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;327:1459All rapid responses
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A satire as it appears on the surface of it, Smith and Pell's article
reflects the serious side of our obsession with Evidence Based Medicine.
The fundamental issue is what is it that we call as evidence. If it is the
class I evidence supported by multicentre double blind randomised clinical
trials, how many of our day to day well-accepted practices are supported
by such evidence? Do we have to go back and create evidence to show that
morphine is an analgesic or mannitol decreases brain oedema?
If we have to depend solely on Class I evidence, do we have such
evidence on all those thousands of clinical issues that we deal with
everyday? What do we do until we have that evidence? Given the financial
implications of multicentre randomised trials, is it ever possible to have
that kind of evidence on all the issues? We must understand that, as of
today, even the best of the clinical practice guidelines are often
influenced by a handful of studies.
If our definition of evidence is not flawed, why is that year after
year we have so many studies ending up with negative results - studies
that have been started right honestly based on strong evidence from
experimental and single centre clinical trials? Does it mean that all
those experimental and single centre clinical trials are uniformly flawed?
Does it mean that we are always asking wrong or irrelevant questions most
often when we start a multicentre randomised trial? Or is there something
wrong with the way the multicentre randomised trials are conducted? Have
we not come across inter-institutional differences among the results of
major randomised trials? Have we not seen the co-coordinators of these
trials agree that the experience of the individual institutions strongly
influences the results? If such are the fallacies of these studies how do
we base our clinical practices on these trials? To put it in other words,
under the cover of good evidence, are we systematically killing all the
potential therapies and advocating therapies that are only to be proven
wrong in course of time? I have witnessed patients in whom nitric oxide
improved oxygenation and prevented them from succumbing immediately to
life-threatening hypoxia caused by acute respiratory distress syndrome
(ARDS), before the large randomised trials were published. Based on the
good evidence that later showed no improvement in clinical outcomes with
nitric oxide, should I have denied these patients this beneficial therapy?
The reason for the whole malady probably lies somewhere in the
process of generation of this Class I evidence. Should we look at that
more critically? Agreed that medicine should not be left to the whims and
fancies of individual physicians. But time has come for us to seriously
ponder over our definitions of Evidence and probably to very meticulously
supervise the process leading to generation of this evidence.
Competing interests:
None declared
Competing interests: No competing interests
Thank you for this study. Subsequent to publication, the use of
parachutes by hang glider pilots in Southern California has been
abandoned. Many of us felt they were bulky anyway, and recognition of the
lack of randomized trials opened our eyes. Most hang glider pilots here
subscribe only to the New England Journal of Medicine and JAMA, so we came
very near missing this paper. Upon considering the hegenomy of the
Parachute Industry, perhaps the suppression of information was not
accidental.
Thank you again.
C Williams
Competing interests:
None declared
Competing interests: No competing interests
I interpret the parachute study as illustrating that, in life or
death situations, one must make judgements based upon preponderance of
available evidence as opposed to proof beyond reasonable doubt. It seems
obvious, but the parachute study makes the point that "evidence-based
medicine" proponents may fail to apply this common sense standard on a
consistent basis.
To cite just one example, the American Society of Clinical Oncology
established a policy recommending against the use of cell culture drug
resistance testing (CCDRT) as an aid to drug selection in cancer
chemotherapy, based on reviews (refs. 1,2) which specifically excluded
from consideration studies reporting the predictive accuracy of CCDRT (of
which there were many), and including only studies relating to the
"efficacy" of CCDRT in improving treatment outcomes (of which there were
virtually none). This was especially curious, as predictive accuracy is
the chief criterion traditionally used to validate all laboratory tests
currently in use in cancer medicine (including hormone receptors,
Her2/neu, gene expression-based assays, and all immunohistochemical
staining tests). Were proof of efficacy (particularly in prospective,
randomized trials) to be the standard for evaluating laboratory tests,
then clinical oncologists should immediately abandon all the laboratory
tests currently used in the management of cancer patients, as no tests
would pass this standard.
Clinical oncology investigators have too often descended into an
exhaustive study of hypotheses which are ultimately of limited importance.
Many cancer treatments are of such limited effectiveness that they do not
deserve to be protected from the competition of other approaches which
are well grounded in peer review science, but which have not yet met the
most demanding standards of "evidence based medicine."
Larry M Weisenthal MD PhD
Huntington Beach, CA
mail@weisenthal.org
Literature Cited:
1. Schrag D, Garewal HS, Burstein HJ, Samson DJ, Von Hoff DD,
Somerfield MR. American Society of Clinical Oncology technology
assessment: chemotherapy sensitivity and resistance assays. J Clin Oncol
22:3631-8, 2004.
