by Exercise intolerance, a common symptom experienced by individuals with long COVID, refers to the inability to perform physical activities at the expected or desired level. Yale researchers have conducted a study that helps provide an explanation for this symptom, offering valuable insights for patients and guiding future research directions.
Typically, when patients report shortness of breath or exercise intolerance, physicians conduct tests, such as CT scans, echocardiograms, or pulmonary function testing, to identify whether the symptom is caused by limitations in the lungs or the heart. However, in some cases, these tests reveal no lung or heart limitations, indicating that another factor is influencing exercise intolerance in these patients.
Evidence has emerged suggesting that long-term COVID-19 patients who experience exercise intolerance without any lung or heart limitations fall into this category.
For these patients, the next step often involves a cardiopulmonary exercise test, where the patient engages in physical activity on a stationary bike or treadmill while physiological activity is monitored. However, in certain cases, this test fails to identify the cause of exercise intolerance.
Yale is one of the few institutions in the United States where an advanced version of this evaluation, known as the invasive cardiopulmonary exercise test (iCPET), is available. This test involves the insertion of pressure-sensing catheters into the pulmonary artery and an artery in the wrist. Physicians track various measures while patients exercise to observe the functioning of the heart, lungs, blood vessels, and muscles.
In the recent study conducted at Yale, 55 patients with post-COVID exercise intolerance were evaluated, including 41 who showed no evidence of lung or heart limitations after initial tests. These patients then underwent the iCPET.
The study revealed that patients who experienced exercise intolerance after COVID had compromised oxygen extraction by the body’s tissues, even though the heart was pumping oxygenated blood and the lungs were providing adequate amounts of oxygen.
According to Peter Kahn, the lead author of the study and a pulmonary and critical care fellow at Yale School of Medicine, these findings provide insight into the symptoms experienced by patients and offer reassurance that there is a physiological abnormality underlying their condition.
Philip Joseph, a co-author of the study and an assistant professor of internal medicine at Yale School of Medicine, stated that having this information alone can be sufficient for many long COVID patients, although there are limited treatment options available for exercise intolerance. Currently, treatment options include high-dose vitamins and pyridostigmine, a medication for muscle weakness. However, these treatments have not yet been tested in clinical trials for post-COVID exercise intolerance.
Additionally, the study helps dispel misconceptions surrounding exercise intolerance in post-COVID patients. Some patients have been told that their symptoms are a result of being out of shape or lack of physical activity, suggesting that reconditioning alone would address the intolerance. However, the study’s findings contradict this hypothesis and support the presence of a clear physiological abnormality.
While the iCPET is invasive and time-intensive and not widely available in most medical centers, the researchers believe that future studies can explore less invasive diagnostic tests that can yield similar results based on the finding of impaired oxygen extraction among post-COVID patients.
Peter Kahn further adds that the study provides not only mechanistic insights into exercise intolerance in post-COVID patients but also an opportunity to consider less invasive diagnostic testing and focus on targeted therapies.
In conclusion, the study conducted by Yale researchers sheds light on the underlying cause of exercise intolerance in post-COVID patients and offers valuable information for patients and researchers. The findings emphasize the need for further exploration of less invasive diagnostic tests and the development of targeted therapies for this debilitating symptom.
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