Two studies published today reveal new findings on prolonged COVID, one showing a potential role for cardiopulmonary exercise testing (CPET) for assessment of persistent symptoms, and the other finding a link between symptomatic infection and poor quality of life and Reduced ability to complete daily activities.
Lower average peak oxygen consumption
in a systematic review and meta-analysis published in Open JAMA NetworkA team led by scientists at the University of California, San Francisco (UCSF) analyzed 38 studies of CPET, mostly case series or cross-sectional studies of post-hospitalized patients before widespread COVID-19 vaccination, in 2,160 patients from 3 to 18 months after infection.
A total of 1,228 patients had prolonged COVID symptoms and 714 had reduced exercise capacity. Studies were extracted on December 20, 2021 and May 24, 2022, with a preliminary search performed on June 9, 2022.
CPET, the gold standard for measuring exercise capacity and determining differential diagnostic considerations for exercise limitations, is useful for evaluation of unexplained shortness of breath, heart failure, pulmonary disease, and preoperative evaluations, the study authors said. It is a type of stress test and has also been used in the investigation of persistent symptoms after severe acute respiratory syndrome (SARS), shortness of breath in HIV patients, and exercise intolerance in patients with chronic fatigue syndrome.
After measuring participants’ resting cardiopulmonary indicators, they exercise on a stationary bike or treadmill while their cardiopulmonary and gas exchange parameters are monitored. “Measurement of oxygen consumption (V̇otwo) allows objective and reproducible determination of exercise capacity, determination of anaerobic threshold, and classification of limitations,” they wrote.
More than 3 months after infection, the average maximal oxygen consumption (VOtwo max) was lower by 4.9 milliliters per kilogram per minute (mL/kg/min) (95% confidence interval [CI], -6.4 to -3.4) in symptomatic patients, based on nine studies of 464 patients with prolonged COVID and 359 asymptomatic patients. Cardiac, ventilatory, and pulmonary vascular limitations were infrequent.
Decline equivalent to a 10-year drop in capacity
The 4.9 mL/kg/min difference is equivalent to 1.4 metabolic equivalents of tasks (METs), an indicator of energy expended during exercise, said first author Matthew Durstenfeld, MD, in a UCSF study Press release.
“This decrease in maximal oxygen rate would roughly translate to a 40-year-old woman with an expected exercise capacity of 9.5 METs, falling to 8.1 METs, the approximate expected exercise capacity for a 50-year-old woman.” , said.
Four studies used longitudinal CPET in a subgroup of patients and found that median VOpeaktwo it increased from 18.0 to 20.5 mL/kg/min from 2 to 6 months, but remained lower than controls (28.1 mL/kg/min).
One study did not identify any change in VOpeaktwo for 3 months in patients with reduced exercise capacity, while another study showed a higher VOpeaktwo in young athletes 5 months after symptom resolution, and another found that mean VOpeaktwo increased from 17.8 to 20.5 ml/kg/min after 8 weeks of cardiac rehabilitation.
“Most studies suggest that greater acuity during acute infection (patients treated in the intensive care unit vs hospitalized vs non-hospitalized patients) is associated with poorer exercise capacity, although this is not a universal finding” , the researchers wrote.
The researchers said reduced exercise capacity can be attributed to deconditioning, inefficient breathing, chronotropic intolerance (inability to increase heart rate), and abnormal peripheral oxygen extraction (ratio of oxygen consumption to oxygen delivery or oxygenation of tissues), all of which were common in the included studies.
The authors cautioned that their findings had a very low level of certainty. “Despite the large number of included participants, the overall quality of the evidence is poor, due to the small sample size of most studies, selection bias, variability in symptom determination, and interpretation of CPET, inadequate methods to address confounders, and lack of appropriate statistical data. methods,” they wrote.
The researchers called for future research, including studies on the mechanisms of dysfunctional breathing and chronotropic incompetence; longitudinal evaluations to understand patterns in exercise capacity after COVID-19; and intervention trials of potential treatments, including the use of rehabilitation to address deconditioning.
Symptoms linked to prolonged COVID
In Scotland, researchers from the University of Glasgow conducted a to study of 31,486 symptomatic COVID-19 patients and 62,957 never-infected patients followed up at 6, 12, and 18 months with questionnaires and linkage to hospitalization and death records. The research was published in nature communications.
The median age of the participants was 45 years, 39% were men, 91% were white, 30% had at least one chronic condition, 16% had two or more chronic conditions, and 4% had received at least one dose of the COVID-19 vaccine per base.
Of the 31,486 symptomatic COVID-19 patients, 6% had not recovered at follow-up and 42% had only partially recovered. Lack of recovery was related to hospitalization, age, female sex, socioeconomic deprivation, black and South Asian race, respiratory illness, depression, and underlying medical conditions.
Previously symptomatic patients had poorer quality of life, decreased ability to participate in daily activities, and 24 persistent symptoms such as shortness of breath (odds ratio [OR], 3.43), palpitations (OR, 2.51), chest pain (OR, 2.09), and confusion (OR, 2.92). Asymptomatic infections were not associated with adverse outcomes, and COVID-19 vaccination was associated with a decreased risk of 7 symptoms.
The most common symptoms among the 21,525 infected patients with persistent symptoms were fatigue, headache, and muscle aches or weakness, but these symptoms were also frequently reported by participants who were never infected.
Patients with symptomatic infection were also more likely to have three or more symptoms than their never-infected counterparts (14,236 [45%] against 19,613 [31%]). While taste and smell generally improved from 6 to 12 months, there was an increase in reports of dry or productive cough from 6 to 18 months.
“Sequelae were more likely after severe infection and were not seen after asymptomatic infection, and vaccination prior to infection might be protective,” the authors concluded.
