Using the Pulse Oximeter

A pulse oximeter is a medical device that is used to measure how much oxygen is being carrying in a person’s blood. More specifically, it measures how much oxygen is being carried in a person’s hemoglobin. The measured result is termed “percent saturation.” The normal blood oxygen saturation for a healthy adult is 97% +/- 3%. Hemoglobin is attached to our red blood cells and carries the oxygen leaving the lungs to the cells. Hemoglobin also carries carbon dioxide—the end-product of energy—back to our lungs so that it can be exhaled.

The pulse oximeter can quickly measure the hemoglobin that is saturated with oxygen, providing a digital readout on a display screen. Pulse oximeters also measure the pulse rate, which is also displayed on the screen. Pulse oximeters can be powered by electricity, battery, or both. They come in various shapes and sizes. Hospitals and medical facilities more frequently use commercial-grade, electrically- and battery-powered units, while the much smaller, more affordable finger pulse oximeters are widely used by medical professionals and patients alike.

Pulse oximeters are very easy to use. The most common form of measuring oxygen saturation in an adult is using the finger probe which gently clamps onto a finger. Within seconds, the saturation and pulse are displayed. There are a variety of other probes which can also be used with the pulse oximeter. There are probes that attach to the ear lobe, and for newborns, infants and neonates, there are several styles of adhesive probes that attach to the finger, toe, wrap around the foot, and can also be used on the hand and forehead.

So how does a pulse oximeter work? Simply put, the pulse oximeter shoots both a red light and an infrared light source through the finger. At the other end of the probe is a light detector. Using a logarithm that calculates the speed by which the lights reach the detector and how much of the light was absorbed by the hemoglobin, the percent of oxygen saturation is determined.

Pulse oximetry is not a perfect science as there are some things that can affect the reading. An anemic individual with low hemoglobin levels could show a normal oxygen saturation but may require supplemental oxygen. Poor circulation in the fingers may cause the pulse oximeter not to give a reading at all. In cases like this, warming the hands will usually correct the problem. Fingernail polish can also cause the pulse oximeter difficulty in providing a readout.

Altitude will have a direct effect on your blood saturation. For example, if you went to Denver, Colorado, the air is thinner and atmospheric oxygen is lower, which will cause your oxygen saturation to drop to between 80% and 85% for a healthy adult. If you have COPD, (Chronic Obstructive Pulmonary Disease), your saturation levels will be significantly lower. Check with your doctor if you are traveling to high altitude places like Denver. Your doctor may want you to have supplemental oxygen for that trip.

Today, pulse oximeters have become very affordable with many brands to choose from costing under $50.


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