Pressures Under 3.8cm, 5.1cm, and Side-by-Side 3.8cm-Wide Tourniquets.

BACKGROUND: Applications of wider tourniquet are expected to occlude arterial flow at lower pressures. We examined pressures under 3.8cm-wide, 5.1cm-wide, and side-by-side-3.8cm-wide nonelastic strap-based tourniquets. METHODS: Ratcheting Medical Tourniquets (RMT) were applied mid-thigh and mid-arm for 120 seconds with Doppler-indicated occlusion. The RMTs were a Single Tactical RMT (3.8cm-wide), a Wide RMT (5.1cm-wide), and Paired Tactical RMTs (7.6cm-total width). Tightening completion was measured at one-tooth advance past arterial occlusion, and paired applications involved alternating tourniquet tightening. RESULTS: All 96 applications on the 16 recipients reached occlusion. Paired tourniquets had the lowest occlusion pressures (ρ < .05). All pressures are given as median mmHg, minimum-maximum mmHg. Thigh application occlusion pressures were Single 256, 219-299; Wide 259, 203-287; Distal of Pair 222, 183-256; and Proximal of Pair 184, 160-236. Arm application occlusion pressures were Single 230, 189-294; Wide 212, 161-258; Distal of Pair 204, 193-254, and Proximal of Pair 168, 148-227. Pressure increases with the final tooth advance were greater for the 2 teeth/cm Wide than for the 2.5 teeth/cm Tacticals (ρ < .05). Thigh final tooth advance pressure increases were Single 40, 33-49; Wide 51, 37-65; Distal of Pair 13, 1-35; and Proximal of Pair 15, 0-30. Arm final tooth advance pressure increases were Single 49, 41-71; Wide 63, 48-77; Distal of Pair 3, 0-14; and Proximal of Pair 23, 2-35. Pressure decreases occurred under all tourniquets over 120 seconds. Thigh pressure decreases were Single 41, 32-75; Wide 43, 28-62; Distal of Pair 25, 16-37; and Proximal of Pair 22, 15-37. Arm pressure decreases were Single 28, 21-43; Wide 26, 16-36; Distal of Pair 16, 12-35; and Proximal of Pair 12, 5-24. Occlusion losses before 120 seconds occurred predominantly on the thigh and with paired applications (ρ < .05). Occlusion losses occurred in six Paired thigh applications, two Single thigh applications, and one Paired arm application. CONCLUSIONS: Side-by-side tourniquets achieve occlusion at lower pressures than single tourniquets. Additionally, pressure decreases under tourniquets over time; so all tourniquet applications require reassessments for continued effectiveness.

Significant Pressure Loss Occurs Under Tourniquets Within Minutes of Application.

BACKGROUND: Pressure decreases occur after tourniquet application, risking arterial occlusion loss. Our hypothesis was that the decreases could be mathematically described, allowing creation of evidence-based, tourniquet-reassessment- time recommendations. METHODS: Four tourniquets with width (3.8cm, 3.8cm, 13.7cm, 10.4cm), elasticity (none, none, mixed elastic/nonelastic, elastic), and mechanical advantage differences (windlass, ratchet, inflation, recoil) were applied to 57.5cm-circumference 10% and 20% ballistic gels for 600 seconds and a 57.5cmcircumference thigh and 31.5cm-circumference arm for 300 seconds. Time 0 target completion-pressures were 262mmHg and 362mmHg. RESULTS: Two-phase decay equations fit the pressure-loss curves. Tourniquet type, gel or limb composition, circumference, and completionpressure affected the curves. Curves were clinically significant with the nonelastic Combat Application Tourniquet (C-A-T), nonelastic Ratcheting Medical Tourniquet (RMT), and mixed elastic/nonelastic blood pressure cuff (BPC), and much less with the elastic Stretch Wrap And Tuck-Tourniquet (SWATT). At both completion-pressures, pressure loss was faster on 10% than 20% gel, and even faster and greater on the thigh. The 362mmHg completion-pressure had the most pressure loss. Arm curves were different from thigh but still approached plateau pressure losses (maximal calculated losses at infinity) in similar times. With the 362mmHg completion-pressure, thigh curve plateaus were -68mmHg C-A-T, -62mmHg RMT, -34mmHg BPC, and -13mmHg SWATT. The losses would be within 5mmHg of plateau by 4.67 minutes C-A-T, 6.00 minutes RMT, 4.98 minutes BPC, and 6.40 minutes SWATT and within 1mmHg of plateau by 8.18 minutes C-A-T, 10.52 minutes RMT, 10.07 minutes BPC, and 17.68 minutes SWATT. Timesequenced images did not show visual changes during the completion to 300 or 600 seconds pressure-drop interval. CONCLUSION: Proper initial tourniquet application does not guarantee maintenance of arterial occlusion. Tourniquet applications should be reassessed for arterial occlusion 5 or 10 minutes after application to be within 5mmHg or 1mmHg of maximal pressure loss. Elastic tourniquets have the least pressure loss.

Tourniquet pressures: strap width and tensioning system widths.

BACKGROUND: Pressure distribution over tourniquet width is a determinant of pressure needed for arterial occlusion. Different width tensioning systems could result in arterial occlusion pressure differences among nonelastic strap designs of equal width. METHODS: Ratcheting Medical Tourniquets (RMTs; m2 inc., http://www.ratcheting buckles.com) with a 1.9 cm-wide (Tactical RMT) or 2.3 cm-wide (Mass Casualty RMT) ladder were directly compared (16 recipients, 16 thighs and 16 upper arms for each tourniquetx2). Then, RMTs were retrospectively compared with the windlass Combat Application Tourniquet (C-A-T ["CAT"], http://combattourniquet.com) with a 2.5 cm-wide internal tensioning strap. Pressure was measured with an air-filled No. 1 neonatal blood pressure cuff under each 3.8 cm-wide tourniquet. RESULTS: RMT circumferential pressure distribution was not uniform. Tactical RMT pressures were not higher, and there were no differences between the RMTs in the effectiveness, ease of use ("97% easy"), or discomfort. However, a difference did occur regarding tooth skipping of the pawl during ratchet advancement: it occurred in 1 of 64 Tactical RMT applications versus 27 of 64 Mass Casualty RMT applications. CAT and RMT occlusion pressures were frequently over 300 mmHg. RMT arm occlusion pressures (175-397 mmHg), however, were lower than RMT thigh occlusion pressures (197-562 mmHg). RMT effectiveness was better with 99% reached occlusion and 1% lost occlusion over 1 minute versus the CAT with 95% reached occlusion and 28% lost occlusion over 1 minute. RMT muscle tension changes (up to 232 mmHg) and pressure losses over 1 minute (24±11 mmHg arm under strap to 40±12 mmHg thigh under ladder) suggest more occlusion losses may have occurred if tourniquet duration was extended. CONCLUSIONS: The narrower tensioning system Tactical RMT has better performance characteristics than the Mass Casualty RMT. The 3.8 cm-wide RMTs have some pressure and effectiveness similarities and differences compared with the CAT. Clinically significant pressure changes occur under nonelastic strap tourniquets with muscle tension changes and over time periods as short as 1 minute. An examination of pressure and occlusion changes beyond 1 minute would be of interest.