Page 32 - Journal of Special Operations Medicine - Summer 2016

Materials and Methods Of note, half the volunteers had the pneumatic tourni-
quet randomly applied first, and the other half had the
Following institutional review board approval, 20 non- C-A-T applied first, to eliminate bias that may be intro-
obese volunteers, who were without significant active duced from ischemic reactive vasoconstriction.
medical problems and between 18 and 50 years old, were
recruited to participate in the study. None of the partici- The primary end point of the study was the absence of a
pating volunteers had a history of limb trauma, vascular palpable pulse in the dorsalis pedis and the posterior tib-
disease, or previous vascular surgical interventions. Addi- ial arteries after tourniquet application. The secondary
tionally, individuals receiving any vasoactive medications end point was the amplitude of the plethysmographic
were excluded from the study unless they were using waveforms after tourniquet application. The data col-
asthma inhalers on an as-needed basis, oral contracep- lected also included the patients’ basic demographics,
tive pills, or a single antihypertensive agent. Volunteers medical history, and body mass index (BMI).
were informed that complications from participation in
the study (psychological and physical) would be man- All data analyses were performed using STATA version
aged by the host medical institution. The procedure was 13.1 (StataCorp, https://www.stata.com). Numeric vari-
explained in detail during the informed consent process ables were summarized as means and standard deviations,
to every participant by the principal investigator of the and were analyzed with the Wilcoxon rank-sum test. Cat-
study, who was also responsible for applying the tour- egorical variables were summarized as proportions and
niquets. Study volunteers were encouraged to withdraw were analyzed using the McNemar test. A p value ≤.05
from the study at any time if they experienced unbearable was used to define statistical significance for all tests.
discomfort or simply did not want to continue.

All volunteers donned the Crye Precision G3 Combat Results
Pant (Crye Precision, https://cryeprecision.com) fol-
lowed by the JSLIST over-garment CBRN protective A total of 20 healthy volunteers were enrolled in the
pant. Baseline clinical examination was performed to study. Of note, none of these volunteers experienced any
confirm the presence of palpable pulses in the dorsa- discomfort requiring withdrawal from the study and no
lis pedis and posterior tibial arteries (using the standard clinical complications were observed. The mean age
0–4 clinical pulse examination scale). Moreover, base- of volunteers was 33.7 years and their mean BMI was
2
line quantitative measurements to characterize arterial 26.39 kg/m . Fifty-five percent of them (11 of 20) were
flow were performed using impedance plethysmography male and 45% (nine of 20) were female. At baseline, all
to create pulse volume recordings (PVRs). The PVR test had 3+ palpable distal dorsalis pedis and posterior tibial
can detect small segmental volume changes that occur as pulses on clinical examination. The mean plethysmo-
a result of alterations in blood flow. The cuff is placed graphic waveform amplitude, at baseline, was 33.95mm
around an extremity segment and is subsequently in- with a standard deviation of 4.61mm.
flated so the venous return is occluded yet the arterial
flow remains unchanged. A waveform, which is the re- No technical issues were encountered during the appli-
sult of the ongoing arterial circulation, can then be re- cation of the tourniquets. In all cases, the tourniquet size
corded. In this study, the amplitude of these waves was was at least half that of the limb diameter, indicating that
characterized. the correct size of pneumatic tourniquet was used. Af-
ter inflation of the pneumatic tourniquet to 300mmHg,
The gold standard for achieving complete circulatory no dorsalis pedis or posterior tibial pulses could be pal-
occlusion in this investigation was a standard operat- pated. The amplitude of the PVR waveforms was 0 for
ing-room pneumatic tourniquet (Briggs Healthcare, every volunteer.
http://www.mabisdmi.com), which was applied on the
proximal thigh, over the JSLIST, and was subsequently After C-A-T application, dorsalis pedis and posterior
inflated to 300mmHg and left inflated for 90 seconds. tibial pulses could not be palpated in any volunteer.
Arterial pulse examination and noninvasive plethys- The PVR amplitude was 0 in 17 of the 20 subjects, but
mography were performed to measure the degree of ar- small waves were recorded for three volunteers despite
terial vascular occlusion. Subsequently, this tourniquet the absence of palpable pulses. The overall mean of the
was removed and volunteers recovered for 1 hour. plethysmographic waveform amplitude was 0.85mm
with a standard deviation of 2.11mm. The difference
The C-A-T tourniquet was then applied over the JSLIST between the average amplitude of the waveforms did
on the proximal thigh. A double routing technique was not reach statistical significance (p = .08). No differ-
used, with 180º turns of the windlass. The C-A-T re- ences were observed between those volunteers who had
mained tightened for 90 seconds. Clinical pulse examina- the pneumatic tourniquet applied first and those that
tion and noninvasive plethysmography were performed. had the C-A-T applied first.

18 Journal of Special Operations Medicine Volume 16, Edition 2/Summer 2016