Page 39 - JSOM Summer 2023

FIGURE 1 Internet advertisement and purchasing information for the identity of the tourniquet provided. Three device lots were
the Military Tactical Emergency Tourniquet. used for the CATs (Nos. 101K116, 120E599, and 210B200).
There were no lot numbers found for the MTETs used. Cohort
groups were (1) CAT on left thigh first, (2) CAT on right thigh
first, (3) MTET on left thigh first, and (4) MTET on right thigh
first.

Volunteers were randomized to cohorts for tourniquet and
limb on first iteration and then used the other tourniquet on
the contralateral limb for a second iteration. Time began once
volunteers received the tourniquet. Once volunteers applied
the tourniquet to their satisfaction, investigators checked the
previously marked dorsalis pedis artery for flow with a Dop-
pler ultrasound. Volunteers were encouraged to secure the
windlass rod to complete tourniquet applications properly
within 60 seconds of being given the tourniquet, but otherwise
were not provided explicit criteria for successful application.
Once volunteers removed their hands from the tourniquet
device and verbalized completion, cessation of arterial flow
was sonographically ensured for 5 seconds over the previously
FIGURE 2 Within each identified site. If arterial flow was sonographically verified to
image section, the side-by-side be halted for 5 seconds, timing was stopped, and the time was
comparison shows the Combat recorded. Failure was defined as an inability to occlude dor-
Application Tourniquet (CAT) salis pedis arterial flow for a 5-second period within 1 minute
(ON THE LEFT), and the Military of initial application. Volunteers could continue tourniquet
Tactical Emergency Tourniquet application attempts beyond 1 minute and have their times
(MTET) (ON THE RIGHT). recorded if they felt initial attempts were unsuccessful or if ar-
terial flow continued on Doppler, but they were reminded that
times would still be annotated as a failed attempt.

We performed all statistical analysis using Microsoft Excel
Given the lack of evidence for the MTET, despite its near- (version 10) and JMP Statistical Discovery from SAS (version
identical appearance and dimensions, we developed and ex- 13.2). We reported descriptive statistics to include numbers
ecuted a prospective randomized crossover study to evaluate and percentages for nominal variables and median values with
and compare self-application success rates of the MTET with ranges for scale variables. The Kruskal-Wallis test was applied
those of the CAT in a military population. to examine time data, and a Fisher’s exact test was used to
analyze the tourniquet application success rates.
Methods
Results
Investigators solicited volunteers from a population of US
Army Combat Medics (military occupational specialty 68W) Fifty medics were solicited as a convenience sample for par-
serving as instructors at the Combat Medic Specialist Training ticipation, each self-applying a tourniquet twice for a total of
Program at Joint Base San Antonio–Fort Sam Houston, Texas, 100 observed applications. Volunteer data are summarized in
to undergo study execution on June 2 and 9, 2021. Potential Table 1.
volunteers were excluded when they had known injuries to the
lower limbs or physical profile limitations that would hinder TABLE 1 Volunteer Demographics
their ability to apply a tourniquet. All volunteers provided ba- Gender Number (%)
sic demographics and were measured for thigh circumference Male 43 (86%)
at the approximate site of planned tourniquet placement over
standardized physical training shorts. After locating the dor- Female 7 (14%)
salis pedis artery via Doppler ultrasound, investigating team Measurements Median (Range)
members annotated the location with a skin marker to confirm Age 33 (25–45)
pulse location prior to attempted tourniquet placement. Height (cm) 175 (152–193)
Weight (lbs) 189 (116–263)
Although all volunteers had received multiple iterations of Thigh Circumference (cm) 53 (43–65)
tourniquet instruction, given their military medical profes-
sional training, investigators provided brief instruction on All 50 participants (100%) successfully applied the CAT in
proper tourniquet self-application, including the goal of dis- under 1 minute, with a complete cessation of dorsalis pedis
tal arterial flow cessation and expectations of discomfort and arterial flow confirmed by Doppler ultrasound (Table 2). In
skin color changes. After being given a short, standardized contrast, 40 participants (80%) applied the MTET success-
scenario, investigators placed volunteers into one of four co- fully with a higher median time (Figure 3). All MTET failures
horts for tourniquet application and instructed them to place exceeded the 1-minute time limit. Additionally, mechanical
either an MTET or a CAT at mid-thigh level on the designated reasons for MTET failure included bent windlass rod, ripped
lower extremity while in a seated position, without disclosing stitching, and/or a deformed buckle (Figure 4).

Arterial Occlusion: MTET versus CAT | 37