2. Samson DJ, Seidenfeld J, Ziegler K, and Aronson N. Chemotherapy
sensitivity and resistance assays: a systematic review. J Clin Oncol
22:3618-30, 2004
Competing interests:
I direct a private clinical reference laboratory which provides cell culture drug resistance testing as a service to patients and oncologists. (information at http://weisenthal.org )
Competing interests: No competing interests
Let me begin by saying that I do not intend to address the debate on
whether or not male circumcision should be offered as a public health
intervention to reduce HIV transmission. However, I am surprised that
repeatedly one of the main arguments against this has been the "absence of
randomized clinical trials". In fact to quote a cochrane review,
‘Despite the positive results of a number of observational studies, there
are not yet sufficient grounds to conclude that male circumcision, as a
preventive strategy for HIV infection, does more good than harm. The
results of current ongoing RCTs will need to be carefully considered
before circumcision is implemented as a public health intervention for
prevention of sexually transmitted HIV’ (Sigfried et al., 2003).
Here is a disease for which there were an estimated 4.8 million new
infections in the year 2003 (UNAIDS, 2004) and I ask myself if we can
afford to wait for randomized clinical trials. No stone should be left
unturned in the fight against the HIV pandemic. The absence of RCTs on
parachute use never precluded their use. Just like parachute use, and
considering the currently available evidence from observational studies,
the use of male circumcision to reduce HIV transmission should be based on
technical feasibility determinants and not wait for RCTs.
1.Siegfried N, Muller M, Volmink J, Deeks J, Egger M, Low N, Weiss H,
Walker S, Williamson P. Male circumcision for prevention of heterosexual
acquisition of HIV in men (Cochrane Review). In: The Cochrane Library,
Issue 3, 2003. Oxford: Update Software.
2.UNAIDS. 2004 report on the global HIV/AIDS epidemic : 4th global
report.
Competing interests:
None declared
Competing interests: No competing interests
Maybe they should have used Stata 8.
Competing interests:
None declared
Competing interests: No competing interests
This is a rapid response(!) having just read this thought provoking
article and earlier contributors. In the lighter vein, if parachutes
really are effective why do airlines not provide them - they are
potentially more use than lifejackets, which have no evidence base for
crash landings on the ground. Their introduction would make the pre-flight
briefing much more interesting.
More seriously, perhaps one outcome is we should ask where is the
Evidence Base for the place of EBM? There undoubtedly is a need for help
in deciding risks and benefits of marginal effects. However, data can
only be gathered by observation in some areas, such as studies in
premature babies or treatments of very rare conditions. Much of
paediatric medicine operates from previous observations and many medicines
are used outside their market authorisation by paediatricians. This does
not break any laws and is potentially life saving.
On the other side of the coin, often significant differences
statistically in trials are not significant clinically. Products
legitimate claims to increase outcomes by 100% could only increase lives
saved from 12 to 24 per 1,000 at a very high cost. Clinical trials in
volunteers may bear little relation to to real patients. Cancer risks
100% higher by rising from say 10 to 20 per 100,000 often hit the news
headlines. So, are we in need of a reality check? Have Smith and Pell
cleverly started a process of deciding where Evidence Based Practice best
fits? I hope so.
Competing interests:
None declared
Competing interests: No competing interests
Smith and Pell's call for a randomized controlled trial of parachute
efficacy is visionary. The authors, however, underestimate the difficulty
in obtaining the approval of an institutional review board for the use of
human subjects in such an experiment--no matter how antipathetic the board
might be towards the devotees of evidence-based medicine, volunteers or
not.
In order to test this important hypothesis, I recommend using a
variety of animals pushed from the cargo doors of specially outfitted
troop transports. Higher primates and lesser animals could be randomized
to parachute or free fall. The use of a variety of animals would permit
the proper statistical extrapolation to humans. I also recommend using
"active controls," such as chickens or guinea fowl randomized to parachute
or free fly.Although animal rights advocates might protest this
experiment, it could probably be executed without too much controversy in
a developing country anxious for the collateral economic benefits of
research and academic prestige.
Competing interests:
I am not a vegetarian.
Competing interests: No competing interests
Missing thus far is a broader discussion of the philosophical
dimensions of EBM -- a point which I believe is the unspoken (perhaps
overriding) agenda of the authors who conceived of this piece; and BMJ,
for offering this article as a catalyst for further discussion.
Evidence Based Medicine is a Postmodern phenomenon that
encompasses aspects of a unique ontology (worldview) and
epistemology (way of knowing - since the 1970s,
a dependence upon the Randomized Controlled Trial). A cultural historian
might suggest to us that Evidence Based Medicine has been the predictable
outgrowth of Postmodernism -- that phase of human development
associated with the confluence of logical positivism,
biostatistics, digital technologies, and the nihilism that has arisen from
the continuing tragedies of the nuclear age. What few physicians seem to
contemplate is the possibility that the "acceptance" of EBM is inherently
a philosophical (ontological) act. It rests upon the assumptions that
Evidence CAN be determined, and that Evidence SHOULD be determined (and
applied) as a basis for medical decision making.
