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APPENDIX

Script for a lesson plan suitable for the learning of impair efforts to stop the bleed. The guideline to put a tourni-
medic students, as in course materials like documents quet 2–3 inches above the wound aims to avoid the pitfall of
or presentations: inadvertently putting the tourniquet over a hidden part of the
How do tourniquets work? Tourniquets compress the underly- wound. As such, the 2–3 inches is a safety margin to improve
ing skin to squeeze tissues including blood vessels underneath. the reliability of bleeding control; in caregiving, the 2–3 inches
Closing the vessels enough stops their flow. is considered to be the best practice.
Instructors’ support document suitable The evenness of compression is important with respect to
for preparing instructors: two aspects: fit and width. A conforming fit of the tourniquet
Given normal tissues underlying, an applied tourniquet com- shape to the underlying skin is optimal, safe, and lessens pain.
presses the skin surface of the limb. At the surface, skin tis- Uneven compression can fail to control bleeding and cause
sues bear the load of a compressive force. The force spreads skin blisters or pain. Wallets, smartphones, or holsters can
through tissues under the tourniquet. Past the tourniquet edge, block compression and bleeding control. The shape of the fit is
the force tapers off abruptly, whereas farther tissues remain important because the limb in cross-section is nearly circular,
unloaded. The compression applied across the walls of blood allowing a circumferential band to be efficient in sending com-
vessels is the key to closing off their blood flow within. Stop- pression forces radially deeper toward the center of the limb.
ping the flow controls the bleeding. The width of compression is particularly important because
tourniquets compressing a wider surface of the skin will com-
For tourniquets to compress best, the underlying tissues can- press a longer length of the blood vessels, thus closing blood
not be disrupted, such as when skin, muscle, or bone is miss- vessels better. Largely, wider compression is more efficient in
ing. If such injuries are compressed, then the spread of the stopping flow and in bleeding control.
force can be blocked at gaps within tissues. Such blocks may

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