Page 40 - Journal of Special Operations Medicine - Winter 2016

Figure 5 Examples of temporary indentations on thigh and pressure decay curves with and without the tubular
20% ballistic gel immediately following Ratcheting Medical webbing are shown in Figure 6.
Tourniquet removal.

Discussion
Pressure losses unrelated to changes in muscle tension
occur within minutes under completed applications of
nonelastic tourniquets. Slower and smaller losses oc-
cur under completed applications of elastic tourniquets.
Proper initial application does not guarantee arterial
occlusion will be maintained. Given the opportunity,
tourniquet applications should be assessed for contin-
ued arterial occlusion 5 or 10 minutes after application.

Field users are not likely to know the pressure exerted
by an applied tourniquet or the tourniquet pressure
needed to maintain limb arterial occlusion. Well-trained
users know applying unlimited pressure is neither easy
nor desirable. Therefore, even well-trained users may
apply tourniquets that provide arterial occlusion at
application-completion but will lose arterial occlusion
(A) Thigh within minutes, even in the absence of tourniquet move-
ment, increases in recipient blood pressure, or decreases
in limb muscle tension. This is especially true for non-
elastic tourniquets.

The pressure losses are not from tourniquet fabric tear-
ing or stretching. We propose tourniquet pressure losses
result from tissue and, to a lesser extent, fluid move-
ment away from pressure. During tourniquet applica-
tion, a high-pressure zone is created. Fluid moves down
pressure gradients; so fluid in blood vessels and inter-
stitial spaces should move out from under a tourniquet.
We believe such fluid movement occurs predominantly
during, not after, application and does not account for
pressure-loss curves following application-completion.
Our reasoning is the ballistic gels do not have vascu-
lar or interstitial fluid and yet have pressure-loss curves
bearing a resemblance to those of same-circumference,
pressure-matched thigh tourniquet applications.

(B) 20% ballistic gel We did not detect changes in thigh or gel distortion from
application-completion to tourniquet removal. Easily
and considering the lesser amount of tissue protecting discernable limb and gel shape changes occurred under
the nerve in the arm than in the thigh, 362mmHg appli- and to either side of each tourniquet during the process of
cations of the SWATT to the arm were not done. application (Figures 4 and 3). Pressure increases during
tourniquet application were 200–300 or more mmHg
Measurement System Constraint Experiments greater than pressure losses following application-com-
Use of the tubular webbing increased the bleb size cre- pletion. If shape changes occurred during the pressure
ated by the pressure measurement system underneath losses after application-completion, they were too small
each tourniquet strap. Use of the tubular webbing re- for the sensitivity of our tools (two-dimensional images
sulted in statistically different two-phase decay equa- of approximately 95 pixels per centimeter).
tions (p < .001). The equation differences, however,
were minor and insufficient for inadequate-bladder- Our data support the following as determinants of
constraint-against-expansion to be the cause of the ob- pressure-loss curve profiles: tourniquet type, material
served tourniquet pressure-loss curves. The two-phase on which the tourniquet is applied, completion-pressure

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