Pulse Oximeter: Understanding What It Measures & Why

A pulse oximeter is a device that measures several vital signs. It is used to monitor heart rate and to detect respiratory problems.

Parameters Measured

• A pulse oximeter measures two parameters: heart rate and hemoglobin oxygen saturation. Heart rate is an important vital sign, but the main purpose of pulse oximetry is usually to monitor oxygen saturation.

Respiratory Function

• Although a pulse oximeter does not directly measure lung function or breathing rate, it is used to monitor respiratory function. Decreased oxygen saturation in hemoglobin is a sign of respiratory dysfunction.

Hypoxia

• Pulse oximeters continuously monitor oxygen saturation in the extremities. The health care team can be notified if the patient falls into danger of hypoxia (saturation below 90%).

Heart Function

• A pulse oximeter can continuously monitor pulse. With this device, the health care team can be notified immediately if the patient's pulse becomes too fast or too slow.

Limitations

• Pulse oximetry can measure only oxygen saturation of hemoglobin, not dissolved blood oxygen or hemoglobin levels. Results are averaged over several seconds, so there is a reporting delay.