Ambulatory infusion devices and methods with blockage detection
View Patent ↗Infusion devices with blockage detection capability and methods of monitoring infusion devices.
1. A method of operating an infusion device including a fluid transfer device and a catheter, the method comprising the steps of:
transferring fluid to the catheter with the fluid transfer device a plurality of times during a measurement window;
sensing catheter pressure a plurality of times during the measurement window;
storing a plurality of sensed pressures in a queue in the order that the pressures were sensed;
computing the pressure differences between time adjacent pairs of sensed pressures; and
determining whether an increase in sensed pressure during the measurement window corresponds to an increase in sensed pressure that would result from a catheter blockage.
2. A method as claimed in claim 1 , wherein the sensing step comprises sensing catheter pressure immediately after a transfer by the fluid transfer device.
3. A method as claimed in claim 1 , wherein the determining step comprises:
determining whether each of the pressure differences is within a predetermined range; and
determining whether the sum of the pressure differences is greater than a predetermined sum threshold.
4. A method as claimed in claim 3 , wherein the predetermined range is between the largest decrease that would be associated with the weather and a value that is slightly larger than the pressure increase that would result from a blockage.
5. A method as claimed in claim 1 , wherein the measurement window is a first-in first-out measurement window, the method further comprising the step of:
deleting the oldest sensed pressure from the queue after the queue becomes full.
6. A method of operating an infusion device including a fluid transfer device and a catheter, the method comprising the steps of:
transferring fluid to the catheter with the fluid transfer device a plurality of times during a measurement window of a plurality of hours;
sensing catheter pressure a plurality of times during the measurement window;
storing a plurality of sensed pressures in a queue in the order that the pressures were sensed;
computing the pressure differences between time adjacent pairs of sensed pressures; and
determining whether there are consistent blockage-based additions to catheter pressure during the measurement window that correspond to a catheter blockage.
7. A method of operating an infusion device including a fluid transfer device and an outlet, the method comprising the step of:
signaling that a blockage has been detected in response to consistent blockage-based additions to outlet pressure that are within a predetermined range and persist over a plurality of hours.
8. A method as claimed in claim 7 , wherein the predetermined range is between the largest decrease that would be associated with the weather and a value that is slightly larger than the pressure increase that would result from a blockage.
9. A method as claimed in claim 7 , wherein the predetermined range is between the largest decrease that would be associated with the weather and a value that is 10% to 20% greater than the pressure increase that would result from a blockage.
10. An infusion device for use with a catheter, comprising:
an outlet port configured to be secured to the catheter;
a fluid transfer device operably connected to the outlet port;
a pressure sensor located between the fluid transfer device and the outlet port; and
a controller that differentiates between increases in sensed pressure that are the result of changes in environmental pressure and increases in sensed pressure that are the result of a catheter blockage by calculating a plurality of individual pressure differences, calculating the sum of the plurality of individual pressure differences only if each of the pressure differences is within a predetermined range, and comparing the sum to a predetermined sum threshold.
11. An infusion device as claimed in claim 10 , wherein the fluid transfer device comprises an electromagnet pump.
12. An infusion device as claimed in claim 10 , wherein
the controller is configured to determine whether a plurality of pressures sensed periodically throughout a predetermined measurement window correspond to consistent blockage-based additions to pressure.
13. An infusion device for use with a catheter, comprising:
an outlet port configured to be secured to the catheter;
a fluid transfer device operably connected to the outlet port;
a pressure sensor located between the fluid transfer device and the outlet port; and
a controller configured to
store a plurality of sensed pressures in a queue,
compute the pressure differences between time adjacent pairs of sensed pressures in the queue,
determine whether each of the pressure differences is within a predetermined range, and
determine whether the sum of the pressure differences is greater than a predetermined sum threshold.
14. An infusion device as claimed in claim 13 , wherein the predetermined range is between the largest decrease that would be associated with the weather and a value that is slightly larger than the pressure increase that would result from a blockage.
15. An infusion device as claimed in claim 13 , wherein the predetermined range is between the largest decrease that would be associated with the weather and a value that is 10% to 20% greater than the pressure increase that would result from a blockage.
16. An infusion device as claimed in claim 13 , wherein the controller is further configured to
delete the oldest sensed pressure from the queue after the queue is full.
17. An infusion device for use with a catheter, comprising:
an outlet port configured to be secured to the catheter;
a fluid transfer device operably connected to the outlet port;
a pressure sensor located between the fluid transfer device and the outlet port; and
means for storing a plurality of pressures sensed during a measurement window; and
means for calculating a plurality of individual pressure differences between pairs of sensed pressures, calculating the sum of the plurality of individual pressure differences only if each of the pressure differences is within a predetermined range, and comparing the sum to a predetermined sum threshold to determine whether an increase in sensed pressure during the measurement window corresponds to an increase in sensed pressure that would result from a catheter blockage.
18. An infusion device as claimed in claim 17 , wherein the fluid transfer device comprises an electromagnet pump.
19. A method as claimed in claim 7 , wherein
the fluid transfer device comprises a pump; and
the consistent blockage-based additions to outlet pressure that are within a predetermined range comprises blockage-based additions to outlet pressure within the predetermined range that occur after each pump stroke.
20. An infusion device as claimed in claim 10 , wherein the changes in environmental pressure comprise changes in altitude.
21. An infusion device as claimed in claim 10 , wherein the changes in environmental pressure comprise changes in weather.
22. A method as claimed in claim 6 , wherein the sensing step comprises sensing catheter pressure immediately after a transfer by the fluid transfer device.
23. A method as claimed in claim 6 , wherein the measurement window is a first-in first-out measurement window, the method further comprising the step of:
deleting the oldest sensed pressure from the queue after the queue becomes full.