Page 53 - JSOM Summer 2019

Secured-Strap Pressures in secured-strap pressures were statistically significant by
Secured-strap pressures with thigh applications using different technique and tourniquet (p < .0001 for technique and for
holding locations and pulling directions are shown in Figure tourniquet, with p = .0033 for interaction when including the
2A. One experienced applier with a 41.50kg, single-arm pull- pulling-only-outward techniques; and p < .0001 for technique
ing force did the applications with the highly ineffective pull- and tourniquet, with p = .0357 for interaction when excluding
ing technique of pulling only directly outward from the limb the pulling-only-outward techniques).
(90° angle). He found it difficult not to follow the outward
pull with additional downward pulling, especially with the The inappropriateness of pulling only directly outward was
C-A-T7, which requires the applier to secure the strap hook- borne out by data from gel applications (Figure 2B). With
and-loop to hook-and-loop. Video replay of the applications a consistent strap-pulling force of 226N (50.84lbf) applied
confirmed this difficulty, and some downward pulling during only at a 90° angle to the gel surface (Figure 3), inadequate
C-A-T7 strap securing occurred. This is the likely explanation secured-strap pressures were achieved (range, 53 to 82mmHg).
for the 131mmHg achieved C-A-T7 secured-strap pressure The differences in secured-strap pressures were statistically
with the “holding above and instructed to pull only directly significant by technique and tourniquet (p < .0001 for tech-
outward from the limb (90° angle)” technique. The other nique, tourniquet, and interaction).
nine applications done with the intent to pull only directly
outward from the limb all achieved inadequate secured-strap As shown in Table 1, when considering all the tourniquet de-
pressures (range, 12 to 59mmHg; Figure 2A). The differences signs, the best technique for appliers to achieve the greatest
FIGURE 2 Secured strap pressures achieved with thigh and gel tourniquet applications using different application techniques.

(A) (B)

On each panel, the “minimum threshold” and “desirable threshold” differences in secured-strap pressures are statistically significant: p <
secured-strap pressures come from thigh C-A-T data. 7–10 (A) Thigh .0001 for technique and for tourniquet with p = .0033 for interaction
secured-strap pressures achieved by individual appliers holding each when including the pulling only outward techniques and p < .0001
tourniquet in the indicated location relative to the redirect buckle (i.e., for technique and for tourniquet with p = .0357 for interaction when
above, below, or the buckle itself) and actively pulling the free end excluding the pulling only outward techniques. (B) Gel secured-strap
of the tourniquet strap in the indicated direction relative to the thigh pressures achieved in each of triplicate applications on the 20% bal-
at the redirect buckle (i.e., tangential, outward and then tangential, listic gel cylinder with the free end of the tourniquet strap attached to
or only outward). Individual symbols represent results for individual 23.06kg for a pulling force of 226N (50.84lbf) in the indicated direc-
applications. Shaded boxes show interquartile range, and the ends tion relative to the gel at the redirect buckle (i.e., tangential, outward
of the whiskers show the minimum and maximum values. The two and then tangential, or only outward). Individual symbols represent
sections under “discarded techniques” show individual application se- results for individual applications; the horizontal bar indicates the me-
cured-strap pressures achieved by one experienced, strong applier when dian. The worst pulling direction was only outward. Unlike the results
directed to actively pull the strap only in the outward-from-the-thigh with human appliers shown in (A), pulling outward and then tangen-
direction. Across all tourniquet designs and all appliers, the application tial to the gel at the redirect buckle garnered considerably higher se-
technique that most frequently garnered the highest secured-strap pres- cured-strap pressures for the Tac RMT, TMT, Parabelt, and SOFTTW
sure was holding above the redirect buckle and actively pulling the free than did pulling only tangential at the redirect buckle. The differences
end of the tourniquet strap tangential to the thigh at the redirect buckle in secured-strap pressures are statistically significant: p < .0001 for
2
(χ test, p = .0109). The worst pulling direction was only outward. technique, for tourniquet, and for interaction. C-A-T7, Generation 7
Among techniques that included actively pulling tangential to the thigh Combat Application Tourniquet; Tac RMT, Tactical Ratcheting Medi-
at the redirect buckle, the technique that most frequently garnered the cal Tourniquet; SOFTTW, Generation 3 Special Operations Forces Tac-
lowest secured-strap pressure was holding the redirect buckle and ac- tical Tourniquet–Wide; TMT, Tactical Mechanical Tourniquet.
2
tively pulling outward and then tangential (χ test, p = .0119). The
Tourniquet Strap Technique | 51