Page 32 - Journal of Special Operations Medicine - Winter 2016

Inc.; www.ratchetingbuckles.com), and Stretch Wrap At time 0, each tourniquet was applied three times
And Tuck-Tourniquet (SWATT; TEMS Solutions; www at two target completion-pressures (262mmHg and
®
.swattourniquet.com) were donated. The extra-long-arm 362mmHg) on each gel and the thigh. On the arm, the
adult blood pressure cuff (Hokanson; www.deh-inc.com) C-A-T, RMT, and SWATT were used, and the SWATT
was borrowed from the UnityPoint Health Iowa Method- only at 262mmHg. Each application was in place on
ist Medical Center Vascular Services Department. ballistic gel for 600 seconds (10 minutes) and the thigh
and arm for 300 seconds (5 minutes). Arm tourniquet
Tourniquets use was limited because the arm was primarily used to
Four tourniquets of differing widths, elasticities, and allow investigation of limb circumference effects, and,
tightening systems were used: 3.8cm-wide, nonelastic, even with the 3.8cm-wide C-A-T and RMT, both com-
windlass C-A-T (generation 6) ; 3.8cm-wide, nonelastic, pletion-pressures were higher than necessary for arterial
2,3
ratcheting RMT (November 2014 manufacturing lot) ; occlusion with the involved arm.
2,3
13.7cm-wide, elastic pneumatic bladder within nonelas-
tic fabric, extra-long-arm adult blood pressure cuff; and The use of two target completion-pressures allowed the
10.4cm-wide, elastic SWATT. The nonelastic-strap tour- effects of variations in completion-pressure to be ex-
2,3
niquets had friction buckles to secure the tightly pulled plored. The completion-pressure targets were a pressure
straps prior to engaging the windlass or ratchet tightening already known to be arterially occlusive for the narrow-
systems. The C-A-T also had hook-and-loop material on est two tourniquets (C-A-T and RMT) on the involved
the strap. The blood pressure cuff had hook-and-loop ma- thigh and a pressure 100mmHg lower. Thigh arterial
terial to secure the fabric strap prior to bladder inflation. occlusion with those two tourniquets was previously
determined using Doppler ultrasound monitoring of
As TCCC approved, the C-A-T strap was single routed the distal pulse. Thigh and arm arterial occlusion moni-
6
through the friction buckle. The C-A-T had two discom- toring during the experiments was via pulse oximetry,
fort-reducing modifications by the authors: the wind- which is less sensitive for detecting the loss of tourniquet
lass-securing clip skin-side hook-and-loop was covered, arterial occlusion (unpublished data).
and the base plate corners were taped.
Size and Shape Changes
Pressure Measurements Photographs containing each entire cylinder and the
Tourniquet pressures were measured using one size #1 thigh distal and proximal to the tourniquet, including
neonatal blood pressure cuff (2.2cm × 6.5cm bladder; sin- boundary lines drawn on the thigh distal and proximal
gle tube). 1–3,7 The baseline was atmospheric pressure. The to the tourniquet placement line, were taken at the fol-
cuff bladder was inflated 10–15mmHg above baseline. lowing time points: no tourniquet; tourniquet placed
The cuff was taped under the strap at equivalent distances without pressure applied; completed application; 10,
from the C-A-T base plate and RMT ratcheting buckle. 20, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and
On the SWATT and adult blood pressure cuff, the neo- 600 seconds (tourniquet off thigh); and 30 minutes (bal-
natal cuff was taped the same distance from the starting listic gel only). Pictures were analyzed for size and shape
edge as on the RMT. The bladder was connected to a gas changes via the stack function and polygon traces using
pressure sensor system (Vernier Gas Pressure Sensor, Ver- the Fiji version of ImageJ (fiji.sc/Fiji, downloaded Au-
nier LabPro interface, and Logger Pro Software; Vernier gust 2015). At least 30 minutes passed between tourni-
8
Software and Technology; www.vernier.com) with contin- quet applications.
uous graphic display and numeric values every second. 2,3
Measurement System Constraint Experiments
Tourniquets, Compositions, To determine if inadequate bladder constraint could be
Completion-Pressures, and Circumferences responsible for decreasing pressures under the nonelas-
Tourniquets were applied to 10% and 20% synthetic tic tourniquets, a neonatal cuff was placed under the
ballistic gel cylinders (Clear Ballistics; clearballistics. C-A-T and RMT in a bare condition or sewn within
com) and a live, relaxed human thigh and upper arm. 1-inch polyester tubular webbing. Each bladder-condition
Each gel cylinder had a central, longitudinal, 1 inch tourniquet combination was applied three times to 20%
diameter stainless steel tube. Gel and limb circumfer- ballistic gel (600 seconds each) and to the thigh (300
ences were 57.5cm for the cylinders and thigh location, seconds each) at 362mmHg.
and 31.5cm for the arm. The use of two different com-
positions of ballistic gel and a human thigh, all of the Statistical Analyses
same circumference at the location of tourniquet place- Pressure data were organized in Microsoft Office
®
ment, allowed circumference to be held constant while Excel 2003 (Microsoft Corp.; www.microsoft.com).
tourniquet type, material composition, and completion- Pressure changes per second since tourniquet-application-
pressure were varied. completion were calculated. Nonlinear regression was

16 Journal of Special Operations Medicine Volume 16, Edition 4/Winter 2016