attempts at ventilation (when attempting ventilation via a tracheal tube the criteria for ‘sustained exhaled carbon dioxide’ must be met to confirm alveolar oxygen delivery) OR via detection of a RISING oxygen saturation with ventilation (taking into account the delay between changes in blood oxygen saturation and SpO2 readings) when carbon dioxide detection is unfeasible. Note that a STATIC adequate oxygen saturation in isolation does not provide any information about delivery of fresh oxygen to the alveoli as this may reflect persistent high alveolar oxygen concentrations following pre-oxygenation, despite the presence of an obstructed upper airway or misplaced tracheal tube.

‘Adequate’ alveolar oxygen delivery does not require that the measured SpO2 is normal, only that it can be sustained at a level that is unlikely to cause harm due to hypoxaemia if it were maintained in the short term (e.g. ~15 mins). In general a SpO2 reading ≥ 80% would reflect ‘adequate’ oxygenation but this may not be the case in some clinical situations. Conversely, an SpO2 ≥ 80% is not necessarily a prerequisite for defining ‘adequacy’ (especially in situations when a value ≥ 80% could not be achieved following pre-oxygenation). As such the adequacy of the SpO2 must always be interpreted in context.

Airway Time Out: a deliberate pause in the process of airway management, undertaken in the situation of ‘airway success’, to enable optimisation, strategisation & mobilisation of resources before further instrumenting the airway. An ‘airway time out’ may be taken prior to initiating airway management for the purposes of completing an airway pre-brief or during the process of airway management whenever airway success has been achieved.

No previous dedicted term exists to describe this pause though it is recognised as an opportunity of the ‘Stop, think, communicate’ moment of the Difficult Airway Society guidelines and of the Green Zone of the Vortex Approach. The term was developed to provide critical language that enables airway practitioners to easily declare the need for such a pause.

B

Backing out: the process of restoring spontaneous maintenance of airway patency and ventilation by the patient.

This is most commonly referred to in the literature as ‘waking the patient’ but this term was felt to be suboptimal as it is typically associated with anaesthetic practice and the concept of returning the patient to a state of normal consciousness and airway protection state and potentially ‘cancelling the case’. As neither return to a normal state of consciousness/airway protection nor the ability to indefinitely defer airway management are necessities for exploiting this option, it was felt that ‘backing out’ would better convey the potential relevance of this approach to critical care medicine where it might otherwise be overlooked. Unlike ‘waking the patient’ which can be interpreted simplistically as a one-step intervention, the term ‘backing out’ also reinforces that this is a process requiring a detailed strategy, including plans for airway rescue if patency is lost, just as would be required at the initiation of airway management.

Best Effort: the situation in which all reasonable interventions (in context) to achieve airway success via a given core upper airway option have been implemented.

The term ‘best effort’ is derived from the Vortex Approach. It is distinct from a ‘plan’ as described in the Difficult Airway Society guidelines, as the latter is prospectively determined before initiating airway management whereas (while a plan to achieve a ‘best effort’ at each of the core upper airway options can and should be made prior to initiating airway management) the term best effort describes an endpoint, achievement of which can also be declared in real-time during airway management, incorporating information obtained during the process of performing airway interventions, that was not available when the plan was developed.

C

Composite failure: refers to the significantly elevated risk of alternative core airway options being challenging or failing once one option has declared itself to be challenging or has failed. The term is derived from this article.

Core airway options: this is the umbrella term for facemask, supraglottic airway, tracheal tube and neck rescue. Facemask, supraglottic airway and tracheal tube represent the core upper airway options (also referred to as ‘lifelines’ by the Vortex Approach). The literature generally refers to these as different ‘techniques’ or ‘methods’ for establishing an airway but this terminology leaves potential for ambiguity as awake tracheal intubation, use of a hyperangulated videolaryngoscope and direct laryngoscopy might all legitimately be considered different ‘techniques’ for establishing an airway, despite all referring to the same core airway option. Similarly referring to them as different ‘types’ of airway may cause confusion as different brands of supraglottic airway might legitimately be thought of as different airway ‘types’ despite referring to same core airway option.

F

Front-of-neck airway: umbrella term describing any technique for creating a passage for oxygen delivery between the anterior neck and trachea, whether performed in a time-critical (i.e. neck rescue) or non-time-critical (e.g. surgical tracheostomy) setting. When referring to the need for a front-of-neck airway in the time-critical setting of insurmountable upper airway obstruction, the more specific term ‘neck rescue’ is preferred in order to unambiguously communicate that immediate implementation of a suitably rapid technique is required.

M

Margin of safety: the ‘margin of safety’ for airway management is a qualitative parameter to be concluded following airway management risk evaluation that reflects the likelihood of exposing the patient to significant desaturation, considering the potential for one or more elements of airway management to unexpectedly prove more challenging than the risk evaluation suggests.

The term was originally used by the Vortex Approach. No other terms for this concept have previously been described in the literature.

N

Neck Rescue: the emergency procedure for urgently restoring airway patency by creating a passage for oxygen delivery between the anterior neck and trachea in the time-critical situation of insurmountable upper airway obstruction.

