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Arguably the most important piece of the evidence-based-medicine puzzle is when we ask ourselves:
"Is this evidence significant? – Is this relevant to my patients and my practice?"

When we talk about the 'quality' of a published research work we largely mean what the epidemiologists refer to as 'internal validity' – the extent to which the study's conclusions are actually warranted given the methodology and results. Internal validity looks only at the study design, conduct and interpretation, and takes into account bias and confounders. While important, internal validity is not alone sufficient.

The significance of a piece of evidence to medicine in general, along with it's relevance to our own practice, is referred to as the external validity. I think that for your and my practice this is often what matters most.

Really, external validity just describes how well the results and conclusions can be generalized to situations and people beyond those in the study.

I think of significance as the cumulative generalizability of a piece of evidence for the specialty and for wider medicine, integrated with how well the evidence agrees with what is already known. Relevance describes how applicable the evidence is to my hospital, my practice – and my patients.

It has significance for you, and relevance for me.

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Our understanding of what makes for quality medical research has improved dramatically over the past three decades. We understand that research must be ethical; should be reproducible; free of bias, so that we may make accurate conclusions; and that confounders be minimised and controlled for. We understand that prospective is best, and large blinded randomized trials are king.

We can articulate that a study must be appropriately powered to answer the question we are asking – but also not over-powered so that we waste resources and goodwill, or continue a study after an answer is known.

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The number of new medical articles published each month is accelerating. PubMed has over 23 million indexed going back to 1966¹, adding around 500,000 every year – but that's just the articles they index. There are an estimated 50 million scholary articles in total ever written ², and currently over 28,000 peer-reviewed journals in print, publishing almost 2 million new articles in 2012 – and that's growing by 3% every year.³

If we focus only on MEDLINE® citations (publications indexed with MeSH, Medical Subject Headings) the number of publications each year is increasing exponentially. The graph below shows annual (not cumulative) MEDLINE® citations. The trendline in orange highlights the challenge of staying-up-to-date: annual medical publications is not just increasing, its accelerating.

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Ah, videolaryngoscopes – wonderful toys increasingly common in operating rooms, intensive care units and emergency departments throughout the world.

After the first video laryngoscope was conceived by New York emergency physician Jon Berall in 1998, commercial success quickly followed with the 2001 Glidescope (designed by a vascular surgeon nonetheless!). Our love of the videolaryngoscope has grown ever since.

Like many anaesthetists and anesthesiologists I've used several different videolaryngoscopes over the past few years. The character that sets apart the videoscopes I like to use from those I do not is how well they enhance airway techniques I use every day rather than requiring a new technique specific to their device.

Overwhelmingly this comes down to how similar the laryngoscope is to a standard Macintosh blade rather than inventing a whole new shape. While there may be theoretical (or even real!) benefits to increasing the angle of the blade or adding extra conduits, when I have a difficult airway I want to augment the tools and techniques I use every day rather than change to something completely different. (When I want to change to something completely different I'll pick up a fibreoptic bronchoscope or something sharp!)

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The evidence-based medicine movement started excitedly in the 1990s, filled with much promise and hope. The way we practice medicine has been improved by EBM, along with the health of our patients. However it has not been all smooth sailing, and the challenges to evidence-based medicine are growing not lessening.

While we know more about the human body, critical care, anesthesia, and resuscitation than ever before, it is conversely more difficult to integrate evidence and guide decisions where they matter: for an individual patient.

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