A nurse is preparing to measure a client’s oxygen saturation and notes edema of the client’s hands and thickened toenails.
Where should the nurse apply the pulse oximeter probe?

Choice A rationale
Slough, which is a layer of yellowish, dead tissue that can develop on the surface of a wound, is not a defining characteristic of a stage 3 pressure ulcer.
Choice B rationale
Persistent reddening of the skin is typically associated with a stage 1 pressure ulcer, not a stage 3. In a stage 1 pressure ulcer, the skin remains intact but may be red and may not blanch (lose color briefly) when you press your finger on it.
Choice C rationale
A stage 3 pressure ulcer involves full-thickness skin loss that appears as a deep crater. The ulcer may extend into the subcutaneous tissue layer, but not through it to the underlying

muscle or bone. This description matches the statement in Choice C, making it the correct answer.
Choice D rationale
A fluid-filled area under the skin could potentially indicate a blister or a stage 2 pressure ulcer, not a stage 3. In a stage 2 pressure ulcer, the outer layer of skin (epidermis) and part of the underlying layer of skin (dermis) are damaged or lost.

Choice A rationale
Applying the pulse oximeter probe to the toe might not provide an accurate reading if the client has poor peripheral circulation. Additionally, thickened toenails can interfere with the reading.
Choice B rationale

Edema in the hands can affect the accuracy of a pulse oximeter reading. The probe might not fit properly or provide a reliable reading if the finger is swollen.
Choice C rationale
Applying the pulse oximeter probe to a skin fold is not recommended. The probe needs to be placed on a relatively flat, thin area of skin to accurately measure oxygen saturation.
Choice D rationale
The earlobe is a suitable alternative site for pulse oximetry if the fingers and toes are not viable options. The earlobe is typically less affected by peripheral vasoconstriction, which can occur with hypothermia, certain medications, and certain diseases. Therefore, Choice D is the correct answer.