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Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials

BMJ 2003; 327 doi: https://doi.org/10.1136/bmj.327.7429.1459 (Published 18 December 2003) Cite this as: BMJ 2003;327:1459

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Comment on: Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials

Comment on: Parachute use to prevent death and major trauma related
to gravitational challenge: systematic review of randomised controlled
trials

Nibu A George

Department of Biomedical Engineering

University Medical Center Groningen and University of Groningen

9713AV Groningen, The Netherlands

e-mail: n.a.george@med.umcg.nl

Abstract

Randomised controlled trials to prove the effectiveness of a medical
intervention is not necessary if it can be proved with the help of
fundamental theoretical analysis and or with the identical problems that
are well established.

Introduction

Smith et al challenged the effectiveness of parachutes in saving
human life claiming that no controlled randomised trials have been
conducted to prove it [1]. The authors also claim that the perception that
the parachutes are a successful intervention is merely based on a casual
observation rather than a rigorous scientific analysis. In order to
support their claim the have used some reports of morbidity and mortality
associated with the failure or iatrogenic complications of the
intervention [see ref 1-4 in the above ref.]. In this paper we would like
to answer to the questions raised by the above authors using the
fundamental laws of physics.

Discussion

Reply to: Evidence based pride and observational prejudice

Based on reference 7 in the above quoted manuscript, the authors
concluded that all medical interventions justified by observational data
need verifications through randomised controlled trials. In fact the
article they quoted was referring to few different pure medical cases to
describe the biasing in data analysis. Here we like to point out few
things. First of all generalizing such reports of some selected cases and
making it a universal truth is unhealthy and challenging the entire
scientific community. Secondly, the comparing the parachute scenario with
a pure medical situation is unacceptable since the parachute jump is
rather a physical situation and it become a medical situation only if the
jump caused any physical harm to the person involved.

Reply to: Natural history of Gravitational Challenge

Based on some references, the authors claimed that the effectiveness
of an intervention needs to be judged with a non-intervention. The authors
used few manually selected cases to prove the success of free fall without
a parachute and fatal jumps involving parachutes. Ironically, the data
biasing discussed above is more applicable here. Number of people jump
every day with the help of parachutes and any successful jump is not
recorded in any medical or scientific literature, simply because it has no
significance. On the other hand, large number of people dies everyday
worldwide resulting from trauma caused by free fall from heights of few
meters to several tens of meters. In fact, here the authors approached the
present problem with a clear prejudice in their mind and consequently they
picked up some exceptional historical evidences that match their claim.

Reply to: The parachute and healthy cohort effect

The authors compared the individuals jumping from an aircraft without
a parachute as high psychiatric morbidity group relative to individuals
who perform a parachute assisted jump. But the conclusion that
parachutists enjoy the protective effect of the “healthy cohort” effect of
the group of individuals who possess less psychiatric morbidity is
absolutely baseless and challenging the commonsense of the entire
scientific community. Dragging the role of “income” and “cigarette use”
into the protection gained from scientific inventions such as parachutes
are questionable. The “healthy cohort” effect in cardiac deceases etc due
to the proper exercise, dieting, better life style etc of a group of a
individuals are not comparable to the present parachute scenario.

Reply to: The medicalisation of free fall

The authors statement of induced fear and dependency and doctors
obsession with the parachutes due to its wide spread use are also
questionable. This situation can be compared to crossing a road. Although
it is only meant to cross the road during a green signal, it could be
possible sometimes to safely cross even in red signal. But an individual
crossing during a red signal may be more nervous and cautious and this
cannot be simply neglected as an induced fear, but it is a fact that this
particular individual can harm himself or others by his act. Following a
traffic rule does not require any randomised controlled trials to prove
its effectiveness and mental and physical protection that offers to each
and every individual.

Reply to: Parachutes and military industry complex

Any technological and product development involves man power and
financial expenses and all successful industries exist simply because they
make profit from their business. Many of the widely used medical
interventions such as X-rays, radiation therapy, and many of the drugs
used for treatments have adverse short and long term side effects. But
that does not stop people from using them, even if they are aware of the
side effects. Then what is the meaning of any randomised controlled trials
to prove the success or failure rate of parachutes as a life saving
intervention.

Reply to: A call to (broken) arms

Not the common sense but simple laws of physics can prove the
effectiveness of the parachute as a life saving intervention. When a
person jumps from a height accelerates towards the earth and eventually
reaches the “terminal velocity”. For an average person this terminal
velocity is about 200km/hour and it takes only about 3 seconds to reach
the terminal velocity. The damages caused to an individual hitting the
ground at this speed is not just broken arms! Now, introducing a parachute
reduces this terminal velocity to less than 10km/hour. This is comparable
to crashing an old car without any airbags to a solid concrete wall at
200km/h and 10km/h.

Reference

1. Smith G C S and Pell J P. Parachute use to prevent death and major
trauma related to gravitational challenge: systematic review of randomised
controlled trials. British Journal of Medicine 2003; 327: 1459-1461.

Competing interests:
None declared

Competing interests: No competing interests

08 December 2007
Nibu .A . George
Scientist
Department of Biomedical Engineering, University Medical Center Groningen, 9713AV Groningen