Few would doubt that physicians in the Industrialized World are
currently expected to embrace the validity of each of these ontological
assumptions. However, the epistemology of a distinctly Postmodern EBM is,
I believe, something which has motivated the timing and saliency of the
Parachute article to which we now respond. In the Postmodern landscape,
Evidence has come to be based upon quantities, similarities, populations,
and averages -- rather than qualities, idiosyncracies, individual
narratives, and specifics.
This medical epistemology might not be so critical, were it not for
the ethical crises which now denude the integrity of the prevailing
Evidence: 1) publication bias; 2) concealment of negative findings (file
drawer effect; 3) manipulations in clinical research designs (placebo
washouts, preference for LOCF vs. OC outcomes, non-comparative dosing
strategies, underpowered studies, paltry effect sizes.)
Recognizing the dubious reliability of the Evidence upon which
clinical practice has increasingly come to depend
(e.g., the information presented by journals, textbooks, government
agencies, the news media), the time has come for physicians to contemplate
the ramifications of Postmodern philosophy within their profession.
It is time for providers to reassess the value of direct observation, and
to trust more readily both the empirical and intuitive discoveries they
make each day in their personal experience (even if those discoveries are
contradicted by the "best available Evidence"). Though Smith and Pell
speak to us from behind the veil of parody, there could be nothing more
serious at this juncture than their call for healers to reconsider what it
means
to be authentic and true.
Competing interests:
None declared
Competing interests: No competing interests
Many if not most major medical "advances" have never been subjected
to a prospective randomised study before being introduced into routine
management because their beneficial effects have been obvious. Examples
include the appendectomy and the discovery of insulin and its development
for the treatment of diabetes. Consider the consequences in the case of
insulin.
Decades after the adoption of insulin in routine care prospective
randomised studies were done to improve the efficacy of its application
in diabetic care. If insulin were discovered today would it be best if its
application to patient care were to be deferred until the completion of
such trials as were thopught to be necessary at the time and the
subsequenct approval for use by a regulatory body and/or a healthcare
tsar? If so how long would it take for the evidence base to be complete?
More importantly could it ever be complete?
In reading a book about the French Heugenots who arrived in England,
Fiddian being said in our family records to be a derivative of Fideon, I
was interested to learn that it had been estimated that some 70% of the
English had acquired some Heugenot blood in succeeding two to three
centuries.
If so what proportion of the population will have acquired the
recessive genes of juvenile diabetics one century after the introduction
of insulin into routine medical care? More importantly, according to Tsar-
Professor Sir George Alberti former President of the Royal College of
Physicians, would be the extent to which the increasingly costly problem
of type II diabetes might be the product of the same medical "advance".
Might it be that 70% or more of the population will have acquired these
recessive genes within one to three centuries? If so will humanity be
better or worse off for the medical profession having introduced insulin
into routine patient care?
The case of appendectomy would seem much easier because not only can
it be life-saving but also because it has no chance of having a long-term
effect....unless the appendix does have an exotic but as yet undiscovered
physiological property.
Perhaps Professor Solomon Benatar, a juvenile diabetic and current
President of the International Association of Bioethics, could provide us
with an answer to the above questions. In so doing could he declare
whether his answer applies to drug, dietary, and surgical treatments or
whether he has different answers for each.
Competing interests:
None declared
Competing interests: No competing interests
Non-medical response
Prior to taking my current job, I had worked for a number of military
businesses. There are many applications for a technique for making
inferences from noisy and incomplete data in that domain, and I often
wondered why life sciences people did not use the same tools that we did,
ie., Bayesian methods.
It occurs to me now that the answer to my question is that in the
particular applications that I worked with, we had good models of the
phenomena we were interested in based on solid physics. In the past, the
life sciences were not so similarly blessed, and so presumably were forced
to persevere with classical statistics.
The obvious exceptions, like trauma caused from extreme deceleration
of the body from very high speed, have a model where even software
programmers such as myself understand the consequences of making no
intervention to a patient with substantial continuing blood loss and
severe soft tissue damage. Bayesian methods would indicate making a
decision in favour of intervention even in the case of the Smith and Pell
paper.
The more interesting point is that in many areas of the life
sciences, it seems that researchers are now in possession of pretty good
models of even complicated biological phenomena. That opens up the
possibility of using Bayesian methods in those areas.
As Laplace (the real genius behind Bayesian methods) is purported to
have said:
"Probability is nothing more than the quantification of common
sense."
Give it a try.
Competing interests:
None declared
Competing interests: No competing interests