COMMENTARY

What a Parachute Study Tells Us About RCTs

Mamas A. Mamas, BM, BCh, MA, DPhil, FRCP

Disclosures

December 22, 2018

My name is Professor Mamas Mamas. I'm Professor of Cardiology at Keele University and today we're going to discuss a very interesting study that was recently published in the Christmas BMJ , given that it's only a week before Christmas, looking at the efficacy of parachutes when jumping from an aircraft.

So this was called Parachute Trial. So there's a widely held belief that parachutes reduce major injury and trauma when jumping from aircraft. This is not really based on any randomised controlled trial data, but rather expert opinion and biological plausibility. So the study was led by Robert Yeh and Brahmajee Nallamothu, and what they set out to do was to study whether parachute prevents death or major traumatic injury when jumping from an aircraft in a randomised controlled trial manner.

Jumping to Conclusions

This was a randomised controlled trial in which 90 participants were screened, and a total sample size of 23 individuals were deemed eligible for randomisation.

This was a randomised trial in which participants were randomised to a parachute pack versus an empty backpack.

Interestingly, the study was undertaken in two different airfields. And they jumped from either a helicopter or a biplane.

Now the interesting or amusing thing about this study was that the biplane or helicopter was stationary on the ground. And the altitude was about 0.6 m – about half a metre - off the ground.

They initially approached over 92 individuals to participate in the trial. But these were undertaken during jet journeys. And so this was several thousand feet off the ground, around 10,000 feet off the ground, flying at speeds of around 700 or 800 kilometres an hour.

The primary endpoint of the study was mortality or major trauma as defined by the major trauma score that they used.

'Parachutes Don't Prevent Death'

So unsurprisingly, in this trial, which they randomised to parachute versus backpack, the event rates were very low – 0% to be exact. And there was no statistically significant difference in the event rates across the two arms.

So there was no major deaths or trauma in either the parachute arm or in the empty backpack arm.

So this is, you know, a really quite amusing, randomised trial. And obviously, you know, a great headline caption that parachutes do not prevent a major injury or death from jumping from an aeroplane.

I think this is actually quite an important study, perhaps not for the satirical perspective, although it was rather amusing, but rather the implications for evidence based medicine. I mean, a lot of things that we do in medicine enter clinical practice because of widely held beliefs or biological plausibility. And they often enter without data derived from randomised control trials. So they become very well established and then they're very difficult to move away from.

Case Studies

So examples of this is Impella in cardiogenic shock or in complex, high-risk indicated PCI CHIP cases, has become a mainstay of treatment.

And many people believe in the biological plausibility or now suggest this is a standard of care. And yet, you know, there is very little evidence around this. And there's a great difficulty in trying to undertake a randomised controlled trial in this arena because of the belief that it's efficacious and it will be unethical to do such a trial.

Recent lessons from trials such as ORBITA suggest that, you know, perhaps some of our beliefs around efficacies of interventions may be very much out of place.

So I think, you know this, this amusing trial is important. I think it sort of raises questions around, first and foremost, you know, should we be allowing, as a community, many of these interventions to gradually creep into clinical practice without the appropriate evidence base, because then it becomes very difficult to rigorously assess their efficacy in a randomised manner.

So, Impella being the point. I think, secondly, you know, that there should be some sort of guideline as to, when do you not need a randomised controlled trial in treatments that we offer.

But it's not possible to undertake a randomised controlled trial in every treatment that we offer in medicine. So what would the guidelines be? What are the exceptions? When should we not allow or not require randomised control trials in this arena?

And I think another important point, which was brought out in the discussion, but also in some of the letters of reply, relates to the risk profile of the individuals enrolled in randomised controlled trials. Often randomised controlled trials are in low-risk populations and they're often then applied to much higher-risk populations. And so whether the results of the randomised trial are applicable to these populations? Or that you may get a falsely negative trial in that those most likely to benefit from any intervention are excluded from the randomised controlled trial. And only lower-risk patients that don't have as much to benefit from the intervention are included.

And again, this can complicate matters. So I think it's important when assessing randomised control trials to really look at the, you know, the risk profile of the participants, the inclusion-exclusion criteria, and so forth, and to realise that perhaps it's not possible to do randomised controlled trials in every intervention that we offer.

Creeping Technology

I think the final thought really, which comes back to what I said earlier, is that you know, in interventional cardiology, and in other areas of medicine, particularly we allow creep of technology into our practice that hasn't been robustly assessed. And there is a real danger then that it becomes ingrained in clinical practice because of biological plausibility. And then this serves to really inhibit assessment of the efficacy and we may actually be causing patient harm in such cases.

So that's it for Christmas 2018. I hope you've enjoyed our videos from Medscape UK. I wish everybody a very happy Christmas and a prosperous new year and hope to see you after Christmas and in the New Year. All the best.

You can follow Mamas Mamas on Twitter

References:

BMJ 2018;363:k5094 Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial. Paper .

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....