Some COVID-19 patients are far lower on oxygen than we doctors would expect. That’s where pulse oximetry, measured by devices like this standard one from Nonin, enters the picture. Subtle shifts in the color of blood as it moves through a dense network of blood vessels can be a potent clue that a person has COVID-19, even if other signs of physical problems are absent. Normal oxygen saturation for most persons at sea level is 94 to 100 percent; Covid pneumonia patients would have oxygen saturations as low as 50 per cent.they only became short of breath the day they come to the emergency department.
In most cases, COVID-19 causes mild to no symptoms, but as many as 5% of people who get it will require critical care in a hospital. Some of them will need invasive mechanical breathing machines called ventilators, which add oxygen and remove carbon dioxide through a breathing tube after their lungs are badly compromised by COVID-related pneumonia.
The coronavirus attacks lung cells that make surfactant. This substance helps the air sacs in the lungs stay open between breaths and is critical to normal lung function. As the inflammation from Covid pneumonia starts, it causes the air sacs to collapse, and oxygen levels fall. Yet the lungs initially remain “compliant,” not yet stiff or heavy with fluid. This means patients can still expel carbon dioxide — and without a buildup of carbon dioxide, patients do not feel short of breath. Patients compensate for the low oxygen in their blood by breathing faster and deeper — and this happens without their realizing it.
We are just beginning to recognize that Covid pneumonia initially causes a form of oxygen deprivation we call “silent hypoxia” — “silent” because of its insidious, hard-to-detect nature. Their pneumonia had clearly been going on for days, but by the time they felt they had to go to the hospital, they were often already in critical condition.
There is a way we could identify more patients who have Covid pneumonia sooner and treat them more effectively — and it would not require waiting for a coronavirus test at a hospital or doctor’s office. It requires detecting silent hypoxia early through a common medical device that can be purchased following expert advice-a pulse oximeter.
Pulse oximetry is no more complicated than using a thermometer. These small devices turn on with one button and are placed on a fingertip. In a few seconds, two numbers are displayed: oxygen saturation and pulse rate. Pulse oximeters are extremely reliable in detecting oxygenation problems and elevated heart rates. They can be used at home for people with underlying health conditions and are sold online and in pharmacies and other common marketplaces. pulse oximeters as a potential way to identify more patients with COVID-19, making it possible to treat them sooner and more effectively. Holding your breath for a minute or two leads to strong discomfort in most people, yet that would hardly cause a blip in oxygen levels.
First, it underscores the need to get pulse oximetry on patients early, because low oxygen-saturation levels may be a sign that a severe case of COVID-19 is developing, even without other apparent symptoms.
Of course, ICMR approved/WHO endorsed testing is the confirmation for COVID infection, pulse oximetry can also deliver important COVID-19 clues for people at home, though there are asterisks. An early-warning signal like a low-oxygen saturation could cause people to call the hospital or clinic for help sooner, which is why the devices are becoming more common in first-aid kits at home — for those who can buy them. Besides device quality, other factors that can lead to erroneous readings from a pulse oximeter include opaque fingernail polish that interferes with the fingertip scanner and cooler temperatures that give skin a bluish tint.
Courtesy: New York Times, Star Tribune
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