Stretch and wrap style tourniquet effectiveness with minimal training.

UNLABELLED: The objective was to determine if proper application of the Stretch, Wrap, and Tuck Tourniquet (SWAT-T) would stop arterial flow and would occur with minimal training. METHODS: Fifteen undergraduates watched a 19 second video three times, practiced twice, and applied the tourniquet to volunteers at 10 locations: 3 above the elbow or knee and 2 below. RESULTS: Successful occlusion (60 second Doppler signal elimination) was more frequent than proper stretch (96 versus 75), more frequent on arms than legs (59 versus 37), and achieved before completed application (16 +/- 8 versus 33 +/- 8 seconds; each p < 0.05). Proper stretch (correct alteration of shapes printed on the tourniquet) was more frequent on legs than arms (30 versus 45; p <0.05). Applications were rated Easy (101), Challenging (37), Difficult (12) with discomfort None (53), Little (62), Moderate (34), Severe (1). The 8 appliers with <70% proper stretch rates received 10 minutes additional training and then retested at mid upper arm, mid-thigh, and below knee (24 applications) for improved proper stretch and occlusion (5 versus 18 and 10 versus 20; p < 0.01). CONCLUSIONS: Proper application of the SWAT-T is easy and can stop extremity arterial flow but requires some training for many appliers.

Pressure Responses of Tourniquet Practice Models to Calibrated Force Applications.

BACKGROUND: Tourniquet training sometimes involves models, and a certification process is expected to use something other than human limbs; therefore, investigating model- and limb-pressure responses to force application is important. METHODS: Pressure response to force was collected for a 3.8cm-wide nonelastic strap and a 10.1cm-wide elastic strap placed over 14 objects. Each object was suspended; an inflated neonatal blood pressure cuff was placed atop the object with the strap over the bladder; and strap ends were connected below with 4.54kg weights attached at 20-second intervals to 27.24kg. RESULTS: Pressure-response curves differed by strap, thigh aspect (medial, lateral, ventral, dorsal; n = 2 subjects; p < .0001); subject (medial thigh; n = 3 subjects; p < .0001); and object (thighs; small and large pool noodles ± central metal rod, foam yoga roller, coffee can, 20% ballistic gel cylinder [Gel; Clear Ballistics; clearballistics.com] with central metal tubing, rolled pair of 5mm yoga mats ± central metal rod, hemorrhage-control training thigh [Z-Medica], sand-filled training manikin limb [Drumm Emergency Solutions]; p < .0001). Compliance, circumference, support techniques, and surface interactions, especially with the 10.1cm-wide elastic strap, affected pressure responses: smaller circumference, lower compliance, and lower surface coefficient of friction were associated with higher pressure/force applied. CONCLUSIONS: Different objects have different pressure-response curves. This may be important to acquisition and retention of limb tourniquet skills and is important for systems for certifying tourniquets.

Limb Tourniquet Holding Location: Model Results Fail to Translate to Human Results.

BACKGROUND: During strap pulling, how limb tourniquet sliding is prevented affects secured pressure achievement. Data from model setups indicated moving the Tactical Ratcheting Medical Tourniquet (Tac RMT; m2 inc.) holding loop location could be advantageous regarding strap-pulling pressure achievement. METHODS: Self- and buddy-strap pull applications to the arm and mid-thigh were done with the commercially available Tac RMT with the holding loop adjacent to the strap redirect buckle (NEAR) and with a modified Tac RMT with the holding loop moved to the far end of the toothed ladder from the redirect (FAR). Arm applications had the strap redirect buckle on the lateral aspect of the arm. Thigh applications had the strap redirect buckle on the lateral aspect and included applications with the strap's free end pulled downward and applications with the strap free end pulled upward. Buddy- arm and thigh pull-upward applications with FAR allowed a nonstandard technique of including thumb assistance of the strap into the redirect. RESULTS: With standard technique, five of six pairs had lower FAR secured pressures (median difference, 16mmHg). When thumb assistance was used, four of five NEAR-FAR pairs had higher FAR secured pressures (median difference, 40mmHg). The thumb strap feeding technique was neither simple nor obvious. CONCLUSIONS: Moving the holding loop location is unlikely to be advantageous for Tac RMT actual applications. Model setup findings need to be checked with applications by humans to humans.

