Persistent Exertional Dyspnea and Perceived Exercise Intolerance After Mild COVID-19: A Critical Role for Breathing Dysregulation?

Risk Factors and Predictors for Persistent Dyspnea Post-COVID-19: A Systematic Review

The most frequently reported post-coronavirus disease of 2019 (COVID-19) symptoms include shortness of breath, fatigue, and cognitive disturbances, with reports of persistent dyspnea ranging between 26% and 41%. There is an urgent need to understand the risk factors and predictors for persistent COVID-19 dyspnea in individuals at all levels of COVID-19 illness severity, to enable the implementation of targeted interventions for those likely to be most affected with persistent dyspnea. Thus, the purpose of this systematic review is to explore the risk factors and predictors that are associated with persistent dyspnea in the post-COVID-19 population. This review was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines and registered prospectively in PROSPERO as CRD42023466713. A search strategy was conducted across PubMed, CINAHL, Web of Science, and EMBASE databases, that included studies conducted from 2020 to March 2024. The Covidence platform was used for screening studies, scoring methodologic quality, and performing data extraction using a two-step independent review process. This review included 33 studies, addressing 83,920 participants across 20 countries. The strongest predictive risk factors for persistent dyspnea included the following: female sex, elevated body mass index, pulmonary comorbidities, pre-existing anxiety and depression, pre-COVID-19 physical limitations, the severity of the COVID-19 illness, and socioeconomic differences. Potential risk factors included increased age, smoking history, and COVID-19 variant type. The presence of biomarkers for persistent dyspnea in the post-COVID-19 population can be used by clinicians to prospectively identify those individuals who should be flagged. Early identification may then be leveraged for timely referral for prophylactic and rehabilitative interventions for dyspnea. A personalized plan to target those risk factors that are modifiable should follow.

Impact of sodium-glucose cotransporter-2 inhibitors on pulmonary vascular cell function and arterial remodeling

Sodium-glucose cotransporter-2 (SGLT-2) inhibitors represent a cutting-edge class of oral antidiabetic therapeutics that operate through selective inhibition of glucose reabsorption in proximal renal tubules, consequently augmenting urinary glucose excretion and attenuating blood glucose levels. Extensive clinical investigations have demonstrated their profound cardiovascular efficacy. Parallel basic science research has elucidated the mechanistic pathways through which diverse SGLT-2 inhibitors beneficially modulate pulmonary vascular cells and arterial remodeling. Specifically, these inhibitors exhibit promising potential in enhancing pulmonary vascular endothelial cell function, suppressing pulmonary smooth muscle cell proliferation and migration, reversing pulmonary arterial remodeling, and maintaining hemodynamic equilibrium. This comprehensive review synthesizes current literature to delineate the mechanisms by which SGLT-2 inhibitors enhance pulmonary vascular cell function and reverse pulmonary remodeling, thereby offering novel therapeutic perspectives for pulmonary vascular diseases.

Persistent symptoms and clinical findings in adults with post-acute sequelae of COVID-19/post-COVID-19 syndrome in the second year after acute infection: A population-based, nested case-control study

BACKGROUND

Self-reported health problems following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are common and often include relatively non-specific complaints such as fatigue, exertional dyspnoea, concentration or memory disturbance and sleep problems. The long-term prognosis of such post-acute sequelae of COVID-19/post-COVID-19 syndrome (PCS) is unknown, and data finding and correlating organ dysfunction and pathology with self-reported symptoms in patients with non-recovery from PCS is scarce. We wanted to describe clinical characteristics and diagnostic findings among patients with PCS persisting for >1 year and assessed risk factors for PCS persistence versus improvement.

