Page 31 - Journal of Special Operations Medicine - Winter 2014

1 neonatal blood pressure cuff was used. The cuff was signal confirmed that prior audible signal loss was due
taped to the recipient’s skin; then, the strap near the to arterial occlusion and not Doppler probe movement
CAT’s base plate was positioned over the cuff. Addition- away from the artery.
ally, the CAT data points were recorded by hand from
the computer display in real time without a continuous Subjects
graphic display or a marked and saved data file. Tourniquet recipients and appliers were volunteers fa-
miliar with each tourniquet protocol through a research
Pressure Time Point Information course. Exclusion criteria for recipients were self-reported
Friction pressure (Friction) refers to the pressure pres- blood clotting or circulation irregularities, implants in
ent just prior to engagement of the mechanical advan- relevant locations, systolic blood pressure greater than
tage tightening system. Friction pressure is the pressure 140mmHg, pain syndromes, or peripheral neuropathies.
achieved by the applier by pulling tight the strap threaded There were no exclusion criteria for tourniquet appliers.
through the friction buckle. Friction pressures were re-
corded with the applier’s hands off the tourniquet. Participants were allowed unlimited training access to
all tourniquets, printed instructions from the manufac-
Occlusion pressure (Occlusion) refers to the pressure re- turers, and instructional videos. Practice sessions were
quired to achieve arterial occlusion. The indicator for held, and verbal feedback was given to ensure correct
achievement of arterial occlusion was loss of the audible applications. All RMTs were applied to a recipient by
distal arterial pulse signal (wrist radial artery and an- an applier. The CAT data from the prior study involved
kle posterior tibial artery or dorsalis pedis artery). The self and nonself applications by a different group of re-
pulse signal was monitored using Doppler ultrasound cipient and applier volunteers. 5
(Ultrasonic Doppler Flow Detector Model 811 with
9.5MHz adult flat probe, Parks Medical Electronics, All Protocols
Aloha, Oregon). All tourniquet applications were directly on skin. Each
recipient had the same applier for all of their RMT tour-
Occlusion pressure values were “hands off” with the niquet applications.
RMTs and “hands on” with the CAT. This results from
the differences in mechanical advantage tightening sys- Muscle Tension Experiments
tems. RMT tightening occurred tooth by tooth as the Changes in muscle tension occur with limb use, pain
self-securing pawl was advanced. RMT Occlusion val- relief, and loss of consciousness. Muscle tension experi-
ues, therefore, were with no audible pulse signal with ments were to determine if changes in muscle tension
the ratcheting buckle in its “rest” location (hands off). under the RMTs would be similar to what had previ-
CAT tightening occurred by turning the non–self-secur- ously been observed with the CAT. The muscle tension
5
ing windlass. CAT Occlusion values, therefore, were experiments recorded pressures one click past Occlusion
with no audible pulse signal with the windlass held in with the underlying muscles tensed for 10 seconds and
position by the applier (hands on). relaxed for 10 seconds across three tension/relaxation
cycles. The muscle tension experiments were done with
Completion pressure (Completion) refers to the pressure the Old Tactical RMT and the Old Mass Casualty RMT,
after Occlusion with the applier’s hands off the secured each on the mid-thigh and mid-upper arm of one author,
tourniquet. We defined RMT Completion as a ratchet randomized as to which was applied on the right side
buckle advance one click past Occlusion. For CAT and which to the left side.
Completion, the windlass was advanced and placed in
the securing bracket after Occlusion. Tactical Versus Mass Casualty RMT Protocol
1. The recipient information shown in Table 1 was
Following Completion, tourniquets were left secured for collected.
1 minute. Pressure at the time point 60 seconds after 2. Either the Old Tactical RMT or the Old Mass Casu-
Completion is referred to as the 1 Minute pressure. Im- alty RMT was used first (randomized order).
mediately following measurement of the 1 Minute pres- 3. The first RMT design was applied to the right mid-
sure, tourniquets were released. thigh (Thigh) followed by the right mid-upper arm
(Arm).
If the audible pulse signal returned within 60 seconds of 4. The second RMT design was applied to the left
Completion, that return time and pressure were noted Thigh followed by the left Arm.
(failure of the tourniquet to maintain arterial occlusion). 5. Friction, Occlusion, and Completion pressures were
Following each tourniquet’s release after the 1 Minute recorded.
pressure was measured, the return or absence of the au- 6. The length of the ladder not pulled through the
dible pulse signal was noted. Return of the audible pulse ratcheting buckle at Completion was recorded.

Tourniquet Pressures: Strap Width and Tensioning System Widths 21