Vacuum-assisted venous drainage system with rigid housing and flexible reservoir

The present invention relates generally to reduced prime volume cardiopulmonary bypass systems and, more particularly, to vacuum-assisted venous drainage systems and methods. A vacuum-assisted venous drainage reservoir for cardiopulmonary bypass surgery with both hard and soft shell reservoirs. The system utilizes a wall vacuum or other source of negative pressure to create a negative pressure via a regulator within a sealed hard shell reservoir, or within a sealed housing surrounding a soft shell reservoir. The addition of a negative pressure in the venous return line enables the use of smaller cannulas suitable for minimally invasive surgery. The reservoir need not be positioned well below the patient as in conventional gravity venous drainage configurations, thus adding flexibility to the operating room layout and enabling a reduction in the extracorporeal blood prime volume needed. In one embodiment, a flexible membrane in the hard shell reservoir expands to contact the blood surface and reduce blood/air interactions. In another embodiment, a moisture trap is provided between the source of vacuum and hard shell reservoir to reduce environmental contamination. A volume sensor for the hard shell reservoir may be used in a feedback loop for controlling the vacuum, circulation pump, or other device. A pressure relief valve may be included in both systems for safety, and a vacuum stabilizer reduces the severity of large changes in vacuum pressure. A piece of air-permeable material may form a portion of the soft shell reservoir to vent air from within.