Limb Position Change Affects Tourniquet Pressure.

BACKGROUND: Limb position changes are likely during transport from injury location to definitive care. This study investigated passive limb position change effects on tourniquet pressure and occlusion. METHODS: Triplicate buddy-applied OMNA® Marine Tourniquet applications to Doppler-based occlusion were done to sitting and laying supine mid-thigh (n=5) and sitting mid-arm (n=3). Tourniqueted limb positions were bent/straight/bent and straight/bent/straight (randomized first position order, 5 seconds/position, pressure every 0.1 second, two-way repeated measures ANOVA). RESULTS: Sitting thigh occlusion pressures leg bent were higher than straight (median, minimum-maximum; 328, 307-403mmHg versus 312, 295-387mmHg, p = .013). In each recipient, the pressure change for each position change for each limb had p < .003. In each recipient, when sitting, leg bent to straight increased pressure (326, 276-415mmHg to 371, 308-427mmHg bent first and 275, 233-354mmHg to 311, 241-353mmHg straight first), and straight to bent decreased pressure (371, 308-427mmHg to 301, 262-388mmHg bent first and 312, 265-395mmHg to 275, 233-354mmHg straight first). When laying, position changes from leg bent first resulted in pressure changes in each recipient but not in the same directions in each recipient. From laying leg straight first, in each recipient changing to bent increased the pressure (295, 210-366mmHg to 328, 255-376mmHg) and to straight decreased the pressure (328, 255-376 mmHg to 259, 210-333 mmHg). Sitting arm bent occlusion pressures were lower than straight (230, 228-252mmHg versus 256, 250-287mmHg, p = .026). Arm position changes resulted in pressure changes in each recipient but not in the same directions in each recipient. Changes in pressure trace character (presence or absence of rhythmically pulsatile traces) and Doppler-based occlusion were consistent with limb position-induced changes in tourniquet pressure (each p ≤ .001 leg, p = .071 arm traces, and p = .188 arm occlusion). CONCLUSIONS: Passive limb position changes can cause significant changes in tourniquet pressure. Therefore, tourniquet adequacy should be reassessed after any limb position change.

OMNA Marine Tourniquet Self-Application.

BACKGROUND: The OMNA Marine Tourniquet is a 5.1cm-wide, simple redirect buckle, hoop-and-loop secured, ratcheting tourniquet designed for storage and use in marine environments. This study evaluated self-application effectiveness and pressures. METHODS: Triplicate secured, occlusion, and completion pressures were measured during 60 subjects pulling down or up thigh applications and nondominant, single-handed arm applications. Arm pressure measurements required circumferences =30cm. RESULTS: Thirty-one subjects had arm circumferences ≥30cm. All 540 applications were effective; 376 of 453 applications had known secured pressures >150mmHg (89 of 93 arm). Thigh down versus up pulling directions were not different (secured, occlusion, and completion pressures and ladder tooth advances). Occlusion pressures were 348mmHg (275-521mmHg) for combined thighs and 285mmHg (211-372mmHg) for arms. Completion pressures were 414mmHg (320-588mmHg) for combined thighs and 344mmHg (261-404mmHg) for arms. Correlations between secured pressures and occlusion ladder tooth advances (clicks) were r2 = 0.44 for combined thighs and 0.68 for arms. Correlations between occlusion pressures and occlusion clicks were poor (r2 = 0.24, P < .0001 for combined thighs and r2 = 0.027, P = .38 for arms). CONCLUSIONS: The OMNA Marine Tourniquet can be self-applied effectively, including one-handed applications. Occlusion and completion pressures are similar to reported 3.8cm-wide Ratcheting Medical Tourniquet pressures.

Characterizing a System for Measuring Limb Tourniquet Pressures.

