Ambulatory infusion devices and associated methods
View Patent ↗A method of operating an infusion device that includes the steps of actuating a fluid transfer device, which is configured to deliver a predetermined volume during each actuation, in accordance with a delivery profile that includes a plurality of fluid transfer device actuations, determining, based on sensed pressure, whether an actual volume delivered during a fluid transfer device actuation is the predetermined volume, and adjusting the number of actuations in the delivery profile in response to the actual volume delivered differing from the predetermined volume.
1. A method of operating an infusion device, comprising the steps of:
actuating a fluid transfer device, which is configured to deliver a predetermined volume during each actuation, in accordance with a delivery profile that includes a plurality of fluid transfer device actuations;
determining whether an actual volume delivered during a fluid transfer device actuation is the predetermined volume by sensing pressure, at a single location with a single pressure sensor that is located upstream of a flow restrictor and that has a compliant diaphragm, a compliance value and a sensor apparatus located in spaced relation to the compliant diaphragm, and determining the magnitude of the of a pressure spike associated with the fluid transfer device actuation and multiplying the magnitude of the pressure spike by the compliance value; and
adjusting the number of actuations in the delivery profile in response to the actual volume delivered differing from the predetermined volume.
2. A method as claimed in claim 1 , wherein
the fluid transfer device includes an electromagnet pump; and
the actuation of the fluid transfer device includes a single pump stroke that creates a pressure spike.
3. A method as claimed in claim 1 , wherein
determining the magnitude of the pressure spike comprises sampling pressure sensed by the pressure sensor before and during the single pump stroke.
4. A method as claimed in claim 3 , wherein
determining the magnitude of the pressure spike comprises using a scaling factor to adjust for changes in head pressure.
5. A method as claimed in claim 1 , wherein
adjusting the number of actuations in the delivery profile comprises adding an actuation equivalent of an over-delivery volume to a feedback accumulator in response to the actual volume delivered being greater than the predetermined volume.
6. A method as claimed in claim 5 , wherein
adjusting the number of actuations in the delivery profile comprises subtracting an actuation equivalent of an under-delivery volume from the feedback accumulator in response to the actual volume delivered being less than the predetermined volume.
7. A method as claimed in claim 6 , wherein
actuating the fluid transfer device in accordance with the delivery profile includes storing the number of actuations in a delivery accumulator; and
adjusting the number of actuations in the delivery profile comprises adding the actuation equivalent in the feedback accumulator to the delivery accumulator.
8. A method as claimed in claim 7 , wherein
adding the actuation equivalent in the feedback accumulator to the delivery accumulator comprises adding a whole number actuation equivalent to the delivery accumulator.
9. A method as claimed in claim 7 , wherein
the fluid transfer device comprises a fixed displacement fluid transfer device.
10. A method as claimed in claim 1 , wherein
the compliant diaphragm defines a first compliant diaphragm; and
the sensor apparatus includes a second compliant diaphragm and a strain gauge.
11. A method as claimed in claim 10 , wherein
the compliance value is a function of the compliance of the first and second compliant diaphragms.
12. An ambulatory infusion device, comprising:
an outlet port;
a fluid transfer device configured to deliver a predetermined volume during each actuation thereof;
a fluid path that operably connects the fluid transfer device to the outlet port;
a pressure sensor associated with the fluid path;
a flow restrictor between the pressure sensor and the outlet port; and
means for actuating the fluid transfer device in accordance with a delivery profile that includes a plurality of fluid transfer device actuations, determining based on pressure sensed only upstream of the flow restrictor whether an actual volume delivered during a fluid transfer device actuation is the predetermined volume, and adjusting the number of actuations in the delivery profile in response to the actual volume delivered differing from the predetermined volume.
13. An ambulatory infusion device as claimed in claim 12 , wherein
the fluid transfer device includes an electromagnet pump that creates a pressure spike.
14. An ambulatory infusion device as claimed in claim 13 , wherein
the electromagnet pump comprises a fixed displacement electromagnet pump.
15. An ambulatory infusion device as claimed in claim 12 , wherein
the pressure sensor includes compliant diaphragm with a compliance value.
16. An ambulatory infusion device as claimed in claim 12 , wherein
adjusting the number of actuations in the delivery profile comprises adding an actuation equivalent of an over-delivery volume to a feedback accumulator in response to the actual volume delivered being greater than the predetermined volume.
17. An ambulatory infusion device as claimed in claim 16 , wherein
adjusting the number of actuations in the delivery profile comprises subtracting an actuation equivalent of an under-delivery volume from the feedback accumulator in response to the actual volume delivered being less than the predetermined volume.