Page 33 - Journal of Special Operations Medicine - Winter 2014

Statistical comparisons of RMT versus CAT pressure Figure 1 Narrower ladder Tactical RMT pressures were not
data were not performed because of the differences in higher than Mass Casualty RMT pressures. (A) Tactical and
pressure data collection. Contingency tables (occlusion Mass Casualty RMTs Ladder and Strap pressures on thighs,
loss, ease, discomfort, tooth skipping) were analyzed us- p = .0766. Strap pressures for Tactical versus Mass Casualty
ing either Fisher’s exact test or χ test. Graphing and RMT. (B) Tactical and Mass Casualty RMTs Ladder and
2
Strap pressures on arms.
statistical analyses were done using GraphPad Prism
version 5.02 for Windows (GraphPad Software Inc., (A)
San Diego, California). Medians are shown with mini-
mums and maximums. Means are shown with standard
deviations. Statistical significance was set at p ≤ .05. The
p values are reported when <.10.

Results
Tourniquets were applied to seven men and nine women.
Recipient characteristics are shown in Table 1.

Muscle Tension Experiments
The muscle tension experiments data are shown in Ta- (B)
ble 2. Following Occlusion, purposely tensing the mus-
cles under each RMT resulted in large pressure increases
(54–182mmHg, Table 2). Large pressure decreases were
present from Occlusion to the end of the final relaxation
cycle (decreases of 30–60mmHg, Table 2). Values from
the 3 tense/relax cycles were combined for the two RMT
designs. The largest possible muscle-tension-induced
pres sure differences are shown in Table 2 as the me-
dians, minimums, and maximums of 6 measurements.
The largest possible muscle-tension–induced pressure
differences varied from 82mmHg up to 232mmHg. The
mean muscle-tension–induced pressure differences are and therefore combined (Figure 1). Pressure measure-
also shown in Table 2 as the medians, minimums, and ments from the Old and New tourniquets in each design
maximums of 6 measurements. The mean muscle-ten- were pooled for subsequent Tactical versus Mass Casu-
sion–induced pressure differences varied from 47mmHg alty RMT comparisons.
up to 212mmHg. The magnitude of the pressure changes
would be more than sufficient to result in loss of arterial Tactical and Mass Casualty RMT Equivalence
occlusion. Friction pressures were similar between the Tactical and
Mass Casualty RMTs (Figure 1). Additionally, the lin-
Old and New RMT Equivalence ear regression comparisons between Friction pressure
Pressures beneath the comparable locations on the Old and ratchet buckle travel along the ladder at Completion
and New Tactical RMTs were statistically equivalent indicated that the Tactical and Mass Casualty RMTs
and therefore combined (Figure 1). Similarly, pressures were equivalent when comparing Ladders to Ladders or
beneath the comparable locations on the Old and New Straps to Straps for comparable limb locations. The r
2
Mass Casualty RMT were also statistically equivalent values for the thigh ranged from 0.25 to 0.45 and for

Table 2 Muscle Tension Effects on Tactical and Mass Casualty RMT Tourniquet Pressures
Occlusion – Peak Tensed – Mean Tensed –
First Tensed – Last Relaxed Lowest Relaxed Median, Mean Relaxed Median,
Occlusion Both Values Both Values Minimum-Maximum Minimum-Maximum
Location (mmHg) (mmHg) (mmHg) (mmHg)
Thigh ladder 69, 87 60, 27 189, 128–223 146, 73–212
Thigh strap 54, 77 33, 30 130, 82–158 103, 47–150
Arm ladder 182, 137 38, 47 178, 152–232 152, 125–193
Arm strap 73, 85 31, 42 97, 84–107 81, 71–95

Tourniquet Pressures: Strap Width and Tensioning System Widths 23