[A volume-variable reservoir-pump for a manually operated cardiopulmonary bypass circuit for emergency]

We developed a manually operated portable cardiopulmonary bypass circuit for resuscitation. The circuit is composed of, in turn, a venous drainage catheter, one-way valve, self-inflating reservoir, one-way valve, artificial lung, and an arterial catheter. These components are interlocked with conducting tubes with quick connectors. The priming volume of the circuit is about 300 ml including the self-inflating reservoir of 120 ml in capacity. For a patient with small stature, stroke volume is easily controlled by changing manual compression of the reservoir, but dilution of circulating blood with the priming solution is inevitable. For a controllable reduction of the reservoir volume, we incorporated a thin-walled balloon, which is inflatable from the outside, into the room of the reservoir. If the balloon is inflated with some amount of liquid, the same volume of functional capacity of the reservoir is lost. Thus the reservoir volume is adjusted, the hemodilution with a priming solution is minimized, and an excessive stroke volume with an inadvertent compression of the reservoir-pump is prevented as well. This innovation will make our standard size bypass circuit applicable to almost all patients, except for a newborn or infant who requires a special size of bypass circuit, and improve the survival rate of cardiopulmonary resuscitation.