JPH0796033A - Transfusion tube - Google Patents

Abstract

PURPOSE:To obviate the generation of a change in flow rate at the time of fatiguing of the transfusion tube of the transfusion pump for which a linear peristaltick system is adopted by determining the minor diameter of the ellipse when the tube is flattened to an elliptic shape and specifying the moving distance of fingers. CONSTITUTION:This transfusion pump is mounted with a body having a door and the transfusion tube in the wall part covered with the door. A part of the plural fingers 6 in a transfusion operation part 1 in the state of closing the door are successively pushed in the transfusion direction by rotation of many cams 4 disposed at a shaft 5, by which the medicined liquid in the transfusion tube is fed. The radius (a) of the minor diameter after the use of the transfusion tube having a radius (r) and thickness (m) for the prescribed period of time is determined in such a case. The moving distance of the fingers 6 is specified by the cams 4 in such a manner that the distance from the closing state of the transfusion tube to the position where the tube is opened to the max. extent is confined to <=(2a+2m).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infusion pump adopting a linear peristaltic system.

[0002]

2. Description of the Related Art FIG. 1 is a perspective view when a door of a general infusion pump is opened. 2 and 3 are diagrams for explaining the operating principle of the linear peristaltic system of a general infusion pump. FIG. 4 is a diagram for explaining the moving distance of the finger. FIG. 5 is a diagram for explaining the flatness of the infusion tube.

As shown in FIGS. 1 and 2, a general infusion pump has a main body having a door and an infusion tube 7 attached to a wall portion covered by the door, and a plurality of fingers 6 are provided with the door closed. The liquid transfusing section 1 is composed of a part of the liquid transfusing tube 7 is sequentially pressed against the door in the liquid transfusing direction to transport the drug solution in the liquid transfusing tube 7, which is generally called a linear peristaltic system. There is a groove 2 for mounting a tube 7 on a wall portion, and an infusion solution operating portion 1 composed of fingers 6, and a pressure plate that is opposed to the infusion solution operating portion 1 and is pressed against the fingers 6 by a spring 9 on a door portion. There are three.

Next, the operating principle of the linear peristaltic liquid delivery section will be described with reference to FIG. A cam 4 eccentric to the shaft 5 rotated by a motor is attached by 2 mm, and when the cam 4 rotates, the finger 6 reciprocates by 4 mm (see FIG. 4). The pressure plate 3 is pressed against the reference surface with a strong pressure by the spring 9, and when the cam 4 reaches the top dead center, the tube 7 is sandwiched between the fingers 6 and the pressure plate 3 and closed (the state shown by the solid line in FIG. 3). ). Then, when the cam 4 reaches the bottom dead center, the finger 6 moves to the tube 7
Is maximally released from the closed state (state shown by the broken line portion in FIG. 3).

In this example, eight fingers 6 are attached, and the cam 4 that operates as described above has the shaft 5
It is fixed by being deviated by 45 ° (360 ° / 8) from each other (eccentric angle: 45 °). By associating the fingers 6 with the cams 4 and rotating the shaft 5,
The fingers 6 of # 8 sequentially close the tube 7 and discharge the drug solution in the tube 7.

Although the liquid can be delivered as described above, when the liquid is infused for a long time, if the finger is pushed for a long time, the tube becomes fatigued, and the restoring force of the tube that tries to return to its original shape deteriorates. It gradually becomes flat, the circular tube becomes elliptical, and the liquid flow rate per unit time changes. Therefore, as a method for correcting the liquid transfer rate when a liquid has been infused for a long time, a method has been proposed in which a correction formula for the liquid transfer rate is derived as a function of the liquid transfer rate and the elapsed time, and the liquid transfer rate is changed at regular intervals. . (Described in Japanese Examined Patent Publication No. 4-74027).

[0007]

In the conventional infusion device,
Pushing the tube with fingers for a long time gradually flattens the tube (see Figure 5). If the moving distance of the finger (moving distance 2d of the cam in FIG. 4) is almost the same as or larger than the tube diameter before fatigue, the finger moves when the tube is fatigued and flattened, and the finger moves when the tube is opened. Does not contact the tube and the finger does not push the tube. In addition, the flatness of the tube changes the internal volume of the tube. Due to these causes, the liquid supply flow rate per unit time changes. Therefore, as a method for correcting the liquid transfer rate when a liquid has been infused for a long time, a method has been proposed in which a method for correcting the liquid transfer speed is derived as a function of the liquid transfer speed and the elapsed time, and the liquid transfer speed is corrected at regular intervals. However, this method does not consider the variation due to the tube, the degree of fatigue of each tube is different, and the flattening rate for the same stress is different, so the change rate of the inner volume of the tube is different and the tube variation is different. It becomes a flow rate error.