BACKGROUND: Pressure is an important variable in emergency use limb tourniquet science. This study characterizes one system for measuring tourniquet-applied pressure. METHODS: A neonatal blood pressure cuff bladder was inflated to target pressures over atmospheric. Unconstrained or constrained within 1-inch tubular polyester webbing, the neonatal cuff was placed in a 500mL Erlenmeyer flask. A 3-hole stopper provided connections to flask interior (chamber) and bladder pressure sensors and a 60mL syringe for altering chamber pressure: atmospheric to >1500mmHg absolute to atmospheric. RESULTS: Within a finite range of chamber pressures, the neonatal cuffbased system accurately indicates applied pressure (minimum and maximum 95% confidence interval linear regression slopes of 0.9871 to 0.9953 and y-intercepts of -0.1144 to 2.157). The visually defined linear response ranges for bladder inflation pressures were as follows for unconstrained/ constrained: 100 to 400mmHg unconstrained/450mmHg constrained for 10mmHg, 150 unconstrained/100 constrained to 450mmHg for 12mmHg, 150 to 500mmHg for 15mmHg, 150 to 500mmHg unconstrained/550mmHg constrained for 18mmHg, 150 to 550mmHg for 21mmHg. Below the linear response range, the inflated bladder system indicated higher pressures than chamber pressures. Above the linear response range, the system indicated progressively lower pressures than chamber pressures. CONCLUSIONS: Within the linear response range, the bladder pressure accurately indicates surface-applied pressure.

Clothing Effects on Limb Tourniquet Application.

BACKGROUND: Sometimes tourniquets are applied over clothing. This study explored clothing effects on pressures and application process. METHODS: Generation 7 Combat Application Tourniquets (C-A-T7), Generation 3 SOF® Tactical Tourniquets-Wide (SOFTTW), Tactical Ratcheting Medical Tourniquets (Tac RMT), and Stretch Wrap And Tuck Tourniquets (SWATT) were used with different clothing conditions (Bare, Scrubs, Uniform, Tights) mid-thigh and on models (ballistic gel and yoga mats). RESULTS: Clothing affected pressure responses to controlled force applications (weight hangs, n=5 thighs and models, nonlinear curve fitting, p < .05). On models, clothing affected secured pressures by altering surface interactions (medians: Gel Bare C-A-T7 247mmHg, SOFTTW 99mmHg, Tac RMT 101mmHg versus Gel Clothing C-A-T7 331mmHg, SOFTTW 170mmHg, Tac RMT 148mmHg; Mats Bare C-A-T7 246mmHg, SOFTTW 121mmHg, Tac RMT 99mmHg versus Mats Clothing C-A-T7 278mmHg, SOFTTW 145mmHg, Tac RMT 138mmHg). On thighs, clothing did not significantly influence secured pressures (n=15 kneeling appliers, n=15 standing appliers) or occlusion and completion pressures (n=15). Eleven of 15 appliers reported securing on clothing as most difficult. Fourteen of 15 reported complete applications on clothing as most difficult. CONCLUSIONS: Clothing will not necessarily affect tourniquet pressures. Surface to tourniquet interactions affect the ease of strap sliding, so concern should still exist as to whether applications over clothing are dislodged in a distal direction more easily than applications on skin.

Review: Getting Tourniquets Right = Getting Tourniquets Tight.

