Many people with long-COVID experience ongoing breathing difficulties. Despite normal lung function and structure, people with long-COVID suffer from breathlessness at rest and during exercise, leading to exercise intolerance. These symptoms are also observed in heart failure, and are partially driven by the carotid chemoreflex, which controls breathing and feelings of breathlessness. When people get infected with the COVID-19 virus, the virus enters the carotid bodies, which are the small organs that drive the carotid chemoreflex, and disrupt their function. This could explain why some people with long-COVID are breathless at rest and during exercise.
During our previous study, we tested the carotid chemoreflex sensitivity using the hypoxic ventilatory response test and assessed breathing efficiency during cardiopulmonary exercise using the VE/VCO2 slope, in 14 non-hospitalised participants with long-COVID, and compared to 14 healthy controls.
We showed that the hypoxic ventilatory response (HVR) was increased in participants with long-COVID, compared to healthy controls, showing that the carotid chemoreflex sensitivity is elevated.
The hypoxic ventilatory response (HVR) based on minute ventilation, where a more negative response indicates a greater HVR. The red dots represent control participants that did not have COVID-19 (n=6).
Furthermore, we demonstrated that the breathing efficiency (VE/VCO2 slope) during exercise was worse in participants with long-COVID compared to healthy controls, indicating excessive hyperventilation during exercise.
Finally, we found that carotid chemoreflex sensitivity correlated with hyperventilation and poor breathing efficiency during exercise, suggesting that excessive hyperventilation may be related to the carotid body hypersensitivity.
These findings may explain why participants with long-COVID have symptoms of dysregulated breathing and exercise intolerance.
If you would like to read the full article published in Nature Communications Medicine, click here: Carotid body dysregulation contributes to Long COVID symptoms – PMC