Ask the Doctor: Covid-19: should we use home oximeter?

By | May 11, 2020

Q A friend of mine has bought a pulse oximeter to have at home in case anyone in her family gets coronavirus. She says she heard that it is too late, a lot of the time, when people get to hospital and this would alert her sooner than normal symptoms that there is a risk for serious illness. Is she right? Would a hospital take the results of her home oximeter seriously and admit her or test her on the basis of it?

A pulse oximeter is a simple device that is placed over the finger and can tell the amount of oxygen circulating in our blood stream. They are a very accurate way of determining if adequate amounts of oxygen are passing from the air we breathe into our circulating blood and are very helpful in determining the severity of certain acute or chronic lung and heart diseases. In a hospital setting, an arterial blood gas (ABG) test is needed to confirm that circulating blood-oxygen levels are low.

The principle mechanism of morbidity and mortality associated with Covid-19 disease is a viral pneumonia. Being viral, means antibiotic therapy does not work and delivering oxygen to the patient is the mainstay of care, for now. There are some peculiar features with this viral pneumonia that are somewhat atypical. Namely, a drop in oxygen within our circulating blood stream that is out of keeping with the degree of pneumonia seen on chest X-ray and sometimes even out of keeping with symptoms of mild breathlessness are two such peculiarities.

That is to say that some patients present to hospital with modest chest X-ray abnormalities and without complaining excessively of breathlessness but are found to have very low blood oxygen levels. This is perhaps one of the reasons why some patients present late.

Furthermore, we have learned that patients often do not develop severe symptoms until at least a week into their illness, once again another peculiar feature that provides challenges for the health care team. So, what happens when someone presents early to hospital with mild symptoms, are they likely to improve (as the majority of cases do) or deteriorate leading to a life-threatening situation after the first week?

One way that aids decision making is to discharge relatively well patients with a pulse oximeter probe and check in on them regularly to ensure oxygen levels remain normal (generally above 95pc is considered normal). This is a safety net that has been employed by hospitals in Ireland and throughout the world.

You are wondering whether a hospital would take the results of a pulse oximeter seriously. The answer is both yes and no, and really depends on the patient’s past medical/surgical history and putting all factors into clinical context. An isolated transient drop in oxygen levels on an oximeter probe is common and often not of any clinical significance.

In the correct clinical context such as having recently been in close contact with a confirmed Covid-19 positive case, and subsequent development of new symptoms, a persistently low oxygen saturation of <92pc would be taken very seriously indeed by all medically trained personnel.

If you have any queries, email askthedoctor@independent.ie

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