Tourniquet application to stop limb bleeding is conceptually simple, but optimal application technique matters, generally requires training, and is more likely with objective measures of correct application technique. Evidence of problems with application techniques, knowledge, and training can be ascertained from January 2007 to August 2018 PubMed peer-reviewed papers and in Stop The Bleed-related videos. Available data indicates optimal technique when not under fire involves application directly on skin. For nonelastic tourniquets, optimal application technique includes pulling the strap tangential to the limb at the redirect buckle (parallel to the limb-encircling strap entering the redirect buckle). Before engaging the mechanical advantage tightening system, the secured strap should exert at least 150mmHg inward, and skin indentation should be visible. For Combat Application Tourniquets, optimal technique includes the slot in the windlass rod parallel to the stabilization plate during the single 180° turn that should be sufficient for achieving arterial occlusion, which involves visible skin indentation and pressures of 250mmHg to 428mmHg on normotensive adult thighs. Appropriate pressures on manikins and isolated-limb simulations depend on how the under-tourniquet pressure response of each compares to the under-tourniquet pressure response of human limbs for matching tourniquet-force applications. Lack of such data is one of several concerns with manikin and isolated-limb simulation use. Regardless of model or human limb use, pictures and videos purporting to show proper tourniquet application techniques should show optimal tourniquet application techniques and properly applied, arterially occlusive limb tourniquets. Ideally, objective measures of correct tourniquet application technique would be included.

Masimo Perfusion Index Versus Doppler for Tourniquet Effectiveness Monitoring.

BACKGROUND: In addition to a plethysmograph, Masimo pulse oximeters display a Perfusion Index (PI) value. This study investigated the possible usefulness of PI for monitoring limb tourniquet arterial occlusion. METHODS: Tactical Ratcheting Medical Tourniquets were applied to the thighs of 15 subjects. Tightening ended at one ratchet-tooth advance beyond Doppler- indicated occlusion. The times and pressures of Doppler and PI signal absences and returns were recorded. RESULTS: Intermittent PI signal error occurred in 149 of 450 runs (PI, 33% versus Doppler, 0%; p < .0001). PI signal loss lagged Doppler-indicated occlusion by 19 ± 15 seconds (mean ± standard deviation, p < .0001). PI Signal Return lagged tourniquet release by 13 ± 7 seconds (Doppler Signal Return took 1 ± 1 seconds following tourniquet release; p < .0001). PI failed to detect early Doppler audible pulse return in 30 of 39 occurrences. CONCLUSION: The PI available on Masimo pulse oximeters is not appropriate for monitoring limb tourniquet effectiveness.

Best Tourniquet Holding and Strap Pulling Technique.

BACKGROUND: Appropriate strap pressure before tightening-system use is an important aspect of nonelastic, limb tourniquet application. METHODS: Using different two-handed techniques, the strap of the Generation 7 Combat Application Tourniquet (C-A-T7), Tactical Ratcheting Medical Tourniquet (Tac RMT), Tactical Mechanical Tourniquet (TMT), Parabelt, and Generation 3 SOF® Tactical Tourniquet-Wide (SOFTTW) was secured mid-thigh by 20 appliers blinded to pressure data and around a thigh-sized ballistic gel cylinder by gravity and 23.06kg. RESULTS: Pulling only outward (90° to strap entering buckle) achieved the lowest secured pressures on thighs and gel. For appliers, the best holding location was above the buckle, and the best strap-pulling direction was tangential to the thigh or gel (0° to strap entering buckle). Preceding tangential pulling with outward pulling resulted in higher secured pressures on the gel but did not aid appliers. Appliers generally did not reach secured pressures achievable for their strength. Of 80 thigh applications per tourniquet, 77 C-A-T7, 41 Tac RMT, 35 TMT, 16 Parabelt, and 10 SOFTTW applications had secured pressures greater than 100mmHg. CONCLUSIONS: The default for best tourniquet strap-application technique is to hold above the buckle and pull the strap tangential to the limb at the buckle. Additionally, neither strength nor experience guarantees desirable strap pressures in the absence of pressure knowledge.

From Pull to Pressure: Effects of Tourniquet Buckles and Straps.

