Page 44 - Journal of Special Operations Medicine - Winter 2015

one-way analysis of variance (ANOVA) with the Tukey Figure 2 Friction Pressures of tourniquets with friction
multiple comparison test, one-way repeated measures buckles. Calf Friction Pressures were commonly lower than
ANOVA with Tukey multiple comparison test, linear forearm Friction Pressures: CAT: p = .60; SOFTT-W:
regression, and the test for differences between vari- p = .0001; RMT-P: p < .0001. SOFTT-W applications most
ances of two independent samples. Contingency tables frequently had the lowest Friction Pressures.
14
(ease, discomfort, occlusion loss) were analyzed using a
chi-square test. Graphing and statistical analyses were
performed using GraphPad Prism version 5.02 for Win-
dows (GraphPad Software Inc., www.graphpad.com).
Medians are shown along with minimums and maxi-
mums. Statistical significance was set at p ≤ .05. All p
values < .10 are reported.

Results
Tourniquets were applied to eight men and eight women.
Six male and nine female undergraduate students were
appliers (one female applier was paired with two recipi-
ents). Recipient characteristics are shown in Table 1.

Friction Pressure
Friction Pressure depends on applier technique and
strength, and influences the extent of tightening system
use needed to reach Occlusion. Previous work indicates
that Friction Pressures of at least 150mmHg are desir-
able for achieving thigh Occlusion with only one CAT Occlusion Pressure is affected by recipient blood pres-
6,7
windlass turn, thereby minimizing CAT tourniquet sure, limb circumference, and tourniquet width. Oc-
15
deformation. Friction Pressures for each tourniquet clusion Pressures are shown organized by tourniquet in
16
application are shown in Figure 2 along with a dotted Figure 3. Despite having the same 3.8cm width, the re-
150mmHg-threshold line. corded RMT-P Occlusion Pressures were lower than the
CAT and SOFTT-W recorded Occlusion Pressures. The
For a given tourniquet, appliers tended to achieve higher 10.4cm-wide SWATT had the lowest Occlusion Pressures.
Friction Pressures on the forearm than on the calf (fore-
arm versus calf: CAT, p = .60; SOFTT-W, p = .0001; To account for differences in limb circumference, the
RMT-P, p < .0001). Even on the forearm, however, Occlusion Pressures are graphed in Figure 4 against the
many of the Friction Pressures were not greater than or ratio of limb circumference divided by tourniquet width.
equal to 150mmHg. Larger ratios were generally associated with higher Oc-
clusion Pressures. The linear regression slopes and in-
One recipient-applier pairing was different for the tercepts for each tourniquet are shown in the legend on
RMT-P versus the CAT and SOFTT-W, so only 15 data Figure 4; the curve fits were not high.
sets were used for determining the tourniquet frequency
of highest and lowest Friction Pressures. For each ap- Completion Pressure
plier-recipient pair, the highest calf Friction Pressure The Completion Pressures are shown in Figure 5A. The
was most frequently achieved with the CAT (10 of 15 Completion Pressures were the starting pressures for
application sets) and the highest forearm Friction Pres- completed tourniquet applications. As such, the Com-
sure was most frequently achieved with the RMT-P (11 pletion Pressures represent the pressures at which the ap-
of 15 application sets). The SOFTT-W most frequently pliers stop increasing the tourniquet applied pressures;
had the lowest Friction Pressure for an applier-recipient ideally, therefore, the Completion Pressures should be
pair regardless of limb (24 of 30 application sets). as high as or higher than the Occlusion Pressures. Two
CAT calf and three CAT forearm Completion Pressures
Occlusion Pressure were lower than their respective Occlusion Pres-
Every tourniquet application achieved Occlusion. Two sures. Five SOFTT-W calf and one SOFTT-W forearm
forearm applications achieved Occlusion during strap Completion Pressures were lower than their respective
pulling to Friction Pressure. Those two applications had Occlusion Pressures. No RMT-P and no SWATT Com-
the highest two Friction Pressures: one was with the pletion Pressures were lower than their respective Oc-
CAT, the other was with the RMT-P. clusion Pressures.

32 Journal of Special Operations Medicine Volume 15, Edition 4/Winter 2015