Page 49 - Journal of Special Operations Medicine - Winter 2015
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its occurrence and, therefore, accurate marking of Oc- Completion Pressure, 120second Pressure,
clusion Pressure. With the windlass systems, appliers and Occlusion Maintenance
tended to rotate each windlass 180° at a time. Appliers The windlass designs had the highest Completion Pres-
often did not rotate the windlasses especially slowly, sures but, unlike the self-securing RMT-P and elastic
so the actual pressure at which Occlusion occurred SWATT, sometimes had Completion Pressures below
could have been missed. A delay in Occlusion detec- their data-marked Occlusion Pressures. This seems un-
tion would result in recording incorrectly high Occlu- desirable and suggests an advantage to the self-securing
sion Pressures. RMT tightening system.
Evidence exists to support the possibility of delays in The windlass designs also had the greatest pressure
Occlusion detection with the windlass tourniquets. Oc- losses between Completion and 120-seconds. All three
clusion Pressure data from under-the-strap portions of nonelastic strap designs, however, had considerably
repeated thigh applications of the 3.8cm-wide CAT and larger pressure losses between Completion and 120-
Tactical RMT show differences in Occlusion Pressures seconds than occurred with the SWATT. The fact that 10
between recipients but similar Occlusion Pressures for failures to maintain arterial Occlusion for 120-seconds
each tourniquet on each recipient. The majority of the happened with the nonelastic strap designs while none
15
tourniquet applications in the Slaven et al. study were happened with the elastic SWATT is probably related
15
done by one applier who was quite experienced with each to the differing magnitude of pressure losses. We plan
tourniquet and the data points being investigated. This further investigation of the pressure-loss curves.
supports an expectation of similar distal limb-segment
occlusion pressures for same-width nonelastic strap tour- We believe pressure loss plays a mechanistic role in tour-
niquets independent of tightening system. niquet failures to maintain Occlusion, but a simple pres-
sure threshold relationship may not be present. Table
Occlusion Pressure Relationship With 2 clearly indicates that some tourniquet applications
Limb Circumference and Tourniquet Width with 120-second Pressures below their respective data-
A relationship has been shown to exist between tour- marked Occlusion Pressures were still without arterial
niquet width and Occlusion Pressure, with wider tour- pulses at 120-seconds.
niquets achieving Occlusion at lower pressures. With
6,7
pneumatic tourniquets, a linear relationship has been Ease of Application
suggested between the ratio of tourniquet width divided Clearly, appliers were able to successfully apply each
by limb circumference and Occlusion Pressure. 6,17 An tourniquet to each limb segment. In this study, we had
examination of distal limb segment circumferences and assistants help hold the limb segments because we spe-
Occlusion Pressures (even of only RMT-Ps) along with cifically requested recipients to remain muscle relaxed
previously reported thigh 8,15 and arm 3.8cm-wide tour- throughout the entire application and subsequent
8
niquet strap Occlusion Pressures (Table 6) does not sup- 120-second time periods. Because stretch is an impor-
port the presence of a strong linear relationship between tant part of correct SWATT application, limb motion
the ratio of tourniquet width divided by limb circumfer- can easily be imparted during SWATT applications.
ence and Occlusion Pressure with nonelastic, nonpneu- Minimizing limb motion makes SWATT applications
matic strap tourniquets. easier; so SWATT applications on a limb attached to a
Table 6 3.8cm-wide, Nonelastic Strap Tourniquet Occlusion Variables
Limb Circumference/Tourniquet Width Occlusion Pressure
Tourniquet Location (Median, Minimum–Maximum) (Median, Minimum – Maximum, mmHg)
RMT 1 Thigh, n = 31 13.7, 10.4–17.1 348, 247–483
CAT 2 Thigh, n = 12 14.3, 10.9–16.3 319, 288–404
RMT 3 Thigh, n = 12 14.3, 10.9–16.3 326, 195–443
RMT 1 Arm, n = 32 8.0, 5.7–9.9 235, 177–339
RMT-P Calf, n = 16 10.1, 8.3–10.9 305, 189–327
RMT-P Forearm, n = 16 6.6, 5.2–7.9 221, 184–350
See Table 2 legend for expansion of abbreviations.
1 Combined Tactical and Mass Casualty RMT strap pressure data from reference 8
2 CAT strap pressure data from reference 15, each Occlusion Pressure value an average of 7 measurements on each recipient, same 12 recipients
as RMT in next table row
3 Tactical RMT strap pressure data from reference 15, each Occlusion Pressure value an average of 6 measurements on each recipient, same 12
recipients as CAT in previous table row.
Emergency Tourniquets on Distal Limb Segments 37
