The Application of Thoracic Impedance-Based End-Tidal Carbon Dioxide Estimate in Cardiopulmonary Resuscitation: A Rat Study

Thoracic impedance (TI) correlates with end-tidal carbon dioxide (ETCO2) in large animals. This pilot study in Sprague-Dawley rats investigated whether TI can estimate ETCO2 and dynamically guide compression depth. A dataset of TI and ETCO2 measurements in rats was established to analyze the correlation between the two and construct a regression model. TI peak was strongly and positively correlated with ETCO2 (r = 0.78, p < 0.001) and exhibited a progressive decay during prolonged compression. This pilot study demonstrated the feasibility of using TI-estimated ETCO2 to guide compression depth in a rat model. The TI-guided strategy maintained ETCO2 closer to the target value of 20 mmHg; however, no significant differences were observed between groups in ROSC rates, survival rates, blood gas parameters, or histopathological damage. Larger-scale studies are needed to evaluate clinical efficacy.