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Exercise testing hints at what’s driving Long COVID

One of the first reports describing the abnormal exercise physiology accounting for exercise intolerance in people with long COVID has been published by a team of clinicians from Yale New Haven Hospital and Yale School of Medicine’s Department of Pulmonary, Critical Care and Sleep Medicine, among others. The findings validate the experience of many people living with chronic symptoms following their initial infection, one of the most common being inability to exercise. 

In the first months of the pandemic, people who tested positive, many of whom experienced mild illness, faced additional symptoms months after a negative test result. These patients gathered evidence and advocated to have recognized their longer course of symptoms.

Alongside them, researchers have been tracking what’s become known as Long COVID. The CDC  estimates about 1 in 10 people will develop new symptoms after their diagnosis; including shortness of breath, fatigue and muscle weakness— all of which limits a person’s ability to carry out even the most routine of physical activities like climbing stairs or going for walks. 

“When Long COVID patients describe their inability to exercise, we first focus on whether there is damage to their heart and lungs from the acute illness,” said Inderjit Singh MD, lead author, Pulmonary Medicine physician at Yale New Haven Hospital and Director of the Pulmonary Vascular Program at Yale School of Medicine.

Dr. Singh explains that most of the time organ injury is not the cause of these symptoms. 

“Many Long COVID patients have persistent exertional intolerance that is not explained by conventional investigative testing, including, CT chest, resting echocardiogram, non-invasive CPETs, lung function test or cardiac MRIs,” said Dr. Singh. 

Dr. Singh and his colleagues at the Winchester Center for Lung Disease's Post-COVID Clinic began performing invasive cardio-pulmonary exercise tests (iCPET) in November of 2020, becoming one of a handful of centers across the nation to offer this method of evaluating exercise limitations. 

Invasive CPET is one of the most precise ways to understand unexplained exercise intolerance. It involves patients riding a stationary bike with catheters placed in their neck and wrist blood vessels, all continuously monitoring their heart, lung, and skeletal muscle function while also obtaining objective assessment of their exercise capacity. 

After performing iCPET tests on post-COVID patients with unexplained exercise intolerance, researchers observed that these patients’ muscles were not efficiently extracting oxygen delivered by the heart and lungs. Researchers also observed that patients were involuntarily breathing rapidly creating the shortness of breath sensation. 

The study marks the first description of this type of exercise pathophysiology in post-COVID patients in the literature. Of note, this similar pathophysiology is seen in some people who have recovered from Lyme disease, those who have chronic fatigue syndrome and people with other post-viral syndromes. 

“These findings highlight that Long COVID is real and clinicians at Yale New Haven Health are working with patients to learn as much as we can to better understand the condition and continue to help people get back to their lives,” said Phillip Joseph, MD, co-author of the study, Pulmonary Medicine physician at Yale New Haven Hospital and Associate Director of the Pulmonary Vascular Program at Yale School of Medicine.