In a 2003 article in the British Medical Journal,
“Parachute use to prevent death and major trauma related to gravitational challenge: A systematic review of randomised controlled trials,” Drs Gordon Smith and Jill Pell point out that
“the effectiveness of parachutes has never been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of ‘evidence based medicine” organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.” (BMJ 2003;327:1459-1461 (20 December)).
From the ACEP blog: http://acepblog.wordpress.com/2010/08/13/are-ep-modalities-evidence-based/