Abstract
Gaseous microemboli remain a concern during cardiac surgery under a cardiopulmonary bypass(CPB). We therefore measured basic changes in microbubbles within a CPB circuit to experimentally determine the performance of the bubble trap. Difficulties with controlling air bubble size were overcome by designing a novel bubble generator that produces bubble groups of arbitrary sizes. We then measured changes in the size of the bubbles in a tube(inside diameter, 9.5mm; length, 165cm). The generator produces bubbles of hydrogen and oxygen by electrolyzing a liquid that flows through the CPB circuit. We examined the difference between normal air bubbles(AB)and bubbles generated by electrolysis(EB). We then assessed changes in the size of the air bubbles produced by EB, and investigated the internal circuit pressure and temperature. The size of both EB and AB decreased in the tube and they behaved in a similar manner. The decrease in size correlated with the initial size of the air bubble and the reduction rate was faster for larger bubbles. Whereas temperature(25-38°C)minimally affected the bubble reduction rate, internal circuit pressure significantly affected the diameter of the air bubbles. We concluded that the experimental design was appropriate for evaluating changes in the bubble diameter. To design a bubble trap for the CPB circuit, parameters such as pressure, timing(blood path length)of the bubbles, and the circuit itself need to be considered. In addition, the bubbles produced by electrolysis were useful to assess the performance of the bubble trap.
