Gelsomino 1 Assessment of a Continuous Blood Gas Monitoring System in Animals during Circulatory stress. Short Title: Continuous Blood Gas Monitoring

Introduction: The study was aimed to determine the measurement accuracy of The CDI TM blood parameter monitoring system 500 (Terumo Cardiovascular Systems Corporation, Ann Arbor MI) in the real-time continuous measurement of arterial blood gases under different cardiocirculatory stress conditions Methods: Inotropic stimulation (Dobutamine 2.5 and 5 μg/kg/min), vasoconstriction (Argininevasopressin 4, 8 and 16 IU/h), hemorrhage (–10%, –20%, –35%, and –50% of the theoretical volemia), and volume resuscitation were induced in ten swine (57.4 ± 10.7Kg). Intermittent blood gas assessments were carried out using a routine gas analyzer at any experimental phase and compared with values obtained at the same time settings during continuous monitoring with CDI TM 500 system. The Bland-Altman analysis was employed. Results: Bias and precision for pO2 were − 0.06 kPa and 0.22 kPa, respectively (r 2 = 0.96); pCO2 − 0.02 kPa and 0.15 kPa, respectively; pH -0.001 and 0.01 units, respectively ( r 2 =0.96). The analysis showed very good agreement for SO2 (bias 0.04,precision 0.33, r 2 =0.95), Base excess (bias 0.04,precision 0.28, r 2 =0.98), HCO3 (bias 0.05,precision 0.62, r 2 =0.92),hemoglobin (bias 0.02,precision 0.23, r 2 =0.96) and K + (bias 0.02, precision 0.27, r 2 =0.93). The sensor was reliable throughout the experiment during hemodynamic variations. Conclusions: Continuous blood gas analysis with the CDI TM 500 system was reliable and it might represent a new useful tool to accurately and timely monitor gas exchange in critically ill patients. Nonetheless, our findings need to be confirmed by larger studies to prove its reliability in the clinical setting.