BACKGROUND: Limb tourniquet pressures > 100 mmHg before tightening system use eases achieving arterial occlusion, minimizes tightening system problems, and probably minimizes discomfort. This study examined effects of buckle and strap features on converting pulling force to strap pressure. STUDY DESIGN: Twenty-two buckle and strap combinations were evaluated using a thigh-diameter, ballistic gel cylinder and 3 thighs. Weights of 14.11, 27.60, and 41.11 kg provided pulling force. The contribution of buckle movement was evaluated: all buckles on gel and 12 on thighs allowed limited vertical movement, 12 on gel and 4 on thighs held static. RESULTS: Force conversion patterns per combination were similar on gel and thighs, including greatest force conversion with some buckle movement allowed. Smooth, round redirect buckles without engagement of a strap-securing mechanism had the best conversions of pulling force to tourniquet pressure; 2 achieved arterially occlusive pressures, neither commercially available. Among hook-and-loop secured tourniquets and threaded for self-securing tourniquets, the Generation 7 Combat Application Tourniquet (C-A-T7) and the Tactical Ratcheting Medical Tourniquet (Tac RMT) had the best conversions of pull to pressure (thigh applications/each weight, mean ± SD: C-A-T7 91 ± 11, 164 ± 30, 228 ± 34 mmHg; Tac RMT 82 ± 13, 150 ± 16, 222 ± 17 mmHg). Other Ratcheting Medical Tourniquets with the same buckle but different strap fabrics performed less well. Even lower pressures occurred with the Tactical Mechanical Tourniquet, the Special Operations Forces Tactical Tourniquet, the Parabelt, and the SAM XT Extremity Tourniquet (165 ± 11, 178 ± 13, 131 ± 14, and 106 ± 14 mmHg, all at 41.11 kg, respectively). CONCLUSIONS: Buckle design and strap fabric affect the conversion of pulling force to tourniquet strap pressure. Low-friction, smooth, round redirects allow the best conversion.

Effects of Distance Between Paired Tourniquets.

BACKGROUND: In practice, the distance between paired tourniquets varies with unknown effects. METHODS: Ratcheting Medical Tourniquets were applied to both thighs of 15 subjects distally (fixed location) and proximally (0, 2, 4, 8, 12cm gap widths, randomized block). Applications were pair, single distal, single appropriate proximal. Tightening ended one-ratchet tooth advance past Doppler-indicated occlusion. Pairs had alternating tightening starting distal. RESULTS: Occlusion pressures were higher for: each single than respective individual pair tourniquet, each pair distal than respective pair proximal, and each single distal than respective single proximal (all p < .0001). Despite thigh circumference increasing proximally, occlusion pressures were lower with proximal tourniquet involvement (pair or single, p < .0001). Occlusion losses before 120 seconds occurred most frequently with pairs (0cm 4, 2cm 4, 4cm 6, 8cm 7, 12cm 5 for 26 of 150), in increasing frequency with increasingly proximal singles (0cm 0, 2cm 1, 4cm 1, 8cm 2, 12cm 6 for 10 of 150, p < .0001 for trend), and least with single distal (2 of 150, p < .0001). Paired tourniquets required fewer ratchet advances per tourniquet (pair distal 5 ± 1, pair proximal 4 ± 1, single distal 6 ± 1, single proximal 6 ± 1). Final ratchet tooth advancement pressure increases (mmHg) were greatest for singles (distal 61 ± 10, proximal 0cm 53 ± 7, 2cm 51 ± 9, 4cm 50 ± 7, 8cm 45 ± 7, 12cm 36 ± 7) and least in pairs (distal 41 ± 8, proximal 32 ± 7) with progressively less pair interaction as distance increased (pressure change for the pair tourniquet not directly advanced: 0cm 13 ± 4, 2cm 10 ± 4, 4cm 6 ± 3, 8cm 1 ± 2, 12cm -1 ± 2). CONCLUSIONS: Occlusion pressures are lower for paired than single tourniquets despite variable intertourniquet distances. Very proximal placement has a pressure advantage; however, pairs and very proximal locations may be less likely to maintain occlusion. Increasingly proximal placements also increase tissue at risk; therefore, distal placements and minimal intertourniquet distances should still be recommended.

Effectiveness of Pulse Oximetry Versus Doppler for Tourniquet Monitoring.

