Understanding the Effects of COVID-19 on Respiratory Function:Insights from Interstitial Lung Disease

<bold>Introduction:</bold> Interstitial Lung Disease Pneumonia (ILDP),one of the most frequent manifestations of COVID-19,can affect significantly lung function and exercise tolerance. Aims:To assess COVID-19's impact on lung function and to determine correlations between clinical and functional parameters. Methods:It was cross-sectional study of 229 post-discharge COVID-19 pneumonia patients who underwent spirometry,DLCO measurement, and the Six-Minute Walk Test(6MWT). We evaluated the 6-Minute Walk Distance(6MWTD),the hemoglobin O2 saturation (SpO2) and the chronotropic response. The Physiological Cost Index (PCI) is defined by dividing the difference between maximal and minimal Heart Rate (beats/min) by walking speed. Results:The median age was 57.58 years, with a mean Body Mass Index of 30.44±5.2kg/m2. According to the WHO criteria,21% of patients exhibited a severe form. Spirometry revealed a restrictive ventilatory defect in 14.4% and a proximal obstructive defect in 5.2%.DLCO measurement indicated mild impairment in 24.9%,moderate in 16.6%, and severe in 3.1%. The 6MWT demonstrated reduced 6MWTD in 51.1%,decreased SpO2 in 22.7%,and a median PCI of 0.12beats/meter. Desaturation during 6MWT was correlated significantly with duration of respiratory support and maximum oxygen requirement. Also a positive correlation between DLCO decline and both initial lung parenchyma damage and duration of oxygen therapy.PCI was negatively correlated with oxygen therapy duration,DLCO,and 6MWTD. Conclusion:The 6MWT parameters and PCI provide valuable insights into lung disease severity. Thus, its inclusion in the initial assessment and follow-up of ILDP is strongly recommended.