Autopriming a micro-cassette while minimizing the formation of air bubbles in a pumping chamber

A method for priming a disposable cassette used for infusing a liquid into a patient so as to prevent a migration of air bubbles from an air trap into a pumping chamber of the disposable cassette, comprising the steps of:

• (a) introducing sufficient liquid into said air trap of said disposable cassette such that a layer of the liquid is deposited within the air trap, separating said pumping chamber from an interior volume of said air trap;
• (b) then introducing more liquid into the disposable cassette and pumping said more liquid from the disposable cassette in a proximal direction back toward a source of the liquid until no air is detected by a proximal air sensor within said disposable cassette;
• and
• (c) then introducing additional liquid into the disposable cassette, and pumping said additional liquid through the cassette in a distal direction until a desired volume of the additional liquid is distally delivered.

A method of priming a cassette used in an infusion pump system for infusing a liquid into a patient, which substantially prevents an accumulation of air bubbles within a pumping chamber of the cassette, comprising the steps of:

• (a) providing a cassette having a housing that defines a liquid path between an inlet port adapted to couple in fluid communication with a source, and an outlet port adapted to couple in fluid communication with an infusion site on the patient, said cassette also including an inlet air sensor that produces a signal indicative of a presence of air proximate the inlet port, said liquid path within the cassette including:
• (i) a pumping chamber covered by an elastomeric membrane that when forced into the pumping chamber by a driven member displaces the liquid from the pumping chamber through one of said inlet port and said outlet port;
• and
• (ii) an air trap disposed between said inlet air sensor and said pumping chamber;
• (b) introducing sufficient liquid into said air trap of said cassette such that a layer of liquid disposed within the air trap separates said pumping chamber from an interior volume of said air trap;
• said layer of liquid acting as a one-way valve that allows air from said pumping chamber to pass into said air trap, while preventing air from said air trap from passing into said pumping chamber;
• (c) back priming the cassette to remove air from a proximal volume of the infusion pump system;
• and
• (d) forward priming the cassette to remove air from said pumping chamber and a distal volume of the infusion pump system.

A pump system that substantially prevents air bubbles from being trapped within a pumping chamber during priming of the pump system, said pump system being employed to infuse a liquid flowing from a source into an infusion site at a patient, comprising:

• (a) a cassette having a housing that defines a liquid path from an inlet port that is adapted to couple in fluid communication with the source, to an outlet port that is adapted to couple in fluid communication with the infusion site, said liquid path being disposed within the cassette and including:
• (i) a pumping chamber covered by an elastomeric membrane that when forced into the pumping chamber, displaces liquid from the pumping chamber through one of said inlet port and said outlet port;
• (ii) an inlet air sensor that produces a signal indicative of a presence of air proximate said inlet port;
• and
• (iii) an air trap disposed between said inlet air sensor and said pumping chamber;
• (b) a proximal liquid line that provides fluid communication between said source and said inlet port;
• (c) a distal liquid line, a first end of said distal liquid line being in fluid communication with said outlet port, and a second end of said distal liquid line being adapted to couple to said infusion site;
• (d) a drive unit adapted to couple with said cassette and including at least one prime mover and a plunger, said at least one prime mover moving the plunger relative to the pumping chamber to deform the elastomeric membrane, a deformation of the elastomeric membrane into the pumping chamber displacing liquid from the pumping chamber toward one of said inlet port and said outlet port;
• and
• (e) a control unit, coupled to receive the signals from said air sensor, and coupled to the drive unit to control said at least one prime mover and thereby controlling movement of the plunger, said control unit including a processor coupled to a memory in which machine instructions are stored, said machine instructions, when executed by the processor, causing the processor to establish a layer of liquid within said air trap to separate an interior volume of said air trap from said pumping chamber before priming the cassette, thereby preventing air bubbles from said air trap from entering into said pumping chamber.

A pump system for substantially preventing air bubbles from being trapped in a pumping chamber during priming of said pump system, said pump system being employed for producing a liquid flow through an intravenous line, comprising:

• (a) a pump chassis;
• (b) a pump in fluid communication with the intravenous line and mountable within the pump chassis to receive a driving force from a driven member that is included in the pump chassis, said pump including:
• (i) an inlet port;
• (ii) an outlet port;
• and
• (iii) a liquid path that includes the pumping chamber and extends between the inlet port and outlet port, said driven member displacing the liquid from said pumping chamber and into one of said inlet port and outlet port;
• (c) an air sensor disposed proximate said inlet port, said air sensor producing a signal indicative of a presence of air;
• (d) an air trap disposed in said liquid path between said pumping chamber and said inlet port;
• and
• (e) a controller disposed within the pump chassis and electrically coupled to said air sensor to receive signals therefrom during a pump cycle, said controller operating the pump before initiating a priming sequence to produce a layer of liquid within said air trap, said layer of liquid separating said air trap from said pumping chamber and preventing air from moving from said air trap to said pumping chamber, but allowing air from said pumping chamber to move into said air trap.

An autopriming pump system that substantially prevents air bubbles from being trapped within a pumping chamber when the pump system is autoprimed, comprising:

• (a) a pump unit having an outlet at a distal end and an inlet at a proximal end, a liquid path connecting said distal end to said proximal end, said liquid path including
• (i) said pumping chamber, liquid driven from said pumping chamber by the pump being selectively driven in one of a proximal direction and a distal direction;
• (ii) an air sensor disposed proximate said proximal end, said air sensor producing a signal indicative of a presence of air proximate said proximal end;
• and
• (iii) an air trap disposed between said air sensor and said pumping chamber;
• (b) a liquid supply in fluid communication through a proximal liquid with the inlet at said proximal end of said pump unit, said proximal liquid line defining a proximal volume that is less than a volume of liquid expelled from the pumping chamber in said pump unit during a single pump cycle;
• (c) a drive unit drivingly connected to said pump unit to provide a force that drives liquid from the pumping chamber during a pump cycle;
• and
• (d) a control unit electrically coupled to said drive unit and said air sensor, said control unit controlling a flow of liquid through said pump system, said control unit including a processor coupled to a memory in which machine instructions are stored, said machine instructions being executed by the processor and causing the processor to:
• (i) control said flow of liquid that is pumped by the pump unit to establish a layer of liquid within said air trap, said layer of liquid separating an interior volume of said air trap from said pumping chamber, thereby substantially preventing air bubbles from said air trap from entering said pumping chamber;
• (ii) control said flow of liquid that is pumped by said pump unit to back prime said pumping system, until air is removed from said proximal liquid line, and
• (iii) control said flow of liquid that is pumped by said pump unit to forward prime said pumping system, until air is removed from said pumping chamber and a portion of said liquid path between said pumping chamber and said distal end of said pump unit.