Don’t Bother With the Parachute!

Most folks erroneously believe a parachute is necessary when jumping from an aircraft. There’s never been evidence to support such a belief in the form of a true randomized-controlled trial. That said, it would be hard to achieve the ethics board approval to perform such a study – and this concept of treatments and medical devices as “parachutes” persists, supposedly obviated from prospective evaluation. The lesson here is a cautionary one, actually, that too many medical practices are inappropriately characterized as parachutes, not so much that parachutes require an RCT.

However, this is precisely what we’ve received for Christmas – an RCT of parachute use for preventing death and major trauma. In this trial, 92 aircraft passengers were screened, and ultimately 23 were randomized to jump from an aircraft wearing either a parachute or an empty backpack. This was an unblinded trial, as well, in which all participants knew whether they were wearing a parachute or an empty backpack at the time of jump. With regard to their primary outcome of death from impact with the ground, there was 0% mortality in the parachute cohort and – wait for it – 0% mortality in the empty backpack cohort.

There were some important differences noted – not between those randomized, but between those screened and those randomized. The altitude of those screened but not randomized was 9,146m, at a velocity of 800 km/h. The altitude of those randomized is best described by the following representative photo:

It should probably be noted zero parachutes were actually deployed by jumpers randomized to that arm.

The lesson here is another fabulous one. The results from clinical trials cannot necessarily be applied to all those included in the eligibility criteria, but can rather be best generalized from those actually receiving the intervention. Insidiously controlling the population undergoing an intervention, among many others, is one of the various tricks those who design clinical trials can use to bias their results, and ultimately mislead.

“Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial”
https://www.bmj.com/content/363/bmj.k5094