Researchers have observed ongoing airflow obstruction in some patients who have recovered from COVID-19. This condition is typically treated with inhalers that deliver medications that open up the airways. Such treatments may also be helpful while recovering from COVID-19.

Another form of lung disease is referred to as restriction, or difficulty expanding the lungs. Restriction decreases the volume of the lungs and, subsequently, the amount of air they can take in. Restriction often results from the formation of scar tissue, also called fibrosis, in the lungs due to injury.

Fibrosis thickens the walls of the alveoli, which makes gas exchange with the blood more difficult. This type of scarring can occur in chronic lung diseases, such as idiopathic pulmonary fibrosis, or as a result of severe lung damage in a condition called acute respiratory distress syndrome, or ARDS.

ARDS can be caused by injuries originating in the lungs, like pneumonia, or severe disease in other organs, like pancreatitis. Around 25% of patients who recover from ARDS go on to develop restrictive lung disease.

Researchers have also found that patients who have recovered from COVID-19, especially those who had severe disease, can later develop restrictive lung disease. COVID-19 patients who require a ventilator may also have recovery rates similar to those who require a ventilator for other conditions. Long-term recovery of lung function in these patients is still unknown. Drugs treating fibrotic lung disease after COVID-19 are currently undergoing clinical trials.

Finally, even when air flow and lung volume are unaffected, the lungs cannot complete their function if blood flow to the alveoli, where gas exchange occurs, is impaired.

COVID-19 is associated with an increased risk for blood clots. If blood clots travel to the lungs, they can cause a life-threatening pulmonary embolism that restricts blood flow to the lungs.

In the long term, blood clots can also cause chronic problems with blood flow to the lungs, a condition called chronic thromboembolic pulmonary hypertension, or CTEPH. Only 0.5% to 3% of patients who develop a pulmonary embolism for reasons other than COVID-19 go on to develop this chronic problem. However, there is evidence that severe COVID-19 infections can damage the blood vessels of the lung directly and impair blood flow during recovery.

Lungs can work less optimally in these three general ways, and COVID-19 can lead to all of them. Researchers and clinicians are still figuring out ways to best treat the long-term lung damage seen in long COVID.

For clinicians, closely following up with patients who have recovered from COVID-19, particularly those with persistent symptoms, can lead to quicker diagnoses of long COVID. Severe cases of COVID-19 are associated with higher rates of long COVID. Other risk factors for development of long COVID include preexisting Type 2 diabetes, presence of virus particles in the blood after the initial infection and certain types of abnormal immune function.

For researchers, long COVID is an opportunity to study the underlying mechanisms of how different types of lung-related conditions that result from COVID-19 infection develop. Uncovering these mechanisms would allow researchers to develop targeted treatments to speed recovery and get more patients feeling and breathing like their pre-pandemic selves once again.

In the meantime, everyone can stay up to date on recommended vaccinations and use preventive measures such as good hand hygiene and masking when appropriate.

This article is republished from The Conversation, an independent nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Jeffrey M. Sturek, University of Virginia and Alexandra Kadl, University of Virginia. The Conversation has a variety of fascinating free newsletters.

Read more:
Long COVID-19 and other chronic respiratory conditions after viral infections may stem from an overactive immune response in the lungs

When COVID-19 or flu viruses kill, they often have an accomplice – bacterial infections

Jeffrey M. Sturek has received funding from the National Institutes of Health.

Alexandra Kadl does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.