
Parachute use to prevent death and major trauma when jumping from aircraft - pentestercrab
https://www.bmj.com/content/363/bmj.k5094
======
nabla9
Remember to reard the linked editorial for context:
[https://blogs.bmj.com/bmj/2018/12/13/we-jumped-from-
planes-w...](https://blogs.bmj.com/bmj/2018/12/13/we-jumped-from-planes-
without-parachutes-and-lived-to-tell-the-tale/)

> We conducted the PARACHUTE trial to illustrate the perils of interpreting
> trials outside of context. When strong beliefs about the standard of care
> exist in the community, often only low risk patients are enrolled in a
> trial, which can unsalvageably bias the results, akin to jumping from an
> aircraft without a parachute. Assuming that the findings of such a trial are
> generalisable to the broader population may produce disastrous consequences.

>Before you jump to the conclusion that we’re suggesting we jettison RCTs from
clinical research, let us clarify that that is not our intention. In an ideal
world, new interventions would always be carefully evaluated through rigorous
RCTs before widespread adoption. But when pre-existing convictions about an
untested intervention affect the population enrolled, even a well conducted
RCT can provide misleading results. Without careful attention to context,
extrapolating findings from such an RCT to the patient in front of us may be,
well, a leap too far.

~~~
joker3
It's also essential to read the first cited article
([https://www.bmj.com/content/327/7429/1459?ijkey=3b8c1a70a8d2...](https://www.bmj.com/content/327/7429/1459?ijkey=3b8c1a70a8d21a7e0a17d524eb5376914857d03a&keytype2=tf_ipsecsha))
which very much inspired this paper and is also quite a bit funnier.

~~~
marcosdumay
$37 for 1 day access to download the paper. If that's not part of the satire,
I don't know what it is.

~~~
nkurz
That might be the suggested amount, and it is a great paper, but I think you
are allowed to donate less if you choose: [http://sci-
hub.tw/10.1136/bmj.327.7429.1459](http://sci-hub.tw/10.1136/bmj.327.7429.1459)

------
yason
I've _always_ known the parachute manufacturers mostly ride on fear,
uncertainty and doubt on this. They ruthlessly cash in on people's lack of
knowledge and fear of death, advertising parachutes as a safer option which
people buy because it's like insurance; if you'd happen to fall, you'd at
least want to feel having prepared.

So I'm glad to hear there's now some scientific evidence pointing to the
futility of parachutes. Surely, the experiments were carried out in a
constrained environment with some unavoidable assumptions baked in but it does
rather convincingly suggest that parachutes consistently do _not_ offer any
help in the event of freefall.

A corollary might appear that parachutes might even do more harm, adding
weight to the falling person which could cause further injuries unnecessarily
upon touchdown.

I'll look forward to follow-up research.

The big question is how would altitude affect the results.

For experiments at higher altitudes they might need to locate an airstrip
situated on a mountain, with enough runway to allow larger planes to land
there and enough free space on the tarmac for several planes while they carry
out the jumps. It will likely shed much more light and build confidence to the
applicability of this new research and the obvious conclusion.

Also, I'd like to see jumps done from different kinds of aeronautic vehicles,
by more people, different brands of parachutes etc if should there be any
differences regarding that. But it looks like after a few rounds of serious
experiments we should quickly conclude the benefits are thin and see no need
for excess research but, rather, reaching a steady conclusion.

~~~
ainiriand
I suspect that landing on water has no discernible effect on the health of the
suspect. And he will be completely soaked, so avoid jumping over water and
always try to land on land.

~~~
akavel
Notably, as to choosing land vs. water when falling from high altitude, see
the ever fresh:
[https://news.ycombinator.com/item?id=11748528](https://news.ycombinator.com/item?id=11748528)

------
stcredzero
A coworker of mine once made this proposal. 5 of us would start a company. The
company would buy key man insurance for everyone, then go on a company team
building trip. On this trip, we'd all skydive, but one of the 5 parachutes
would be non-functional...Profit!

This coworker of mine soon after left the company by storming out of the
meeting room and slamming the door, then took up playing online poker for a
living.

~~~
nostrademons
[https://en.wikipedia.org/wiki/Tontine](https://en.wikipedia.org/wiki/Tontine)

~~~
Freeboots
There's a short term group loaning 'game' in Cambodia called and based on
Tontine, which I would guess comes from the French influence.

The game is played by groups who agree on a monthly stake. Each month players
offer an interest rate they're willing to pay (more like a tax), the highest
rate is awarded the collective pot, less the interest which is redistributed
to the other 'living' players.

Players who have already received the pot are 'dead' and do not collect their
share of interest in future rounds (meaning they must pay the full stake).
Once everyone is dead, the game ends. Some will have come out ahead, others
may have been able to get a lump of cash when they needed it

~~~
himlion
Also in Thailand and Laos. These games are hugely popular. Called a "share" in
Thailand and "houay" in Laos.

