Anti-thrombogenic blood pump

An anti-thrombogenic centrifugal blood pump, comprising:

• (a) a housing including an impeller chamber;
• (b) driving means disposed in said housing outside said impeller chamber;
• (c) impeller means disposed in said impeller chamber, for centrifugally pumping blood through said impeller chamber;
• (d) shaft means associated with said motor means and impeller means for driving said impeller means;
• (e) said shaft means being rotatably supported in said housing by hydrodynamic journal bearing means operating in a blood-compatible bearing fluid;
• (f) said shaft means and housing forming an interface at said impeller chamber;
• and
• (g) purge seal means including:
• (i) a source of blood-compatible purge fluid;
• (ii) a continuous passageway formed by said shaft means and said housing between said purge fluid source and said interface, said passageway having a close-clearance, substantially uniform cross section over its entire length from said purge fluid source to said interface;
• and
• (iii) means for causing said purge fluid to flow continuously and substantially uniformly through said passageway and into said blood stream at said interface;
• (h) whereby said flow substantially prevents the accumulation of blood elements at said interface.

An anti-thrombogenic axial blood pump, comprising:

• (a) stator means defining an elongated housing;
• (b) rotor means mounted for axial rotation within said housing to convey a blood stream axially of said housing, said rotor means and stator means defining between them an interface in contact with said blood stream;
• (c) bearing means for rotatably supporting said rotor means on said stator means;
• and
• (d) purge seal means interposed between said bearing means and said blood stream at said interface for producing an outflow of purge fluid into said blood stream at said interface sufficient to prevent penetration of blood elements into said interface;
• (e) said purge seal means including:
• (i) a source of blood-compatible purge fluid;
• (ii) a continuous passageway formed between said rotor means and stator means between said purge fluid source and said interface, said passageway having a substantially uniform, close-clearance cross section over its entire length from said purge fluid source to said interface, and forming a hydrodynamic bearing;
• and
• (iii) means for causing said purge fluid to flow continuously through said passageway and into said blood stream at said interface;
• (f) whereby by said flow substantially prevents the accumulation of blood elements at said interface while providing the bearing fluid for said hydrodynamic bearing.

The method of preventing the accumulation of blood elements in a blood pump having a rotor means and stator means cooperating to convey a blood stream through said pump, an interface between said rotor means and stator means being exposed to said blood stream;

• and
• purge seal means including;
• (i) a source of blood-compatible purge fluid;
• (ii) a continuous passageway formed between said rotor means and stator means between said purge fluid source and said interface, said passageway having a close-clearance, substantially uniform cross section over its entire length from said purge fluid source to said interface;
• and
• (iii) means for causing said purge fluid to flow continuously and substantially uniformly through said passageway and into said blood stream at said interface, comprising the steps of
• (a) so shaping the rotary and stationary parts of said pump that together they form a continuous surface across the interface between them at which said rotating and stationary parts are in contact with the blood being pumped;
• and
• (b) causing a blood-compatible fluid to continuously flow into the pumped blood at all points of said interface;
• (c) whereby said flow substantially prevents the accumulation of blood elements at said interface and prevents entry of blood elements into said interface.