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.