It's some basic banking services for the unbanked in essence.

------
calibas
This isn't just for giggles. It's evidence that when there's a high perceived
risk, "normal" people don't sign up for trials and it skews the results.

------
lygaret
> The study also has several limitations. First and most importantly, our
> findings might not be generalizable to the use of parachutes in aircraft
> traveling at a higher altitude or velocity. Consideration could be made to
> conduct additional randomized clinical trials in these higher risk settings.
> However, previous theoretical work supporting the use of parachutes could
> reduce the feasibility of enrolling participants in such studies.16

> 16\. Newton SI. Law of Universal Gravitation.Philosophiæ Naturalis Principia
> Mathematica, 1687.

------
scythe
>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).

This is an amusing didactic example of how the "fine print" can invalidate a
study's conclusion.

------
jusssi
In case anyone else got curious about parachuting injury statistics, Google
found me this (also cited by the article):

"Parachuting injuries: a study of 110,000 sports jumps", 1987,
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478603/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478603/)

All 6 deaths they observed, were either failures to activate the parachute (4
cases), or parachute malfunction (2 cases).

------
jxramos
> PArticipation in RAndomized trials Compromised by widely Held beliefs aboUt
> lack of Treatment Equipoise (PARACHUTE)

That has got to be one of the most torturous acronyms I've ever seen. That's a
bit of a stretch.

~~~
Fomite
Oh my sweet summer child...

Biomedicine has gone whole hog into torturing acronyms to make useful sounding
cohort names.

~~~
avar
Also NASA. They just landed InSight on Mars. Interior Exploration using
Seismic Investigations, Geodesy and Heat Transport.

Most of the names are something where they're clearly trying to squeeze out a
cute cohort name at all costs.

------
vamos_davai
Would you indicate this is a satirical article? Half the time I was looking
for jump height or understanding if adding parachutes to commercial aircraft
that suddenly experienced breakage such as a missile would improve passenger
survival.

~~~
oh_sigh
I've done over 900 jumps so I can fill you in, no references ATM because I'm
on my phone.

If you jump with a parachute, you will see chance of death go from 0% at zero
feet, to approximately 100% at 35 feet. From there, it will remain near 100%
until you reach about 600 feet, which is about the minimum distance it takes a
parachute to open. Above 1000 feet and chance of death floors out near 0%

~~~
b_tterc_p
Will jumping from high enough without a parachute ever decrease the odds of
death than they the odds of death at a lower altitude?

~~~
oh_sigh
Not that I know of. Maybe, if you jump from high enough that you pass out due
to lack of oxygen, and you land in a manner that benefits from you being a
ragdoll vs an actively bracing person, then it could help, but that seems
unlikely(you'd probably also wake back up before you hit the ground, as I've
heard stories about this happening to WWII pilots).

But overall, I believe it is better to be conscious. If you are falling from 3
miles up, you can glide to maybe 1 mile in any direction. This gives you the
chance to try to land in a snow drift, in some mud, maybe a hay bail, or even
a thick shrubbery, etc.

~~~
basicplus2
First you must find... another shrubbery! Then, when you have found the
shrubbery, you must place it here, beside this shrubbery, only slightly higher
so you get a two layer effect with a little path running down the middle. ("A
path! A path!") Then, you must cut down the mightiest tree in the forrest...
with... a herring!

------
lucisferre
Anyone know if these results have been reproduced by anyone? I'm a bit
skeptical.

~~~
paulcole
Assuming you’re serious, you can reproduce this yourself. Put on a backpack,
stand on a chair and step off. The trial participants “jumped” from 0.6
meters.

------
EamonnMR
I wonder if they where gunning for an Ig Nobel Prize. I'm sure they'll be
nominated.

~~~
Fomite
They were submitting to the BMJ Christmas Issue, which is an excellent read
every year. Usually a bit of satire and humor mixed in with interesting
methods.

------
flippyhead
> A key strength of the PARACHUTE trial was that it was designed and initially
> powered to detect differences in the combination of death and major
> traumatic injury. Although the use of softer endpoints, such as levels of
> fear before and after jumping, or its surrogates, such as loss of urinary
> continence, could have yielded more power to detect an effect of parachutes,
> we believe that that our selection of bias-resistant endpoints that are
> meaningful to all patients increases the clinical relevance of the trial.

I love how much detail into which they go.

------
xvilka
But not a placebo-controlled one? Shame.

