P53: Dynamics of Intracardiac Carbon Dioxide Concentration During Insufflation

Abstract

Background: Insufflation of Carbon Dioxide (Co2) during cardiac surgery is a common practice during open chamber cardiac surgery. Co2 fills the pericardial space, displaces the air and due to its high solubility in blood and tissues the risk of air embolism is significantly reduced. Previous studies have measured the Co2 or oxygen (O2) in the surgical field only. In this study concentration of Co2 and O2 inside the heart and in the field were measured in different insufflation scenarios. Methods: A phantom of the chest with a pericardial cavity and a heart model was constructed to simulate the adult heart surgery. To simulate an open chamber heart procedure, the aorta of the model was tunneled towards left ventricle chamber to achieve open communication. Co2 and O2 concentration were measured in the left ventricle by sensors implanted in the left ventricle chamber and then in the field during the study. Results: In the standard Co2 insufflation of 5 L/min in the lower midline corner of the pericardial well, the intracardiac Co2 reached to 40000 ppm (the upper range of the sensor) in 17 seconds and O2 reached to lowest level of 5.6% in 130 seconds. The Co2 and O2 concentrations were not different on lower insufflation of Co2 of 2 and 1 L/min. After discontinuation of Co2 insufflation, Co2 and O2 concentration were back to baseline in 3min. Placement of Co2 line in other locations of the pericardial well did not change the above parameters (Figure 1A). Despite the common belief, while using a strong suction in the field, intracardiac Co2 and O2 concertation did not change significantly, 40000 ppm and 7.5%, respectively. Co2 concentration measured at 10, 20 and 30cm above the surgical field were 2580, 1130 and 922 ppm, respectively and at the level of surgeon’s face was similar to that of ambient air (Figure 1B). Conclusion: This study provides information on intracardiac Co2 concentration in different Co2 insufflation settings. Lower than 5 L/min, different locations of Co2 cannula, and using suction does not affect the efficiency of Co2 insufflation. It takes up to 3 minutes for Co2 to be cleared from the heart chamber. The risk of breathing Co2 from insufflation of Co2 in the field is negligible.Figure 1. A: Co2 insufflation in the phantom of pericardial cavity, locations a-d: Indicate different positions of Co2 line placement: a= standard location, b-d: variations; star: Co2 and O2 sensors implanted in the heart chamber, connected to microprocessors; arrow: opening in the aorta, connecting to left ventricle. B: Co2 concentration changes and dissipation from the field up to the surgeon’s face level. ppm: parts per million Co2: Carbon dioxide, O2: Oxygen