What Is Silent Hypoxia? How Do You Know If You Have Silent Hypoxia?

silent hypoxia

Silent Hypoxia

Silent hypoxia is a condition when pulse oximetry check on a patient who does not appear to be short of breath, results in oximetry finding lower than a physician would expect. It is a condition when oxygen levels in the body are abnormally low, which can irreparably damage vital organs if gone undetected for a long time. It is also known as hypoxemia which refers to the low oxygen level in the blood, which is less than 90 percent.

Silent hypoxia (also happy hypoxia ) is hypoxia that doesn’t coincide with shortness of breath which is also known to be the complication of coronavirus disease 2019. It is expected that this condition is caused by SARS-coV-2 affecting the blood flow of the lungs airway. In addition to the blood vessels within the lungs, which must match in order to allow proper airflow without affecting them enough to cause the shortness of the breath.

It is also speculated that silent hypoxia may be caused by the formation of blood clots within the lungs. It has been shown that the breathing rates of the patient with COVID-19 gradually increase which leads to a turn in silent hypoxia. It has also shown that COVID-19 patients experience less level of shortness of breath after exercise comparatively with non-COVID-19 patients. This condition is also known to be caused by walking pneumonia and altitude sickness.

What Is Meant By Term ‘Silent’ In Silent Hypoxia?

The term silent comes from the fact that the patients don’t appear to be short of breath. They are not gasping, they do not have any sign of an increase in respiratory rate, and they are not complaining of feeling air hunger or looks uncomfortable.

Most individuals, when their oxygen levels start to drop into the eighties or lower, will feel air hunger and start to breathe rapidly with feeling uncomfortable.

Breathing tends to be very natural for all the living as it is an easy thing for us to do. But when the oxygen level drops to that level, most individuals will have a sense of what is called dyspnea.

The reasons we feel shortness of breath can include both a low level of oxygen as well as a high level of carbondioxide.

There are some physicians saying that the reason people are not appearing short of breath is that carbon dioxide levels may be still normal in individuals. Therefore, it is not signaling any distress at this time.

How Do You Know If You Have Silent Hypoxia?

Sign to look out for in silent hypoxia/ hypoxemia;

  1. Patients who have happy hypoxia will often have light symptoms of COVID-19 for a couple of days before they start to experience tightening of the chest
  2. Patients are unable to take deep breaths because of the pain that is caused when inhaling. Breathing can become more rapid when the patient gets panic.
  3. Oxygen level usually drops below 60 percent of the total level. A pulse oximeter used to check the oxygen levels should be kept handy.
  4. There will be profuse sweating, if you are sweating a lot without any reason like exercise or excessive hot temperature, you may have a condition like hypoxia.
  5. You may also notice blue lips or a change of color in the skin. Some patients may experience a change in their skin color, ranging from cherry red to blue, as the body is trying to fight against this disease condition.


A tool used to detect that you are having silent hypoxia is the “six-minute walk test” (6MWT ). In order to monitor the physiological response of patients, they are asked to walk at a normal place for six minutes. It has been proven that, after performing the 6MWT, COVID-19 patients were more likely to develop exercise-induced hypoxia without any symptoms than this non-COVID-19 patient who suffered from unidentified pulmonary fibrosis. The condition can also be first identified by using prehospital pulse oximetry.

– Pulse Oximetry:

It is a noninvasive method for monitoring a person’s oxygen saturation where the peripheral oxygen saturation reading is typically within 2% accuracy of the more desirable reading of arteria; oxygen saturation from arterial blood gas( ABG ) analysis. But the two are concentrated well enough that the safe, inexpensive, and noninvasive pulse oximetry method is valuable for identifying oxygen saturation in clinical use.

The most common approach is transmissive pulse oximetry, whereas reflectance pulse oximetry is a less common alternative to transmissive pulse oximetry.