Page 37 - Journal of Special Operations Medicine - Winter 2014

Table 7 RMT Tooth Skipping
Narrow Ladder Small Buckle Wide Ladder Large Buckle
Old Mass New Mass Flexible Mass
Old Tactical New Tactical Casualty Casualty Casualty
Did Not Skip 31 32 16 21 27
Skipped 1 0 16 11 5
Fisher’s exact test p values versus
Old Tactical .4848 <.0001 .0027 .1961
New Tactical .4848 <.0001 .0001 .0225
Old Mass Casualty <.0001 <.0001 .3144 .0070
New Mass Casualty .0027 .0001 .3144 .1477
Flexible Mass Casualty .1961 .0225 .0070 .1477
Note: Skipping incidence was not significantly different between thighs (20 of 80) and arms (13 of 80).

was disconcerting for users and meant that additional were clearly not the cause (Figure 3 Panel B and linear
pivots of the ratcheting buckle were required. Since the regression equation fits). Whether the arm differences
Tactical RMT does not tend to skip, it has a clear ad- relate to tensioning system differences, discomfort differ-
vantage over the Mass Casualty RMT. ences potentially affecting muscle tension, or data cap-
turing differences requires further study.
From our tooth skipping experience, the best applica-
tion process with RMTs includes putting pressure on Pressure Changes after Completion
the pivoting point of the ratcheting buckle toward the Similar to observations with the secured CAT, signifi-
5
ladder during the ratcheting process. This application cant RMT pressure losses occurred in the 60 seconds
tip was not present in the RMT instructions and was not following Completion. Surprisingly, arterial occlusion
obvious to all of the appliers. was lost much less frequently over that minute with the
RMTs than had been observed with the CAT. The shape
Ladder Versus Strap and extent of pressure loss for longer time periods and
We hypothesized that RMT pressures would be evenly whether the difference in occlusion maintenance would
distributed under different regions of the tourniquet. persist between the windlass versus ratchet designs
This was not the case; pressures under the Ladder were over longer time periods are both questions of interest.
not the same as under the Strap. This indicates that the Causes for pressure loss under tourniquets include fluid
location of pressure measurements, relative to tour- movement in blood vessels, lymphatics, and interstitial
niquet components, is important. The location of the spaces. An additional cause of pressure change can be
tourniquet component, relative to limb structures, may alteration in muscle tension.
also matter (lateral, dorsal, medial, ventral). The RMT
Ladder and Strap pressure data suggest that pressures Changing muscle tension created large and sudden
under the CAT might also be nonuniform since the CAT pressure changes under both the RMTs and the CAT.
5
has a nonflexible base-plate portion and a strap portion. We believe this is a shared characteristic for nonelas-
This possibility along with the pressure-data–capturing tic strap-based tourniquet designs regardless of the
differences in the previously done CAT study led us to strap-tightening mechanism (windlass, ratchet, or block
5
only present graphic comparisons of RMT and CAT and tackle). Our previous data indicate this pressure
pressures without statistical comparisons. change is dampened by tourniquets that have an elastic
component. With nonelastic strap-based tourniquets,
5
RMTs Versus CAT the magnitude of muscle-induced pressure changes can

We visually compared pressures under the RMTs and easily be 100 to 200mmHg.
CAT. The Friction pressures were quite similar. The
Occlusion, Completion, and 1 Minute pressures shared Clinical Relevance of
ranges. The RMTs had occlusion pressures with a Pressure Changes after Completion
roughly linear relationship to limb circumference divided Loss of arterial occlusion is the clinically important con-
by tourniquet width. This was in contrast to what had sequence of tourniquet pressure drops. Return of venous
been observed with the CAT; CAT arm occlusion values flow is prevented by tourniquet pressures well below
were frequently as high or higher than CAT thigh oc- those required for arterial occlusion. Resumption of arte-
clusion values. Recipient limb circumference differences rial flow with maintained venous occlusion is potentially

Tourniquet Pressures: Strap Width and Tensioning System Widths 27