OBJECTIVE: Carbon dioxide field flooding during open-heart surgery is intended to avoid blood-air contact, bubble formation, and embolism, and therefore potential neurologic and other ischemic complications. The inert gas is invisible, and thus its use and effectiveness are heavily debated. We intended to provide better insight in the behavior of the gas via direct concentration measurements and visualization of the gas cloud.
METHODS: A transparent rectangular model of the open thorax was created, foreseen with carbon dioxide concentration sensors in 2 locations (atrial and aortic incisions), and placed in an optical test bench that amplifies the diffraction gradients. Six different commonly used carbon dioxide diffusors (3 commercial, 3 improvised) were tested with different flow rates of gas delivery (1, 4, 7, 10 standard liter per minute [SLPM]) and combined with the application of suction.
RESULTS: The imaging reveals that commercially available diffusors generally create less turbulent flow than improvised diffusors, which is supported by the concentration measurements where improvised diffusors cannot generate a 100% carbon dioxide atmosphere at the aorta incision location. The atrial incision is easier to protect: 0% air with all commercial devices for all flow rates greater than 1 SLPM. A flow rate of 1 SLPM does not create an inert atmosphere with any device.
CONCLUSIONS: The optically observed carbon dioxide atmosphere is unstable and influenced by many factors. The device used for diffusion and the flow rate are important determinants of the maximum gas concentration that can be achieved, as is the location where this is measured.