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Thursday, June 20, 2024
Dr. Brown: The pathology of COVID-19lungs

Dr. William Brown

Special to The Lake Report

Given that the most common cause of death in COVID-19 is what’s been aptly called ARDS (Acute Respiratory Disease Syndrome), understanding what’s going on in the lungs is a major priority in managing this disease.

CT scans reveal characteristic ground-glass opacities in the peripheral lung fields, regions populated by the thousands of terminal sacs – the alveoli – where gas exchange takes place.

These radiographic changes are typically associated with laboured breathing and progressive hypoxemia, which all too often, alarmingly progresses to need assisted ventilation in a pattern similar to what was earlier observed in SARS and MERS coronal viral epidemics.

Until recently there were no comprehensive studies of the lungs of patients who died with COVID-19 that were designed to reveal the underlying pathology in the alveoli and the nearby micro circulation, upon both of which the exchange of oxygen for carbon dioxide depend.

These issues were addressed in a May 21 article in the New England Journal of Medicine, which examined the lungs of seven patients who died from COVID-19. The salient features in this study revealed:

* Diffuse alveolar damage accompanied by destruction of the cells that line the alveoli.

* Inflammatory cell infiltrates in the alveolae.

* Thrombi in small sized (1-2 mm in diameter) pulmonary arteries.

* Widespread fibrin thrombi within alveolar capillaries.

Destruction of so many alveoli and widespread thrombi blocking small arteries and alveolar capillaries certainly explain the hypoxemia and make a strong case for the use anticoagulants in the management on the pneumonia, especially in the middle to late stages of the disease in the ICU.

Moreover, the inflammatory infiltrate and fluid in and about the alveoli would make the affected regions of the lungs stiff and hard, if not impossible, to inflate with assisted ventilation, whatever the pressure used – indeed too high a pressure might add to the destruction in the lungs.

Thorough studies like this one are hard to do in the midst of the hurly burly of pandemics because it’s an all-hands-on-deck proposition just dealing with the urgencies of the moment.

Sometimes, however, mistakes are made for lack of evidence, and studies such as this are very important because they help physicians make decisions about patient care that are based on evidence, rather than best guesses.

I thought you might be interested in this one, because there was so much controversy about what was going on in the lungs of patients with COVID-19 in February through early May, some of which controversies were dispelled with this study.

Dr. William Brown is a professor of neurology at McMaster University and co-founder of the Infohealth series held on the second Wednesday of each month at the Niagara-on-the-Lake Public Library.  


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