Parachute no better than empty backpack jumping from plane: BMJ study

A parachute provides no more protection than an empty daypack when jumping from an airplane according to a study just published by the prestigious British Medical Journal. What!? Yes, doctors in the UK conducted a randomized controlled trial to determine ...

"if using a parachute prevents death or major traumatic injury when jumping from an aircraft."

Out of 92 aircraft passengers aged 18 and over who were screened for participation, the 23 who agreed to be enrolled and were randomized jumped from an aircraft with either a parachute or empty backpack.

This calls for evidence-based medicine

The authors note that parachutes are routinely used by individuals jumping from aircraft. Even so...

"However, evidence supporting the efficacy of parachutes is weak and guideline recommendations for their use are principally based on biological plausibility and expert opinion.12 Despite this widely held yet unsubstantiated belief of efficacy, many studies of parachutes have suggested injuries related to their use in both military and recreational settings,34 and parachutist injuries are formally recognized in the World Health Organization’s ICD-10 (international classification of diseases, 10th revision).5 This could raise concerns for supporters of evidence-based medicine, because numerous medical interventions believed to be useful have ultimately failed to show efficacy when subjected to properly executed randomized clinical trials.67

To address these important gaps in evidence, we conducted the first randomized clinical trial of the efficacy of parachutes in reducing death and major injury when jumping from an aircraft."

The authors describe in detail their study design in which they approached and screened prospective participants on commercial or private aircraft. This proved to be difficult, so they included members of the investigative team, friends, and family. All were randomized (1:1) to the intervention or the control.

Jumps were conducted at two sites in the US: Katama Airfield in Martha’s Vineyard, MA (conducted by investigators from the Beth Israel Deaconess Medical Center), and the Yankee Air Museum in Belleville, MI (conducted by investigators from the University of Michigan). The same protocol was followed at each site, but the type of aircraft (airplane v helicopter) differed between the two sites...The interventions were not blinded to either participants or study investigators.

Outcomes?

They were looking for as primary outcome composite of death and major traumatic injury, defined by an Injury Severity Score greater than 15, within five minutes of impact. After conducting a thorough statistical analysis, the result was startlingly clear:

"There was no significant difference in the rate of death or major traumatic injury between the treatment and control arms within five minutes of ground impact (0% for parachute v 0% for control; P>0.9) or at 30 days after impact (0% for parachute v 0% for control; P>0.9)...In subgroup analyses, there were no significant differences in the effect of parachute use on outcomes when stratified by type of aircraft or previous parachute use (P>0.9 for interaction for both comparisons).

We have performed the first randomized clinical trial evaluating the efficacy of parachutes for preventing death or major traumatic injury among individuals jumping from aircraft. Our groundbreaking study found no statistically significant difference in the primary outcome between the treatment and control arms. Our findings should give momentary pause to experts who advocate for routine use of parachutes for jumps from aircraft in recreational or military settings.

Beliefs about the efficacy of commonly used, but untested, interventions often influence daily clinical decision making. These beliefs can expose patients to unnecessary risk without clear benefit and increase healthcare costs.11 Beliefs grounded in biological plausibility and expert opinion have been proven wrong by subsequent rigorous randomized evaluations.12 The PARACHUTE trial represents one more such historic moment.

Should our results be reproduced in future studies, the end of routine parachute use during jumps from aircraft could save the global economy billions of dollars spent annually to prevent injuries related to gravitational challenge.

A minor caveat

Yes, there is a "minor caveat" that could put the conclusions drawn from this trial in a different light.

"A minor caveat to our findings is that the rate of the primary outcome was substantially lower in this study than was anticipated at the time of its conception and design, which potentially underpowered our ability to detect clinically meaningful differences, as well as important interactions. Although randomized participants had similar characteristics compared with those who were screened but did not enroll, they could have been at lower risk of death or major trauma because they jumped from an average altitude of 0.6 m (SD 0.1) on aircraft moving at an average of 0 km/h (SD 0).

Clinicians will need to consider this information when extrapolating to their own settings of parachute use."

Indeed.

An important lesson after all

In fact, the authors are calling attention to the profound flaws that afflict the medical literature when studies are structured to investigate interventions that do not apply to realistic conditions of clinical practice. All too often misleading conclusions are touted by the media. Examples include recent papers asserting there is no cardiovascular benefit from omega-3 fatty acids when the dose given was far too low (while around the same time a large study using a sufficient dose showed outstanding benefit; and the numerous papers investigating other nutrients or cofactors where the participants were not selected for existing deficiencies, hence no benefit would occur.

The authors comment on this:

"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

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. In addition, our study highlights that studies evaluating devices that are already entrenched in clinical practice face the particularly difficult task of ensuring that patients with the greatest expected benefit from treatment are included during enrolment.

To safeguard this last issue, we see several solutions. First, overcoming such a hurdle requires extreme commitment on the part of the investigators, clinicians, and patients; thankfully, recent examples of such efforts do exist.17 Second, stronger efforts could be made to ensure that definitive trials are conducted before new treatments become inculcated into routine practice, when greater equipoise is likely to exist. Third, the comparison of baseline characteristics and outcomes of study participants and non-participants should be utilized more frequently and reported consistently to facilitate the interpretation of results and the assessment of study generalizability.14 Finally, there could be instances where clinical beliefs justifiably prevent a true randomized evaluation of a treatment from being conducted."

Conclusion

BMJ is one of my favorite journals, and life wouldn't be the same without British humor. Thanks to the editors of one of most venerable and valuable medical publications for publishing this paper, filled with humor yet with serious intent and a truly important message. The authors conclude:

"Parachute use compared with a backpack control did not reduce death or major traumatic injury when used by participants jumping from aircraft in this first randomized evaluation of the intervention. This largely resulted from our ability to only recruit participants jumping from stationary aircraft on the ground. When beliefs regarding the effectiveness of an intervention exist in the community, randomized trials evaluating their effectiveness could selectively enroll individuals with a lower likelihood of benefit, thereby diminishing the applicability of trial results to routine practice. Therefore, although we can confidently recommend that individuals jumping from small stationary aircraft on the ground do not require parachutes, individual judgment should be exercised when applying these findings at higher altitudes."

"What is already known on this topic

• Parachutes are routinely used to prevent death or major traumatic injury among individuals jumping from aircraft, but their efficacy is based primarily on biological plausibility and expert opinion

• No randomized controlled trials of parachute use have yet been attempted, presumably owing to a lack of equipoise

What this study adds

• This randomized trial of parachute use found no reduction in death or major injury compared with individuals jumping from aircraft with an empty backpack

• Lack of enrollment of individuals at high risk could have influenced the results of the trial"