Causes of Low Pulse Oximetry Reading

Pulse oximetry allows a rapid noninvasive estimate of arterial oxygen saturation.

Since its development, it has made a significant impact, particularly in the fields of perioperative and intensive care medicine.

Most modern pulse oximeters determine arterial hemoglobin saturation through the use of two light-emitting diodes in the red (660 nm) and infrared (940 nm) spectrum.

The differential absorption of these two wavelengths of light by oxygenated and deoxygenated hemoglobin during pulsatile blood flow allows for accurate estimation of arterial oxygen saturation under most conditions.

Reasons for low pulse ox reading

However, pulse oximeters can give erroneous from a variety of causes, including hypoperfusion, nail polish, darker skin pigmentation, venous pulsations, and, perhaps most frequently, motion artifact.

Clinicians must consider these possible causes of error when interpreting pulse oximetry results, especially those that are not consistent with a patient’s clinical status and medical history.

Clinically significant desaturations in an ambulatory setting are uncommon in patients without significant pathological pulmonary conditions or pulmonary vascular disease.

The potential of erroneous readings must be considered, especially measurements made during exercise.

Continuous pulse oximetry is commonly combined with a 6-min walk test in the ambulatory setting when evaluating dyspnea.

Prior studies have shown significant inaccuracies in this setting, likely due to motion artifact.

In addition, many handheld pulse oximeters available in the office setting do not display oximetry waveforms or alternative evaluations of measurement quality.

This leads to a greater risk of misinterpretation, as a digital readout is assumed to be accurate without a proper understanding of how that measurement is made.

However, more recent guidelines for field walking tests support the use of continuous oximetry because of evidence showing that the lowest saturation does not necessarily occur at the end of the test.

What causes low pulse oximetry reading?

Patients suspected of having desaturations by pulse oximetry during a 6MWT are regularly referred to the facility for formal cardiopulmonary exercise testing.

The referred patients have frequently undergone extensive diagnostic evaluations on the basis of their 6MWT oximetry results.

These evaluations are a source of significant expense, including that of the cardiopulmonary exercise testing itself, as well as risk to the patient from invasive procedures or radiation exposure that may be unnecessary if their pulse oximetry testing results were inaccurate.

What happens when there are low levels of oxygen in the blood?

May have hypoxemia, hypoxemia occurs when levels of oxygen in the blood are lower than normal. If blood oxygen levels are too low, your body may not work properly.
If your blood does not have enough oxygen, it cannot deliver enough oxygen to the organs and tissues that need it. This situation can be fatal if severe in the short term and can affect the heart or brain if it persists over a long period of time.