BACKGROUND: Pulse oximeters are common and include arterial pulse detection as part of their methodology. The authors investigated the possible usefulness of pulse oximeters for monitoring extremity tourniquet arterial occlusion. METHODS: Tactical Ratcheting Medical Tourniquets were tightened to the least Doppler-determined occluding pressure at mid-thigh or mid-arm locations on one limb at a time on all four limbs of 15 volunteers. A randomized block design was used to determine the placement locations of three pulse oximeter sensors on the relevant digits. The times and pressures of pulsatile signal absences and returns were recorded for 200 seconds, with the tourniquet being tightened only when the Doppler ultrasound and all three pulse oximeters had pulsatile signals present (pulsatile waveform traces for the pulse oximeters). RESULTS: From the first Doppler signal absence to tourniquet release, toe-located pulse oximeters missed Doppler signal presence 41% to 50% of the times (discrete 1-second intervals) and missed 39% to 49% of the pressure points (discrete 1mmHg intervals); fingerlocated pulse oximeters had miss rates of 11% to 15% of the times and 13% to 19% of the pressure points. On toes, the pulse oximeter ranges of sensitivity and specificity for Doppler pulse detection were 71% to 90% and 44% to 51%, and on fingers, the respective ranges were 65% to 77% and 78% to 83%. CONCLUSION: Use of a pulse oximeter to monitor limb tourniquet effectiveness will result in some instances of an undetected weak arterial pulse being present. If a pulse oximeter waveform is obtained from a location distal to a tourniquet, the tourniquet should be tightened. If a pulsatile waveform is not detected, vigilance should be maintained.

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.

Different Width and Tightening System: Emergency Tourniquets on Distal Limb Segments.

BACKGROUND: Tourniquets are used on distal limb segments. We examined calf and forearm use of four thigh-effective, commercial tourniquets with different widths and tightening systems: 3.8 cm windlass Combat Application Tourniquet® (CAT, combattourrniquet.com) and Special Operations Forces® Tactical Tourniquet-Wide (SOFTTW, www.tacmedsolutions.com), 3.8 cm ratchet Ratcheting Medical Tourniquet - Pediatric (RMT-P, www.ratchetingbuckles. com), and 10.4 cm elastic Stretch-Wrap-And-Tuck Tourniquet® (SWATT, www.swattourniquet.com). METHODS: From Doppler-indicated occlusion, windlass completion was the next securing opportunity; ratchet completion was one additional tooth advance; elastic completion was end tucked under a wrap. RESULTS: All applications on the 16 recipients achieved occlusion. Circumferences were calf 38.1±2.5 cm and forearm 25.1±3.0 cm (p<.0001, t-test, mean±SD). Pressures at Occlusion, Completion, and 120-seconds after Completion differed within each design (p<.05, one-way ANOVA; calf: CAT 382±100, 510±108, 424±92 mmHg; SOFTT-W 381±81, 457±103, 407±88 mmHg; RMT-P 295±35, 350±38, 301±30 mmHg; SWATT 212±46, 294±59, 287±57 mmHg; forearm: CAT 301±100, 352±112, 310±98 mmHg; SOFTT-W 321±70, 397±102, 346±91 mmHg; RMT-P 237±48, 284±60, 256±51 mmHg; SWATT 181±34, 308±70, 302±70 mmHg). Comparing designs, pressures at each event differed (p<.05, one-way ANOVA), and the elastic design had the least pressure decrease over time (p<.05, one-way ANOVA). Occlusion losses differed among designs on the calf (p<.05, χ²; calf: CAT 1, SOFTT-W 5, RMT-P 1, SWATT 0; forearm: CAT 0, SOFTT-W 1, RMT-P 2, SWATT 0). CONCLUSIONS: All four designs can be effective on distal limb segments, the SWATT doing so with the lowest pressures and least pressure losses over time. The pressure change from Occlusion to Completion varies by tourniquet tightening system and can involve a pressure decrease with the windlass tightening systems. Pressure losses occur in as little as 120 seconds following Completion and so can loss of Occlusion. This is especially true for nonelastic strap tourniquet designs.

Initial tourniquet pressure does not affect tourniquet arterial occlusion pressure.

