Ventilation heterogeneity after COVID-19

Abstract

<b>The aim:</b> To investigate the influence of COVID-19 on ventilation heterogeneity (VH) using multiple-breath nitrogen washout test (MBNW, using the module <i>Easy-One Pro ndd Medizintechnik AG</i>) in convalescence phase and to identify the relationship of the lung clearance index (LCI) with other pulmonary functional parameters. <b>Materials and methods:</b> 26 patients (96% of males, median age was 46 yrs) were enrolled in the cross-sectional study. No patients had chronic lung diseases. Сonventional pulmonary function tests (PFTs) such as spirometry, body plethysmography, diffusion test as well as MBNW and impulse oscillometry (IOS) were performed. <b>Results:</b> The median of the duration from COVID-19 onset to&nbsp;PFTs was 63 (42-78) days. The median of the maximum abnormal chest high-resolution CT changes in the acute period of COVID-19 was 50%, at the time of the study was 12%. VH was detected in 22 (85%) cases. The medians of all measured PFTs and IOS parameters were within the normal ranges. Nevertheless decrease of DLCO, airway obstruction, restrictive ventilatory defect were established in 31%,15%,11.5% of cases, respectively. Significant correlation dependences of LCI with intrathoracic lung volume (r=-0.54, p&lt;0.01), expiratory reserve volume (r=-0.55, p&lt;0.01), transfer-factor CO (DLco) (r=-0.44, p=0.02), absolute (r=0.51, p&lt;0.01) and relative (r=-0.47, p=0.01) frequency dependence of resistance, resonance frequency (r=0.48, p=0.01), area of reactance (r=0.45, p=0.02) were revealed. <b>Conclusion:</b> 63 days after the onset of COVID-19 the ventilation heterogeneity was detected in 85% cases. Correlation dependences of LCI&nbsp;with parameters of PFTs and IOS were established.