METHODS AND FINDINGS

This nested population-based case-control study included subjects with PCS aged 18-65 years with (n = 982) and age- and sex-matched control subjects without PCS (n = 576) according to an earlier population-based questionnaire study (6-12 months after acute infection, phase 1) consenting to provide follow-up information and to undergo comprehensive outpatient assessment, including neurocognitive, cardiopulmonary exercise, and laboratory testing in four university health centres in southwestern Germany (phase 2, another 8.5 months [median, range 3-14 months] after phase 1). The mean age of the participants was 48 years, and 65% were female. At phase 2, 67.6% of the patients with PCS at phase 1 developed persistent PCS, whereas 78.5% of the recovered participants remained free of health problems related to PCS. Improvement among patients with earlier PCS was associated with mild acute index infection, previous full-time employment, educational status, and no specialist consultation and not attending a rehabilitation programme. The development of new symptoms related to PCS among participants initially recovered was associated with an intercurrent secondary SARS-CoV-2 infection and educational status. Patients with persistent PCS were less frequently never smokers (61.2% versus 75.7%), more often obese (30.2% versus 12.4%) with higher mean values for body mass index (BMI) and body fat, and had lower educational status (university entrance qualification 38.7% versus 61.5%) than participants with continued recovery. Fatigue/exhaustion, neurocognitive disturbance, chest symptoms/breathlessness and anxiety/depression/sleep problems remained the predominant symptom clusters. Exercise intolerance with post-exertional malaise (PEM) for >14 h and symptoms compatible with myalgic encephalomyelitis/chronic fatigue syndrome were reported by 35.6% and 11.6% of participants with persistent PCS patients, respectively. In analyses adjusted for sex-age class combinations, study centre and university entrance qualification, significant differences between participants with persistent PCS versus those with continued recovery were observed for performance in three different neurocognitive tests, scores for perceived stress, subjective cognitive disturbances, dysautonomia, depression and anxiety, sleep quality, fatigue and quality of life. In persistent PCS, handgrip strength (40.2 [95% confidence interval (CI) [39.4, 41.1]] versus 42.5 [95% CI [41.5, 43.6]] kg), maximal oxygen consumption (27.9 [95% CI [27.3, 28.4]] versus 31.0 [95% CI [30.3, 31.6]] ml/min/kg body weight) and ventilatory efficiency (minute ventilation/carbon dioxide production slope, 28.8 [95% CI [28.3, 29.2]] versus 27.1 [95% CI [26.6, 27.7]]) were significantly reduced relative to the control group of participants with continued recovery after adjustment for sex-age class combinations, study centre, education, BMI, smoking status and use of beta blocking agents. There were no differences in measures of systolic and diastolic cardiac function at rest, in the level of N-terminal brain natriuretic peptide blood levels or other laboratory measurements (including complement activity, markers of Epstein-Barr virus [EBV] reactivation, inflammatory and coagulation markers, serum levels of cortisol, adrenocorticotropic hormone and dehydroepiandrosterone sulfate). Screening for viral persistence (PCR in stool samples and SARS-CoV-2 spike antigen levels in plasma) in a subgroup of the patients with persistent PCS was negative. Sensitivity analyses (pre-existing illness/comorbidity, obesity, medical care of the index acute infection) revealed similar findings. Patients with persistent PCS and PEM reported more pain symptoms and had worse results in almost all tests. A limitation was that we had no objective information on exercise capacity and cognition before acute infection. In addition, we did not include patients unable to attend the outpatient clinic for whatever reason including severe illness, immobility or social deprivation or exclusion.

CONCLUSIONS

In this study, we observed that the majority of working age patients with PCS did not recover in the second year of their illness. Patterns of reported symptoms remained essentially similar, non-specific and dominated by fatigue, exercise intolerance and cognitive complaints. Despite objective signs of cognitive deficits and reduced exercise capacity, there was no major pathology in laboratory investigations, and our findings do not support viral persistence, EBV reactivation, adrenal insufficiency or increased complement turnover as pathophysiologically relevant for persistent PCS. A history of PEM was associated with more severe symptoms and more objective signs of disease and might help stratify cases for disease severity.

Clinical and functional assessment of SARS-CoV-2 sequelae among young marines - a panel study

Background

Long-term SARS-CoV-2 adverse health outcomes are of significant concern, especially among young adults with the potential for the greatest long-term morbidity. We sought to assess and characterize these outcomes in a cohort of Marines.

