Page 38 - Journal of Special Operations Medicine - Winter 2016

Table 3 Two-Phase Decay Equations for Each Tourniquet Application
Tourniquet Application:
Target Completion-Pressure, Two-Phase Decay Equation *
Gel or Limb, Tourniquet y = Plateau + SpanFast × e (−KFast × x) + SpanSlow × e (−KSlow × x)
262mmHg
10% ballistic gel
C-A-T y = −48.2 + 11.4 × e (−0.02602 × x) + 36.7 × e (−0.002195 × x)
RMT y = −43.0 + 8.93 × e (−0.05258 × x) + 34.1 × e (−0.001843 × x)
Blood pressure cuff y = −46.6 + 17.7 × e (−0.04800 × x) + 28.9 × e (−0.003585 × x)
SWATT y = −22.3 + 4.61 × e (−0.04758 × x) + 17.6 × e (−0.002339 × x)
20% ballistic gel
C-A-T y = −36.9 + 11.6 × e (−0.04735 × x) + 25.3 × e (−0.003082 × x)
RMT y = −32.3 + 5.69 × e (−0.03433 × x) + 26.6 × e (−0.002412 × x)
Blood pressure cuff y = −38.5 + 15.8 × e (−0.05111 × x) + 22.7 × e (−0.003253 × x)
SWATT no equation †
Human thigh
C-A-T y = −31.7 + 17.5 × e (−0.09503 × x) + 14.1 × e (−0.006532 × x)
RMT y = −37.7 + 15.9 × e (−0.08286 × x) + 21.7 × e (−0.008788 × x)
Blood pressure cuff y = −29.7 + 11.2 × e (−0.07786 × x) + 18.5 × e (−0.006611 × x)
SWATT y = −11.4 + 0.581 × e (−1.5000 × x) + 10.8 × e (−0.002461 × x)
Human arm
C-A-T y = −38.7 + 12.2 × e (−0.1659 × x) + 26.5 × e (−0.008205 × x)
RMT y = −66.1 + 13.0 × e (−0.1468 × x) + 53.1 × e (−0.008805 × x)
SWATT no equation †
362mmHg
10% ballistic gel
C-A-T y = −63.8 + 16.1 × e (−0.01550 × x) + 47.7 × e (−0.002245 × x)
Blood pressure cuff y = −54.7 + 17.9 × e (−0.02797 × x) + 36.8 × e (−0.003179 × x)
SWATT y = −41.7 + 7.46 × e (−0.01879 × x) + 34.2 × e (−0.001409 × x)
20% ballistic gel
C-A-T y = −49.6 + 10.6 × e (−0.03634 × x) + 38.9 × e (−0.002242 × x)
RMT y = −41.2 + 6.05 × e (−0.03318 × x) + 35.1 × e (−0.001754 × x)
Blood pressure cuff y = −48.7 + 17.7 × e (−0.05404 × x) + 31.0 × e (−0.003649 × x)
SWATT y = −33.7 + 3.87 × e (−0.01639 × x) + 29.8 × e (−0.001138 × x)
Human thigh
C-A-T y = −67.9 + 26.1 × e (−0.1425 × x) + 41.8 × e (−0.007609 × x)
RMT y = −62.4 + 19.7 × e (−0.06742 × x) + 42.7 × e (−0.005958 × x)
Blood pressure cuff y = −33.7 + 9.55 × e (−0.09724 × x) + 24.2 × e (−0.005283 × x)
SWATT y = −13.0 + 0.516 × e (−1.009 × x) + 12.5 × e (−0.002379 × x)
Human arm
C-A-T y = −50.4 + 20.9 × e (−0.1399 × x) + 29.5 × e (−0.007206 × x)
RMT y = −86.8 + 26.7 × e (−0.08723 × x) + 60.1 × e (−0.005583 × x)
C-A-T, Combat Application Tourniquet; RMT, Ratcheting Medical Tourniquet; SWATT, Stretch Wrap And Tuck-Tourniquet.
*Definitions of equation parameters:
y = pressure drop at time x.
y0 = y when x = 0 (y0 constrained to a value of 0 for the tourniquet applications).
x = time from completion (x = 0 at completed tourniquet application).
e = 2.718, the base of the natural logarithm.
Plateau = y at infinite times (the maximum pressure loss from completion to infinity).
SpanFast = (y0 − Plateau) × PercentFast × 0.01.
SpanSlow = (y0 − Plateau) × (100 − PercentFast) × 0.01.
KFast = the fast rate constant.
KSlow = the slow rate constant.
PercentFast = the percentage of the span from y0 to Plateau accounted for by the faster decay rate.
† No single value because many combinations of parameter values led to equally good curve fits.

temporary indentations occurred that visually matched occurred in the location of the C-A-T and RMT friction
those seen on the ballistic gels (Figure 5). The greatest in- buckles. With arm applications, some minor skin bruis-
dentation depths occurred under the strap bunches of the ing occurred with C-A-T and RMT applications, and
RMT created by advancing the ratcheting buckle (Table some arm tingling occurred for several minutes post-
1). These indentations were resolved within 30 minutes. C-A-T and RMT removals. Arm SWATT applications
at 262mmHg also had post-removal arm tingling. Con-
With same-day repeated thigh applications, some minor sidering that 262mmHg was already much higher than
skin irritation and transient post-application tenderness needed for arm arterial occlusion with this tourniquet

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