Page 56 - JSOM Fall 2020

up and thigh versus arm pressure data. Pearson correlation achieved arm occlusion without any ratcheting buckle ad-
was used for all correlations (thigh down versus thigh up, vancement (four subjects each time and four subjects only on
pressure versus single arm pull, etc.). Statistical significance their third arm application). A need for fewer clicks in arm
was set at P ≤ .05. applications coincides with arm secured pressures (223mmHg,
141–372mmHg) generally being higher than combined thigh
secured pressures (185mmHg, 122–327 mmHg, P < .0001)
Results
and arm occlusion pressures (285mmHg, 211–372mmHg)
Subjects generally being lower than combined thigh occlusion pres-
For subject information, see Table 1. All subjects had arm ap- sures (347mmHg, 284–536mmHg, P < .0001). Only one sub-
plications (arm circumferences ≥23.0cm). Thirty-one subjects ject who achieved arm occlusion without ratcheting buckle
had arm pressure data collected (circumferences ≥30.0cm). advancement had an arm circumference too small for pressure
measurements (26.5cm). The arm circumferences and weights
TABLE 1 Subject Information lifted by the eight subjects who achieved arm occlusion
Arm Circumference Arm Circumference without ratcheting buckle advancement were 33.5cm, 26.5–
<30.0cm* ≥30.0cm* 39.0cm and 36.3kg, 27.2–49.9kg; values for the other 52 sub-
Sex 9 males, 21 females 24 males, 8 females jects were 29.3cm, 23–38.5cm and 22.7kg, 13.6–54.4kg (P =
Age (yr) 21 (18–25) 21 (18–65) .01 for circumference and P < .0001 for strength).
Height (cm) 167.6 180.3
(152.4–182.9) (157.5–195.6) Although thighs are larger circumference than arms and thigh
Weight (kg) 63.5 88.5 applications tended to have higher occlusion pressures than
(49.9–80.3) (65.8–128.8) arm applications, there was not a strong correlation between
Systolic pressure (mmHg) 102 (84–128) 112 (100–136) limb circumference and occlusion pressure for either limb (Fig-
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2
Handedness 27 right, 3 left 29 right, 3 left ure 6A–B, r = 0.24 with P < .0001 for thigh and r = 0.027
Single arm pull (kg) 22.68 27.22 with P = .38 for arm). There was not a strong correlation be-
2
(13.61–36.29) (18.14–54.43) tween occlusion pressure and clicks to reach occlusion (r =
2
Thigh circumference (cm) 50.3 58.0 0.047 with P < .0001 for thigh and r = 0.18 with P < .0001
(42.0–61.4) (47.5–76.0) for arm); this rules out suggesting a set number of clicks as
Arm circumference (cm) 27.1 32.5 likely to be occlusive and supports the important influence of
(23.0–29.8) (30.0–39.0) secured pressure on tightening system use to reach occlusion.
*Arm circumferences <30.0cm did not have pressures measured; arm
circumferences ≥30.0cm had pressure measured. During the 5 seconds after occlusion but before clicking to
completion, 52 of the 540 applications had pulsatile Doppler
All applications achieved occlusion and completion. The se- signal return (21 thigh down, 17 thigh up, 14 arm). All 52
cured, occlusion, and completion pressures are shown in Fig- were re-occluded at completion without a second Doppler sig-
ure 2A–C. One of 360 thigh and 0 of 93 arm applications with nal return. One thigh up completion had a pulsatile Doppler
pressure measurements had secured pressures <100mmHg; signal return within 5 seconds of completion. The secured,
73 thigh and 4 arm applications had secured pressures occlusion, and completion pressures; clicks to occlusion; and
<150mmHg (P < .0001 for thigh versus arm). The per subject limb circumferences of applications with Doppler signal re-
pressure coefficients of variation were predominantly <10% turn within 5 seconds of occlusion were within the ranges for
and are shown in Figure 2D. applications that maintained occlusion.

For thigh applications, pulling down was not statistically dif- As shown in Table 2, sitting subject, mid-thigh, bare skin oc-
ferent from pulling up (Figure 3A–D). Forty thigh down and clusion and completion pressures for the 5.1cm-wide OMNA
33 thigh up applications had secured pressures <150mmHg. Marine Tourniquet were generally in the ranges reported for
Secured pressures were 185mmHg, 111–298mmHg thigh sitting subject, mid-thigh, bare skin applications of the 3.8cm-
down and 185mmHg, 121–356mmHg thigh up with group wide Tactical Ratcheting Medical Tourniquet (m2 Inc., www
®
coefficients of variation of 23.5% and 24.3%. Occlusion .ratchetingbuckles.com) and Generation 3 SOF Tactical
®
pressures were 348mmHg, 275–521mmHg thigh down and Tourniquet–Wide (Tactical Medical Solutions, www.tacmed
®
351mmHg, 292–551mmHg thigh up with group coefficients solutions.com), and lower than those reported for the 3.8cm-
of variation of 13.4% and 13.5%. Completion pressures wide Generation 7 Combat Application Tourniquet (C-A-T
were 414mmHg, 320–588mmHg thigh down and 417mmHg, Resources, http://combattourniquet.com/). 16
351–629mmHg thigh up with group coefficients of variation
of 12.2% and 12.5%. Issues
During thigh practice applications involving unlimited re-
There were relationships between strength and secured pres- peated uses of the same tourniquet, we encountered some in-
sures (thigh down r = 0.44, thigh up r = 0.31, arm r = 0.24), stances of the round stock, rounded corner rectangle, metal
2
2
2
but technique clearly matters (Figure 2A and Figure 4A–C). As redirect buckle (Figure 1) sliding to a 90° reorientation within
expected, there were also relationships between secured pres- the fabric sleeve attaching it to the tourniquet. This was un-
sures and clicks for occlusion (Figure 5A–C, thigh down r = pleasant for the subject and diminished the secured pressure
2
0.44, thigh up r = 0.44, arm r = 0.68), so achieving a good but did not preclude reaching occlusion, and we were able to
2
2
secured pressure is important. force the redirect buckle back to its original, intended orienta-
tion after removal from the limb. Because of the instances of
All thigh applications required at least one ratcheting buckle buckle reorientation during practice, we had each subject use a
advancement to achieve occlusion (Figure 5). Eight subjects new tourniquet for his or her set of nine research applications.
54 | JSOM Volume 20, Edition 3 / Fall 2020