Methods

We used a cohort of US Marines from a previous longitudinal, prospective observational study of acute SARS-CoV-2, most of whom were enrolled prior to infection. A panel study was established to assess for post-acute sequelae of COVID-19 (PASC), defined as symptoms at least 4 weeks after symptom onset or diagnosis. Symptoms were assessed through questionnaires and validated quality of health metrics. Periodic US Marine Corps fitness testing metrics provided an additional standardized functional assessment and were compared to a pre-pandemic cohort.

Findings

Globally dispersed Marine participants (n = 899) seen an average of 330 days following initial enrollment were predominately male (n = 825, 91.7%), White (n = 613, 71.6%) or Black (n = 149, 17.4%) with a median age of 18 years (interquartile range: 18-19). Among 798 SARS-CoV-2 infected participants, 197 (24.7%) developed PASC. The most prevalent symptoms were loss of taste and/or smell (n = 82; 41.6%), shortness of breath (n = 74; 37.6%), and cough (n = 45; 22.8%). Those with PASC had higher rates and severity of somatic (p < 0.0001), general depressive (p < 0.0001), and anxiety (p = 0.005) symptoms. Compared to a historic cohort of Marines, participants with PASC scored worse on their physical fitness assessments due to slower run times (p = 0.002). Those with PASC continued to have decreased physical performance one year after completing initial training.

Interpretation

In this population of healthy young adult US Marines with mostly either asymptomatic or mild acute COVID-19, one fourth reported physical, cognitive, or psychiatric long-term sequelae of infection. The Marines affected with PASC showed evidence of long-term decrease in functional performance suggesting that SARS-CoV-2 infection may negatively affect health for a significant proportion of young adults.

Funding

Defense Health Agency and Defense Advanced Research Projects Agency.

Dyspnea and long COVID patients

Patients with prior COVID-19 infections often develop chronic post-COVID symptoms, such as fatigue and dyspnea. Some patients have residual pulmonary disorders with abnormal pulmonary function tests and/or chest radiographs to explain their dyspnea. However, other patients appear to have dyspnea that is out of proportion to any measurable change in lung function. Some of these patients have abnormal cardiopulmonary exercise testing with definite cardiac or respiratory limits. However, others have normal cardiopulmonary exercise testing based on VO2 measurement but pronounced dyspnea during this testing. These patients often have abnormal respiratory patterns, referred to as dysfunctional breathing, with irregular and variable respiratory rates and/or tidal volumes. Consequently, their control of breathing is impaired, and this may represent residual effects from prior COVID-19 infection involving the central nervous system. Alternatively, patients may have acquired "a memory" of respiratory symptoms during their infection which persists post-infection. These patients should participate in pulmonary rehabilitation and breathing retraining.

Body Mass Index and Thoracic Expansion in Post-COVID Dyspnea: A Secondary Analysis

Dyspnea secondary to lung impairment can persist following the acute phase of COVID-19. Thoracic expansion measurements have been used as a diagnostic tool to evaluate chest wall mobility, respiratory function, and the effects of respiratory muscle strength training. Changes in chest wall mobility may occur because of altered chest biomechanics in individuals with respiratory diseases and an elevated body mass index (BMI). The purpose of this secondary analysis was to evaluate whether BMI influences thoracic expansion or forced expiratory volume over 1 second (FEV1) in individuals with persistent dyspnea following COVID-19. This study assessed the relationship between BMI and thoracic expansion, pulmonary symptoms, and exercise capacity following a home-based pulmonary rehabilitation intervention. A secondary data analysis was conducted with a sample of 19 adults with persistent dyspnea following COVID-19 infection who participated in a 12-week, home-based pulmonary rehabilitation study. Participants received expiratory muscle strength training devices and were instructed to perform pulmonary rehabilitation exercises three times per week over the study period. Pulmonary function, pulmonary symptoms, exercise capacity, and BMI measurements were collected. For analysis, study participants were divided into obese (BMI > 30 kg/m2) or nonobese (BMI < 30 kg/m2) categories. Correlations using the change scores from baseline to 12 weeks between thoracic expansion, FEV1, pulmonary symptoms, and exercise capacity were assessed. In addition, the minimal detectable change (MDC) in thoracic expansion was explored. Thoracic expansion was significantly improved after 12 weeks of training (p = .012) in the nonobese group. There was a significant correlation between the change in walking distance and pulmonary symptoms (r = -.738, p < .001) and in thoracic expansion (r = .544, p = .020), and walking distance, when controlling for BMI, but no change in FEV1. Average MDC was 1.28 for inspiration and 0.91 for expiration. Measurements of thoracic expansion were significantly lower in post-COVID individuals with an increased BMI. Individuals with persistent dyspnea and a higher BMI may require additional measures to increase chest mobility or to detect pulmonary changes following COVID-19.

