Lung perfusion estimation by saline-contrast EIT without breath hold: a randomized cross-over trial

INTRODUCTION: This study aimed to develop and validate a non-breath-holding contrast-enhanced electrical impedance tomography (EIT) method using low-pass filtering for bedside assessment of regional lung perfusion in mechanically ventilated ICU patients. METHODS: This was a randomized cross-over trial. Each patient received two 10 mL 10% NaCl bolus injections via a central venous catheter, performed respectively during an end-expiratory pause (apnea) and during ongoing mechanical ventilation (non-apnea). In the non-apnea method, a 0.17 Hz low-pass filter was used to remove respiratory interference during perfusion analysis. Pixel-wise correlation was assessed using Spearman correlation analysis. RESULTS: 20 mechanically ventilated ICU patients were included in the final analysis. Pixel-wise perfusion correlation between apnea and non-apnea methods showed good overall consistency (median r = 0.94, IQR 0.90-0.97). Global V/Q match%, dead space%, and shunt% were comparable between the two methods. The impedance drop duration was significantly shorter in the non-apnea method (5.3 s vs. 6.1 s, p = 0.008). CONCLUSION: The non-apnea contrast-EIT method provides consistent lung perfusion images with the conventional apnea method, expanding EIT applicability to patients intolerant to apnea and potentially yielding more physiologically realistic results.