Patent Description:
In general, dialysis treatment is performed by using a blood circuit for allowing blood collected from a patient to extracorporeally circulate and return into the patient's body. Such a blood circuit basically includes, for example, an arterial blood circuit and a venous blood circuit that are connectable to a dialyzer (a blood purifier) including hollow fiber membranes. The arterial blood circuit and the venous blood circuit are provided at distal ends thereof with an arterial puncture needle and a venous puncture needle, respectively. Extracorporeal circulation of blood in the dialysis treatment is performed while the patient is being punctured with the puncture needles.

In particular, the arterial blood circuit includes a squeezable tube and a peristaltic blood pump. The blood pump is capable of delivering liquid by squeezing the squeezable tube with rollers. When the blood pump is activated, the patient's blood can be caused to extracorporeally circulate through the blood circuit. Accordingly, the blood in extracorporeal circulation undergoes blood purification treatment in the dialyzer.

Typically, the arterial blood circuit and the venous blood circuit each include an air-trap chamber for trapping bubbles contained in liquid (such as blood, a priming solution, or a substitution solution) flowing in the blood circuit. As the liquid flows through the air-trap chamber, a liquid pool (a liquid layer) is formed on the lower side of the chamber, while an air layer is formed on the upper side of the chamber. Bubbles contained in the liquid flowing therethrough move from the liquid layer to the air layer with their buoyancy. Thus, the bubbles can be trapped (see <CIT>, for example).

In the above known blood purification apparatus, however, if the bubbles in the liquid flowing in the blood circuit are small, the buoyancy that moves the bubbles from the liquid layer to the air layer may be insufficient. Consequently, such bubbles may flow toward the downstream side without being trapped. Therefore, to trap bubbles having relatively low buoyancy, the air-trap chamber needs to have a large capacity. In such a case, however, the volume of blood to be collected for extracorporeal circulation (the priming volume) increases. As an alternative method for assuredly trapping bubbles including relatively small ones, the flow rate of the liquid may be reduced by reducing the driving speed of the blood pump throughout the entire process of the blood purification treatment. However, such a method lowers the efficiency of treatment.

<CIT> describes a blood purification apparatus with a bubble-detecting unit attached to a position of the blood circuit on a downstream side with respect to the air-trap chamber and that is configured to detect bubbles contained in the liquid flowing in the blood circuit.

The present invention has been conceived in view of the above circumstances and provides a blood purification apparatus including an air-trap chamber that has a reduced capacity but is capable of assuredly trapping bubbles including relatively small ones while suppressing the reduction in treatment efficiency, and also provides a method of trapping bubbles therein.

According to the invention of Claim <NUM>, there is provided a blood purification apparatus that includes a blood circuit including an arterial blood circuit and a venous blood circuit and having a flow route that allows a patient's blood to extracorporeally circulate from a distal end of the arterial blood circuit to a distal end of the venous blood circuit; a blood purifier connected to a proximal end of the arterial blood circuit and to a proximal end of the venous blood circuit and that is configured to purify the blood flowing through the blood circuit; an air-trap chamber connected to the blood circuit and that traps bubbles contained in liquid flowing in the flow route of the blood circuit; and a blood pump provided to the arterial blood circuit and being capable of delivering the liquid within the blood circuit. The blood purification apparatus includes an upstream bubble-detecting unit attached to a position of the blood circuit on an upstream side with respect to the air-trap chamber and that is configured to detect bubbles contained in the liquid flowing in the blood circuit; and a control unit that upon detection of any bubbles by the upstream bubble-detecting unit is configured to reduce a flow rate of the liquid flowing into the air-trap chamber.

According to the invention of Claim <NUM>, in the blood purification apparatus according to Claim <NUM>, the control unit is configured to reduce the flow rate of the liquid flowing into the air-trap chamber upon detection of any bubbles by the upstream bubble-detecting unit by reducing a driving speed of the blood pump at the detection of any bubbles by the upstream bubble-detecting unit.

According to the invention of Claim <NUM>, the blood purification apparatus according to Claim <NUM> further includes a substitution pump configured to perform substitution or priming by introducing dialysate into the blood circuit. Furthermore, the control unit is configured to reduce the driving speeds of the blood pump and the substitution pump upon detection of any bubbles by the upstream bubble-detecting unit.

According to the invention of Claim <NUM>, the blood purification apparatus according to Claim <NUM> further includes a narrowing unit provided at a position of the blood circuit between the air-trap chamber and the upstream bubble-detecting unit and that is configured to reduce the flow rate of the liquid by narrowing the flow route of the blood circuit. Furthermore, the control unit is configured to reduce the flow rate of the liquid flowing into the air-trap chamber upon detection of any bubbles by the upstream bubble-detecting unit by activating the narrowing unit to narrow the flow route.

According to the invention of Claim <NUM>, in the blood purification apparatus according to any of Claims <NUM> to <NUM>, the control unit is configured to reset the flow rate of the liquid flowing into the air-trap chamber to a preset flow rate upon an elapse of a predetermined time period after reducing the flow rate of the liquid.

