A silent condition is impacting COVID-19 patients across the country. The damage it causes can lead to death, and in many cases, patients don’t know they have it.

It is called silent hypoxia. Dr. Dipen Kadaria outlined the infection, the reason behind the “silent” term, and the things patients can do to protect themselves from it.

What is hypoxia — and why is this variation of the infection called ‘silent?’

Hypoxia is when our body is deficient of oxygen needed for various functions. There are many causes for this. Usually, we measure it by a device called pulse oximetry. It actually tells us the amount of oxygen attached to our hemoglobin. The hemoglobin transfers our oxygen from the lungs to different organs. Level of more than 95 % are considered normal.

Normally when someone is hypoxic — meaning they need oxygen or their system lacks oxygen — they show some symptoms like shortness of breath, fast breathing and tachycardia, which is an abnormally high heart rate among other symptoms.

Patients who are infected with COVID-19 are not presenting the same way. Even if patients are hypoxic, they are not showing these symptoms. That’s why we call it silent; there are no traditional symptoms of hypoxia. Some people also called it happy hypoxia because even though there is a lack of oxygen, people are not complaining

Why are silent hypoxia patients presenting differently than those with traditional hypoxia?

The most plausible explanation is that COVID-19 patients — even though people don’t get enough oxygen — are still able to exhale carbon dioxide.

Normally, high carbon dioxide stimulates or makes patients’ brain centers/ receptors aware regarding hypoxia. The body then acts appropriately. However, in COVID patients we have found that even though people are not able to get enough oxygen, they are able to breathe out carbon dioxide thus mitigating the protective effect it provides. So, they don’t display the traditional hypoxia symptoms. Since they aren’t displaying symptoms, patients do not know they have hypoxia — hence impacting patients silently.

In reality, there is an imbalance in the levels of oxygen and carbon dioxide in these patients because of the inability to take in enough oxygen, and this begins to “silently” damage the lungs.

We also think silent hypoxia happens because the mechanism for this type of hypoxia is different from other types of pneumonia. For example, in COVID-19 cases, we have not seen lungs filled with pus or other necrotic debris, which would be expected in other types of hypoxia or pneumonia-like infections. In the case of silent hypoxia, the lungs are still open and may be able to get some oxygen.

Another reason which has been put forward is that in COVID 19 patients, there is a discrepancy between the areas which are participating in gas exchange and the areas where there are good blood flows. This discrepancy causes less blood to go to areas where there is more oxygen and vice versa. Since patients are getting some oxygen, they don’t show the typical symptoms.

We are in the early parts of understanding this disease and as our knowledge about it grows, we hope to understand this phenomenon better to better serve our patients.

What symptoms do silent hypoxia patients have when they get to the hospital?

It is very unusual for patients to present to the hospital with only silent hypoxia. However, we have seen that occasionally. Usually, it is found in patients who have COVID-19 — and have other symptoms like high fever, nasal congestion, diarrhea, nausea, vomiting, malaise, etc.

With these people, when they come to the emergency room or when they finally get their oxygen levels checked, we have found their saturation levels (commonly referred to as ‘O2 sats’) are way below the normal limit even though they were not complaining of shortness of breath or having any trouble breathing.

The problem is by the time these patients seek help, a portion of the lungs might already be significantly damaged by the hypoxia.

Early intervention, typically within the first 48 to 72 hours, is important in cases of hypoxia, especially when the patient is progressing to a condition called ARDS (Acute Respiratory Distress Syndrome — an entity commonly associated with COVID-19). This is because if not treated early these patients will quickly develop fibrosis (scarring of lungs) — a state which occurs when lung tissue is damaged and does not heal normally, making it more difficult for lungs to work properly.

All of the intervention/ therapies that can prevent the lung from going into this state work best when given early. Hence, the importance of early diagnosis and management

Unfortunately, since patients aren’t displaying symptoms associated with breathing issues, they are often waiting beyond the recommended 48 to 72-hour threshold to seek help. And, when they ultimately show up, most of the times it is too late to do anything.

What should patients do?

You don’t need to necessarily seek medical care if you’ve only had one or two episodes of fever, but you do need to be careful and closely monitor your symptoms, especially oxygen saturation.

That means if you’re having the traditional symptoms of COVID-19, check your oxygen saturation levels. You can do this by purchasing a pulse oximeter from your nearest grocery or drug store.

Once you have the pulse oximeter, check your numbers.

If your numbers are between 95 and 100, that would be considered normal.

If it is below 95 or you notice that it is dropping quickly, you should seek medical help.

If you have COPD and you’re are on home oxygen, your normal saturation levels might normally be under 95. For example, if your normal level is usually 92-93 and they drop to 88-90, you should seek medical care.

As a reminder, there is no need to panic and wear a pulse oximeter at all times. Silent hypoxia is not presenting by itself. You will have other symptoms that will begin to indicate you might have COVID-19. That is the indicator that you should begin checking your oxygen saturation levels.

What should patients who can’t find a pulse oximeter do?

If you are experiencing symptoms associated with COVID-19 and you can’t purchase or find a pulse oximeter, there are measures you can take to guard your health.

Visit a pharmacy at a Walgreens, Kroger, or CVS — or go to an urgent care center — to get your oxygen saturation checked. The medical professionals will be able to measure your levels and determine the next course of action.

Where should I seek medical care?

It depends on how quickly you can get evaluated.

If you call your lung doctor or primary care physician and get seen within a few hours, go that direction. But if you can’t be seen quickly by them, go to a Minor Medical Center or an emergency room to be evaluated.

In either case, the medical professionals will likely conduct a chest x-ray and a COVID-19 test.

It is very important not to wait several days to be seen. By then, the damage can be significant. If it’s a Friday or weekend, go to a Minor Medical Center rather than wait.

If you have any questions or concerns about your health, reach out to your primary care physician. If you don’t have a primary care physician, visit www.methodisthealth.org/primarycare and you can find one near you.