Investigation of In-hospital COVID-19 Mortality and One-year Follow-up of Lung Function and Health Status with Respect to the Initial Disease Severity

Background: Globally, thousands of patients suffer from long-term COVID-19 symptoms, often referred to as post-acute COVID-19 syndrome, a condition that already affects our health systems. Although there is a growing literature upon the long-term effects of SARS - CoV - 2 infection, there are up to date only a few reports on long-term follow up of pulmonary function after severe COVID-19. Methods: : The study is an observational cohort of patients who were admitted to hospital care with confirmed COVID-19 during the first pandemic wave and those who required some form of supplementary oxygen delivery. Baseline characteristics, demographic data and information about hospital stay including mortality were obtained by medical charts. Patients were divided in to 3 groups: group 1 (intensive care unit (ICU)-invasive mechanical ventilation (IMV), group 2 (high-flow nasal-cannula (HFNC) and/or none-invasive ventilation (NIV) and group 3 (regular oxygen delivery treatment). All patients were required to answer questionnaires (mMRC scale, Post-COVID-19 Functional Status Scale (PCFS), Hospital anxiety and depression scale (HAD) and 36-Item Short Form Health Survey (SF-36)) at one year after acute infection, while patients in groups 1 and 2 performed also dynamic spirometry. The R-language of statistics was used for all calculations and visualisations. Results: : The study population consisted of 130 patients. Forty five (35%) patients died at the hospital. Risk factors for in-hospital mortality were age, hypertension, ischemic heart disease and renal disease. Patients who survived had, on average, a longer period from symptoms onset to hospital admission. No significant difference in all health scales between the 3 patient groups were found. Mean values of both FEV1% and FVC% in the groups 1 and 2 were detected within the lower normal limits while no difference was found between the two groups who were examined with spirometry. Conclusions: : The main result of the study is lung function values in the lower limit of normal evaluated with dynamic spirometry at one-year follow-up. There were no significant differences related to initial disease severity in lung function and long-term health status at 12 months, which suggests that more generous lung function testing even in less severe individuals with lingering symptoms could be indicated.