Oxygen uptake kinetics and chronotropic responses to exercise are impaired in survivors of severe COVID-19.

The post-acute phase of coronavirus disease 2019 (COVID-19) is often marked by several persistent symptoms and exertional intolerance, which compromise survivors' exercise capacity. This was a cross-sectional study aiming to investigate the impact of COVID-19 on oxygen uptake (V̇o2) kinetics and cardiopulmonary function in survivors of severe COVID-19 about 3-6 mo after intensive care unit (ICU) hospitalization. Thirty-five COVID-19 survivors previously admitted to ICU (5 ± 1 mo after hospital discharge) and 18 controls matched for sex, age, comorbidities, and physical activity level with no prior history of SARS-CoV-2 infection were recruited. Subjects were submitted to a maximum-graded cardiopulmonary exercise test (CPX) with an initial 3-min period of a constant, moderate-intensity walk (i.e., below ventilatory threshold, VT). V̇o2 kinetics was remarkably impaired in COVID-19 survivors as evidenced at the on-transient by an 85% (P = 0.008) and 28% (P = 0.001) greater oxygen deficit and mean response time (MRT), respectively. Furthermore, COVID-19 survivors showed an 11% longer (P = 0.046) half-time of recovery of V̇o2 (T1/2V̇o2) at the off-transient. CPX also revealed cardiopulmonary impairments following COVID-19. Peak oxygen uptake (V̇o2peak), percent-predicted V̇o2peak, and V̇o2 at the ventilatory threshold (V̇o2VT) were reduced by 17%, 17%, and 12% in COVID-19 survivors, respectively (all P < 0.05). None of the ventilatory parameters differed between groups (all P > 0.05). In addition, COVID-19 survivors also presented with blunted chronotropic responses (i.e., chronotropic index, maximum heart rate, and heart rate recovery; all P < 0.05). These findings suggest that COVID-19 negatively affects central (chronotropic) and peripheral (metabolic) factors that impair the rate at which V̇o2 is adjusted to changes in energy demands.NEW & NOTEWORTHY Our findings provide novel data regarding the impact of COVID-19 on submaximal and maximal cardiopulmonary responses to exercise. We showed that V̇o2 kinetics is significantly impaired at both the onset (on-transient) and the recovery phase (off-transient) of exercise in these patients. Furthermore, our results suggest that survivors of severe COVID-19 may have a higher metabolic demand at a walking pace. These findings may partly explain the exertional intolerance frequently observed following COVID-19.

Benefits of Home-Based Exercise Training Following Critical SARS-CoV-2 Infection: A Case Report

In the current scenario, in which an elevated number of COVID-19 survivors present with severe physical deconditioning, exercise intolerance, persistent symptoms, and other post-acute consequences, effective rehabilitation strategies are of utmost relevance. In this study, we report for the first time the effect of home-based exercise training (HBET) in a survivor patient from critical COVID-19 illness. A 67-year-old woman who had critical COVID-19 disease [71 days of hospitalization, of which 49 days were in the intensive care unit (ICU) with invasive mechanical ventilation due to respiratory failure] underwent a 10-week HBET aiming to recovering overall physical condition. Before and after the intervention, we assessed cardiopulmonary parameters, skeletal muscle strength and functionality, fatigue severity, and self-reported persistent symptoms. At baseline (3 months after discharge), she presented with severe impairment in cardiorespiratory functional capacity (<50% age predicted VO2peak). After the intervention, remarkable improvements in VO2peak (from 10.61 to 15.48 mL·kg−1·min−1, Δ: 45.9%), oxygen uptake efficiency slope (OUES;from 1.0 to 1.3 L·min−1, Δ: 30.1%), HR/VO2 slope (from 92 to 52 bpm·L−1, Δ: −43.5%), the lowest VE/VCO2 ratio (from 35.4 to 32.9 L·min−1, Δ: −7.1%), and exertional dyspnea were observed. In addition, handgrip strength (from 22 to 27 kg, Δ: 22.7%), 30-s Sit-to-Stand (30-STS;from 14 to 16 repetitions, Δ:14.3%), Timed-Up-and-Go (TUG;from 8.25 to 7.01 s, Δ: −15%) performance and post-COVID functional status (PCFS) score (from 4 to 2) were also improved from baseline to post-intervention. Self-reported persistent symptoms were also improved, and Fatigue Severity Scale (FSS) score decreased (from 4 to 2.7) from baseline to post-intervention. This is the first evidence that a semi-supervised, HBET program may be safe and potentially effective in improving cardiorespiratory and physical functionality in COVID-19 survivors. Controlled studies are warranted to confirm these findings.

Home-Based Exercise Training During COVID-19 Pandemic in Post-Bariatric Patients: a Randomized Controlled Trial.

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