When is ring cushion used?

A ring cushion (also called a ring pad or doughnut cushion) is a traditional first-aid support device shaped like a ring with a hollow centre. Its classic working principle is pressure redistribution: placing the vulnerable area over the ring's hollow centre removes direct contact between that area and the supporting surface, so the surrounding ring bears the body's weight instead of the single pressure point, which was long taught as a way to keep local blood circulation intact.

A bedsore (pressure sore or pressure ulcer) forms when a person stays in one position for a long time and sustained pressure on a bony area, such as the tailbone, hips, heels, or elbows, cuts off blood supply to the skin and underlying tissue, causing the tissue to break down. In standard first-aid and nursing training, a ring cushion is positioned so the affected or at-risk spot rests in the ring's hollow centre to relieve this sustained pressure — this is the classic reason a ring cushion is associated with bedsore care.

None of the other listed conditions involve sustained, localised pressure damage to skin, so a ring cushion has no established first-aid role for them:

• Cold: a common chilling ailment managed with warmth, rest, and fluids.

• Cholera: an infectious diarrhoeal illness managed with oral rehydration and, if needed, medical treatment.

• Sprain: a ligament injury managed with rest, ice, compression, and elevation (RICE).

Hence, among the given options, a ring cushion is used during a bedsore.

Note: more recent pressure-ulcer guidelines (for example, NICE) advise against ring or doughnut-shaped cushions for pressure-sore prevention, since the raised rim can itself concentrate pressure at its edge, and instead recommend pressure-redistributing foam supports. This does not change which option is correct here, since cold, cholera, and sprain still have no established connection to a ring cushion, but it means a ring cushion is the traditional first-aid answer taught in exams such as this one rather than current best clinical practice.