Numerous alternative term are in use including: (emergency) front-of-neck airway (eFONA) (DAS guidelines), (emergency) front-of-neck access (eFONA) (DAS guidelines), emergency surgical airway, cricothyroidotomy (or cricothyrotomy or ‘cric’), tracheostomy (or tracheotomy or ‘trach’), invasive airway access (ASA guidelines), direct tracheal access (NAP4), percutaneous emergency oxygenation, percutaneous emergency airway access, infraglottic rescue (ANZCA transition document), CICO rescue (Vortex Approach), emergency subglottic transtracheal access (CAFG guidelines), ‘cut the neck’.

The issues involved in selecting appropriate terminology for this procedure are discussed in detail in this article. In particular terminology that is simple, concise, intuitive (in context to those previously unfamiliar with it), precise (with respect to the time-critical nature of the procedure), flexible (with respect to the exact anatomical site - cricothyroid membrane or trachea - at which it is performed) and unitimidating is desirable. It was not felt that any of the current legacy terms adequately satisified all these criteria, hence the term ‘neck rescue’ was introduced. In particular emergency front-of-neck airway/access (currently the dominant legacy term in the literature) can cause confusion due to the tendency to drop the ‘emergency’ prefix for brevity (something that even the Difficult Airway Society (who developed the term) have done in their own guideline publications), leading to a lack of clarity about the need for suitably rapid techniques to restore airway patency in the time-critical situation of insurmountable upper airway obstruction, that could compromise patient safety. Emergency front-of-neck airway/access also predisposes to contraction to the acronym eFONA which if verbalised in an emergency would be incomprehensible to the uninitiated.

Neck Rescue Emergency: the situation of insurmountable upper airway obstruction in which best efforts at all three core upper airway options have been unsuccessful in achieving airway success and neck rescue must be initiated.

A variety of terms are used in the literature to describe this situation including ‘can’t intubate, can’t ventilate' (CICV - ASA guidelines), ‘can’t intubate, can’t oxygenate’ (CICO - DAS guidelines), ‘can’t ventilate, can’t oxygenate’ (CVCO - Canadian Airway Focus Group guidelines) and ‘complete ventilation failure’ (All India Difficult Airway Association guidelines). As well as a lack of clarity regarding the meaning of the terms ‘oxygenation’ and ‘ventilation’ and an excessive emphasis on intubation in the terms CICO & CICV, this multitude of legacy terms can also erroneously create the impression that they each refer to distinct clinical situations, some of which may not necessarily be perceived as being inextricably linked to the need to perform neck rescue. This could lead to a lack of clarity about the need for performance of neck rescue when they are declared. Rather than use a term that focuses on the problem, whose meaning & implications are potentially subject to confusion, it was felt that a term to which the solution was intrinsic was preferable. Declaring a ‘neck rescue emergency’ clearly and unavoidably communicates to the team that performance of neck rescue is required.

P

Priming: escalation in readiness to perform neck rescue undertaken before the occurrence/recognition of a neck rescue emergency. Priming includes both preparatory activities that take place in the more static setting before the initiation of airway management and those implemented during an evolving airway crisis in parallel with ongoing attempts to restore airway success by one of the 3 core upper airway options.

The term was developed by the Vortex Approach to facilitate understanding of the process of transition to neck rescue (simultaneous priming for neck rescue in parallel with ongoing efforts at upper airway rescue) as described by the Australian & New Zealand College of Anaesthetists.

R

Routine use of a videolaryngoscope: the default use of a laryngoscope capable of providing an indirect view of the glottis, whenever rigid laryngoscopy is undertaken, independent of whether there is an increased risk of challenges arising with tracheal intubation or an intention to perform direct laryngoscopy. The feasibility of adopting such an approach requires adequate availability of equipment and staff training.

Other terms in use which would be considered synonymous to ‘routine use of a videolaryngoscope’ include routine videolaryngoscopy, default videolaryngoscopy and universal videolarynoscopy. These terms have not been adopted for PUMA as they fail to clearly differentiate between the routine use of a videolaryngoscope (device) and the routine use of videolarygoscopy (technique) when the former may in fact be undertaken without the latter when using a Macintosh blade, so as to augment both the safety and efficacy of the acquisition and maintenance of direct laryngoscopy skills. The term ‘universal laryngoscopy’ is avoided in particular as it is commonly misinterpreted as implying indiscriminate use of a videolaryngoscopy for all tracheal intubations, even when other techniques (e.g. awake tracheal intubation with a flexible bronchoscope) are indicated.

S

Safe apnoea time: the duration for which the blood oxygen saturation can be maintained at a safe level in the face of an interruption to alveolar ventilation.

Sustained exhaled carbon dioxide: exhaled carbon dioxide detection sufficient to satisfy the criteria for excluding oesophageal intubation. These criteria are:

1. Amplitude rises during exhalation & falls during inspiration

2. Consistent or increasing amplitude over at least 7 breaths

3. Peak amplitude more than 1 kPa (7.5mmHg, 0.1%) above baseline

4. Reading is clinically appropriate

All four criteria must be satisfied in order to declare that ‘sustained exhaled carbon dioxide’ is present.

Previously the only term in use to address this concept was ‘adequate’ carbon dioxide. The term sustained exhaled carbon dioxide was developed to precisely define what is meant by ‘adequate’ thereby providing a clear trigger below which airway practitioners are obligated to actively exclude oesophageal intubation.

Note that this term only applies when an airway is being established via tracheal intubation. It has no relevance to determining the adequacy of exhaled carbon dioxide when ventilation is being attempted with a facemask, supraglottic airway or during monitoring of CO2 via an open system in a sedated patient.