Patent ID: 8043277

Claim:
In a system for delivering a therapeutic substance at a flow rate to a patient, said system having a reservoir for holding said therapeutic substance operatively coupled to a delivery path of a known volume for delivering said therapeutic substance to said patient, a method of transitioning from delivery of a first therapeutic substance contained in said reservoir at a first flow rate to delivery of a second therapeutic substance at a second flow rate, comprising the steps of: introducing said second therapeutic substance to said reservoir; delivering first any remaining amount of said first therapeutic substance and then said second therapeutic substance at a known flow rate; calculating a bridge duration equal to said known volume divided by said known flow rate; and then controlling said flow rate following said introducing step: if said second flow rate is lower than said first flow rate, beginning delivery of at least one of said first therapeutic substance and said second therapeutic substance at said second flow rate at least as soon as said bridge duration is over; and if said second flow rate is higher than said first flow rate, beginning delivery of said at least one of said first therapeutic substance and said second therapeutic substance at said second flow rate at least as late as when said bridge duration is over.