------
peterburkimsher
Their methodology has some serious shortfalls ;)

------
frabbit
[https://www.bmj.com/content/327/7429/1459](https://www.bmj.com/content/327/7429/1459)

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1584330/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1584330/)

------
walrus01
I think this is like the medical research paper version of the famous RFC for
IP over Avian Carriers.

[https://tools.ietf.org/html/rfc1149](https://tools.ietf.org/html/rfc1149)

[https://tools.ietf.org/html/rfc2549](https://tools.ietf.org/html/rfc2549)

------
imh
> The PARACHUTE trial satirically highlights some of the limitations of
> randomized controlled trials. Nevertheless, we believe that such trials
> remain the gold standard for the evaluation of most new treatments. The
> PARACHUTE trial does suggest, however, that their accurate interpretation
> requires more than a cursory reading of the abstract. Rather, interpretation
> requires a complete and critical appraisal of the study.

I love this paper. Whenever you see pop news articles saying "Study shows X is
good/bad for you," if you dig in to the paper, it's often something like this.
When you read the specific details, you realize the study doesn't generalize
to "You should/shouldn't do X." But not enough people read the details, so it
gets circulated into conventional wisdom :(

------
jkim1258
Must have been a fun IRB approval process. Wish we could also see those
applications/disclosures!

>Ethical approval: This research has the ethical approval of the Institutional
Review Board of the Beth Israel Deaconess Medical Center (protocol no
2018P000441).

------
mormegil
Immediately sprung to my mind:
[http://www.lukesurl.com/archives/comic/444-fall-in-
all](http://www.lukesurl.com/archives/comic/444-fall-in-all)

------
mlthoughts2018
I know this is a boring response, but I feel like there’s a formalism here to
consider why a RCT would be “obvious.”

Let’s say you’re going to use some causal model, like a regression adjustment
technique. You could for example assign people to the treatment group
(receives parachutes) and the control (no parachutes), and then observe who
lives and dies, as well as a bunch of potential confounders like altitude,
age, fitness, whatever.

Fit a logistic regression to predict the outcome (survival) based on the
treatment (parachute) controlling for the other characteristics. Then read off
some effect size and ststistical significance.

Or better yet, and here’s the important part, you could make it a Bayesian
logistic regression by considering prior distributions for the regression
model’s fitted coefficients, and sampling draws from the posterior
distribution of coefficients using the data set and your priors.

So what is the prior on the coefficient for the treatment term (parachutes)?
Well, probably pretty damn high. Definitely some strongly informative prior,
take your pick of historical data or effectiveness rates of physical safety
equipment, whatever.

From this prior, and making some neutral assumptions via the priors on other
weights, you could figure of what the effective sample size would be for a
data set to disconfirm your prior (e.g. a posterior with a mode on the
parachute coefficient far away from your strong prior). Sort of like a power
analysis, but assuming a fake data set that shows nothing but failed
parachutes. How much of that silly data would you need based on your prior?

What this would tell you is that you’d need some insane, physically ludicrous
amount of data that flies in the face of an obvious prior, that what would be
the point of running the study? You’re just going to confirm your prior.

So the real question is how often is this a realistic description of other
situations when you want to study a treatment?

That’s the thing, right? That the author kind of wants to be snarky about.

But really, it’s pretty fair to say you don’t have such a strong prior that
the study would be futile, even in cases when you sort of do feel like the
conclusion is obvious (e.g. taking Tylenol leads to less pain, college kids
prefer drinking instead of homework). While it passes some gut test of what’s
obvious, that’s different from really betting on such a one-sided prior that a
study is futile.

