Gathering the Evidence: Clinical Study of New Technologies

Why This Chapter?

Vascular and endovascular trauma management is a rapidly developing field, which is dominated by medical devices. The preceding chapters in this section have highlighted key developments, such as stentgrafts, coils, plugs, resuscitative endovascular balloon occlusion of the aorta (REBOA), selective aortic arch perfusion (SAAP), and extracorporeal life support (ECLS) systems. New devices (and modifications of existing ones) are being developed and brought to market with astonishing speed.

This presents challenges for the clinical evaluation and adoption of these new technologies. Medical devices are not subject to the same regulatory requirements as new medicines, which have to be proven to be effective, or at least be as effective as existing treatments. Medical devices, in contrast, only have to be shown to be “safe” before they can be marketed and used. This makes it difficult for researchers to “keep up,” particularly as indications expand, and devices are modified. In addition, these new devices may also mandate acquisition of new skills by the clinicians utilizing them. Buxton’s Law of Health Services Research which states, “it is always too early to evaluate, until it is too late,” is highly applicable to endovascular technology. The aim of this chapter is to provide the reader with an understanding of the process of evaluating new technologies, and the options available to clinicians and researchers.

Medical Devices Are Not Parachutes

Medical students are often taught that multicenter, prospective, randomized clinical trials represent the highest quality evidence, and that new treatments should, whenever possible, be evaluated in this way. However, in reality, clinical trials are difficult to design, expensive, and take a long time to plan and execute. As a result, some innovators like to invoke the “parachute metaphor,” particularly when innovations are conceptually attractive, or have shown great promise in the preclinical setting, or in small case series. The arguments usually revolve around statements such as “we know that it works,” and “you would never perform a randomized trial of parachutes – it wouldn’t be ethical.” These claims often reference two satirical articles, by Smith and Pell (2003) and Yeh et al. (2018), published in the Christmas editions of the British Medical Journal. Both of these are worth reading, as they make important points (albeit tongue-in-cheek).

It is, of course, true that we would never perform a randomized trial of parachutes – so why do we have to conduct clinical trials? Many clinicians are flummoxed by this argument. Unfortunately, the parachute metaphor is almost never applicable in medicine. Humans are complex, and most therapies and devices have multiple unintended consequences (some of which may even be harmful) that complicate the intended effect. This is not true of parachutes. Even more importantly, a parachute has a number needed to treat that comes very close to 1. Although some people have survived falls from planes without parachutes, or complete malfunctions of their parachutes ^a

a Modern parachute rigs consist of two canopies, a main and a reserve, although evaluations of the effectiveness of these devices usually refers to the system as a whole.

; and although there are deaths despite a parachute being used, the risk is very low, ^b

b Personal communication with Brig. DTN Munasinghe, MD, verbal communication on 23 March 2019 and CDR Tamara J Worlton, MD, email communication on 12 October 2018.

, and the absolute reduction in mortality is therefore very close to 100%. There are no medical therapies that offer comparable benefits. Simply put, medical devices are not parachutes – and therefore have to be carefully and thoroughly evaluated.