Page 41 - Journal of Special Operations Medicine - Winter 2015

Medical Solutions Inc., www.tacmedsolutions.com) was 4.0 cm-diameter metal rings with a rough, friction-
purchased. enhancing coating to secure the correctly routed strap
around the limb. Throughout tightening by advancing
Tourniquets the ratcheting buckle along the teeth of the ladder, the
The four tourniquets of different widths and tighten- RMT-P ratcheting buckle is self-securing by ladder-
ing systems were the 3.8cm-wide windlass CAT and tooth engagement of its internal pawl.
SOFTT-W; the 3.8cm-wide ratchet RMT-P; and the
10.4cm-wide elastic SWATT. The CAT, SOFTT-W, and The SWATT is a 10.4cm-wide rubberlike strap (Figure
RMT-P are each composed of a nonelastic fabric strap, 1D). The first wrap of the SWATT around the limb is se-
friction buckle, tightening system, and mechanism for cured by the friction of the following wrap. The SWATT
securing the tightening system for application comple- is tightened by user stretching of the strap and by elastic
tion (Figure 1A-C). The SWATT is composed solely of recoil of the strap. Tightness increases with each wrap.
an elastic strap (Figure 1D). During the last wrap, the end of the strap is tucked un-
der a previous wrap to secure the tight tourniquet.
The CAT has a 3.8cm-wide strap covered with hook-
and-loop and connected on one end to a 9.3cm-long Pressure Measurements
plastic base plate (Figure 1A). Inside the strap covered Skin surface-applied pressures under the tourniquets were
with hook-and-loop is another strap, 2.5cm wide, that measured using two size #1 neonatal blood pressure cuffs
runs from the friction buckle across the base plate, (2.2cm × 6.5cm bladder, single tube). Each cuff was in-
through a slot in the windlass, and then through the flated to 10–15mmHg above atmospheric pressure, with
entire length of the hook-and-loop covered outer strap. the resulting pressure used as a baseline. The air-filled cuffs
The CAT friction buckle is plastic and has two slits with were taped to the tourniquets. On the CAT and SOFTT-
rough edges that grip. The CAT can be secured around W, one cuff was taped under the base; the second was
the limb by using a single slit of the friction buckle com- taped under the strap alone at the same distance from the
bined with adherence of the hook-and-loop, 12,13 which first cuff as was the case with the RMT-P. On the RMT-P,
was done in this study, or by using both slits of the fric- one cuff was taped under the strap beneath the ladder at
tion buckle with or without use of the hook-and-loop. the ladder attachment point to the strap; the second was
Following tightening by windlass turning, the CAT taped under the strap alone just beyond the ratcheting
windlass is secured by placement of one end within the buckle attachment point to the strap. On the SWATT, one
windlass securing clip. The CAT had one discomfort- cuff was taped near the starting end of the strap; the sec-
reducing modification made by the authors: the bare ond was taped under the strap at the same distance from
hook surface of the hook-and-loop on the skin side of the first cuff as was the case with the RMT-P.
the windlass securing clip was covered.
The cuffs were connected to a gas pressure sensor system
The SOFTT-W has a 3.8cm-wide strap connected on one (Vernier Gas Pressure Sensor, Vernier LabPro interface,
end to a 17.4cm-long stiff webbing base and to a metal and Logger Pro Software; Vernier Software and Tech-
clip that connects to the friction buckle (Figure 1B). The nology, www.vernier.com). Pressures were continuously
3.8cm-wide strap runs from the connection on the stiff displayed graphically with numeric values displayed
webbing base, through a slot in the windlass (around every second. Each tourniquet application’s data were
which the strap is also connected), and then through a saved as complete, combined graphic and numeric data,
7.3cm-long double portion of stiff webbing (part of the with markers placed on the graph at each time point
17.4cm-long base). The SOFTT-W friction buckle is metal for pressure comparisons at the following events: strap
and has a center sliding portion that secures the correctly secured around limb (Friction), arterial occlusion (Oc-
routed strap around the limb. After tightening by windlass clusion), and completion of application (Completion).
turning, the SOFTT-W windlass is secured by placement
of one end within the windlass-securing triangle. After data collection was complete, a decision was made
to only use the pressure data from under the second cuff
The RMT-P has a 3.8cm-wide strap connected on one because the differing base portions of the two windlass
end to a friction buckle (Figure 1C). The 3.8cm-wide tourniquets and the ladder-covered portion of the RMT-
strap has a 1.9cm-wide by 10.0cm-long, plastic, toothed P provided differing amounts of expansion-constraint
ladder riveted to it near the friction buckle and a 3.0cm- on the first cuff. Experiments showed that differences
wide ratcheting buckle riveted to it at the other end of in cuff expansion-constraint clearly affected the pres-
the ladder. The ladder material of the RMT-P is more sure measurement from the cuff (less cuff expansion-
flexible than that of other RMT models and is designed constraint resulted in lower cuff pressures [data not
with a much lower tooth-load failure rating. The RMT- shown]). Because the nonbase, nonladder portions of
P friction buckle is composed of two overlapping, the tourniquets offered the most complete and consistent

Emergency Tourniquets on Distal Limb Segments 29