In situ tubing measurements for infusion pumps
View Patent ↗An infusion pump uses sensors and a computer program to detect tubing in a tube-loading section of the pump. The pump and the computer program also measures one or more of the tubing outer diameter, outer circumference, inner diameter, inner circumference, and tubing wall thickness. The infusion pump utilizes proximity sensors, such as an ultrasonic sensor, a capacitive sensor, or even an air-in-line sensor to detect proximity between two infusion pump surfaces, such as the surfaces that clamp the tubing in the pump, to determine thickness. At least one of the clamping surfaces is equipped with sensors to indicate contact length of the tubing with the surface. Using these measurements, the tubing wall thickness and inner diameter can be determined. Knowing the actual tubing inner diameter, increased volumetric accuracy is possible, up to a three or four percent improvement over present measurements.
1. A method of measuring tubing, the method comprising:
loading tubing into a fixture;
compressing the tubing between opposed surfaces of the fixture;
receiving a signal indicative of compression of the tubing while compressing;
receiving a signal indicative of a contact length of the tubing against at least one of the opposed surfaces; and
calculating a diameter and a thickness of the tubing.
2. The method of claim 1 , further comprising monitoring the signal indicative of compression of the tubing or the signal indicative of the contact length.
3. The method of claim 1 , wherein the signal indicative of compression of the tubing is indicative of a distance between the opposed surfaces of the fixture.
4. The method of claim 1 , wherein the signal indicative of compression of the tubing is generated by an LVDT, an ultrasonic sensor, an air-in-line sensor, or a capacitive sensor.
5. The method of claim 1 , wherein the signal indicative of a contact length is generated by a sensor, a pressure sensor, a sensor array, a switch array, or a capacitive sensor.
6. The method of claim 1 , wherein the opposed surfaces are part of an infusion pump.
7. The method of claim 1 , wherein the step of calculating calculates a diameter of the tubing using two half-circles and a contact length of tubing with the opposed surfaces.
8. A method for measuring a diameter and a thickness of tubing, the method comprising:
loading tubing into a fixture;
compressing the tubing between opposed surfaces of the fixture;
generating and receiving a signal indicative of a distance between the opposed surfaces while compressing;
generating and receiving a signal indicative of a contact length of the tubing against at least one of the opposed surfaces; and
calculating an inner diameter and a thickness of the tubing.
9. The method of claim 8 , wherein the signal indicative of the distance is generated by an air-in-line sensor.
10. The method of claim 8 , wherein the signal indicative of the contact length is generated by at least one sensor array.
11. The method of claim 8 , further comprising calculating a volume of liquid infusate using the calculated inner diameter.
12. An infusion pump, comprising:
a tubing clamping section comprising a movable portion and a stationary portion;
a first sensor mounted on one of the movable portion or the stationary portion for detecting a distance between the movable portion and the stationary portion;
at least one second sensor for detecting a contact length of tubing with at least one of the movable portion and the stationary portion;
an inlet valve;
an outlet valve; and
a shuttle comprising a shuttle stationary portion and a shuttle moveable portion configured for squeezing a length of tubing between the shuttle stationary portion and the shuttle movable portion, wherein the shuttle moveable portion moves toward and away from the shuttle stationary portion to operate the infusion pump.
13. The infusion pump according to claim 12 , wherein the first sensor comprises an LVDT, an ultrasonic sensor, an air-in-line sensor, or a capacitive sensor.
14. The infusion pump according to claim 12 , wherein the second sensor comprises a sensor, a pressure sensor, a sensor array, a switch array, or a capacitive sensor.
15. The infusion pump according to claim 12 , further comprising a target mounted on the other of the moving portion and the stationary portion.
16. An infusion pump, comprising:
a housing;
a tubing clamping section comprising a movable portion and a stationary portion, the tubing clamping section mounted on the housing;
a first sensor mounted on one of the movable portion or the stationary portion for detecting a distance between the movable portion and the stationary portion;
at least one second sensor for detecting a contact length of tubing with at least one of the movable portion and the stationary portion; and
a positive displacement pump for manipulating the tubing to accurately deliver a medicament.
17. The infusion pump according to claim 16 , wherein the positive displacement pump is a shuttle pump or a peristaltic pump.
18. The infusion pump according to claim 16 , wherein the first sensor is an air-in-line sensor or a proximity sensor.
19. The infusion pump according to claim 16 , wherein the at least one second sensor comprises two spaced-apart sensors or microswitches.
20. The infusion pump according to claim 16 , further comprising a computer program on a computer-readable disc for calculating a length and a diameter of the tubing.