What Is the Purpose of Pulse Oximetry?

Pulse oximetry is a non-invasive process that monitors the oxygenation levels of a patient's blood. A sensor is placed usually on a fingertip or earlobe--or on the foot of an infant--and it measures the oxygenation levels by passing infrared wavelengths back and forth, and then noting the absorbency changes from each wavelength.

Function

• Patients require pulse oximeters when their oxygenation is unstable. They're mostly used in intensive care units, emergency rooms and critical care departments.

Misconceptions

• Pulse oximetry does not measure ventilation, the metabolism of oxygen, or all levels of blood gases; it only determines the amount of oxygen contained in the blood.

False Low Readings

• Hypoperfusion of the sensored extremity, inappropriate application of the sensor, calloused skin and extraneous movement can all cause falsely low oximetry readings, which can make health personnel treat the patient for hypoxemia when there is no need.

False High Readings

• If hemoglobin is bound to something else besides oxygen, or if the patient has carbon monoxide or cyanide poisoning, the oximeter can produce a falsely high reading. Such readings can mask signs of hypoxemia, a potentially dangerous condition.

Additional Function

• Kirk Shelley of Yale University has discovered that the pulse oximeter can also help detect blood loss by applying an algorithm that converts the absorption changes to blood volume estimates.