Page 44 - Journal of Special Operations Medicine - Fall 2016

Figure 4 Composite score by tourniquet model. Figure 5 Pump count, by tourniquet model.

Composite score is calculated as counts, with higher indicating better. The fifth and 95th percentiles are represented by the whiskers. Box
EMT showed overall best composite score. The fifth and 95th percen- tops are 75th percentiles, box bottoms are 25th percentiles, the box
tiles are represented by the whiskers. Box tops are 75th percentiles, cross-line represents the median, and the hashed line represents the
box bottoms are 25th percentiles, the box cross-line represents the mean. TPT3 has 5th and 25th percentiles overlaid and 75th and 95th
median, and the hashed line represents the mean. TPT3 has mean and percentiles overlaid.
median lines overlaid. TPT2 and TPT3 had percentiles overlaid such
as for fifth to 25th and 75th to 95th for TPT3. When a symbol such as to healthcare; it is currently limited to training with cer-
a median overlays another symbol such as a box top, one of the two is
not seen. When data overlap, such as when the 95th percentile is the tain manikins that measure pressure this way.
same as the 75th percentile, the former is not seen. Such is a trait of a
narrow data range and this can be seen as a collapse of a box upon a
line, such as for EMT upon the value of 5, which is also the median. Discussion
EMT, Emergency and Military Tourniquet; TPT2, Tactical Pneumatic
Tourniquet 2-inch; TPT3, Tactical Pneumatic Tourniquet 3-inch. The main finding of this study was that each of the three
pneumatic field tourniquet models was 100% effective
(n = 54). In pairwise comparison, the differences in mean in stopping simulated bleeding and met the critical or
pumps for TPT3-TPT2 (n = 11) and for TPT2-EMT (n = primary outcome of the study: effectiveness of bleeding
14) were statistically significant (p = .0009 and < .0001, control. Similarly, pulse stoppage distal to the tourni-
respectively; Figure 5), whereas the difference in mean quet was 100% effective with all tourniquet models.
pumps for TPT3-EMT (n = 3) was not (p = .6). Additionally, no safety issue occurred and no breakage
occurred. All three tourniquet models may be suitable
An opportunity for refinement in design of a tourni- for a customer assessment in simulated field use to allow
quet model presented during the collection of data from users to measure differential preference by tourniquet
use. This involved changing the way the TPT2 has its model.
batch information recorded on the device; the ink that
is stamped on the fabric of the outer cover wears off, so The first minor finding of the present study was that
the ability to control quality of lots is impaired by an the tourniquet models showed differential performance
inability to identify the batch. A longer-lasting or rub- for some secondary outcomes. In general, the EMT
proof ink is advised. Redesigns that limit the inflatable showed superior performance in time to stop bleeding,
volume of both TPT bladders may allow faster fill with blood loss, and composite outcomes. Whether intended
fewer pumps of the bulb. An unexpected opportunity to by the designers, the TPT2 design conflicted two met-
refine technique was identified when the pump counts rics, pressure and time; the design feature of a narrow,
of devices were higher than expected, because the lay 2-inch width necessitated that pressure and time to stop
of the tourniquets tended to have a minor gap overly- bleeding would unreliably achieve good results simulta-
ing where the pressure transducers were; for example, neously because the pressure-width relationship, which
the devices have asymmetric lies in that small areas do governs all tourniquets, is curved and rises too steeply
not touch evenly upon the skin, such as near the EMT at this width. Operationally, this relationship makes the
clamp or near the TPT band end. Such minor lift off time longer to adequately pressurize the TPT2 because
led to lower pressures, and simply moving the lift-off such higher pressure takes more pumps of the hand
spot away from the transducer remedied the problem. bulb than do wider designs like TPT3 and EMT; wider
In practice, the user should be taught to avoid placing tourniquets work well by more efficiently compressing
zones of lift off over the manikin artery (where a trans- underlying tissues than narrower tourniquets, which
ducer is), but given the greater compressibility of people require higher pressures to achieve comparable effec-
versus the stiffer manikin, this teaching need not apply tiveness by adequately compressing blood vessels. This

26 Journal of Special Operations Medicine Volume 15, Edition 3/Fall 2016