Pulmonary and Extrapulmonary Effects of Prolonged Prone Positioning in a Porcine Model of Acute Respiratory Distress Syndrome.

Abstract

Background: Prone positioning (PP) improves survival in severe acute respiratory distress syndrome (ARDS), but its prolonged effects on pulmonary and extrapulmonary organs remain unclear. This study aimed to investigate the pathophysiological effects of 24-hour PP in a porcine ARDS model.

Methods: Ten female Bama mini swine (49.5 ± 3.7 kg) underwent severe ARDS induction via repeated saline lavage and were randomized to PP (n = 5) or supine position (SP, n = 5). Respiratory parameters, electrical impedance tomography (EIT), haemodynamics, and biochemical serum analysis were performed. After 24 hours, regional lung injury was assessed via histopathology and wet-dry weight (W/D) ratio, and extrapulmonary injury was evaluated by histopathology, apoptosis, oxidative stress, and organ-specific injury biomarkers.

Results: Nine swine were analyzed (PP, n = 5; SP, n = 4). PP significantly improved the PaO2/FiO2 ratio. EIT showed sustained improvements in ventilation, perfusion, and ventilation-perfusion matching (V/Q matching), particularly in the dorsal regions. W/D ratio in the dorsal lung was significantly lower in the PP group, with no significant differences in respiratory mechanics or histopathological lung injury. Haemodynamic parameters, intra-abdominal pressure, and serum biochemical analyses showed no significant differences. Extrapulmonary injury analysis revealed no differences, except for a higher apoptotic index in renal tissue in the PP group.

Conclusions: Prolonged PP improved oxygenation by improving ventilation, perfusion, and V/Q matching, while reducing dorsal lung edema, without significantly affecting respiratory mechanics or histopathological lung injury. Additionally, PP showed no significant damage on haemodynamics and extrapulmonary organ function. However, attention should be given to potential renal impairment during prolonged PP administration.