Page 43 - Journal of Special Operations Medicine - Summer 2016

Tourniquets application goal, and the person collecting the pressure
The study used two different RMT designs: the 3.8cm- data with the computer was to alert the appliers of in-
wide Tactical RMT and the 5.1cm-wide Wide RMT adequate Friction Pressures. When using paired Tactical
(both from November 2014 manufacturing lots). The RMTs, both Tactical RMTs were loosely placed; then
tourniquets were applied as a single Tactical RMT (Sin- the strap of the distal tourniquet was pulled to Friction
gle), a single Wide RMT (Wide), or a side-by-side pair Pressure before the strap of the proximal Tactical RMT
of Tactical RMTs (Paired; Proximal of Pair and Distal was pulled to Friction Pressure.
of Pair).
Occlusion Pressure
Each RMT design consisted of a fabric strap; a friction Occlusion was defined as the absence of the audible distal
buckle composed of two overlapping, 4.0cm-diameter arterial Doppler pulse signal (Ultrasonic Doppler Flow
metal rings with a rough, friction-enhancing coating Detector Model 811 with 9.5MHz adult flat probe; Parks
to secure the correctly routed strap around the limb; a Medical Electronics, www.parksmed.com). The audible
thermoplastic polyamide ladder (linear rack with teeth); pulse signal had to remain absent with the ratcheting
and a ratcheting buckle. The strap width of the Tactical buckle returned to its rest position and the applier’s hands
RMTs was 3.8cm; the ladder dimensions were 1.9cm by off the tourniquet for Occlusion Pressure. With the Single
22.4cm with 2.5 teeth/cm, and the ratcheting buckle was Tactical RMT and the single Wide RMT, tightening to
3.0cm-wide by 4.5cm-long with a 0.762cm long slot to Occlusion occurred tooth-by-tooth as the pawl advanced
allow the cam action of the pawl when ratcheting. The along the single tourniquet ladder. With the paired Tacti-
strap width of the Wide RMT was 5.1cm; the ladder cal RMTs, the ratcheting buckle of the distal tourniquet
dimensions were 2.3cm by 21.0cm with 2 teeth/cm, and was advanced one tooth first; then the ratcheting buckle
the ratcheting buckle was 3.5cm-wide by 5.8cm-long of the proximal tourniquet was advanced one tooth. This
with a 0.889cm long slot to allow the cam action of the alternation continued to Occlusion and then to one-tooth
pawl when ratcheting. past Occlusion to complete the application.

Pressure Measurements Completion Pressure
Pressures under each tourniquet were measured using Completion was defined as one-tooth advance past Oc-
two #1 neonatal blood pressure cuffs (2.2cm × 6.5cm clusion with the applier’s hands not in contact with the
bladder, single tube). The bladder of each cuff was in- tourniquet.
5
flated to 10-15mmHg above atmospheric pressure to
avoid complete collapse of the bladder during tourni- 60-Second and 120-Second Pressures
quet applications. Atmospheric pressure was used as Following Completion, the tourniquet was secured for
baseline pressure. The cuffs were taped to each tourni- 125 seconds. We defined the 60-Second Pressure as the
quet: one under the strap beneath the ladder at the lad- pressure 60 seconds after Completion Pressure. We de-
der attachment point to the strap (Ladder) and the other fined the 120-Second Pressure as the pressure 120 sec-
under the strap alone just beyond the ratcheting buckle onds after Completion Pressure.
attachment point to the strap (Strap).
If the audible pulse signal returned within 120 seconds
The inflated bladders were connected to a gas pres- of Completion, that return time and pressure were
sure sensor system (Vernier Gas Pressure Sensor, Ver- noted, indicating failure of the tourniquet to maintain
nier LabPro interface, and Logger Pro Software; Vernier arterial occlusion. Following each tourniquet’s release
Software and Technology, www.vernier.com). Pressures after the 120-Second Pressure was measured, the return
were continuously displayed graphically with numeric (or absence) of the audible pulse signal was noted. Re-
values displayed every second. Each tourniquet applica- turn of the audible pulse signal confirmed that prior au-
tion’s data were saved as complete, combined graphic dible signal loss was due to arterial occlusion and not
and numeric data, with markers placed on the graph at Doppler probe movement away from the artery.
each time point for pressure comparisons at the follow-
ing events: strap secured around limb (Friction), arterial Tourniquet Appliers
occlusion (Occlusion), and completion of application There were four tourniquet appliers. Each had applied
(Completion). RMTs in one or more prior tourniquet studies. There
were also two applier assistants. The applier assistant
Friction Pressure pulled directly upward on the tourniquet handle while
Friction Pressure was taken when the strap secured the applier pulled the strap directly downward, around
with the friction-buckle was pulled tightly around the the limb through the friction buckle. This assistance is
limb and all hands were off the tourniquet. Obtain- not essential, but was expected to aid the achievement
ing a Friction Pressure greater than 100mmHg was an of Friction Pressures greater than 100mmHg. 6

Single, Wider, and Paired Tourniquet Pressures 29