C52-44 Electrical Impedance Tomography-guided Peep Titration and Lateral Positioning in the Management of Ventilation/perfusion Mismatch Following Type A Aortic Dissection: A Case Report

Type A aortic dissection is a severe vascular condition frequently associated with cardiac and neurological complications as well as malperfusion syndromes. Surgical treatment, requiring cardiopulmonary bypass (CPB) and mechanical ventilation, may cause ventilation/perfusion (V/Q) ratio mismatch. Electrical impedance tomography (EIT) emerges as a noninvasive tool capable of identifying changes in pulmonary ventilation and perfusion. An 89-year-old female patient who was obese, hypertensive, and diabetic, with mild aortic regurgitation, underwent surgical repair of type A aortic dissection with CPB. In the immediate postoperative period, she developed extensive right pneumothorax and cardiogenic shock. Despite chest drainage, while under sedation and neuromuscular blockade (RASS -5) on protective volume-controlled ventilation (PEEP 6 cmH2O, FiO2100%, RR 22 bpm), she presented with static compliance of 32 mL/cmH2O, airway resistance of 13 cmH2O/L/s, PaO2/FiO2 ratio of 60, and diffuse pulmonary infiltrates on chest radiography. EIT assessment revealed a predominance of ventilatory disturbance (Right = 37%, Left = 63%). Based on this finding, EIT-guided PEEP titration was performed and adjusted to 10 cmH2O, combined with lateral positioning (right lung in the non-dependent position) for 2 hours, aiming to optimize ventilation and reduce hypoxemia. Following the intervention, oxygenation improved (PaO2/FiO2 ratio = 162), FiO2 was reduced to 75%, and ventilation distribution became more balanced (Right = 53%, Left = 47%). This case suggests that EIT was a valuable tool for diagnosing V/Q mismatch and monitoring its correction following individualized PEEP adjustment, and that when combined with therapeutic positioning, it promoted improvements in oxygenation and ventilatory distribution.