Cardiorespiratory abnormalities in ICU survivors of COVID-19 with postacute sequelae of SARS-CoV-2 infection are unrelated to invasive mechanical ventilation

Postacute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (PASC) often leads to exertional intolerance and reduced exercise capacity, particularly in individuals previously admitted to an intensive care unit (ICU). However, the impact of invasive mechanical ventilation (IMV) on PASC-associated cardiorespiratory abnormalities during exercise remains poorly understood. This single-center, cross-sectional study aimed to gather knowledge on this topic. Fifty-two patients with PASC recruited ∼6 mo after ICU discharge were clustered based on their need for IMV (PASC + IMV, n = 27) or noninvasive support therapy (PASC + NIS, n = 25). Patients underwent pulmonary function and cardiopulmonary exercise testing (CPX) and were compared with a reference group (CONTROL, n = 19) comprising individuals of both sexes with similar age, comorbidities, and physical activity levels but without a history of COVID-19 illness. Individuals with PASC, irrespective of support therapy, presented with higher rates of cardiorespiratory abnormalities than CONTROL, especially dysfunctional breathing patterns, dynamic hyperinflation, reduced oxygen uptake and oxygen pulse, and blunted heart rate recovery (all P < 0.05). Only the rate of abnormal oxygen pulse was greater among PASC + IMV group than PASC + NIS group (P = 0.05). Mean estimates for all CPX variables were comparable between PASC + IMV and PASC + NIS groups (all P > 0.05). These findings indicate significant involvement of both central and peripheral factors, leading to exertional intolerance in individuals with PASC previously admitted to the ICU, regardless of their need for IMV.NEW & NOTEWORTHY We found cardiorespiratory abnormalities in ICU survivors of severe-to-critical COVID-19 with PASC to be independent of IMV need. Overall, both group of patients experienced dysfunctional breathing patterns, dynamic hyperinflation, lower oxygen uptake and oxygen pulse, and blunted heart rate responses to CPX. PASC seems to impact exertional tolerance and exercise capacity due to ventilatory inefficiency, impaired aerobic metabolism, and potential systolic and autonomic dysfunction, all of these irrespective of support therapy during ICU stay.

Carotid body dysregulation contributes to Long COVID symptoms

BACKGROUND

The symptoms of long COVID, which include fatigue, breathlessness, dysregulated breathing, and exercise intolerance, have unknown mechanisms. These symptoms are also observed in heart failure and are partially driven by increased sensitivity of the carotid chemoreflex. As the carotid body has an abundance of ACE2 (the cell entry mechanism for SARS-CoV-2), we investigated whether carotid chemoreflex sensitivity was elevated in participants with long COVID.

METHODS

Non-hositalised participants with long-COVID (n = 14) and controls (n = 14) completed hypoxic ventilatory response (HVR; the measure of carotid chemoreflex sensitivity) and cardiopulmonary exercise tests. Parametric and normally distributed data were compared using Student's unpaired t-tests or ANOVA. Nonparametric equivalents were used where relevant. Peason's correlation coefficient was used to examine relationships between variables.

RESULTS

During cardiopulmonary exercise testing the VE/VCO2 slope (a measure of breathing efficiency) was higher in the long COVID group (37.8 ± 4.4) compared to controls (27.7 ± 4.8, P = 0.0003), indicating excessive hyperventilation. The HVR was increased in long COVID participants (-0.44 ± 0.23 l/min/ SpO2%, R2 = 0.77 ± 0.20) compared to controls (-0.17 ± 0.13 l/min/SpO2%, R2 = 0.54 ± 0.38, P = 0.0007). The HVR correlated with the VE/VCO2 slope (r = -0.53, P = 0.0036), suggesting that excessive hyperventilation may be related to carotid body hypersensitivity.

