A nurse preparing to measure a client's oxygen saturation finds edema and thickened toenails. Where should the nurse place the pulse oximeter probe?

Placing the pulse oximeter probe on the earlobe is the most suitable choice in this scenario. When measuring oxygen saturation, accurate readings are crucial, and certain factors can interfere with the measurements taken from peripheral sites like fingers and toes, especially when there are complications such as edema and thickened toenails.

In cases where the extremities are compromised—due to swelling, poor circulation, or other issues that may be present in the toes or fingers—the earlobe provides a more reliable alternative. It is less likely to be affected by peripheral circulation issues, which can lead to inaccurate readings. The earlobe has a good blood supply and is typically free from complications that can arise in the hands and feet, making it an effective site for pulse oximetry.

Using the finger or toe would likely result in unreliable readings given the presence of edema and thickened toenails, which can hinder blood flow or affect the sensor's ability to read the oxygen saturation accurately. Placing the probe on the wrist may not provide a consistent or reliable reading compared to the earlobe due to varying circulation and skin conditions. Therefore, using the earlobe ensures a more accurate and dependable measurement of the client's oxygen saturation in this context.