Page 49 - Journal of Special Operations Medicine - Spring 2015

Initial Tourniquet Pressure Does Not Affect
Tourniquet Arterial Occlusion Pressure

Sean E. Slaven, BS; Piper L. Wall, DVM, PhD; Jacob H. Rinker, MD; Meghan E. Halub, MD;
James W. Hopkins, MD; Sheryl M. Sahr, MD; Charisse M. Buising, PhD

ABSTRACT
Background: Effective nonelastic strap­based tourniquets Introduction
are typically pulled tight and friction or hook­and­loop Tourniquet use in the US military is a standard part of
secured before engaging a mechanical advantage system tactical medicine that is taught to all soldiers. Tourni­
1
to reach arterial occlusion pressure. This study examined quets are effective at reducing mortality from extremity
the effects of skin surface initial secured pressure (Friction hemorrhage if used before the onset of shock, and their
Pressure) on the skin surface pressure applied at arterial use carries a low risk of nerve palsy. An effective tour­
2
occlusion (Occlusion Pressure) and on the use of the me­ niquet must, by definition, provide occlusion of arterial
chanical advantage system. Methods: Combat Applica­ blood flow; other desirable qualities include simplicity,
tion Tourniquets (CATs; combattourniquet.com) and light and compact design, and rapid self­application. 3,4
®
Tactical Ratcheting Medical Tourniquets (RMTs; www
.ratchetingbuckles.com) were applied to 12 recipient The most studied and widely used tourniquets consist
thighs with starting Friction Pressures of 25 (RMT only), of a nonelastic strap and a mechanical advantage sys­
50, 75, 100, 125, 150, 175 (CAT only), and 200mmHg tem. The tourniquet currently deployed and most used
(CAT only). The CAT strap was single threaded. Pressure by US soldiers is the Combat Application Tourniquet
®
was measured with an air­filled, size #1, neonatal blood (CAT; Composite Resources, Inc.; combattourniquet.
pressure cuff under the Base (CAT), Ladder (RMT), and com), which features a nonelastic, 3.8cm­wide strap
Strap (CAT and RMT) of each 3.8cm­wide tourniquet. with a windlass mechanism for tightening via winding
Results: Base or Ladder pressure and Strap pressure were of an inner strap (Figure 1A). Another tourniquet de­
4,5
related but increasingly different at increasing pressures, sign that uses a nonelastic strap of the same width but
with Strap pressures being lower (Friction Pressure, r > uses a different mechanical advantage system is the Tac­
0.91; Occlusion Pressure, r > 0.60). Friction Pressure did tical Ratcheting Medical Tourniquet (RMT; m2 inc.,
®
not affect Occlusion Pressure for either design. Across the www.ratchetingbuckles.com) (Figure 1B). The RMT
12 thighs, the correlation coefficient for Strap Friction uses a ratcheting mechanism that moves along a ladder
Pressure versus CAT windlass turns was r = −0.91 ± 0.04, attached to the strap. Both designs are initially secured
and versus RMT ladder distance traveled was r = −0.94 ± with a friction buckle before implementing the mechani­
0.06. Friction Pressures of 150mmHg or greater were re­ cal advantage system.
quired to achieve CAT Occlusion with two or fewer wind­
lass turns. CAT and RMT Strap Occlusion Pressures were In tourniquets such as the CAT and RMT that use a
similar on each recipient (median, minimum – maximum; friction buckle and mechanical advantage system, rel­
CAT: 318mmHg, 260–536mmHg; RMT: 328mmHg, evant pressures involved in a tourniquet application
160–472mmHg). Conclusions: Achieving high initial include the pressure applied when secured via the fric­
strap tension is desirable to minimize windlass turns or tion buckle, the pressure at arterial occlusion, and the
ratcheting buckle travel distance required to reach arterial pressure at completion of application. Failure to remove
occlusion, but does not affect tourniquet surface­applied slack from the strap via the friction buckle has been
pressure needed for arterial occlusion. For same­width, shown to result in overuse of the mechanical advantage
nonelastic strap­based tourniquets, differences in the me­ system. With the CAT, overturning the windlass causes
chanical advantage system may be unimportant to final device deformation, breakage, and reduced effective­
tourniquet­applied pressure needed for arterial occlusion.
ness. 4,6,7 Specifically, bunching of the strap was among
the deformities noticed.
Keywords: tourniquet, hemorrhage control, first aid, emer-
gency treatment
Transduction of pressure from the tourniquet through
the skin to the artery might be affected by bunching in

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