Define friction and shear and explain why shear is more likely to cause deep tissue injury during transfers.

• A. Friction is the surface rubbing skin, causing superficial damage; shear is the layers of tissue sliding in opposite directions while the skin stays in place, which disrupts blood flow and causes deeper injury.
• B. Friction and shear are the same; both cause deep tissue injuries regardless.
• C. Friction causes deeper injury; shear causes minimal damage.
• D. Friction only occurs with water; shear occurs without movement.

Answer: (B)

Friction and shear are distinct forces at work when a patient is moved. Friction is the resistance that occurs when the skin rubs against a surface, which mainly damages the outermost skin layer and can cause superficial skin breakdown or blisters. Shear, on the other hand, happens when the skin stays relatively fixed to the surface while the deeper tissues slide in the opposite direction. This internal sliding distorts and compresses blood vessels, reducing blood flow to deeper tissues such as fat, muscle, and connective tissue.

Why shear is more likely to cause deep tissue injury during transfers comes down to its effect on circulation inside the body. When tissues slide in opposite directions, the vessels that supply deeper structures can be stretched, kinked, or occluded, leading to ischemia and eventual tissue death if the movement continues. Friction mainly harms the surface and may contribute to initial skin damage, but it’s the shear that disrupts perfusion in deeper layers, making deep tissue injury more likely. Reducing both forces—through technique that minimizes sliding and uses lifting or slide sheets—helps protect both superficial and deep tissues during transfers.