Finger Pulse Oximeter

Finger Pusle Oximeter Usage

Finger pulse oximeters calculate blood oxygen saturation levels by determining the ratio of oxygenated to deoxygenated hemoglobin as it passes through a fingertip. By using the ratios of pulsatile to total red light transmitted through the finger, divided by the same ratio for infrared light transmitted, oximeter readings should theoretically be independent of variables that affect light transmission through the finger. Unfortunately, this theory doesn’t hold up well under real world conditions.

The use of light to sense hemoglobin oxygen levels renders the pulse oximeter sensitive to strong external light sources. When bright light can’t be avoided, the oximeter should be covered or wrapped in a towel to ensure an accurate reading.

Through numerous clinical studies and clinical observations, it’s apparent that skin color and the transparency of nail polish can interfere with oximeter readings. The darker the skin or nail polish color, the more inaccurate oximeter readings are likely to be. Awareness of this deficiency has been around for some time, so some of the newer pulse oximeters coming to market claim to have solved this problem, with respect to skin color at least. For anyone wearing dark nail polish you will probably have to remove it prior to using an oximeter.

Gender also influences the accuracy of readings, simply because females tend to have smaller finger sizes. Some oximeters are designed to be used for adolescent or pediatric sized fingers and these should be considered when finger size is an issue.

Movement may cause external light to affect photodetector operation, nudge the oximeter to a different position on the finger, restrict blood flow, or alter blood oxygen levels as muscles consume more oxygen. Ideally, the person should be at rest to obtain a stable and accurate reading, although newer generation oximeters are reportedly more “motion tolerant”.

Make sure the pulse oximeter is clean prior to use. The finger should also be cleaned, and checked for warmth, bruising, or damage. When choosing which arm or leg to place the pulse oximeter on, avoid any with catheters inserted, blood pressure cuffs, fistulas, or tourniquets. Do not place a pulse oximeter on any limbs not supported and maintained near heart level. The first choice is to use the middle or index finger.

Several studies have shown that hospital-grade pulse oximeters do not provide accurate or reliable readings when oxygen saturation levels fall below 70 to75%. Given these findings it’s highly unlikely that pulse oximeters intended for home use will be more accurate below this range. This limitation may be of concern for anyone suffering from chronic severe respiratory diseases, like COPD.

Pulse oximeters measure oxygen saturation of hemoglobin, not hemoglobin concentrations, carbon dioxide saturation levels, or blood flow rates. As a result, underlying problems like anemia, certain forms of hypoxia, and circulation problems won’t be detected by a pulse oximeter, and may lead to inaccurate readings.

By paying attention the many factors that can influence accuracy, customers should not only feel safer, but be safer with a pulse oximeter at home.

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