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.