Can COVID-19 cause permanent lung damage?

Researchers at the Policlinico San Martino Hospital in Genova, Italy, collected lung tissue samples from eight COVID-19 patients who had died after prolonged illness (around 31.3 days) and intensive care. The samples, collected by cryobiopsy (or within 30 minutes of death), between 16 April and 4 May 2020, showed that the patients had “marked fibrotic lung parenchymal remodelling, characterised by fibroblast proliferation, airspace obliteration, and micro-honeycombing in many of the available cryobiopsies”.

The researchers shared their findings in an article in The Lancet Infectious Diseases journal on 28 July 2020. Further, the researchers said that if such scarring could be seen posthumously in patients’ lungs, it is reasonable to expect that patients who survive might also have sustained irreversible lung damage after COVID-19.

Doctors are now calling this damage because of scarring post-COVID fibrosis.

Read more: What is long COVID? The after-effects of COVID-19

After recovering from COVID-19, patients may experience symptoms like fatigue, cough, excess mucus and chest congestion and difficulty breathing for a few weeks or months. These may make it difficult to immediately recognise the symptoms of post-COVID fibrosis. (Read more: Home remedies to get rid of excess mucus)

However, you should alert your doctor if you experience severe shortness of breath or your pulse oximeter shows low blood oxygen saturation (check with your doctor about the optimum reading for you during recovery, as this may vary depending on your overall condition).

Read more: Post-COVID care: what to expect and do once the doctors say you are COVID-free

Viral infections are just one of many reasons why someone could develop pulmonary fibrosis—other causes of pulmonary fibrosis include smoking, genetic diseases, certain medicines, certain health conditions. (Read more: Smoking and COVID-19)

Doctors don’t yet know whether COVID-19-linked lung fibrosis occurs because of the viral infection itself or because of the cytokine storm it sets off in some people.

In people who get severe COVID-19, with symptoms like shortness of breath and pneumonia, there is definite lung involvement. Many of these patients also experience acute respiratory distress syndrome, a potentially life-threatening condition which requires critical care and urgent oxygen support—sometimes in the form of mechanical ventilation (ventilator) or ECMO (extracorporeal membrane oxygenation).

Lung fibrosis occurs for a number of reasons, and in a series of events in these patients:

• Repairing air sacs: Fibroblasts are cells that patch up the “holes” in the air sacs. This leads to scar formation wherever the body lays down new fibres to replace the old damaged ones.
  The degree of lung damage increases with the number of new fibres or scarring needed to patch the holes up. In some cases, the air sacs (alveoli) become so leaky (with fluids and cells going in and out) that a CT scan of the lungs show up as “ground-glass opacity”—large parts of the lungs appear opaque; an indication that they are filled with something other than air. (Read more: Can CT scan be used to diagnose COVID-19?).
• Blood clots, pulmonary hypertension: COVID-19 patient autopsies have shown blood clots in the small blood vessels (capillaries) of the lungs. Blood clots in the lungs may lead to various complications, including:
  • Some parts of the lungs may not get an adequate supply of oxygenated blood from the heart
  • The blood clots may obstruct blood flow through the lungs, causing pulmonary hypertension (where only the blood pressure of the lungs increases).
  • This, in turn, could put more pressure on the blood vessels of the lungs and on the right lower chamber of the heart, leading to heart problems
  • There is also evidence to show that as the lungs become less efficient at exchanging gases with blood, tiny blood vessels also deteriorate because of “ventilatory insufficiency”.
    ​These factors also count as injuries to the lungs and may cause further lung problems.
• Over-reaction by the immune system and cytokine storm: When the lungs, specifically type II alveolar cells in the air sacs of the lungs, mount an immune response to SARS-CoV-2, they set off the release of growth factors and cytokines. In some patients, the immune system can become dysregulated, inviting an unwarranted number of pro-inflammatory cytokines into the cells (cytokine storm). This causes wide-ranging damage to the cells which the cells try to patch with fibres.
  Cytokines are proteins that our immune cells use to talk to each other. There are dozens of types of cytokines that can regulate processes like inflammation.
• In patients who are put on mechanical ventilation, ventilator-induced lung injury could also result in fibrosis.

Diagnosis involves physical examination where the doctor would ask the patient about symptoms like difficulty breathing even after weeks of being declared COVID-free. Imaging techniques, including chest X-ray, lung ultrasound and lung CT scan, allow doctors to get a good look at the lungs. For people who have recently recovered from COVID-19, doctors may also order blood tests to check for markers of inflammation like C-reactive proteins (CRP test) that are released by the liver in response to inflammation in the body.

Fibrosis is usually an irreversible condition. That is why the earlier it is diagnosed, the better the prognosis for the patient usually is. People with lung fibrosis typically need to manage the disease for life with medicines and lifestyle change. Some of the lifestyle changes they would have to make include:

• Moderate level of daily exercise
• Quitting smoking
• Reassessing one's abilities and limitations: Activities like deep-sea diving or mountain climbing may not be feasible now. Depending on the damage, even a gentle trek could leave patients winded. It's important for them to take cognizance of what they can do now. They could also reach out to a physiotherapist. (Read more: What is physiotherapy and how can it help?)
• Patients could also benefit from talking to an occupational therapist who can help them get adjusted to their altered lung capacity and reorganise their surroundings to suit their new needs.
• In severe cases, a lung transplant may be needed to save the patient's life.

COVID-19 seems to affect different people differently. In a comment published in The Lancet Respiratory Medicine on 15 May 2020, the authors explained that the lung damage persists to varying degrees even after recovering from COVID-19.

• Patients may get fibrosis even after the infection is gone from their bodies. (This is not unusual in COVID-19. Another condition—multisystem inflammatory syndrome in children—also typically develops in children in the recovery phase, after they have weathered the COVID-19 infection.)
• Even a little bit of fibrosis can cause wide-ranging and long-lasting problems, especially in older people who might already have some form of lung disease.
• In some patients, these problems may get progressively worse over time.

“Although the virus is eradicated in patients who have recovered from COVID-19, the removal of the cause of lung damage does not, in itself, preclude the development of progressive, fibrotic irreversible interstitial lung disease. Furthermore, even a relatively small degree of residual but non-progressive fibrosis could result in considerable morbidity and mortality in an older population of patients who had COVID-19, many of whom will have pre-existing pulmonary conditions,” they wrote in their comment titled "Pulmonary fibrosis secondary to COVID-19: a call to arms?"