Pulse oximetry is the medical monitoring of blood for hemoglobin, a special protein in the blood that is vital to carrying oxygen to different parts of the body. Results gathered from pulse oximetry are read as saturation levels or "sats," with 100% saturation being the highest amount obtainable. Though it’s possible to measure hemoglobin levels or other things about blood through blood tests, the basic sat reading is usually given through use of the small clip and reading equipment known as the pulse oximeter.
For older children and adults, a pulse oximetry measurement is typically taken on the finger, and uses a small clip, sometimes referred to as an alligator clip, on one of the fingers of one of the hands. The measurement itself is collected by the clip passing different types of light, red and infrared light, back and forth through the finger for a minute or two. The result is read on a small to large monitor, and may also include a reading of heart rate via finger pulse. Most people in good health with have a sat reading in the high 90s, and lower sats may suggest oxygenation or circulation issues that might require more testing. One drawback is that there can be inaccuracies with a short reading and it isn’t always the best indication of oxygen levels.
A brief pulse oximetry measurement might be taken in context of certain doctor’s visits, especially if oxygen compromise is suspected. It could be a routine part of exams for people with certain health conditions like cardiac defects or disease or breathing disorders. It’s also pretty common for a regular doctor to check sats if he/she believes a patient might have a condition like pneumonia.
More frequently, pulse oximetry is used in hospital settings, and instead of taking a short reading, people might continue to wear the alligator clip for several hours or days. This is one way of assessing sats during or after surgeries or illness, though there are ways like checking blood gases that tend to be part of treatment too. The youngest children who require pulse oximetry tend to be too small to wear the alligator clip.
Instead, the equipment used on the finger or more often on one of the toes is a stretchy band that has adhesive. The disadvantage is that long-term use tends to degrade the adhesive and these little clips are known for their ability to fall off. Nurses or parents have to get creative and add extra tape as time goes by so that the pulse oximeter band stays on and keeps the sat monitor from constantly alarming.
There are other places pulse oximetry may be used. Continued advances in the machines that can take sat readings make them part of home equipment for some people, particularly those who have regular periods of desaturation. This might apply to some children with heart defects, or to adults or children with sleep apnea. In all, this form of monitoring makes excellent sense, and though it may be a little inconvenient at times or not 100% accurate on each reading, it is still a non-invasive way to evaluate the health of people as related to their hemoglobin levels.