Page 30 - Journal of Special Operations Medicine - Winter 2014

The objectives of this study were to compare the two RMT was easier to flex than the ladder of the Mass Ca-
RMT designs to each other and to the previously studied sualty RMT. The ladder material of the custom Flexible
CAT. Our general hypothesis was that occlusion pres- Mass Casualty RMT was polyurethane, which is easier
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sure will be primarily determined by overall strap width to flex than is Zytel. This made the ladder portion of the
(3.8cm). Occlusion pressure will not be determined by Flexible Mass Casualty RMT more flexible than the lad-
either the tightening mechanism (windlass or ratchet) der portion of the standard Mass Casualty RMT, despite
or the tensioning system width (internal ribbon strap or having the same width, length, and teeth/cm.
toothed ladder). Furthermore, strap-based tourniquets
will behave similarly concerning pressure loss and oc- The first Tactical RMT and first Mass Casualty RMT
clusion loss over time. Our specific hypotheses: were used for the Muscle Tension Experiments, the Tac-
tical versus Mass Casualty RMT Protocol, and all tour-
1. Tactical and Mass Casualty RMTs will be equivalent niquet training. Thus, each had been used many times
in all aspects (pressures, achieving and maintaining prior to the experiments. They will be referred to as the
occlusion, ease of application, and discomfort). Old Tactical RMT and Old Mass Casualty RMT.
2. RMT pressures will be equivalent under the ladder
and under the strap alone. The Flexible Mass Casualty RMT, a second Mass Ca-
3. Compared with the CAT, RMTs will have higher sualty RMT, and a second Tactical RMT were obtained
friction buckle pressures, similar occlusion pressures, for the Tooth Skipping Comparison Protocol and were
lower completion pressures, and similar pressure only used in that protocol. They will be referred to as
losses over 1 minute. the Flexible Mass Casualty RMT, the New Mass Casu-
4. Compared with the CAT, RMTs will have similar alty RMT, and the New Tactical RMT.
rates for achieving and maintaining occlusion.
5. Compared with the CAT, RMTs will receive similar The retrospective portion of this study was a comparison
ease of application and discomfort ratings. to previously collected pressure data using a CAT. The
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CAT has a fabric strap of the same 3.8cm width as the
RMTs used in this study. The CAT has a 2-slot flat plastic
Methods
friction buckle with grip slot edges and also incorporates
This study was approved by the Drake University Insti- hook and loop material as an additional or alternate strap
tutional Review Board. One RMT was purchased. An securing mechanism. The CAT has a 2.5cm-wide internal
additional four RMTs were requested from and donated ribbon strap running through the windlass and extending
by m2 Inc. The CAT was purchased. the entire length of the CAT strap. Twisting the windlass
®
tightens the CAT by shortening the internal ribbon as it is
Tourniquets wound around the windlass.
The prospective portions of this study used three dif-
ferent ratcheting tourniquet designs: the Tactical RMT, Pressure Measurements
the Mass Casualty RMT, and a custom Flexible Mass Pressures under the RMT tourniquets were measured us-
Casualty RMT. Each design consisted of a 3.8cm-wide ing two No. 1 neonatal blood pressure cuffs. Each cuff
fabric strap, a 2-metal ring friction buckle, a plastic lad- was inflated 10–15mmHg above atmospheric pressure
der (linear rack with teeth), and a ratcheting buckle. (baseline pressure). The air-filled cuffs were then taped
to the tourniquet. One was taped under the strap beneath
The specifications of the ladders and ratcheting buckles the ladder at the ladder attachment point farthest from
varied among the designs. The Tactical RMT had a 1.9cm the ratchet buckle (Ladder). The other cuff was taped
× 22.4cm ladder with 2.5 teeth/cm and a 3.0cm-wide × under the strap alone just beyond the ratchet buckle
4.5cm-long ratcheting buckle with a 0.762cm-long slot attachment point (Strap). The inflated cuffs were con-
to allow the cam action of the pawl when ratcheting. nected to a gas pressure sensor system (Vernier; http://
www.vernier.com/products/sensors/gps-bta). The pres-
Both the Mass Casualty RMT and the Flexible Mass Ca- sures were continuously displayed graphically with nu-
sualty RMT had a 2.3cm × 21.0cm ladder with 2 teeth/ meric values displayed every second. Each tourniquet
cm and a 3.5cm-wide × 5.8cm-long ratcheting buckle application’s Ladder and Strap data set was saved as
with a 0.889cm-long slot to allow the cam action of the complete—combined graphic and numeric data with
pawl when ratcheting. markers placed on the graph for pressure comparisons
at friction buckle secured, occlusion, completion, and 1
The ladder material of the Tactical RMT and the Mass minute after completion.
Casualty RMT was Zytel (http://www.dupont.com/
®
products), a thermoplastic polyamide composed of ny- Pressures under the CAT were measured in a slightly dif-
lon and fiberglass. The narrower ladder of the Tactical ferent fashion. In the CAT experiments, only one No.
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20 Journal of Special Operations Medicine Volume 14, Edition 4/Winter 2014