[0008]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems. According to the invention of claim 1, a main body having a door and a tube are installed on a wall portion covered by the door. , An infusion pump configured to transport a drug solution in an infusion tube by sequentially pressing a part of the infusion tube in the infusion direction by the infusion actuating section composed of a plurality of fingers in a state in which the door is closed. , Radius r, thickness m
The radius a of the short diameter after using the infusion tube for a predetermined time is obtained, and the distance from the position where the infusion tube is closed to the position where the infusion tube is maximally opened from the closed state (2
a + 2 m) or less.

[0009]

According to the present invention, the minor axis of the ellipse when the tube is flattened into an elliptical shape is obtained, and the moving distance of the fingers is set to (the minor axis of the ellipse × 2 + the thickness of the tube × 2) or less. After the tube is exhausted, the fingers always come into contact with the tube even when the tube is opened and always push the tube. Therefore, even after the tube is fatigued, the tube follows the movement of the fingers, and the flow rate change before and after the tube fatigue disappears. Further, if the finger movement distance is determined from the example in which the tube is flattened most among the tube variations, the flow rate change due to the tube variations also disappears.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The infusion pump device incorporating the present invention is not different from the conventional device, and its explanation is omitted.

A method of obtaining the distance from the position where the infusion tube is closed to the position where the infusion tube is fully opened from the closed state will be described below. When the tube is flattened, it resembles an ellipse in shape. In the present invention, the flattened shape is approximated to an ellipse, the minor axis and major axis of the ellipse are determined from the change in the internal volume of the tube, and the movement distance of the finger is calculated as (minor axis of ellipse × 2 + thickness of tube × 2). ) The following.

When the tube is flattened and becomes elliptical, the change in the inner volume of the tube is as follows: the radius of the original circular tube is r, the minor radius is a when elliptical, and the major radius is b.
Then, the outer circumference of the ellipse becomes π (a + b) (1 + ((a-b) / (a + b)) / 4 + ...) ... Equation 1 and (a-b) / (a + b) ... Equation 2 Since the absolute value of Equation 2 is smaller than 1, the outer circumference of the original tube is 2πr ... Equation 4 when the outer circumference is approximated by π (a + b). Therefore, a + b = 2r can be approximated by Equation 5. The area of the ellipse is πab (6), and when the infusion actuation section is driven continuously for 24 hours,
Since the liquid flow rate per unit time is reduced by about 4%, the minor axis and major axis of the ellipse when the flow rate decreases by 4% are
0.96πr ² = πab ... Equation 7 a + b = 2r ... Equation 8 From equations 7 and 8 above, a = 0.8r b = 1.2r is obtained. From this, the moving distance of the finger may be set to (80% of tube inner diameter + tube thickness × 2) or less.

In the above description, the minor axis of the ellipse is based on the data obtained experimentally assuming that the tube is used for 24 hours (the flow rate of the liquid per unit time after use for 24 hours is reduced by about 4%). I asked. The length of the ellipse varies with the length of time the tube is used.

Further, even if the moving distance of the fingers is set to (the minor axis of the ellipse × 2 + the thickness of the tube × 2) or less,
It seems that 5 to 10% or less is suitable.

[0015]

According to the present invention, since the moving distance of the finger is set to (the ellipse minor diameter × 2 + the tube thickness × 2) or less,
After the tube is exhausted, the fingers will always come into contact with the tube even when the tube is opened and will always push the tube. For this reason, even after the tube is fatigued, the tube follows the movement of the fingers, and the flow rate change before and after the tube fatigue becomes worse. Further, if the moving distance of the finger is obtained from the example in which the tube is flattened most among the tube variations, the change in the flow rate due to the tube variations also disappears.

[Brief description of drawings]

FIG. 1 is a perspective view when a door of a general infusion pump is opened.

FIG. 2 is a diagram for explaining an operation principle of a linear peristaltic system of a general infusion pump.

FIG. 3 is a diagram for explaining an operation principle of a linear peristaltic system of a general infusion pump.

FIG. 4 is a diagram for explaining a moving distance of a finger.

FIG. 5 is a diagram for explaining flatness of an infusion tube.

[Explanation of symbols]

 1 Infusion working part 2 Tube mounting part 3 Pressure plate 4 Cam 5 Shaft 6 Finger 7 Tube 8 Spring fixing plate 9 Spring

Claims (1)

[Claims] 1. A body having a door, and an infusion tube attached to a wall covered with the door, and with the door closed, an infusion actuating section composed of a plurality of fingers is used to partially remove the infusion tube. An infusion pump that sequentially pushes a liquid in the infusion tube in the direction of infusion to deliver the drug solution in the infusion tube, and obtains a short radius a after an infusion tube having a radius r and a thickness m is used for a predetermined time. An infusion pump, characterized in that the distance from the position where the tube is closed to the position where the infusion tube is maximally opened from the closed position is (2a + 2m) or less.