Silent Hypoxia Typically Not the First Symptom of COVID-19, Other Early Symptoms Should Be Monitored

Silent hypoxia occurs in some COVID-19 patients when blood oxygen saturation levels are exceedingly low, indicating they aren't getting enough oxygen to their lungs, yet these patients do not show symptoms of breathlessness. In response to suggestions of widespread monitoring for silent hypoxia, American Lung Association Chief Medical Officer Albert Rizzo, M.D., issued the following statement:

“In patients with silent hypoxia, the amount of oxygen carried in our blood, otherwise known as blood oxygen level, is lower than expected compared to the other vital signs. Silent hypoxia is not usually an early symptom to occur in COVID-19 patients. They frequently arrive at the emergency room for other reasons, such as muscle aches, fatigue, fever and cough. Typically, when a patient begins to demonstrate silent hypoxia, they already have other COVID-19 symptoms and may be in critical condition.

“While it has been suggested that widespread monitoring for low blood oxygen is a possible solution, the American Lung Association advises that monitoring blood oxygen levels should not be a form of self-detection for COVID-19. It is important to contact your doctor if you have any signs of COVID-19, instead of solely relying on a pulse oximeter reading. You should monitor for gastrointestinal symptoms, muscle soreness, fatigue, and changes in taste and smell as well as the more common initial symptoms such as fever, cough and shortness of breath.

“Patients with silent hypoxia do not appear like the typical patient with pneumonia or the early phases of acute respiratory distress syndrome (ARDS), which can be associated with COVID-19. Their lungs are not adequately oxygenating the blood, but patients will feel relatively well without shortness of breath, which is why this condition can be considered ‘silent.’

“There are several theories as to why this occurs with COVID-19. One theory is that the virus may affect the airways of the lungs as well as the blood vessels flowing through the lung. For normal oxygen levels to occur, the blood flow through the lung needs to match where the airflow through the lungs is occurring. The virus may be disrupting this normal matching of blood flow and airflow. This disruption may not be enough for us to sense a feeling of shortness of breath since the lung has not become stiffer or congested as it might in other pneumonias or ARDS.  

“A theory for the ‘silent’ nature of this low blood oxygen level is that COVID-19 may not be affecting the lungs’ ability to get rid of carbon dioxide in these patients. If carbon dioxide levels rise, we feel the urge to increase our breathing and sense some shortness of breath. 

“We may not know the real reason behind what is causing silent hypoxia in some patients until further studies are done. An essential part of the mission of the American Lung Association is to provide clear and accurate information, using our mission arms of education, advocacy and research to help find the answers we need.”
Learn more about COVID-19 at Lung.org/covid19. For media interested in speaking with an expert, contact the American Lung Association at [email protected] or 312-801-7629.