Page 86 - JSOM Summer 2020

known bleeding or clotting abnormalities, circulation prob- teeth (clicks), or circumferential wraps (nearest 90°) at occlu-
lems, pain syndromes, peripheral neuropathies, connective sion and completion were recorded. Occlusion was defined
tissue disorders, or conditions counter to the positioning re- as loss of audible Doppler pulse from the dorsal pedal artery
quired for thigh use. (Ultrasonic Doppler Flow Detector Model 811 with 9.5MHz
adult flat probe; Parks Medical Electronics, www.parksmed.
Tourniquets were applied to two thigh models. One was a com). Occlusion was hands off for the Tac RMT but held for
57.5cm circumference, 20% synthetic ballistic gel cylinder the others. Completion was defined as occluded with hands
(Gel, Clear Ballistics; clearballistics.com) suspended via a off with the windlass rod secured at a rotation beyond the
rod through the 2.54cm-diameter central stainless steel tub- occlusion position (C-A-T7 and SOFTTW), one click past oc-
ing. 5,7,8 The other was two 5mm-thick yoga mats (Mats, 61cm clusion (Tac RMT), or the end of the SWATT secured under a
x 173cm, 1002569059, Home Depot, homedepot.com) rolled previous wrap. For applications that were not completed, the
one around the other with a 48.0cm circumference and sus- final pressure; number of turns, clicks, or wraps; and the rea-
pended via a 1.2cm-diameter metal rod through the center. son for incompletion were recorded (applier inability, recipient
discomfort, or other). For secured, occlusion, and completion
Tourniquet Appliers data points, a 5 second pause occurred before moving onward.
Inclusion criteria were age ≥ 18 years, willingness to watch Tourniquets were removed 5 seconds after completion. The
application videos, 9-11 practice applying tourniquets with recipients sat as in Phase 2. Because we realized appliers had
technique feedback and real-time pressure data, and a dom- knelt in Phase 2, appliers stood in Phase 3. Applications were
inant-hand weight pull > 9kg. Exclusion criteria were condi- videoed.
tions counter to tourniquet application (hand, wrist, elbow, or
shoulder injuries). Tourniquet Applications
Nonelastic tourniquet application technique consisted of a
Applier Pulling Force tourniquet-holding location above the redirect buckle and
To determine single-arm downward pulling force, increasing a strap-pulling direction downward, tangential to the limb
weight increments of 4.54kg were attached to a C-A-T7 strap, at the redirect buckle. Appliers pulled with their dominant
8
which was placed over a smooth metal rod (1.2cm-diameter). hand. Nonelastic tourniquets were not replaced unless a prob-
Seated appliers pulled down on the free end of the strap with lem occurred. A new SWATT was used by each applier. Each
encouragement to engage their entire upper body strength and SWATT application consisted of a minimally stretched 450°
weight. wrap followed by fully stretched wraps through occlusion and
completion.
Three-Phases
This study used thighs and tourniquet applications with the Statistical Analysis
following clothing conditions under the tourniquets: bare skin For thigh applications, the order of tourniquet and clothing
(Bare), scrubs (Scrubs), United States Military Army Combat condition were randomized to avoid a potential order effect.
Uniform (Uniform), and compression tights (Tights). For each Double data entry with crosscheck was used for written data
condition involving clothing, the under-tourniquet-pressure and organizing pressure data from LoggerPro into Microsoft
®
was measured with the bladder at skin (Scrubs Skin, Uniform Office Excel 2003 (Microsoft Corp., www.microsoft.com). Be-
Skin, Tights Skin) or thigh model surface (Scrubs Skin, Uni- cause the bladder was not directly visible under clothing and
form Skin) and at clothing surface (Scrubs Clothing, Uniform could be other than under the center of SWATT wraps, pres-
Clothing, Tights Clothing). sure data was validated before analysis: points were removed
for video-detectable evidence of bladder location problems
Phase 1 investigated clothing influence on pressure effects or physiologically incorrect values. Graphing and statistical
of controlled force application. A Tac RMT (0.1000kg) was analyses were performed with GraphPad Prism, version 7.04
draped over bare or clothed, thighs or thigh models. Strap for Windows (GraphPad Software Inc., www.graphpad.com)
ends were joined together (C-clamp, 0.0938kg) and had and with IBM SPSS Statistics for Windows, version 26 (IBM
4.54kg weights attached by carabiners (rope plus three car- Corp., www.ibm.com). Nonlinear curve fitting (least squares
abiners, 0.23761kg) at 20 second intervals for total applied and extra sum-of-squares F test), paired t test, one-way re-
forces from 4 to 271N (0.95 to 61lbf). The inflated bladder peated measures analysis of variance analysis (ANOVA), two-
was 180° from the downward hanging weights. Recipients way ANOVA, and two-way repeated measures ANOVA were
(n=5) lay so the medial mid-thigh was upward. used for pressure data. Values in text are medians, minimums
to maximums. χ test and Fisher’s exact test were used for con-
2
Phase 2 investigated clothing influence on tourniquet appli- tingency data. Statistical significance was set at p≤.05.
cation and secured pressure (ability to pull tight and secure
strap, n=15 appliers on thighs). Only nonelastic tourniquets Results
were involved. For thighs, recipients sat upright, thigh par-
allel to the floor, lower leg at a right angle to the thigh, and Recipients and Appliers
attempted to maintain a relaxed thigh. Applications were vid- For recipient and applier information, see Table 1.
eoed. For thigh models, 22.70kg was attached for 20 seconds
to the end of the model-encircling tourniquet strap. Phase 1: Hanging Weights
Controlled-force-application triplicates had little pressure vari-
Phase 3 investigated clothing influence on the complete tour- ance (coefficient of variation: thighs 1.38%, 0.03 to 8.51%,
niquet application process and pressures (n=15 appliers). Se- thigh models 1.26%, 0.03 to 6.57%). This was a low noise
cured pressures, occlusion pressures, completion pressures, system suitable for answering the physics question: Can cloth-
and the number of windlass 180° turns (nearest 45°), ladder ing cause a pressure response difference?

84 | JSOM Volume 20, Edition 2 / Summer 2020