Friday, 4 September 2020

Testing parachutes

Today's reader mailbag brings a gem of a study. An actual randomised trial on the effectiveness of parachutes in jumping from airplanes. They found no difference in outcomes between those wearing parachutes and control subjects wearing empty backpacks.

Here's the 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.

Some American views that it's impossible to tell whether NZ's April lockdown stopped our outbreak remind me of calls for RCTs on parachute use at height.

Thanks Wayne for the pointer. 

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