A55-21 Effect of Proning Position on Ventilation and Perfusion in Covid-19 Acute Respiratory Distress Syndrome

Rationale Assessment of pulmonary ventilation and perfusion in coronavirus disease 2019 (COVID-19) complicated by acute respiratory distress syndrome (C-ARDS) remains scarce, particularly regarding the response to prone positioning. This study aimed to characterize the physiological effects of prone positioning on respiratory mechanics, regional ventilation, and pulmonary perfusion in C-ARDS patients. Methods Twelve patients fulfilling the Berlin ARDS definition with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection confirmed by nasopharyngeal PCR and twelve healthy controls were enrolled. Patients with contraindications to electrical impedance tomography (EIT) (pacemaker, implantable defibrillator, or skin lesions) were excluded. All participants remained supine breathing room air while receiving supplemental oxygen. Regional ventilation and perfusion were assessed by EIT (Infivision 1910, Beijing Huarui). EIT-derived ventilation and perfusion data were recorded at baseline (supine) and after 3 (2-4) hours of prone positioning. Oxygen saturation was collected before probe insertion, immediately before, and at the end of prone positioning. Results Ventral-to-dorsal redistribution of ventilation was observed in both cohorts after prone positioning (COVID-19: ΔV-ventral -5.9±2.8%, ΔV-dorsal 5.9±2.8%; Controls: ΔV-ventral -0.5±1.6%, ΔV-dorsal 0.5±1.6%;). In healthy controls, perfusion simultaneously redistributed toward ventral regions (ΔP-ventral 4.2±0.3%, ΔP-dorsal -4.2±0.3%), whereas COVID-19 patients exhibited the opposite pattern (ΔP-ventral -6.3±1.1%, ΔP-dorsal 6.3±1.1%). Prone positioning increased the global EIT-ventilated area and S02. Dead-space% tended to decrease (-1.3 %), whereas shunt% rose (+1.5 %), yielding a net improvement in ventilation-perfusion matching (V/Q matching% +0.24%); none of the latter three parameters reached statistical significance. A consistent right-sided predominance was present for both ventilation and perfusion in supine and prone positions (lateral ventilation ratio R/L = 1.1 ± 0.11; perfusion ratio R/L = 1.22 ± 0.09; P < 0.05 for both). Region-of-interest analysis revealed a prone-induced increase in ventilation and perfusion in ROI-3 (dorsal-caudal: ΔV +22 %, ΔP +19 %; P = 0.008 and 0.012, respectively) and a concomitant decrease in ROI-4 (ventral-caudal: ΔV -18 %, ΔP -16 %; P = 0.009 and 0.015) in COVID-19 patients. Conclusion Prone positioning induces a ventral-to-dorsal redistribution of both ventilation and perfusion in C-ARDS, resulting in improved oxygenation and enhanced ventilation-perfusion matching. This abstract is funded by: none