Tough research conditions
Experts say that follow-up in this Chinese study and others to date has not been nearly long enough to allow predictions about lasting lung damage in COVID-19.
They also highlight the tough conditions in which researchers are working. Few autopsies have been performed so far – autopsies take time, extra precautions must be taken to avoid spread of COVID-19, and many patients and families do not consent to an autopsy. Furthermore, autopsy data from patients who died of COVID-19 may not extrapolate to survivors.
“I would not hang my hat on any of the limited data I have seen on autopsies,” said Lina Miyakawa, MD, a critical care and pulmonary medicine specialist at Mount Sinai Hospital in New York City.
“Even though we have answers about how the lungs are damaged at the end stage, this does not elucidate any answers about the earlier lung damage from this disease,” she continued. “It would be informative to have pathological data from the early or transitional phase, to see if that may translate into a treatment modality for COVID-19 patients.”
The problem is that these patients often experience a large amount of sloughing of airway cells, along with mucous plugging (collections of mucous that can block airflow and collapse alveoli). Bronchoscopy, which is used to view the inside of the lungs and sometimes to retrieve biopsy specimens for microscopic evaluation, is too risky for many COVID-19 patients.
In addition, few CT data exist for severely ill COVID-19 patients, who can be so unstable that to transport them to undergo a CT scan can be dangerous, not to mention the concern regarding infection control.
Even if sufficient data did exist, findings from chest x-rays, CTs, pathology studies, and lung function tests do not always match up. A patient who has lung abnormalities on CT may not necessarily have clinically impaired lung function or abnormal pathologic findings, according to Ali Gholamrezanezhad, MD, an emergency radiologist who is with the department of clinical radiology at the University of Southern California, Los Angeles.
Together with colleagues at USC, Dr. Gholamrezanezhad has started a long-term study of patients who were hospitalized with COVID-19. The researchers will follow patients for at least 1 year and will use chest x-ray, chest CT, and exercise testing to evaluate lung recovery over time.
“In the acute phase, we have acute inflammation called ground glass opacities, which usually happen bilaterally in COVID-19. That is totally reversible damage that can return to normal with no scarring,” Dr. Gholamrezanezhad said.
On the basis of data from survivors of other severe pneumonias, such as Middle East respiratory syndrome, SARS-CoV-1 infection, and H1N1 influenza, Gholamrezanezhad thinks that most survivors of COVID-19 will be able to return to work and normal life, although some may show residual lung dysfunction. Age, underlying medical conditions, smoking, length of hospital stay, severity of illness, and quality of treatment may all play a role in how well these people recover.
The lung has a remarkable capacity to recover, he added. Critical illness can destroy type one pneumocytes — the cells that line the alveoli in the lung — but over time, these cells grow back and reline the lungs. When they do, they can also help repair the lungs.
On top of that, the lung has a large functional reserve, and when one section becomes damaged, the rest of the lung can compensate.
However, for some people, total maximum exercise capacity may be affected, he commented.
Mukhopadhyay said: “My feeling is you will get reversal to normal in some patients and you will get long-term fibrosis from ARDS in some survivors. The question is, how many will have complete resolution and how many will have fibrosis? To know the answer, we will need a lot more data than we have now.”