Q&A with Dr. Brent Tatsuno, Pulmonary & Critical Care Medicine at The Queen’s Medical Center

Pulse Oximeter

A pulse oximeter is a digital device that measures the percentage of oxygen in your blood. Dr. Tatsuno shares about the phenomenon of “silent hypoxemia” that occurs when COVID-19 patients feel fine but have low oxygen saturation.

COVID-19 doesn’t always cause obvious breathing problems even when people are heading toward respiratory failure. Honolulu resident Wilma Ogimi recently shared her early detection success story in using a small device – after she received a false negative test result for the virus. The retired medical technician and her family knew something wasn’t right, as Wilma continued to feel fatigued.

Hawaii News Now reported: “Mom had no cough, no shortness of breath, just a slight fever and body ache and was super fatigued,” said Wilma’s daughter, Tricia Araki. “But we didn’t suspect COVID because she wasn’t coughing and she could breathe fine according to her, but not according to the oximeter.”

To get the scoop on pulse oximeters, the Department of Health spoke with Dr. Brent Tatsuno, who works in Pulmonary & Critical Care Medicine at The Queen’s Medical Center. Dr. Tatsuno shares about the phenomenon of “silent hypoxemia” that occurs when COVID-19 patients feel fine but have low oxygen saturation. He explains how a pulse oximeter works, what might contribute to inaccurate readings, and when you should seek medical help.

Q: What is a pulse oximeter and what does it measure?

Dr. Tatsuno: A pulse oximeter is a small device that fits over the tip of your finger to measure the percentage of oxygen in your blood, as well as your heart rate. They can be purchased online or in stores, ranging from less than $10 to a few hundred. Not all of them are FDA approved, and accuracy will vary between models. They all function essentially the same way, using infrared light refraction of the blood in the capillaries in the surface of the skin to measure the user’s oxygen saturation and heart rate.

Q: Is a pulse oximeter helpful in catching COVID-19 early? Why is early diagnosis important?

Dr. Tatsuno: It can be. Keep in mind that the oxygen saturation and heart rate are two pieces of information that apply to human physiology. A pulse oximeter will only tell you if your oxygen saturation and heart rate are abnormal, and many other diseases can cause abnormalities in these besides COVID-19. That being said, early detection is always important. If your pulse oximeter is giving you abnormal readings, you should seek medical evaluation rather than waiting until you feel poorly, so that you can get a proper work-up and start the proper treatments.

Q: Can a pulse oximeter be a helpful tool for monitoring COVID-19 at home?

Dr. Tatsuno: Yes. It is a painless, non-invasive way of monitoring for COVID-19 at home. Even if you are diagnosed with COVID-19, you may be lucky enough to be asymptomatic (feel normal). The phenomenon of “silent hypoxemia” has occurred in patients, where a patient can feel fine but have low oxygen saturation. If the readings on a pulse oximeter are abnormal, you should seek medical evaluation.

Q: For a person with COVID-19, when do oximeter measurements become concerning?
In general, an oxygen saturation less than 90-92% and a resting heart rate greater than 100 or less than 60 are considered abnormal. The oxygen saturation less than that indicates that your lungs are no longer supplying your body with enough oxygen, and you will start putting extra stress on your body. A fast (> 100) or slow (< 60) resting heart rate is also not normal, and can also indicate extra stress put on your body.

Dr. Tatsuno: If you are concerned that you have abnormal readings, double check them by trying measurements on different fingers and the opposite hand. And you can even test it on someone else living with you after cleaning the device.

Q: What might make pulse oximeter readings less accurate?

Dr. Tatsuno: Anything that would block the infrared sensor from the capillaries in the finger tip can cause inaccurate readings. Examples include nail polish and fake fingernails. On the other hand, anything causing poor circulation, including very cold extremities or Raynaud’s Phenomenon, can also lead to less accurate data. Extremes in the heart rate or severely low hemoglobin levels can cause abnormal oxygen saturation readings. Lastly, please ensure that you read the directions that are included with your unit and are placing it properly on your finger.

Q: What advice would you share with patients who are concerned that they may have COVID-19?

Dr. Tatsuno: The first and most important step is always prevention. Please think about whether attending a social gathering is truly necessary at this time. Wear masks, wash your hands, and socially distance.

If you are concerned that you may have been exposed to COVID-19 or have contracted it, quarantine yourself away from the public and your household members and seek medical advice by calling your family doctor.

About Dr. Brent Tatsuno
Dr. Brent Tatsuno works in Pulmonary & Critical Care Medicine at The Queen’s Medical Center. He was born and raised in Honolulu and attended medical school at the John A Burns School of Medicine before training at Cedars Sinai Medical Center in Los Angeles. Dr. Tatsuno says he is very fortunate to be able to come home and work at The Queen’s Medical Center with the best and brightest colleagues. Outside of work, he enjoys spending time with his wife, son, and dogs.

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