Page 55 - Journal of Special Operations Medicine - Summer 2015

machines consisting of a drum or cylinder wound with a painful than a well-designed tourniquet. When the user
rope and turned by a crank. Windlass is an English word continued to wind the knot with a windlass, the strap
derived from the Old Norse language’s combination of often dragged a fold of skin into the crease of the knot
vinda (to wind) + ass (meaning pole), and windlasses are in a swirled, layered fashion. This swirling applies
common in such varied areas as seafaring, industry, rope forceful shearing to the skin, producing damage that
work, and sports that involve ropes like mountaineer- may cause painful pinching. Tourniquet pain varies, in
ing. In the case of improvised tourniquets, limb and part, by the tourniquet design, and there is a historical
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strap are analogous to cylinder and rope, respectively. record that indicates that poorly designed tourniquets
The role of the windlass is to gain mechanical advantage such as improvised tourniquets are more painful than
by increasing the moment arm of applied torque to twist well-designed tourniquets. 4,31,42 The experienced user in
the strap tighter. the present study has made thousands of tests of many
different tourniquet designs and the results that appear
The second major finding of the present study is that al- most painful have been in the present study with the
though a windlass worked when compared to no wind- improvised strap-and-windlass design. The experienced
lass, improvised tourniquet use overall was not reliable user had treated many patients, while the inexperienced
(windlass did not achieve 80% or higher effectiveness). user was minimally trained in tourniquet techniques and
The windlass did provide a mechanical advantage nec- had no healthcare experience. Because of this difference,
essary to increase effectiveness, but the increase was when the expert used the windlass and the tourniquet
insufficient to be reliable. The US Army experience in pinched the skin severely, the user instinctively stopped
training tourniquet users illustrates the ineffectiveness the test early. The swirl avulsed fragments of silicone
problem with improvised tourniquets. Since 2001, the skin and ripped holes in the skin, which made the ex-
Department of Combat Medic Training, a key section of pert wince in empathy for the simulated casualty. The
the US Army Medical Department’s Center and School, other user kept twisting the windlass until the bleeding
made an extensive effort to train medics in improvised stopped without regard for the skin deformity and dam-
tourniquet use. There was a time period when the old age. Without knowing the likely pain and iatrogenic
Second World War strap-and-buckle tourniquet was injury that would have been caused if the subject was
out of favor within the Army, and the current standard living, the less-experienced user had no such experience
issue Combat Application Tourniquet (Composite Re- to limit him in twisting. Aggressively making improvised
sources Inc.; http://composite-resources.com) was yet to tourniquets more effective also made them less safe. The
be adopted. The improvised tourniquet technique of the current understanding of the relationship between effec-
strap-and-windlass design was the remaining candidate tiveness and safety has not been developed fully.
for use. However, trainers assessed the improvised tour-
niquet as unreliable in that it could not be made reli- The second minor finding of the present study was
ably effective in the hands of student medics (Donald that tourniquets with no windlass were mostly venous
Parsons, personal communication, 2013). The experi- tourniquets and not arterial tourniquets. The pressure
ence of the Army medics, of the present investigators, applied to the skin by pulling the tee shirt tight was,
and of the first responders in Boston was similar in that on average, only 46mmHg without windlass use. This
improvised tourniquets are challenging to use well and pressure is too low for a reliable arterial tourniquet but
are unreliable in hemorrhage control. The Boston police provides enough pressure to slow venous bleeding. The
acquired commercial tourniquets for the 2014 Boston strap tourniquet with no windlass was modeled directly
Marathon perhaps because of the poor performance from firsthand accounts from Boston and failed 98% of
of the improvised tourniquets. In 2015, Stewart et al. the time, indicating that most such tourniquets used in
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reviewed improvised tourniquet use and recommended Boston also likely failed to provide effective hemorrhage
their consideration for emergency use when no scientifi- control. The present experiment provides clear, coher-
cally designed tourniquet is available, and Stewart et al ent, and concise evidence that the Boston technique was
improved awareness of a need for improvised tourni- likely a venous tourniquet technique. This explanation
quets and helped legitimize research of improvised tour- at once explains the Boston findings, explains the ex-
niquets. Based on the findings of the present study, a perimental findings, and fulfils the purpose of the study.
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search for better designs of improvised tourniquets is Education may mitigate the confusion of individual
recommended; the designs that are commonly recom- tourniquet users; improved awareness of venous versus
mended or used are now shown to be unreliable. Such arterial tourniquet use may aid users to become more
recommendations and uses should be reconsidered. effective.

The first minor finding from the present study was that The limitations of the present study are based in its ex-
the improvised strap-and-windlass design showed skin perimental design. The results were gathered through
deformation during use that indicated it may be more an experiment and not through patient care. Therefore,

Windlass in Improvised Tourniquet Use 45