Page 36 - Journal of Special Operations Medicine - Fall 2015

the videos, instructions for use, and device design (Table Figure 2 Junctional tourniquet user variability in blood
3). For example, both the SJT video showed the inven- loss by model. This was a manikin study of 30 users and
tor pulling slack out of the strap four times before infla- the metric was blood loss. The index of variability was the
tion; this number indicated the mechanical importance maximum time divided by the minimum time for all users.
of maximal slack removal for optimal use—a principle
of all circumferential tourniquets that may not be per-
ceived by a casual video viewer. Emphases also included
countermeasures to common pitfalls. For example, the
JETT videos showed the user’s nondominant hand hold-
ing the belt to the subject’s torso to provide counter-ten-
sion to the applied tension of the dominant hand’s pull
on the running end of the strap. Without such counter-
tension, the pull from the dominant hand would slide
the belt and twist the device around the torso such that Figure 3 Junctional tourniquet user variability in time
the bladder would slide off the previously targeted point to stop bleeding by model. The column chart shows the
of application and underlying artery. variability of tourniquet use by junctional tourniquet model
from a manikin study of 30 users. The metric was time to
All users in this study were trained to proficiency in an stop bleeding, and the index of variability was the maximum
average of 2.25 hours (range, 2.1–3.25 hours). For all time divided by the minimum time. The times to stop
measures—effectiveness, time to stop bleeding, blood bleeding for the CRoC and the SJT were fast.
loss volumes, and user preference—the SJT and the
CRoC performed well.

One aspect of this latter study was to assess if mod-
30
els had wide variation that might indicate the need for
more training to reach optimal efficacy for a class of
trainees. Indexing via use of the ratio of maximum time
to minimum time helped assess variation by model. The
CROC and SJT had little variation (Figure 2 and 3).
Another aspect of training was made in preparation for Figure 4 The time to stop bleeding for one user in a manikin
the study when one user performed 10 consecutive ap- study with use of one junctional tourniquet model. The trend
plications to make sure the methods were suitable and line is a power curve that has the classic shape of a learning
the time allotted for the plan was sufficient; these data curve as the user became slightly faster with experience.
allowed a first look at a user learning curve (Figure 4).

In the third study, by Kragh et al., two people experi-
31
enced in applying JTs 29,30 assessed users of four JT models
on 10 normal human volunteers. This study evaluated
31
use metrics (i.e., effectiveness [pulse Doppler sound], time

Table 3 List of Examples of Useful, Scalable Feedback
Comments to Users
Great! Well done. You’ve done this before. You are a pro.
to stop pulse, and subject pain). The subjects ranked
Good! Make sure to remove all slack, as it will make the
next steps easier. the CRoC as the best; users ranked the CRoC and SJT
equally as the best. Targeting of the underlying common
Pull like their life depends on it!
femoral artery in human subjects was harder than in the
That’s okay, but by not removing all slack, the number of manikin, and palpation of the femoral pulse aided in ac-
pumps to inflate needs to be more. curate device placement. The users were also subjects, so
In slack removal, you pulled the belt only three times; the one user, who was the most experienced trainer, gained
inventor in the video pulled four times. experience as an early subject, and this would aid in
That’s marginal; if we can’t get the next step to work, then the next test. Targeting the palpable femoral pulse was
we’ll have to redo every step. found to be important during the study for effective-
That won’t work; without counter-tension with your left ness: when the compressive component of the JT was off
hand on the pad, pull of slack removal displaced the pad target even by 2 inches, use was ineffective. Placing the
off-target. Do that over. tourniquet coarsely, then placing the pads of the index

24 Journal of Special Operations Medicine Volume 15, Edition 3/Fall 2015