Abstract
INTRODUCTION: The physiological basis for dyspnea, a hallmark of post-COVID syndrome (PCS), remains poorly understood. METHODS: In this analysis of the prospective, multicenter, population-based, longitudinal COVIDOM study, we studied 936 previously healthy adults assessed ≥6 months after a mostly mild, PCR-confirmed SARS-CoV-2 infection. Participants underwent comprehensive pulmonary function testing including spirometry, body plethysmography, diffusing capacity for carbon monoxide, and airwave oscillometry. Dyspnea was assessed by questionnaires (mMRC ≥1/MDP-A1 domain ≥1). We performed cross-sectional and longitudinal analyses for lung function in relation to both dyspnea and a previously defined PCS severity score (PCS-S). RESULTS: Between 11/2020 and 05/2023, we examined 936 previously healthy COVIDOM participants (median age 37 [IQR 28-51], 56% female). Dyspnea prevalence increased significantly with PCS severity (low PCS-S: 19.3%; intermediate PCS-S: 53.8%; high PCS-S: 81.8%; p < 0.001). Women suffered more frequently from dyspnea and PCS. Small airway dysfunction (SAD), as indicated by abnormal R5-20 Hz or AX5 Hz measures, tended to be more frequent in participants with high PCS severity and dyspnea compared to those with low PCS and no dyspnea (37% vs. 25%, p = 0.058) with corresponding R5-20 Hz of 0.03 [0.01-0.07] vs. 0.01 [0-0.03] kPa·L-1·s-1 (p < 0.01). Longitudinally, however, none of the baseline or follow-up lung function parameters, including measures of SAD, differed between participants with persistent dyspnea and those who became asymptomatic. CONCLUSION: Oscillometry-derived R5-R20 Hz differed significantly between dyspneic PCS patients and controls. The high frequency of SAD and the absence of longitudinal improvement might indicate the potential clinical relevance of SAD assessment, despite its only numeric differences between PCS severity groups.