Infusion pump system with disposable cartridge having pressure venting and pressure feedback

1. A method of venting a cartridge of an infusion pump system, comprising:

providing an infusion pump system including:

a disposable fluid reservoir cartridge including:

a delivery mechanism including:

a delivery mechanism body,

a bore disposed in the delivery mechanism body including a distal end, a proximal end disposed towards a drive mechanism of the infusion pump, an interior volume, a reservoir inlet port, a fluid dispense port, a vent inlet port and a vent outlet port;

a spool slidingly disposed within the bore including:

a collapsible first volume which is positionable to overlap the reservoir inlet port independent of an overlap of the fluid dispense port and which is formed between a first seal around the spool, a second seal around the spool, an outer surface of a spool body between the first and second seals and an interior surface of the bore between the first and second seals, the first and second seals being axially moveable relative to each other, and

a vent second volume which is positionable to overlap the vent inlet port and vent outlet port simultaneously and which is formed by a third seal around the spool, a fourth seal around the spool, an outside surface of the spool between the third and fourth seals and an inside surface of the bore between the third and fourth seals;

a collapsible fluid reservoir bounded by a flexible membrane and including an interior volume in fluid communication with the reservoir inlet port,

a substantially rigid shell disposed about the collapsible fluid reservoir with an interior volume that contains the collapsible fluid reservoir and a vented volume disposed between an outer surface of the flexible membrane and an interior surface of the rigid shell, the vent inlet port being in fluid communication with the vented volume; and

a drive mechanism operatively coupled to the spool of the delivery mechanism;

initiating a dispense cycle by driving the spool with the drive mechanism to a position with the collapsible first volume in communication with the reservoir inlet port;

driving the spool so as to separate the first and second seals of the collapsible first volume and draw fluid into the first volume through the reservoir inlet port from the reservoir and decrease a pressure within the vented volume;

driving the spool with the drive mechanism to a position with the collapsible first volume in communication with the fluid dispense port;

driving the spool so as to at least partially collapse the collapsible first volume and dispense fluid from the collapsible first volume through the fluid dispense port; and

driving the spool to a position with the vent second volume in simultaneous communication with the inlet vent port and vent inlet port to allow the vented volume to arrive at the same pressure as the vent outlet port.

2. The method of claim 1 wherein the vented volume is vented about every 2 dispense cycles to about every 10 dispense cycles.

3. The method of claim 2 wherein the vented volume is vented about every 3 dispense cycles to about every 7 dispense cycles.

4. The method of claim 1 wherein the vent outlet port is at ambient atmospheric pressure and the vented volume is brought to ambient atmospheric pressure during every venting cycle.

5. The method of claim 1 wherein the pressure of the vented volume is measured before and after a dispense cycle and the volume dispensed is determined from a change in pressure. within the vented volume.

6. The method of claim 1 wherein the vented volume is vented upon a threshold pressure difference between the vented volume and an ambient pressure being detected.

7. The method of claim 6 wherein the threshold pressure difference comprises a gauge pressure of up to about 0.1 psi.