When measuring pulse oximetry in a patient with decreased arterial blood flow, which site is most appropriate?

Measuring pulse oximetry at the finger is the most appropriate choice when assessing a patient with decreased arterial blood flow. This site is commonly used because it allows for direct access to peripheral capillary circulation, which is vital for obtaining accurate readings.

In cases of decreased arterial blood flow, sites with poorer perfusion such as the toes may not provide reliable values, as reduced blood flow can lead to inaccurate readings due to inadequate circulation to the extremities. The forehead and earlobe can sometimes be used, but they are not standard sites for routine pulse oximetry. The forehead may be less reliable in terms of detecting hypoxemia, while the earlobe is often affected by the ambient temperature and overall circulation, which can influence the accuracy of the reading.

Thus, the finger remains the preferred site as long as peripheral circulation is adequate, making it suitable for the majority of patients.