I recently learned of something in educational theory that lead me to a small epiphany: threshold concepts.

Critical care specialties are full of threshold concepts.

What is a threshold concept?

The idea of a threshold concept in learning was first introduced by Meyer and Land1, focusing on economics education. They described this as concepts that "...once understood, transform perception of a given subject."

A threshold concept provides a gateway to a greater, more in-depth understanding of an area – but is often difficult to master. Meyer and Land described a threshold concept as having:

"...the notion of transformation (in which students change the way they perceive and practice aspects of their discipline), irreversibility (once learnt rarely forgotten or 'unlearnt'), integrative (whereby connections are made to concepts or knowledge of previously unknown or concealed areas), bounded (in that they help define the boundaries of a subject area) and potentially troublesome." K. Connan (2014)

Thus a threshold concept is something that is often troublesome and struggled with, but then when achieved takes us to a new, permanent level of understanding that often makes important connections with other concepts.

It is a gateway concept to a greater level of mastery of one's craft.

Threshold concepts are different from core concepts, which although similar "...core concepts do not take the learner into a new realm but rather build layers upon learning foundations already possessed."

Threshold concepts have been studied and identified in many disciplines2, and medical specialties are no different.

Anesthesia, emergency medicine and intensive care medicine are littered with threshold concepts. The ideas and perceptions that trainees and specialists struggle with – and perhaps sometimes never master. The understanding of both big and small corners of our craft that propel us to a new level of understanding – sometimes euphorically, sometimes unsettling and disturbing, though always transformative.

"Where ignorance is bliss, 'tis folly to be wise." – Thomas Gray

Threshold concepts in health and medicine

Clouder first wrote of threshold concepts in health (2005) suggesting that caring was such a concept for healthcare students.3 Troublesome to understand and integrate with professional roles, patient interactions and institutional policy, it was nonetheless transformative when contextualized with ethical, moral and personal demands.

Caring and compassion is a significant threshold concept in critical care specialties where a dynamic, pressured environment lends itself to dehumanization of the individual. In anesthesia, intensive care and emergency medicine we walk a fine line maintaining empathy yet avoiding emotional distraction in critical moments. Perhaps the threshold concept here is that empathy and focused, dynamic objectivity are not mutually exclusive. Too great a subject to explore today!

Threshold Concepts in Anesthesia and Critical Care

All of which got me thinking:  there must be value for critical care education if we identify some of the threshold concepts not just for trainees, but for specialists as well.

What are the concepts that you see those new and not-so-new to your specialty struggling with? What concepts have you struggled with, but once understood have launched you to a new level of understanding of your craft? What do you still struggle with?

A few threshold concepts I have pondered...

Technical skill: intubation is about precision and vectors of force

Miller-airway-axes-vertical The classic diagram in Miller showing the need to align oral, pharyngeal and tracheal axes is a core concept, but not a threshold concept (i.e. it's not troublesome to understand). Similarly for patient position, ear-to-sternum and flexion-extension.

What I see the newest laryngoscopists struggling with is the need for precision when wielding the laryngoscope: don't just trap the tongue, sweep it out of the way; ensure the tip of the blade is deep in the vallecula; and lift, don't leverage, along the axis of the handle. The threshold concept here is that all these steps have a single goal: displacing tissue anteriorly beneath the mandible while elevating the laryngeal inlet to allow the three axes to line up. Easy to know, more challenging to understand.

Technical skill: sedation, anesthesia and analgesia are not the same

Anesthesiologist and friend Dr John Zois suggested the understanding of differences and overlap between sedation, anesthesia and analgesia as a threshold concept. They can appear very similar, in fact a patient can transition between each or mix in aspects simultaneously – but the skilled anaesthetist or anesthesiologist needs understand when she's giving one and not the other – and why. (?and captures how the ?lesser? skill of quality sedation can actually be more challenging to provide than general anesthesia.)

Technical skill: awake fibreoptic intubation is not always the answer

Fibreoptic intubation is sexy and fun for the airway doctor. For the trainee it looms as a challenging skill that must be mastered. The first misconception is fixation on the driving of the scope as the primary challenge (this must be mastered, but like all motor skills it's practice practice practice), when in fact quality local anesthetic topicalization of the airway (along with cautious sedation or analgesia) is the more critical skill. The threshold concept however is an appreciation that not all difficult airways benefit from fibreoptic intubation – there are many scenarios when it is the wrong choice.

Bastardizing surgical wisdom:

"...the good know how to fibreoptically intubate, the better know when not to."

Perioperative medicine: it's all about outcome

When we plan perioperative care and anesthesia technique for increasingly complex patients and surgeries, the frame through which everything must be viewed is what are the desirable outcomes? What are we shooting for? Which outcomes matter to the patient, the family and the community?

Too often we lose sight of what the real outcomes may be for surgery and medical care. It is outcomes that matter. But this cuts both ways: not only may particular surgery, intensive care stay or resuscitation be inappropriate, but conversely that which may be considered futile could have significant positive outcome in terms of extra-weeks or quality of life. Considering outcomes provides a framework for decisions. Outcomes do not stop in the recovery – in fact they've barely started.

Prioritising decisions: what's best for the patient?

Flowing from the last, my wise friend NJ tells me that when he meets indecision, disagreement or conflict, bringing it simply back to "What's best for this patient?" almost always clears the fog and realigns a team's goals. The threshold concept here is considering "what's best" in terms of the holistic individual balanced by environmental context and the greater community. I didn't say it was easy...

Safety: you can do everything right and bad things still happen.

When you first begin practicing anesthesia, sometimes little things go wrong. Sometimes big things go wrong. Introspection is a natural state of mind for many of us but leads us to confuse the inevitable mistakes with the consequence of outcome. The false corollary is that if we avoid making mistakes then surely we avoid Things Going Wrong?

Somewhere in the transition from journeyman to specialist we understand that things go wrong even when everything is done right. This is the foundation upon which the anesthesia temple of vigilance is built. (And is why if I see you leave your anesthetised patient I will kick. your. arse.)

Planning: it's how your anesthetic behaves when it fails that matters

The junior anesthesiologist often confuses a smooth anesthetic, an effective block or pleasant emergence as the marker of anesthesia quality. These are important and rule patient experience, but the most significant indicator of your anesthetic quality is how well it behaves when things go wrong.

This is my final threshold concept: resilience is as equally important as safety and efficacy. Do you practice so that failure occurs elegantly or is instead delicate and brittle?

What do you think?

Of course, it will not have been lost on you that idea of threshold concepts has itself been a threshold concept for me. In all its recursive beauty.

  1. Meyer J H F and Land R 2003 "Threshold Concepts and Troublesome Knowledge – Linkages to Ways of Thinking and Practising" in Improving Student Learning – Ten Years On. C.Rust (Ed), OCSLD, Oxford. [ pdf

  2. More reading, lectures and videos: Threshold Concepts, A short introduction and bibliography. UCL Department of Electronic and Electrical Engineering. 

  3. Clouder L (2005). "Caring as a 'threshold concept': Transforming students in higher education into health (care) professionals" Teaching in Higher Education, 10(4), 505-517.