Page 59 - JSOM Winter 2018

Use Your Noodle to Simulate Tourniquet Use
on a Limb With and Without Bone

1
John F. Kragh Jr, MD *; Ning O. Zhao, BS, BA ;
1
James K. Aden 3rd, PhD ; Michael A. Dubick, PhD 1
2

ABSTRACT
Background: The purpose of this study was to simulate first do tourniquets work?” “What does ‘the wound’ mean?” We
aid by mechanical use of a limb tourniquet on a thigh with answered these questions as best we could and, in due course,
and without bone to better understand best caregiving prac- we gradually refined answers to accommodate new knowl-
tices. Methods: Two investigators studied simulated first aid edge. In the pursuit of answering these questions, we thought
on a new pool “noodle,” a plastic cylinder with a central air the answer to these questions may be revealed by mechanical
tunnel into which we inserted a wood dowel to simulate bone. means such as using a limb model in our laboratory. If we
Data were gathered by group (study and control, n = 12 each). could see the pertinent phenomena, we could enlighten our-
The control group comprised data collected from simulated selves about the likelihoods of success or failure of caregiving.
tourniquet use on the model with bone present. The study In this case, others might find the information useful. Notably,
group comprised data from simulated tourniquet use on the of these three questions, we started with the first one, because
model without bone. Results: Comparing compression with its answer might be informative to the others.
and without bone, the mean volumes of compressed soft tis-
sues alone were 303mL and 306mL, respectively. When bone The purpose of this study was to simulate first aid by mechan-
was present, the volume of soft tissues was squeezed more, ical use of a tourniquet on a thigh model with and without
yielding a smaller size by 3mL (1%). The bone had a volume bone so we can better understand best practices in preparing
of 41mL and pressed statically outward with an equal force people to render aid in emergencies. For this study, we used
oppositely directed to the inward compression of the overly- a “noodle,” a flotation aid commonly used for recreational
ing soft tissues. With bone removed and compression applied, swimming, as in a pool. The foam noodle had a thigh-size
the mean residual void was 16mL, because 25mL (i.e., 41mL girth in a cylindrical shape. The central core of the noodle was
minus 16mL) of soft tissues had collapsed inward. The volume a longitudinal tunnel about the width of a thigh bone, and a
of the limb under the tourniquet with and without bone was wood dowel was used to fill the void.
344mL and 322mL, respectively. The collapse volume, 25mL,
was 3mL more than the difference of the mean volume of the Methods
limb under the tourniquet. More limb squeeze (22mL) looked
like better compression, but it was actually worse—an illu- This study was conducted in 2018 within the protocol guide-
sion created by collapse of the hidden void. Conclusion: In lines of the US Army Institute of Surgical Research. Two inves-
simulated first aid, mechanical modeling demonstrated how tigators, a clinician-scientist and a fellow, researched bleeding
tourniquet compression applied to a limb squeezed the soft control. The scientist designed the controlled experiment and
tissues better when underlying bone was present. Bone loss oriented the fellow to its procedures.
altered the compression profile and may complicate control of
bleeding in care. This knowledge, its depiction, and its demon- Largely, data were gathered in groups: a study group, a nega-
stration may inform first-aid instructors. tive control group, and a positive control group (Figure 1). The
study group was called the boneless group, and it consisted
Keywords: caregiver; choice behavior; public health; medical of data collected from simulated tourniquet use (Combat Ap-
device; active learning; tourniquet; mechanics plication Tourniquet, generation 7; www.combattourniquet.
com) on a model of the thigh without its bone. Notably,
bone removal left a void in the previously occupied space.
Introduction The boneless group simulated the clinical problem posed
by segmental loss of the femoral bone. The negative control
In years of tourniquet work, lay persons, Soldiers, medics, in- group was called the band-only group and it comprised data
structors, and doctors around the world have asked us ques- collected from simulated tourniquet placement whereby the
tions such as “Do tourniquets work if bone is missing?” “How band was pulled and secured but the rod of the tourniquet was
*Correspondence to John F. Kragh Jr, MD, 3698 Chambers Pass, Joint Base San Antonio Fort Sam Houston, TX 78234-7767; or john.f.kragh
.civ@mail.mil
1 Dr Kragh, Ms Zhao, and Dr Dubick are affiliated with the US Army Institute of Surgical Research (ISR), Fort Sam Houston, TX, where Dr
Kragh is an orthopedic surgeon conducting research on bleeding control, and Dr Dubick is a resuscitation researcher and the manager of the
Damage Control Resuscitation task area. Ms Zhao was a former research fellow on bleeding control projects at ISR and currently is a medical
student in the McGovern Medical School, University of Texas Health Sciences Center at Houston. Dr Kragh is also an associate professor in
2
the Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD. Dr Aden is a statistician at the Brooke Army
Medical Center, Fort Sam Houston, TX.
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