Reduced Exercise Tolerance in Long-COVID Patients
Bibliographic record
Abstract
Introduction: Because many patients report long-term symptoms including dyspnea and fatigue after an acute COVID-19 infection, we recently developed a comprehensive follow-up clinic to understand and manage these patients. We conducted cardiopulmonary exercise tests (CPET) to characterize the respiratory responses to exercise as a potential cause of dyspnea in long-COVID patients. Methods: Seven long-COVID patients (mean age 53±4 years, 100% female) and seven age, sex and height-matched healthy controls (mean age 55±10 years) completed a pulmonary function test and an incremental CPET to exhaustion. These seven long-COVID patients were assessed due to persistent dyspnea after recovery from the acute infection;three long-COVID patients required hospitalization during the acute infection. The CPET was performed on average 158±59 days since COVID-19 diagnosis. Arterial saturation (SpO2) and breath-by-breath respiratory data, including ventilatory equivalents for carbon dioxide (VE/VCO2), were collected continuously, while inspiratory capacity (IC), inspiratory reserve volume (IRV), and dyspnea (modified Borg scale) were evaluated throughout exercise. Statistical analyses were performed using unpaired t-tests with a significance level of 0.05. Results: Prior to testing, COVID-19 patients reported resting dyspnea (mean modified Medical Research Council Dyspnea scale 2.1±0.7) and elevated post-COVID functional scale (mean 2.1±1.2), revealing persistent symptoms. Spirometric assessment at rest was within expected normal limits, though a reduction in FEV1 was seen in the COVID-19 patients (88.9±16.6% predicted) compared to matched controls (111.1±13.2% predicted;p = 0.02). Lung volumes and diffusion capacity were similar between both groups. Most notably, COVID-19 patients (19.6±7.4 mL/kg/min) had a reduced VO2peak when compared to controls (29.1±8.3 mL/kg/min, p<0.01). As well, VE/VCO2 at rest and anaerobic threshold were elevated in COVID-19 patients as compared to controls. SpO2 at peak exercise was not different between COVID-19 patients and controls (95±4% vs. 94±3%, p=0.57). At peak exercise, there were no between-group differences in tidal volume, breathing frequency, IC, IRV observed. Patient-reported dyspnea and leg fatigue at peak exercise were also similar between groups. Conclusion: Initial results suggest that long-COVID patients demonstrate reduced exercise tolerance and elevated VE/VCO2;however, SpO2, operating lung volumes and dyspnea responses to exercise are similar to healthy controls, suggesting that there may be a non-pulmonary cause for the observed exercise intolerance. Further investigation is required to understand this limitation and its relationship to symptoms in long-COVID patients.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".