A group of researchers has found a microscopic abnormality in the way oxygen travels from the lungs to the blood vessels of Covid-19 infected patients. The anomaly could explain why some patients feel out of breath and unable to engage in strenuous activities post-Covid recovery. The study evaluated about 34 patients over about nine months’ time-frame, out of which 12 had been hospitalized with Covid-19 and another 22 had not been hospitalized. 

The researchers used an MRI technique developed by Western University and found tiny branches of air tubes in the lungs moving to their patients′ red blood cells. Any disruption in the flow of oxygen to the red blood cells will cause the brain to say, ′Breath more,′ leading to a feeling of shortness of breath," stated lead researcher Grace Parraga. All 34 patients who took part in the study had problems with their red blood cell oxygen uptake. 

They all had severe symptoms of long covid such as shortness of breath leading to low scores of exercise. When the blood oxygen levels were measured after exercise, it was found to be in very low ranges.

(Source: https://www.livemint.com/news/india/long-covid-19-symptoms-researchers-find-a-key-clue-11656486052093.html )