Along with a thermometer, a pulse oximeter is perhaps the most useful home diagnostic medical device needed during this COVID-19 pandemic.
This article is not meant as a substitute for medical advice from your healthcare team, but rather to inform you what a pulse oximeter can and cannot do to help CLL patients monitor their disease.
What is a Pulse Oximeter?
A pulse oximeter is a small non-invasive electronic oxygen saturation measuring device that can be gently clipped onto a body part, usually a fingertip, but occasionally elsewhere such as a toe or earlobe, to measure blood oxygen levels.
The device itself and its reading is sometimes abbreviated to pulse ox or even POx.
How does it work and what does it measure?
A POx uses infrared light refraction to measure how well oxygen is binding to your red blood cells. The hemoglobin in our red blood cells carry the oxygen that we breathe in through our lungs. The POx emits and then absorbs a light wave passing through our capillaries and works because the level of oxygen that is “saturating” the hemoglobin changes the color of the blood. Oximeters report blood oxygen levels, or more correctly, peripheral capillary oxygen saturation measurement or SpO2. SpO2 is reported as a percentage of the maximum amount of oxygen (100%) that the blood can carry. This reading is an approximation of the more invasive arterial blood gases (ABG) partial pressure of oxygen (or PO2) that is more accurate. ABG’s provide even more information than just how we well we are oxygenated including the level of carbon dioxide (CO2) that is critical in measuring whether ventilation is adequate.
Simply put, the pulse oximeter just measures if there is enough oxygen in your blood. Low oxygen is called hypoxia and needs urgent medical attention. A POx usually also measures the heart rate/pulse.
How accurate are they?
Like any consumer product, they can have significant variability in their accuracy. Even the best pulse oximeter may show readings anywhere from 2% to 4% higher or lower reading than the actual oxygen level as measured by arterial blood gases.
Cold hands with compromised circulation, dark nail polish, artificial nails and motion such as shivering can impair accuracy.
What is a normal reading and when should I be concerned?
Anything over 95% is reassuringly normal and really there is no clinically significant difference between a reading of 95% and 100%. That whole range is normal and means the patient is well oxygenated.
However, as the percentages fall lower, there is a steep rise in their clinical significance. Readings between 90% and 95%, especially those ≤ 92% are concerning and one should immediately contact their healthcare provider. Any POx reading at or below 90% demands immediate medical attention.
Should I have one to help me during the pandemic?
A pulse oximeter cannot diagnose COVID-19 and a normal reading should not keep you from seeking medical advice if you have COVID-19 concerns. Keep in mind that SARS-CoV-2 can cause a myriad of symptoms (fever, cough, abnormal smell, gut problems, rashes, fatigue and more) that may need medical attention, not just shortness of breath.
Still an accurate pulse oximeter can be a very helpful tool in both knowing when to relax and when to consider seeking medical attention.
If your prominent symptoms are cough, shortness of breath, fatigue, and if your POx is ≥95%, you may not require hospitalization. However, you should still contact your healthcare team to inform them and share any questions or concerns. Please keep in mind, you may still benefit from therapies such as monoclonal antibodies that help those with mild to moderate disease.
If your pulse oximeter is ≤90% you shouldn’t be at home. Talk to your healthcare team and head to the hospital.
The CLL Society’s motto is that Smart Patients Get Smart Care™. For some, that will include closely monitoring their oxygen saturation levels during these challenging times.
Stay strong. Stay in touch. We are all in this together.
Brian Koffman MDCM (retired) MS Ed
Co-Founder, Executive VP and Chief Medical Officer
CLL Society, Inc.
PO Box 3197
Olathe, KS, 66063