CONCLUSIONS

The carotid chemoreflex is sensitised in long COVID and may explain dysregulated breathing and exercise intolerance in these participants. Tempering carotid body excitability may be a viable treatment option for long COVID patients.

Exercise ventilatory response after COVID-19: comparison between ambulatory and hospitalized patients

Inefficient ventilatory response during cardiopulmonary exercise testing (CPET) has been suggested as a cause of post-COVID-19 dyspnea. It has been described in hospitalized patients (HOSP) with lung parenchymal sequelae but also after mild infection in ambulatory patients (AMBU). We hypothesize that AMBU and HOSP have different ventilatory responses to exercise, due to different etiologies. We analyzed CPET realized between July 2020 and May 2022 of patients with persisting respiratory symptoms 3 mo after COVID-19. Chest computed tomography (CT) scan, pulmonary function tests, quality of life, and respiratory questionnaires were collected. CPET data were specifically explored as a function of ventilation (V̇e) and time. Seventy-nine consecutive patients were included (42 AMBU and 37 HOSP, median: 54 [44-60] yr old, 57% female). Patients were hospitalized for a median of 20 [8-34] days, with pneumonia (41%) or acute respiratory distress syndrome (ARDS; 30%). Among HOSP, 12(32%) patients had abnormal values for spirometry and 18(51%) for carbon monoxide diffusing capacity (P < 0.001). CPET showed no differences between AMBU and HOSP in peak absolute O2 uptake (V̇o2) (1.59 [1.22-2.11] mL·min-1; P = 0.65). Tidal volume (VT) as a function of V̇e, was lower in AMBU than in HOSP (P < 0.01) toward the end of exercise. The slope of the V̇e-CO2 production was higher than normal in both groups (30.9 [26.1-34.3]; P = 0.96). In conclusion, the severity of COVID-19 did not influence the exercise capacity, but AMBU demonstrated a less efficient ventilatory response to exercise as compared with HOSP. CPET with exploration of data as a function of V̇e and throughout the exercise better unveil ventilatory inefficiency.NEW & NOTEWORTHY We evaluated the exercise ventilatory response in patients with persisting dyspnea after severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. We found that despite similar peak power and peak absolute O2 uptake, tidal volume as a function of ventilation was lower in ambulatory than in hospitalized patients toward the end of exercise, reflecting ventilatory inefficiency. We call for evaluation of minute ventilation with the exploration of data throughout the exercise and not only peak data to better unveil ventilatory inefficiency.

The smarty4covid dataset and knowledge base as a framework for interpretable physiological audio data analysis

Harnessing the power of Artificial Intelligence (AI) and m-health towards detecting new bio-markers indicative of the onset and progress of respiratory abnormalities/conditions has greatly attracted the scientific and research interest especially during COVID-19 pandemic. The smarty4covid dataset contains audio signals of cough (4,676), regular breathing (4,665), deep breathing (4,695) and voice (4,291) as recorded by means of mobile devices following a crowd-sourcing approach. Other self reported information is also included (e.g. COVID-19 virus tests), thus providing a comprehensive dataset for the development of COVID-19 risk detection models. The smarty4covid dataset is released in the form of a web-ontology language (OWL) knowledge base enabling data consolidation from other relevant datasets, complex queries and reasoning. It has been utilized towards the development of models able to: (i) extract clinically informative respiratory indicators from regular breathing records, and (ii) identify cough, breath and voice segments in crowd-sourced audio recordings. A new framework utilizing the smarty4covid OWL knowledge base towards generating counterfactual explanations in opaque AI-based COVID-19 risk detection models is proposed and validated.

