Measurement of relative lung perfusion with electrical impedance and positron emission tomography: an experimental comparative study in pigs

Abstract

Background: Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique. Methods: Thirteen pigs (50e66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H 2 O to achieve peak airway pressure 45 cm H 2 O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68 Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined. Results: Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9e95.9% of measurements. Conclusions: The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.

Reply to Wang and Zhong: Bedside Evaluation of Pulmonary Embolism by Saline Contrast–enhanced Electrical Impedance Tomography: Considerations for Future Research

“…More and more evidence had shown contrast based-EIT method has the potential to quantitatively assess regional lung perfusion at various pathophysiologic conditions (such as PE, lung collapse, ARDS, response to PEEP change etc.) (1)(2)(3)(4)(5)(6). Further study is required to validate the impact of the described saline-based EIT method on decision making, therapeutic management and outcomes in critically ill patients.…”

High Pleural Pressure Prevents Alveolar Overdistension and Hemodynamic Collapse in Acute Respiratory Distress Syndrome with Class III Obesity. A Clinical Trial

“…Although ARDS is primarily a pulmonary disease, patients with ARDS develop multiorgan failure as a consequence of hemodynamic impairment (6)(7)(8). Recent clinical trials and animal studies showed that inappropriately set mechanical ventilation in ARDS leads to pulmonary edema, heart failure and cardiac arrest (9)(10)(11).…”

Real-Time Detection of Hemothorax and Monitoring its Progression in a Piglet Model by Electrical Impedance Tomography: A Feasibility Study

“…Compared with X-ray, ultrasonography, and CT, EIT has the advantages of small size, low cost, noninvasiveness, no radiation, and high temporal resolution, which make it a promising imaging technique in many biomedical applications, especially in real-time monitoring [23]. Up to the present, EIT has been widely studied on the application of monitoring lung ventilation and perfusion [24][25][26][27]. In addition, due to the significant difference in electrical impedance property between the blood and other human tissues [28,29], EIT has a great potential in long-term and continuous detection of occurrence and progression of internal hemorrhage in human organs, including hemothorax.…”