Page 35 - Journal of Special Operations Medicine - Spring 2014

use and was present when the middle third of the Bagh- performance of the tourniquet use by its placement on
dad tourniquet survey was made in 2006, but he did not the thigh.
participate in the Baghdad survey. Both tourniquet users
were oriented to the manikin and its use. The SOFTT is a strap-and-windlass design. One wind-
lass turn is a 180º excursion arc, which is the limit of
The investigators used a HapMed Leg Tourniquet wrist supination in turning the windlass. The users
™
Trainer (CHI Systems, Fort Washington, PA), a simu- by convention regrip the windlass after 180º; this arc
lated right-thigh body segment (leg number 000F) with is what they deem one turn. The number of turns was
an amputation injury just proximal to the knee; its use recorded. The turn direction (clockwise, counterclock-
in the present study was similar to that described in wise) was recorded. Users were categorized individually.
previous reports. The medial hip–pelvic area had an
3,4
embedded computer interface that included a smart- The present study was an experiment of tourniquet per-
phone-like touchpad. Software (version 1.9) internal to formance by placement in four positions on the thigh.
the manikin allowed the leg to stand alone and be oper- The four positions were with the windlass placed ante-
ated by user input through finger touch on the pad. The rior, posterior, medial, and lateral on the proximal thigh.
manikin was laid on a desk in the laboratory and was Two users made 10 tests, each test in four positions, for
operated in accordance with the manufacturer’s instruc- a total of 80 tests. Performance criteria included hem-
tions. The manikin had no blood-like fluid, but bleeding orrhage control (yes–no), stopping the palpable pulse
was represented by red lights that transilluminated the distal to the tourniquet (yes–no), time to stop bleeding
wound. The number of lights illuminated represented (seconds), pressure applied to the skin by the tourniquet
the intensity of bleeding—all lights on meant no control (mmHg), blood loss volume (mL), and the number of
of bleeding; no lights on meant bleeding had stopped. windlass turns executed (whole number). The user tight-
Intermediate control was indicated by a few lights twin- ened the tourniquet until simulated bleeding was be-
kling on and off. Arterial pulse was noted when pal- lieved to have stopped, based on visual inspection of the
pable in the popliteal and femoral artery areas. lights and palpitation for the distal pulse in the device.

The system reported the blood loss volume as calcu- Statistical analysis included use of descriptive statistics.
lated using a linear equation from the arterial capacity We used a least squares analysis of variance (ANOVA)
and number of pulses before hemorrhage control. The to analyze the effects of tourniquet use on the factors
touchpad readout for each iteration showed the results, of interest. Analysis allowed for detection of intervari-
which included effectiveness of the bleeding control, able associations; namely, if there was an association
time to stop bleeding, pressure exerted under the tour- between the user (User 1 versus User 2) and tourniquet
niquet, and blood loss volume. The measurement of the position. This user-by-position meant that different us-
time to stop bleeding started when the iteration began ers had different results by position overall. Significance
and stopped when the manikin sensed that the thigh level was set at p = .05.
was losing no more blood. Effectiveness was defined as
the stoppage of blood loss and the termination of dis-
tal pulse. Iterations began with a tourniquet device laid Results
out flat undone on the desktop and not yet applied to Effectiveness rates of tourniquet use were 100% in all
the thigh and ended when the user pressed the touch- four positions (medial, lateral, anterior, and posterior);
pad button, believing that the hemorrhage was stopped. there was no statistical or clinical difference among the
A custom scenario was used; in it, the casualty had a effectiveness rates by position.
small build and the setting was care under fire, a setting
resembling civilian emergency care when there is gun- The two tourniquet users were both right-hand dom-
fire or similar danger at the scene of care. The manikin inant and used their right hand to turn the windlass.
settings also included a constant (635mL/min) hemor- The direction in which the windlass was turned differed
rhage rate; the resulting bleed-out time in this scenario between the two users. One user turned the windlass
was 4 minutes, giving the user 240 seconds to success- clockwise and the other counterclockwise. These two
fully apply the tourniquet. Tourniquet devices, users, directions were consistent for both users in all their
test iterations, and outcomes were uniquely identified. tests. Therefore, the results by turn direction and user
The tourniquet was a Special Operations Forces Tacti- were thus confounded as they essentially collapsed to
cal Tourniquet (SOFTT, Wide version, Tactical Medical mean the same thing; user identity and turn direction
Solutions, Anderson, SC). Users tightened the tourni- could not be separated effectively in the model.
quet until simulated bleeding stopped. The manikin was
designed to train users by providing feedback on trainee When modeling time to stop bleeding, the association
performance; and we used the manikin in assessing between tourniquet position and time to stop bleeding

Tourniquet Effectiveness by Position 27