Cardiorespiratory dysautonomia in post-COVID-19 condition: Manifestations, mechanisms and management

A significant proportion of COVID-19 patients experience debilitating symptoms for months after the acute infection. According to recent estimates, approximately 1 out of 10 COVID-19 convalescents reports persistent health issues more than 3 months after initial recovery. This 'post-COVID-19 condition' may include a large variety of symptoms from almost all domains and organs, and for some patients it may mean prolonged sick-leave, homestay and strongly limited activities of daily life. In this narrative review, we focus on the symptoms and signs of post-COVID-19 condition in adults - particularly those associated with cardiovascular and respiratory systems, such as postural orthostatic tachycardia syndrome or airway disorders - and explore the evidence for chronic autonomic dysfunction as a potential underlying mechanism. The most plausible hypotheses regarding cellular and molecular mechanisms behind the wide spectrum of observed symptoms - such as lingering viruses, persistent inflammation, impairment in oxygen sensing systems and circulating antibodies directed to blood pressure regulatory components - are discussed. In addition, an overview of currently available pharmacological and non-pharmacological treatment options is presented.

Endothelial dysfunction in autoimmune, pulmonary, and kidney systems, and exercise tolerance following SARS-CoV-2 infection

Long COVID is characterized by persistent symptoms beyond 3-months of severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) infection that last for at least 2 months and cannot be explained by an alternative diagnosis. Autonomic, immunologic, endothelial, and hypercoagulation are implicated as possible mechanisms of long COVID symptoms. Despite recognition of the public health challenges posed by long COVID, the current understanding of the pathophysiological underpinnings is still evolving. In this narrative review, we explore the long-term effects of SARS-CoV-2 infection on T cell activation such as autoimmune disorders and endothelial cell dysfunction involving vascular impairments within pulmonary and renal architecture. We have described how endothelial dysfunction and vascular abnormalities may underscore findings of exercise intolerance by way of impaired peripheral oxygen extraction in individuals with long COVID.

A temporal examination of inspiratory muscle strength and endurance in hospitalized COVID-19 patients

BACKGROUND

The two most common symptoms associated with COVID-19 are dyspnea and fatigue. One possible cause of such symptoms may be inspiratory muscle weakness.

OBJECTIVES

The purpose of this study was to examine inspiratory muscle performance (IMP) from intensive care unit discharge (ICUD) to hospital discharge (HD) in patients with COVID-19 hypothesizing that IMP would be markedly depressed at both ICUD and HD.

METHODS

IMP was examined at ICUD and HD via the PrO2 device (PrO2 Health, Smithfield, RI) which provided the maximal inspiratory pressure (MIP), sustained MIP (SMIP), inspiratory duration (ID), and fatigue index test (FIT). Patient symptoms were assessed at ICUD, HD, and 1-month post-HD.

RESULTS

30 patients (19 men, 11 women) with COVID-19 were included. The mean±SD age, BMI, and length of ICU and hospital stay was 71±11 yrs, 27.9 ± 6.3 kg/m, 9 ± 6 days, and 26±16 days, respectively. The mean±SD MIP, SMIP, ID, and FIT of the entire cohort at ICUD vs HD were 36±21 vs 40±20 cm H2O, 231±157 vs 297±182 PTU, 8.8 ± 4.2 vs 9.5 ± 4.6 s, and 9.0 ± 9.4 vs 13.1 ± 12.3, respectively, with only SMIP and FIT significantly greater at HD (p=.006 and 0.03, respectively). SMIP at HD was significantly related to resting dyspnea at HD (r=-0.40; p=.02). The SMIP and FIT of men were found to increase significantly from ICUD to HD, but no measure of IMP in the women increased significantly from ICUD to HD. At least one COVID-19-related symptom was present 1 month after HD with the most persistent symptoms being fatigue, cough, and dyspnea in 47%, 40%, and 37% of the patients, respectively.

CONCLUSIONS

A significant reduction in IMP exists in patients with COVID-19 at both ICUD and HD and no measure of IMP in women was observed to increase significantly from ICUD to HD. Impaired inspiratory muscle endurance rather than strength was associated with greater dyspnea at HD.

ERS International Congress 2022: highlights from the Respiratory Clinical Care and Physiology Assembly

It is a challenge to keep abreast of all the clinical and scientific advances in the field of respiratory medicine. This article contains an overview of the laboratory-based science, clinical trials and qualitative research that were presented during the 2022 European Respiratory Society International Congress within the sessions from the five groups of Assembly 1 (Respiratory Clinical Care and Physiology). Selected presentations are summarised from a wide range of topics: clinical problems, rehabilitation and chronic care, general practice and primary care, mobile/electronic health (m-health/e-health), clinical respiratory physiology, exercise and functional imaging.

