Comparison of 5% sodium bicarbonate and 10% sodium chloride as contrast agents for lung perfusion with electrical impedance tomography: a prospective clinical study

Abstract

Introduction: This study aimed to compare sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) as contrast agents for regional lung perfusion imaging with electrical impedance tomography in critically ill patients with respiratory failure. Methods: 15 mL 5% NaHCO3 and 10 mL 10% NaCl were sequentially administered in all the enrolled patients with respiratory failure. EIT maps were divided into four cross-regions: upper right (UR), upper left (UL), lower right (LR), and lower left (LL). Result: A total of 20 pair bolus injections from 16 mechanically ventilated patients were obtained. Compared to NaHCO3, NaCl caused a larger drop of maximum impedance amplitude after the bolus injection (1276 ± 329 vs. 509 ± 159 AU, P < 0.001). Regional perfusion distribution (%) of four cross-regions between two indicators were significantly correlated (R2 = 0.90 for regional perfusion%, p < 0.001; R2 = 0.93 for regional ventilation/perfusion matching, p < 0.001) in 80 pair measurements. The Bland–Altman analysis showed a strong overall agreement in regional perfusion distribution (%) [mean bias 0.09% (95% confidence interval, CI: -0.91%, 1.09%), lower limits of agreement (LOA) -8.03% (95% CI: -9.75%, -6.31%), upper LOA 8.21% (95% CI: 6.48%, 9.93%)] between indicators in 80 pair measurements. Conclusion: EIT with NaHCO3 as a contrast agent yields a high agreement of regional lung perfusion compared to NaCl in critically ill patients with respiratory failure.