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Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial

Robert W Yeh, Linda R Valsdottir, Michael W Yeh

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Changyu Shen, Daniel B Kramer, Jordan B Strom, Eric A Secemsky, Joanne L Healy, Robert M Domeier, Dhruv S Kazi, Brahmajee K Nallamothu

2018 · BMJ

Biology & medicine
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From the abstract

Abstract Objective To determine if using a parachute prevents death or major traumatic injury when jumping from an aircraft. Design Randomized controlled trial. Setting Private or commercial aircraft between September 2017 and August 2018. Participants 92 aircraft passengers aged 18 and over were screened for participation. 23 agreed to be enrolled and were randomized. Intervention Jumping from an aircraft (airplane or helicopter) with a parachute versus an empty backpack (unblinded). Main outcome measures Composite of death or major traumatic injury (defined by an Injury Severity Score over 15) upon impact with the ground measured immediately after landing. Results Parachute use did not significantly reduce death or major injury (0% for parachute v 0% for control; P>0.9). This finding was consistent across multiple subgroups. Compared with individuals screened but not enrolled, participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001). Conclusions Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention. However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps. When beliefs regarding the effectiveness of an intervention exist in the community, randomized trials might selectively enroll individuals with a lower perceived likelihood of benefit, thus diminishing the applicability of the results to clinical practice.

Metadata: Crossref. Abstracts retain their original authors’ rights.

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3 selected excerpts · 3 total mentions

chithanh
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> Me and anyone else reading this. In that case, no "we" don't, because I am reading this and I do not agree with this "standard" nor your characterization of what I wrote. > Mechanisms are inferred from empirical evidence, I don't see how you can treat them as two separate categories. For example, in your crash test dummy analogy, verification through crash tests (with dummies) is empirical evidence. This is not how it works. Crash tests are used for validation, but the data from crash tests is generally not used to infer mechanism. Physicists don't come up with a new theory of mechanics every time a crash test has an unexpected outcome. > If you name proxy experiments…
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that support your views (crash tests) as mechanisms and ones that don't (SSB replacement with NNS RCTs) as "empirical evidence is valid only for the situation in which it was obtained" then sure, everything you want to believe is supported by sound science and everything you don't isn't. I don't think you understand. If you want to support a public health intervention you either have the empirical data with a relevant endpoint, or you can point to mechanism which bridges the part between the data that you have and the outcome which you want to achieve. When it comes to pharmaceutics and food additives, our mechanistic understanding is insufficient so we often have to resort to empirical studies on humans, including RCTs (Pfizer's Covid vaccine trial had tens of thousands of participants) and also observational studies at population level. And it is the last part where artificial sweeteners fail to show benefit so far. When it comes to seat belts, our mechanistic understanding is sufficient so we don't need to resort to empirism. Yes we perform validation but only to check if there are no design oversights in the vehicle nor shortcomings with the simulation software, typically in a low triple-digit number of crash tests. But no humans involved and especially no control arm with humans. (Well if you ignore the one study on the efficacy of parachutes which was done as RCT https://doi.org/10.1136/bmj.k5094 ) > So it doesn't meet your own goalpost It does, because again, mechanism is provided. You could say that the study has weak evidence for the mechanism and it works like that perhaps only for sugar. Because that some mechanism is found in mice does not mean it is also found in humans, and it would be a fair point. This is why many species are tested and so far the results held up (testing humans takes too long for obvious reasons).
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tbrownaw
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> I don't appreciate reading anecdata in response to cited findings. It cheapens the discussion. So does the linked PDF address this proposed "hopelessness" factor, or is it that once someone cites something the discussion becomes restricted to only things that have published study results? Also, if someone were to cite https://doi.org/10.1136/bmj.k5094 on the effectiveness of parachutes, are other commenters then forbidden from citing anecdata that disagree with the findings?
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