ME/CFS and Long COVID share similar symptoms and biological abnormalities: road map to the literature

Some patients remain unwell for months after "recovering" from acute COVID-19. They develop persistent fatigue, cognitive problems, headaches, disrupted sleep, myalgias and arthralgias, post-exertional malaise, orthostatic intolerance and other symptoms that greatly interfere with their ability to function and that can leave some people housebound and disabled. The illness (Long COVID) is similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as well as to persisting illnesses that can follow a wide variety of other infectious agents and following major traumatic injury. Together, these illnesses are projected to cost the U.S. trillions of dollars. In this review, we first compare the symptoms of ME/CFS and Long COVID, noting the considerable similarities and the few differences. We then compare in extensive detail the underlying pathophysiology of these two conditions, focusing on abnormalities of the central and autonomic nervous system, lungs, heart, vasculature, immune system, gut microbiome, energy metabolism and redox balance. This comparison highlights how strong the evidence is for each abnormality, in each illness, and helps to set priorities for future investigation. The review provides a current road map to the extensive literature on the underlying biology of both illnesses.

Exercise Intolerance Following COVID-19: What Is the Role of Dysfunctional Breathing?

N/a.

COVID-19 and athletes: Endurance sport and activity resilience study-CAESAR study

Background: The COVID-19 pandemic and imposed restrictions influenced athletic societies, although current knowledge about mild COVID-19 consequences on cardiopulmonary and physiologic parameters remains inconclusive. This study aimed to assess the impact of mild COVID-19 inflection on cardiopulmonary exercise test (CPET) performance among endurance athletes (EA) with varied fitness level. Materials and Methods: 49 EA (n_male = 43, n_female = 6, mean age = 39.94 ± 7.80 yr, height = 178.45 cm, weight = 76.62 kg; BMI = 24.03 kgm^-2) underwent double treadmill or cycle ergometer CPET and body analysis (BA) pre- and post-mild COVID-19 infection. Mild infection was defined as: (1) without hospitalization and (2) without prolonged health complications lasting for >14 days. Speed, power, heart rate (HR), oxygen uptake (VO₂), pulmonary ventilation, blood lactate concentration (at the anaerobic threshold (AT)), respiratory compensation point (RCP), and maximum exertion were measured before and after COVID-19 infection. Pearson's and Spearman's r correlation coefficients and Student t-test were applied to assess relationship between physiologic or exercise variables and time. Results: The anthropometric measurements did not differ significantly before and after COVID-19. There was a significant reduction in VO₂ at the AT and RCP (both p < 0.001). Pre-COVID-19 VO₂ was 34.97 ± 6.43 ml kg·min^-1, 43.88 ± 7.31 ml kg·min^-1 and 47.81 ± 7.81 ml kg·min^-1 respectively for AT, RCP and maximal and post-COVID-19 VO₂ was 32.35 ± 5.93 ml kg·min^-1, 40.49 ± 6.63 ml kg·min^-1 and 44.97 ± 7.00 ml kg·min^-1 respectively for AT, RCP and maximal. Differences of HR at AT (p < 0.001) and RCP (p < 0.001) was observed. The HR before infection was 145.08 ± 10.82 bpm for AT and 168.78 ± 9.01 bpm for RCP and HR after infection was 141.12 ± 9.99 bpm for AT and 165.14 ± 9.74 bpm for RCP. Time-adjusted measures showed significance for body fat (r = 0.46, p < 0.001), fat mass (r = 0.33, p = 0.020), cycling power at the AT (r = -0.29, p = 0.045), and HR at RCP (r = -0.30, p = 0.036). Conclusion: A mild COVID-19 infection resulted in a decrease in EA's CPET performance. The most significant changes were observed for VO₂ and HR. Medical Professionals and Training Specialists should be aware of the consequences of a mild COVID-19 infection in order to recommend optimal therapeutic methods and properly adjust the intensity of training.