BACKGROUND: Effective nonelastic strap-based tourniquets are typically pulled tight and friction or hook-and-loop secured before engaging a mechanical advantage system to reach arterial occlusion pressure. This study examined the effects of skin surface initial secured pressure (Friction Pressure) on the skin surface pressure applied at arterial occlusion (Occlusion Pressure) and on the use of the mechanical advantage system. METHODS: Combat Application Tourniquets(®) (CATs; combattourniquet.com) and Tactical Ratcheting Medical Tourniquets (RMTs; www .ratchetingbuckles.com) were applied to 12 recipient thighs with starting Friction Pressures of 25 (RMT only), 50, 75, 100, 125, 150, 175 (CAT only), and 200mmHg (CAT only). The CAT strap was single threaded. Pressure was measured with an air-filled, size #1, neonatal blood pressure cuff under the Base (CAT), Ladder (RMT), and Strap (CAT and RMT) of each 3.8cm-wide tourniquet. RESULTS: Base or Ladder pressure and Strap pressure were related but increasingly different at increasing pressures, with Strap pressures being lower (Friction Pressure, r > 0.91; Occlusion Pressure, r > 0.60). Friction Pressure did not affect Occlusion Pressure for either design. Across the 12 thighs, the correlation coefficient for Strap Friction Pressure versus CAT windlass turns was r = -0.91 ± 0.04, and versus RMT ladder distance traveled was r = -0.94 ± 0.06. Friction Pressures of 150mmHg or greater were required to achieve CAT Occlusion with two or fewer windlass turns. CAT and RMT Strap Occlusion Pressures were similar on each recipient (median, minimum - maximum; CAT: 318mmHg, 260 - 536mmHg; RMT: 328mmHg, 160 - 472mmHg). CONCLUSIONS: Achieving high initial strap tension is desirable to minimize windlass turns or ratcheting buckle travel distance required to reach arterial occlusion, but does not affect tourniquet surface-applied pressure needed for arterial occlusion. For same-width, nonelastic strap-based tourniquets, differences in the mechanical advantage system may be unimportant to final tourniquet-applied pressure needed for arterial occlusion.

What do the people who transport trauma patients know about tourniquets?

BACKGROUND: The primary study objectives were to gather information concerning the tourniquet knowledge, experience, training, protocols, preferences, and equipment of civilian prehospital providers. METHODS: This is a survey of 151 prehospital care providers. RESULTS: Survey respondents included 27 basic, 1 intermediate, and 75 paramedic emergency medical technicians; 1 registered nurse; 4 firefighters without medical certifications; 2 respondents not yet certified; and 1 respondent not listing certifications. Respondents had 2 months to 40 years of experience and came from emergency medical services in communities of 101 to 206,688 residents located 10 minutes to 103 minutes from a Level 1 or 2 trauma center. Twenty-five had used tourniquets: 5 in military and 22 in civilian settings. Civilian tourniquets were most frequently used for motor vehicle- then farm- and manufacturing-related injuries with severe bleeding. Tourniquet knowledge was poor for all groupings (with or without tourniquet experience, military experience, all certifications, all years of experience): 91% did not understand that wider tourniquets require less pressure for arterial occlusion, 69% did not know that stopping venous flow without arterial is harmful, and 37% did not know the correct tourniquet locations for distal limb injuries. Of the 81 on a service and without military experience, 44 had received any tourniquet training; 14 of the 44 had commercial emergency tourniquet access, and 27 indicated their service had a tourniquet protocol. Of the 37 on a service with no tourniquet training, 5 had access to a commercial emergency tourniquet, and 5 indicated their service had a tourniquet protocol. CONCLUSION: Civilian prehospital providers encounter situations for tourniquet use, but many do not know information important for optimal tourniquet use. Therefore, if surgeons want civilian prehospital care to include the use of effective, arterial flow occluding tourniquets at appropriate limb locations, they need to communicate with their emergency medical service providers concerning tourniquet knowledge, training, protocols, and appropriate equipment.

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.