A nurse is preparing to assess the oxygen saturation level of a client with a history of peripheral vascular disease using pulse oximetry. The nurse plans to apply the sensor to the client's right index finger. Assessment reveals slow capillary refill and a weak pulse proximal to this finger. Which action by the nurse is appropriate?

A. Apply the sensor to the client's sternum: The sternum is not a reliable site for standard pulse oximetry because it lacks a strong pulsatile arterial signal. Reflectance sensors can be used on the chest in specific settings, but this is generally less accurate for routine oxygen saturation monitoring compared with peripheral sites with good perfusion. B. Place the sensor on the client's right index finger: The right index finger is the typical site for pulse oximetry; however, in this client with peripheral vascular disease, slow capillary refill and a weak pulse indicate poor perfusion. Using this site could produce inaccurate readings, including falsely low SpO₂ values or signal loss, making it inappropriate in this situation. C. Apply the sensor to the client's right great toe: The toe can sometimes be used if upper extremities are unavailable, but peripheral vascular disease may also compromise perfusion in the lower extremities, especially in the presence of arterial disease. This could also result in unreliable readings. D. Place the sensor on the client's earlobe: The earlobe provides a site with more consistent perfusion that is less affected by peripheral vascular disease. It is suitable for pulse oximetry in patients with weak or compromised distal pulses, allowing accurate measurement of oxygen saturation while bypassing poorly perfused fingers or toes.