Page 45 - JSOM Summer 2019

FIGURE 2 Detailing a technique to self-adhere the tourniquet band FIGURE 4 Chart depicting results in ease of use by time to apply a
between the clips. tourniquet.

For each user, greater ease of use (circles) was associated negatively
with time taken to apply the tourniquet (dots show linear regressions).
The data range of the expert user (blue circles) was narrower than
that of the competent user (red circles). Because each user performed
with their own tourniquet, the materiel effect (framed as either model
or device) was controlled so that effect on ease was attributable to the
user, namely accrual of their experience. In this way, ease could be seen
as a user effect.
A close-up view details the tourniquet seen in Figure 1. The self-
adhering band is seen dangling down behind the white time strap at the FIGURE 5 Chart of results of time to apply a tourniquet and ease of
left. The time strap is a tourniquet part which is used to secure the rod use by use number.
within a clip. The smooth, fabric side of the band is visible, while its
self-adhering surface is hidden on the flipside. The band passes between
the two clips, which have their C-shapes open and facing each other.
In this passage, the smooth side of the band is still easily seen, and
underneath that side the self-adhering surfaces are sandwiched facing
each other. That facing occurs after the band routes through the bot-
tom slit in the buckle where it folds over the bottom bar of the buckle
to return toward the clips. Thus, the band has its self-adhering surface
facing itself through the region between the clips. The user, after having
removed the band’s slack, had then pressed the band onto the under-
lying tourniquet and limb here in this region so that the self-adhering
surfaces stuck together. Note that the band is not over the clips and not
blocking access of the rod into the gap between the clips.

FIGURE 3 Chart depicting time to apply a tourniquet by the accrual
of its uses.

For the average of two users, the time to apply the tourniquet (purple
circles) decreased asymptotically. Their ease of use (open green circles)
was a similar but inverted trend.

both the rod and clips separated them by an arc of approxi-
mately 90°. As the rod was turned, its rotation was tangential
to the limb. This is normal in relation to the limb, but it is
abnormal in relation to the clips when the limb is so small. In
For each user, the time to apply a tourniquet decreased by use num- turning, the rod ends passed over the clips, which were angled
ber in a power law of practice. The expert user (blue circles) had an approximately 90° away from the rod: The rod and clips could
estimated initial time that was 42% ([116.75 − 67.994]/116.75) faster not meet, so neither end of the rod could be put into a clip.
than that of the competent user (red circles). Results of both users
eventually overlaid the same asymptote: By this metric in this type of
use, the competent user became expert. Given this new problem, the expert immediately saw an un-
expected solution—that the role of the clip was to be taken
(Figure 6). Again, a modification to the instructions for use by the band. The role of the clip is normally to secure the
was to adhere the band between the clips. However, the rod rod, but the band could take up that role. Given the leftover
could not be put into a clip because the rod and clip were apart length in band after encircling the medium-sized limb, excess
and they were angled away from one another. Their gap was band remained. Also given the expert’s experience in 100 prior
about one-quarter of the circle. On the circle, the positions of uses on the large limb (i.e., handrail) and wrapping its excess

TABLE 1 Information About the Simulated Limbs of Infants
Material of Shape of Limb Perimeter
Limb Girth Simulator of Limb Simulated Limb Limb Orientation in Cross Section Circumference (in.)
Large Handrail Steel Horizontal Circle 5.25
Medium Pipe Steel Vertical Circle 4.25
Small Pole Steel Vertical Circle 3.25

Tourniquets on Simulated Infant Limbs | 43