A finger pulse oximeter is a small device which measures the amount of oxygen present in a patient’s blood. This is an indirect method of measuring blood oxygen levels, as opposed to a direct method such as testing a blood sample. The fingertip pulse oximeter device is worn on the tip of the finger, and uses light of particular wavelengths to measure oxygen saturation in the blood.
These devices are commonly used in hospitals, particularly in intensive care units, operating rooms, surgery recovery wards, and emergency medicine departments. All of these are places where patients may have unstable blood oxygenation. Because low blood oxygen levels are harmful and may indicate a serious problem, the use of a finger pulse oximeter is standard in many medical situations. The device provides important information which assesses whether a patient needs supplemental oxygen, or monitors the efficacy of supplemental oxygen a patient is already receiving.
Finger pulse oximeters measure the amount of oxygen present in the blood which is circulating in the fingertips. The device does this using red and infrared light to measure oxygen saturation. These types of light can measure the amount of oxygen present in blood because hemoglobin absorbs different amounts of the light depending on whether or not it is oxygenated. Hemoglobin is the component of blood which transports oxygen; this protein binds to oxygen molecules in the lungs, and then transports the oxygen around the body as blood circulates through the vascular system.
The red and infrared light rays are absorbed by hemoglobin, and the fingertip device uses the absorption measurements to calculate the ratio of red and infrared light absorption. Because this ratio depends on whether hemoglobin is carrying oxygen or not, it can be used to calculate the ratio of oxygenated to deoxygenated hemoglobin. The device is so sensitive it can ignore any signals which are sent by tissues in the fingertip, as well as non-organic substances such as nail polish. Only the light absorption of hemoglobin is measured. The measurements are taken in time with the heartbeat of the wearer, which helps improve the accuracy of the hemoglobin ratio.
Many types of finger pulse oximeter measure the wearer’s heart rate in addition to their oxygen saturation. The measurements are displayed on a small readout panel. When the patient is in hospital, the device may also be connected to a medical monitor, allowing staff to monitor the patient even when not in the room. Portable oximeters which can be used at home are also available, as well as modified devices such as a digital finger pulse oximeter, which is easier to calibrate and use.