To me it suggests most of the sort of “duh” RCTs carried out are pretty much
fine. Whether or not the study is worth it or is informative would be based on
other priorities like cost, licensing or certification requirements, whether
it’s of value to specialists who care about splitting hairs on accurate effect
size measurement, etc.

~~~
Fomite
It's not actually an argument against "duh" RCTs.

It's an argument against clinical medicine being fixated on RCTs as the one-
and-only form of evidence that can be taken seriously, even when - as you note
- the Bayesian prior for such a situation is extremely high.

This happens more often in the field than many people might think.

------
j7ake
N=92 participants is not big enough of an N to conclude anything. To see
differences you're going to have to go up to 10 times more at least.

------
jdlyga
I'd hate to be part of the control group.

------
peterwwillis
When can we expect a news article telling people scientists advise not to wear
parachutes?

------
dohow
Some comments have touched on a few of these points but I’ll try to bring them
together. So first, yes the headline is a joke (BMJ Xmas has satirical
content), but it also has a history beyond the immediate point of the
paper—that sometimes RCTs can’t accrue properly to a control arm to fairly
evaluate an intervention.

Quick points:

    
    
       - There’s a history to this analogy and paper within
         biomedicine and this journal (BMJ) from a 2003 article,
         which I’ll get to.
    
       - Parachutes are a dangerous metaphor in medicine, 
         where almost nothing has an absolute risk reduction 
         of >99% (note: not 100% because, yes, a handful 
         of people have survived falling from altitude without 
         a parachute), especially over the time-frame 
         of a matter of hours.
    
       - This should not be a call to stop attempting RCTs 
        (which is the conclusion some commenters have made), 
        but an exhortation to find ways to create better ones 
        when conditions are challenging. Frequently, objections 
        to doing an RCT because “how could we withhold X 
        from the control arm!”, are not as obvious once 
        the data are in.
    

Some background: beyond Retraction Watch looking for outright fraud, there’s a
movement toward opening trial data for analysis because abuses in RCT
design/analysis/reporting have gotten more criticism and attention lately.
This is happening at the same time as the FDA has been moving toward
lower/faster evidentiary standards for approval (see Sarepta controversy and
general guidance in 21st Century Cures Act to allow drugs to market with
earlier phase evidence and based on “surrogates” like was the tumor 2in vs 3in
bigger vs hard endpoints like “did this person die later than the control”),
so it couldn’t come at a better time.

The broader point is that the 2003 “parachute” article in the same journal
(BMJ), was frequently incorrectly understood / used.

While “parachutes” makes an easily understandable headline, it is almost
totally unrelated to the field of medicine where we rarely have a shot at
doing something as obviously lifesaving as making someone hit the ground at 10
mph vs 120 mph. The problem is that people have cited the 2003 paper mentioned
in the thread to justify a number of interventions that ended up not being
better than prior care. The interventions were started in good faith because
was “obvious” to their creators that doing X would be helpful (spoiler: it
usually wasn’t or wasn’t that beneficial).

A lot of this is cribbed from Vinay Prasad, who has a twitter thread about
this:
[https://twitter.com/VPplenarysesh/status/1073298754298556416](https://twitter.com/VPplenarysesh/status/1073298754298556416)

He is a controversial figure, but I think he does a good job of hammering home
some important skepticism about a great deal of medical literature and
practice to a broad audience.

I’d appreciate hearing objections to the above, btw.

------
kalmi10
Please fix the title. It's misleading. The linked article in no way claims
that "Parachutes prevent death when jumping from aircraft".

~~~
yakshaving_jgt
Given that it says "randomised trial", it's implied that there would be a
control group — a group of people who are sent to die for the sake of an
experiment.

Given that nobody would ever do this, it's quite obvious that there's some
tongue-in-cheek angle to the story.

It isn't misleading if you can read between the lines.

~~~
nkurz
To the contrary, I think it might be you who is jumping to unfounded
conclusions. Contrast the current title "Parachutes prevent death when jumping
from aircraft: randomized controlled trial" with the first line of from the
Conclusion of the paper: "Parachute use did not reduce death or major
traumatic injury when jumping from aircraft in the first randomized evaluation
of this intervention".

------
ericye16
The current title "Parachutes prevent death when jumping from aircraft:
randomized controlled trial" is exactly the opposite of the article's
conclusion: "Parachute use did not significantly reduce death or major injury
(0% for parachute v 0% for control; P>0.9)." Nor is it the title of the actual
article.

~~~
qwerty456127
Why do people use parachutes then? I felt like I'd like to have a parachute
jump experience one day, do you mean that would equal jumping without a
parachute (guaranteed death)?

~~~
steve_musk
It’s not guaranteed, there’s numerous cases where someone’s parachute
malfunctions and they land with only broken bones and bruises.

~~~
qwerty456127
I know but I have chosen to simplify the idea as the chance to survive (and
recover your health to the level at which you won't regret you have survived)
is negligibly small.

------
delinka
This title has been editorialized from

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

to

"Parachutes prevent death when jumping from aircraft: randomized controlled
trial"

~~~
throw-far-away
It would suck to be in the control group. ;)

Also, as my grandfather was a paratrooper: parachuting isn't a risk free
activity even when the main canopy deploys properly, i.e., broken limbs on
landing. And it's remotely possible to survive a fall without a parachute from
terminal velocity height, i.e., Vesna Vulović. Edit: <\- Edge-cases contrary
to the obvious.

~~~
txcwpalpha
The control group in this study only fell a couple of feet at most. I don't
think it sucked much for them at all.

~~~
throw-far-away
Smh. Poe's law disclaimer wink added.

~~~
txcwpalpha
Ha! Fair enough. I'm leaving my comment just in case other people really do
misinterpret the study.

