Page 63 - JSOM Winter 2018

tissues, and the practical advice is to place tourniquets 2–3 Undetected, such misjudgments become self-erasing errors—
inches above the wound. That range of distance is thought to occurring when people do not know enough to realize they
be a safety margin because the tourniquet may be fully effec- do not know enough. Also, instructors and course directors
tive by avoiding hidden extensions of the wound beneath the may need an explanation to prepare learners optimally. In-
tourniquet (Appendix). structors may need rehearsals before they are ready to answer
tough questions or to detect such misjudgments of learners or
How a limb experiences compression under a tourniquet is not less-experienced peers. The instructors and their directors may
fully understood, but an understanding is gradually emerging find the tissue-disruption science disruptive to their current
from disparate studies. 1–14 For example, an imaging study re- teaching in that lesson plans may need to be revised. Instruc-
vealed that tourniquet use at low-pressure compression oc- tors can underscore the importance of the 2–3 inches above
cluded venous outflow without restricting arterial inflow and the wound as a safety precaution to minimize risk of misplace-
so induced an increase of limb girth that may reflect increased ment atop hidden portions of wounds.
intramuscular pressure from fluid accumulation and appar-
ently increased tissue stiffness. The compressive forces onto During tourniquet placement or handling of the limb, caregiv-
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the skin surface have been shown to form shear forces within ers may feel the effects of motion among underlying bony frac-
underlying skeletal muscle as tissue deformations indicated tures or hear bony crepitus, a crackling sound produced by the
shearing strains. Beyond the edge of the tourniquet, forces rubbing together of fractured fragments of bone. If caregivers
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taper off so that farther tissues remain unloaded. A conform- lift the lying patient’s heel and the mid-thigh sags down to bow
ing fit of the tourniquet shaped to the underlying skin surface into a banana shape while they feel and hear what sounds like
is optimal, safe, and lessens pain. An uneven fit can hurt, be rough, rocky surfaces grinding together inside the thigh, then
ineffective in bleeding control, and causes skin blisters or other they may guess that the wound includes a comminuted frac-
injuries. ture of the femur bone. If fracture is perceived, caregivers may
judge increased risk of tourniquet misplacement. To this end,
The compression width is important because a wider tour- one wonders whether a tourniquet can be reliably effective
niquet compresses more efficiently and compresses longer on a floppy thigh. Such an experience in an emergency would
lengths of blood vessels, thereby making vessel closure easier. likely be rare for a lay bystander. However, such an experience
The applied pressure to the limb surface is transmitted more may be commonplace in war for an orthopedic surgeon at a
efficiently into the soft tissues when the application area is busy hospital. The familiarity with such situations may aid
wider, and efficient compression is key where the arteries are, caregivers such as advanced beginners to begin understand-
namely, deeper within the limb. At a molecular level, the mag- ing the likelihoods of specific problems to troubleshoot, but
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nitude and three-dimensional orientation of cellular forces teaching recognition of such patterns is a heavy cognitive load
have been measured and mapped as traction forces based in for novices in their initial training. Basic first-aid providers
structural proteins of fibroblasts, showing alignment between may be confused or burdened by so much information. Also,
the force-bearing structures and the orientation of applied the problems of WYSIATI may be compounded inadvertently
forces. At the tissue level, compressed interstitial fluid 18,19 in training, such as when instructors have to say what the
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appears to flow away from the compressed area, 20,21 and such wound is (e.g., “what you see is all you got”) or to narrate the
flow out from under tourniquets may plausibly explain why probable response to intervention (e.g., “bleeding stopped”).
pressure magnitudes may lessen over time. Furthermore, the learner may make no assessment because in-
structors just give an answer to speed or ease instruction, thus
The next finding dealt with the question regarding the wound. inadvertently preventing development of learner judgments.
The injury caregivers often observe external appearance. How-
ever, the wound experienced by a patient may differ because Another finding was that how we used our noodle was fun.
the wound’s internal extent may be hidden. In other words, the Piecemeal, we cut the noodle into three thigh-length segments.
patient’s perspective of the wound will differ from those of the The first segment then was further cut into smaller segments
caregivers. Furthermore, the caregiver would necessarily have as used in the present study. The second thigh segment was
to think there might be injured internal structures, and this intended for tourniquet practice. In classes for the “Stop the
thought may require awareness beyond intuition, extra train- Bleed” program, instructors have been asked occasionally to
ing, or clinical experience for it to be routinely considered in suggest a cheap way to allow practice, and the response sug-
assessments of patients. In first aid, untrained bystanders may gesting a noodle for the purpose of practice has been liked.
not think of such a possibility, because what they see may be However, we prefer learners to either self-apply tourniquets
all they perceive, or as psychologists sometimes demonstrate: or apply them to each other so they can learn better or faster.
What you see is all there is: WYSIATI. WYSIATI may be a In cross-learning, the reciprocal practice between two train-
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common occurrence, and it is important because it risks biased ees, alternating as user and recipient, doubles the accrual rate
perceptions to potentially cause a cascade of consequences: of experience for both. They feel pressures and tensions, turn
undetected problems, affected judgments, affected behaviors, rods to provide torques, and hear the twisting of bands. If
and altered outcomes. Misjudging a wound can lead to mis- learners also have a mechanical metric of performance like
placement of the tourniquet atop a partially hidden wound, distal pulse stoppage, then they can also learn reliably from
which, perhaps needlessly, can impair control of bleeding, failures. The third thigh segment was cut into smaller segments
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which, in turn, may lead to a preventable death. so learners in our laboratory can see the unstable thigh bow,
hear crepitus, and feel the grating of the fractures in motion
Furthermore, a caregiver may blame a tool (tourniquet) instead during limb handling (Figure 4).
of oneself (failing to detect the actual extent of the wound).
Given no prior explanation, it may take notable intuition for This study is limited because it is a preliminary laboratory
a caregiver to detect and understand such a misjudgment. experiment. The results indicate additional studies may be

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