Wound, Ostomy and Continence Nurses Society (WOCN) Practice Exam

Which of the following describes the mechanism of shear force causing pressure injuries?

1. Inadequate hydration of the skin

2. Increased friction and gravity

3. Exposure to sunlight

4. Skin contact with rough surfaces

The correct answer is: Increased friction and gravity

The mechanism of shear force causing pressure injuries is best described by the combination of increased friction and gravity. Shear force occurs when layers of tissue move in opposite directions. For instance, when a patient slides down a bed or chair, the skin may stay in place against the surface, while the underlying tissues are pulled in the opposite direction. This movement can result in blood vessel distortion and damage to the soft tissues, leading to pressure injuries. Increased friction can exacerbate shear forces by causing more resistance against the skin's surface, which can lead to further injury, especially in patients who are immobile or have fragile skin. Gravity plays a significant role as it contributes to the downward pull of the body, increasing the potential for shear forces when a patient is repositioned or makes any movement. The other factors listed, such as inadequate hydration of the skin, exposure to sunlight, and skin contact with rough surfaces, do not primarily contribute to the mechanism of shear force. While these factors may affect skin integrity, they do not directly influence the sliding motion of tissues leading to the specific injury caused by shear forces.