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.
ABSTRACT
RATIONALE: Little is known regarding the long-term impact of acute COVID-19 in patients who did not require hospitalization with the acute infection. METHODS: Between June-November 2020, we reviewed patients in our dedicated COVID-19 “long haulers” clinic for those suffering persistent symptoms following recovery from COVID-19 infection. We prospectively collected the following data: pulmonary function test (Forced Expiratory Volume in one second (FEV1), Forced Vital Capacity (FVC);6 minute walk test (6MWT);modified Medical Research Council (mMRC) dyspnea score;and health related quality of life (HRQL) using the Post-COVID-19 Functional Scale (PCFS) and EQ5D-5L questionnaires. All data is presented as mean±standard deviation.RESULTS: 17 patients [3 (17.6%) male] aged 49.2(11.7) years were assessed 105.1(41.4) days from molecular diagnosis of acute COVID-19. Four (23.5%) patients had a pre-morbid diagnosis of asthma. None were current smokers;6 (35.3%) were ex-smokers with a 4.2(4.5) pack year history. 17 (100%) reported at least one respiratory symptom (cough, wheeze, or dyspnea);9 (52.9%) described muscular pain or fatigue;8 (47%) reported chest pain;5 (29.4) reported neurocognitive symptoms (new or worsened headache, word finding difficulties or memory impairment) and 5 (29.4) also described fatigue. Despite an impaired mMRC score 1.9(1.6) and desaturation during the 6-minute walk test, spirometry was normal (Table 1). Patients reported an impaired health related quality of life with an EQ5D-5L Visual analogue score of 67.9(21.2);the mean normal for Albertans in the same matched age group 45-64 years is 76.3(17.9). The PCFS score remained elevated over 3 months' from confirmation of the acute infection 1.94(1.1).CONCLUSIONS: Irrespective of the severity of acute COVID-19 infection, patients may experience chronic persistent symptoms and impaired HRQL necessitating long-term follow up. r> TABLE 1. Baseline Characteristics at first clinic visit 105.1(41.4) days following confirmed acute COVID-19 infection. All data presented as mean±standard deviation. [FEV1= Forced Expiratory Volume in 1 second;FVC= Forced Vital Capacity;6MWT= 6-minute walk test;mMRC = modified Medical Research Council;EQ5D-5L VAS= EQ5D-5L Visual Analogue Scale.].