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Facts, Function, and How a Pulse Oximeter Works

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A pulse oximeter is a device used in the medical field to monitor the oxygen content of the patient’s blood indirectly, as well as to monitor the changes on the blood volume in the skin. It is often plugged in to a medical monitor, producing a photoplethysmograph, so the medic can see the oxygenation of the patient at all times. Most monitors connected to the oximeter also display the heart rate. There are also portable pulse oximeters operated by battery for monitoring of blood-oxygen in homes.

Important Note: Notwithstanding any of the information in this article consult your doctor on the use of this device, and how it can be used to monitor your personal health situation. Also, consult the instructions and warnings for your particular device.

The first oximeter was manufactured in the 1940’s. The first modern pulse oximeter, on the other hand, was developed in the year 1972, using the concept of getting the ratio of red to infrared light absorption of pulsating components at the measured area. It was mass produced and gained popularity in the 1980’s.

How it works

The blood-oxygen monitor attached to the oximeter displays the percentage of the hemoglobin found in the arteries within the oxyhemoglobin configuration. Normal percentage of the arterial hemoglobin ranges from ninety five to one hundred percent, although below ninety percent may still be acceptable. For a patient breathing air at sea level, an approximation of the arterial hemoglobin can be determined from the blood-oxygen monitor reading.

The monitored signal bounces along with the heartbeat due to the expansion and contraction of the arterial blood vessels with each heartbeat. By examining the varying part of the absorption spectrum, a monitor can ignore the other tissues or polished nails, even though black nail polish can alter readings, and recognize only the absorption caused by the blood in the arteries. Therefore, the detection of the pulse is important to the oximeter’s operation, and it will not function at all if there is none.

A pulse oximeter is a convenient non intrusive measuring device. Usually, it has a pair of tiny light-emitting diodes facing a photodiode, which is typically an earlove. One LED is read, having a wavelength of 660 nanometers, while the other is 905, 910 or 940-nanometer infrared. How these wavelengths are absorbed varies considerably between oxyhemoglobin and its deoxygenated nature. Thus, the oxyhemoglobin and deoxyhemoglobin ratio is measured from the ratio red and infrared light absorption. The absorbtion of oxyhemoglobin and deoxyhemoglobin is practically the same, called the isosbestic point. Earlier oximeters used the wavelengths of 590 and 805 nanometers for correction of the concentration of hemoglobin.

Basic facts of the pulse oximeter

-First, you should know what oxygen saturation is. The number of oxygen molecules is compared to the maximum capacity of a hemoglobin blood molecule to contain the oxygen. The blood can contain to as much as 4 oxygen molecules. Thus, if certain hemoglobin has only 3 oxygen molecules, then the oxygen saturation is only 75%.

-It’s important to know a person’s oxygen saturation if he or she has lung and respiratory issues. A normal person would have oxygen saturation in the high 90s percentage. If it is lower than that then that person is definitely sick. Through age and time however, this number steadily decreases.

-A pulse oximeter works with the use of red colored and infrared light. The light is emitted in the sensor usually placed in the finger or the earlobe. The photo detector of the machine will then determine the ratio of red light to the infrared light. The infrared light is absorbed by the oxygenated blood while the red light is absorbed by the deoxygenated blood. So the calculation will be the ratio of the oxygenated blood versus the deoxygenated blood. That is the oxygen saturation.

-A pulse oximeter will only measure oxygen saturation only. Though some models can measure heart rate or calorie count, the primary function remains the same. It is best to test the oxygen levels over time and not just in one instance. You’ll get a more accurate picture of your oxygen saturation level if it is observed over a period of time. If you have sleep apnea or asthma, the use of an oximeter is not advisable.

Main advantages of pulse oximeter

– The main advantage of the pulse oximeter is the quickness of results produced. Instead of minutes, the oxygen saturation is known in seconds. There is no more need to bring samples to a lab as patients just have to wait for the reading to appear on the monitor of the machine. This is extremely useful during emergencies when time is of the essence.

– Aside from speed, a pulse oximeter can be used by any person regardless if he or she has medical training. The basic procedure of using one merely involves the press of a button. You just need to press it, place the sensor in area of the body, and wait for a few seconds for it to produce the readings. Because of its accessibility, there are now portable models that people can use on their own anywhere. You only have to make sure that external factors like the placement of the sensor, pulse, and lights do not affect the accuracy of the readings.

These are the things you get from an oximeter. If you think that the benefits are personally useful for you, buy one today. In many ways, it is better than the traditional way of getting the oxygen saturation of a person.

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