Page 49 - Journal of Special Operations Medicine - Spring 2016

Figure 5 Box-and-whisker plots depicting the pressure Discussion
(mmHg) needed to stop simulated bleeding using three
different tourniquets and a manikin with a simulated above- In this study using a manikin, the two new tourniquet
knee amputation injury. models (RATS and TMT) did not offer any improve-
ment over the currently issued military tourniquet, the
C-A-T. Indeed, one of the new models, the RATS, was
inferior to the C-A-T tourniquet in terms of speed of ap-
plication and simulated loss of blood. It is evident, how-
ever, that a second tourniquet, the TMT, did perform as
well as the C-A-T, and required a lower mean pressure
to stop hemorrhage. Hence, subject to the relative cost
of each, the TMT might prove to be a successful com-
petitor on the open market.

Regarding an opportunity to improve the TMT design,
reinforcing the inner strap or smoothing the edge of the
windlass’ aperture may improve function. To round off
the sharp edge of the windlass aperture may allow the
inner strap to lie over a smoother edge while distribut-
ing strap forces with less stress during strap twisting as
the windlass is turned. Early C-A-T versions had a simi-
All graphic representations and abbreviations are as identified for lar problem that was addressed well in a similar way.
Figure 3. Pressures applied for the C-A-T and TMT tourniquets are
different (p = .04).
It was also evident that the poorest performing tourni-
Figure 6 Box plots depict simulated blood loss occurring quet for secondary measures, the RATS, could be im-
with use of different tourniquets and a manikin with an proved with increased length and improved technical
above-knee amputation injury. training. Lengthening the RATS would permit higher
effectiveness, as the running end may be spiraled more
around the limb. These additional wraps would en-
sure an increase in the length of the artery compressed
and associated tourniquet effectiveness. 14,16,18 However,
if lengthened too much, then the added length would
make handling of the running end more difficult.

Differences among the tourniquet models were clinically
small, although, occasionally, differences were statis-
tically significant. The C-A-T is in its sixth version, as
there have been five sets of design refinements over a de-
cade. In contradistinction to the C-A-T’s present reliabil-
ity after such sequential refinements, the two new models
presently have their first opportunity for refinement.

The limitations of the present study are based in its de-
sign as a focused experiment, which is neither field test-
All representations and abbreviations are as identified for Figure 3.
More fluid loss occurred with RATS use (p < .0001). ing nor healthcare delivery. There were only two users,
only three models, only 10 tests per model, and assess-
ment was on a manikin and not on a real person. The
inner strap. The TMT inner strap had wear and tear on preliminary evidence of new tourniquets has limited
two devices; two devices were replaced, such that three meaning and limited generalization, but it introduces
TMTs were tested altogether. All three devices had wear new tourniquets to the medical literature and instructs
and tear, but the first device was replaced after 10 uses, on their use. The time to hemorrhage control was com-
the second device was replaced after eight uses, and the plex; time was measured from the start of the iteration
third device was used twice, and this number completed until the manikin detected that no more blood was
the data collection. All three had inner-strap wear or lost or the user stopped the iteration; the latter event
tear near the windlass aperture, which had a sharp edge. occurred twice with the TMT. If the user had alterna-
The first TMT had an incomplete tear, the second used tively determined that the broken TMT could be made
had a complete tear, and the third had only wear. to work, then the iteration would have continued and

Comparison of Tactical Tourniquets 33