Method for delivering a therapeutic substance
Apparatus is provided including a therapeutic substance reservoir ( 24 ) configured to hold a therapeutic substance ( 22 ), and an electromechanical pumping assembly ( 26 ). The pumping assembly is shaped to define a pump chamber ( 28 ) having (a) a therapeutic substance inlet ( 30 ), and (b) a therapeutic substance outlet ( 32 ). The pumping assembly includes a plunger ( 34 ) disposed such that therapeutic substance in the pump chamber is in direct contact with the plunger, and control circuitry ( 36 ) configured to drive the plunger to (a) draw the therapeutic substance into the pump chamber during a first pumping phase, and (b) deliver the therapeutic substance from the pump chamber in a plurality of discrete motions of the plunger during a second pumping phase.
1. A method of delivering a therapeutic substance to a subject, the method comprising:
using a plunger to draw the therapeutic substance from a therapeutic substance reservoir into a pump chamber of an electromechanical pumping assembly during a first pumping phase,
the plunger being disposed such that therapeutic substance in the pump chamber is in direct contact with the plunger, and
the pump chamber being in fluid communication with the reservoir and not in fluid communication with the subject during the first pumping phase; and
subsequently, delivering the therapeutic substance from the pump chamber to the subject in a plurality of discrete dosages by delivering the therapeutic substance from the pump chamber in a plurality of discrete motions of the plunger during a second pumping phase, the pump chamber being in fluid communication with the subject and not in fluid communication with the reservoir during the second pumping phase,
the method further comprising reducing an amplitude of negative pressure in the pump chamber during a negative-pressure reduction phase between the first pumping phase and the second pumping phase, by maintaining the pump chamber in fluid communication with the reservoir and not in fluid communication with the subject following the drawing of the therapeutic substance into the pump chamber,
wherein maintaining the pump chamber in fluid communication with the reservoir and not in fluid communication with the subject comprises, following the drawing of the therapeutic substance into the pump chamber, using control circuitry to:
(a) maintain open an inlet valve, the inlet valve disposed in a therapeutic substance inlet of the pump chamber through which the therapeutic substance is received from the reservoir into the pump chamber during the first pumping phase, and
(b) maintain closed an outlet valve, the outlet valve disposed in a therapeutic substance outlet of the pump chamber through which the therapeutic substance is delivered from the pump chamber to the subject during the second pumping phase.
2. The method according to claim 1 , wherein:
(a) using the plunger to draw the therapeutic substance from the therapeutic substance reservoir into the pump chamber comprises (i) opening the inlet valve, and (ii) closing the outlet valve, and
(b) delivering the therapeutic substance from the pump chamber to the subject comprises closing the inlet valve and opening the outlet valve.
3. The method according to claim 1 , wherein using the plunger to draw the therapeutic substance from the therapeutic substance reservoir into the pump chamber comprises using the plunger to draw the therapeutic substance from the therapeutic substance reservoir into the pump chamber in a single motion of the plunger.
4. The method according to claim 1 , wherein using the plunger to draw the therapeutic substance from the therapeutic substance reservoir into the pump chamber comprises using the plunger to draw the therapeutic substance from the therapeutic substance reservoir into the pump chamber in one or more discrete expansion motions of the plunger, wherein each expansion motion is longer in duration than any one of the plurality of discrete motions of the plunger during the second pumping phase.