A portable pulse oximeter is a medical device used to measure oxygen concentration in the blood. In a hospital setting, the pulse oximeter might be a large piece of equipment capable of taking other measurements in addition to oxygen concentration. Often, the oximeter is connected to monitoring equipment so that the patient’s vital signs can be continuously monitored. Someone who needs to measure his or her blood oxygen levels at home can use a portable pulse oximeter. These portable devices are small enough to fit in a bag or pocket and are just as sensitive as the hospital equipment.
Low levels of oxygen in the blood can be harmful, because chronically low blood oxygen levels mean that the body’s tissues also might be oxygen-deficient. Low blood oxygen can indicate a serious medical problem, such as heart disease or a circulatory system disease. In a hospital setting, pulse oximeters are used frequently, because monitoring blood oxygen is important for emergency medical care, during and after surgery and in intensive care situations. At home, a patient with a cardiac, pulmonary or circulatory disease can wear the portable device to monitor his or her blood oxygen. This is useful for people who must take supplemental oxygen as a treatment.
The portable pulse oximeter works by measuring the wavelength of light emitted from a patient’s fingertip. A small sleeve is worn on the fingertip, and the sleeve is connected to a portable unit that displays the measurement. The pulse oximeter is equipped with a sensor that emits red and infrared light and calculates how much of the light is absorbed versus how much is reflected. The device uses these measurements to calculate the amount of oxygen that is present in the blood circulating through the fingertip.
This works because hemoglobin, the protein molecule that carries oxygen in the blood, absorbs light differently when it is carrying oxygen. The portable pulse oximeter detects the reflection and absorption of red and infrared light, then calculates the ratio of oxygenated to deoxygenated hemoglobin. This measurement is then displayed on the device’s digital readout.
Pulse oximetry is an indirect blood oxygen measuring method. In contrast, a direct method of measuring blood oxygen levels is by taking and testing a blood sample. Using a portable pulse oximeter is a much more convenient and rapid way to obtain this measurement, because a patient can wear this device on a fingertip, and readings are taken automatically. Portable pulse oximeters take measurements in time with the wearer’s heartbeat, which increases the accuracy of the displayed hemoglobin ratio.