Also described herein but not forming part of the invention is a method of trapping bubbles in a blood purification apparatus, the apparatus including a blood circuit including an arterial blood circuit and a venous blood circuit and having a flow route that allows a patient's blood to extracorporeally circulate from a distal end of the arterial blood circuit to a distal end of the venous blood circuit; a blood purifier connected to a proximal end of the arterial blood circuit and to a proximal end of the venous blood circuit and that is configured to purify the blood flowing through the blood circuit; an air-trap chamber connected to the blood circuit and that is configured to trap bubbles contained in a liquid flowing in the flow route of the blood circuit; and a blood pump provided to the arterial blood circuit and being capable of delivering the liquid within the blood circuit. The blood purification apparatus further includes an upstream bubble-detecting unit attached to a position of the blood circuit on an upstream side with respect to the air-trap chamber and that is configured to detect bubbles contained in the liquid flowing in the blood circuit. The method includes reducing a flow rate of the liquid flowing into the air-trap chamber upon detection of any bubbles by the upstream bubble-detecting unit.

Advantageously, in the method of trapping bubbles in the blood purification apparatus, the flow rate of the liquid flowing into the air-trap chamber is reduced upon detection of any bubbles by the upstream bubble-detecting unit by reducing a driving speed of the blood.

Further advantageously, in the method of trapping bubbles in the blood purification apparatus, the blood purification apparatus further includes a substitution pump configured to perform substitution or priming by introducing dialysate into the blood circuit. Furthermore, the method includes reducing the driving speeds of the blood pump and the substitution pump upon detection of any bubbles by the upstream bubble-detecting unit.

Advantageously , in the method of trapping bubbles in the blood purification apparatus, the blood purification apparatus further includes a narrowing unit provided at a position of the blood circuit between the air-trap chamber and the upstream bubble-detecting unit and that is configured to reduce the flow rate of the liquid by narrowing the flow route of the blood circuit. Furthermore, the method includes reducing the flow rate of the liquid flowing into the air-trap chamber upon detection of any bubbles by the upstream bubble-detecting unit by activating the narrowing unit to narrow the flow route.

Further advantageously, in the method of trapping bubbles in the blood purification apparatus, the method includes resetting the flow rate of the liquid flowing into the air-trap chamber to a preset flow rate upon an elapse of a predetermined time period after the flow rate of the liquid has been reduced.

According to the invention of Claim <NUM>, the blood purification apparatus includes the upstream bubble-detecting unit attached to a position of the blood circuit on the upstream side with respect to the air-trap chamber and that detects bubbles contained in the liquid flowing in the blood circuit. Furthermore, upon detection of any bubbles by the upstream bubble-detecting unit the flow rate of the liquid flowing into the air-trap chamber is reduced. Therefore, bubbles including relatively small ones can be trapped assuredly in the air-trap chamber having a reduced capacity. Furthermore, the reduction in treatment efficiency can be suppressed.

According to the invention of Claim <NUM>, upon detection of any bubbles by the upstream bubble-detecting unit the flow rate of the liquid flowing into the air-trap chamber is reduced by reducing the driving speed of the blood pump. Therefore, bubbles can be trapped assuredly by controlling the driving speed of the blood pump. Hence, no additional components are necessary.

According to the invention of Claim <NUM>, the blood purification apparatus includes the substitution pump capable of performing substitution or priming by introducing the dialysate into the blood circuit. Furthermore, the driving speeds of the blood pump and the substitution pump are reduced upon detection of any bubbles by the upstream bubble-detecting unit. Therefore, bubbles can be trapped assuredly by controlling the driving speeds of the blood pump and the substitution pump. Hence, no additional components are necessary.

According to the invention of Claim <NUM>, the blood purification apparatus includes the narrowing unit provided at a position of the blood circuit between the air-trap chamber and the upstream bubble-detecting unit and that is capable of reducing the flow rate of the liquid by narrowing the flow route of the blood circuit. Furthermore, upon detection of any bubbles by the upstream bubble-detecting unit the flow rate of the liquid flowing into the air-trap chamber is reduced by activating the narrowing unit to narrow the flow route. Therefore, bubbles can be trapped assuredly without changing the driving speed of the blood pump but by activating the narrowing unit.

According to the invention of Claim <NUM>, the preset flow rate of the liquid is resumed upon the elapse of a predetermined time period after the flow rate of the liquid flowing into the air-trap chamber has been reduced. Therefore, after bubbles are trapped in the air-trap chamber, the flow rate of the liquid flowing in the blood circuit can be reset automatically.

A blood purification apparatus according to a first embodiment is a dialysis apparatus intended for dialysis treatment and basically includes, as illustrated in <FIG>, a blood circuit including an arterial blood circuit <NUM> and a venous blood circuit <NUM>, a dialyzer <NUM> (a blood purifier) connected to a proximal end of the arterial blood circuit <NUM> and to a proximal end of the venous blood circuit <NUM> and that purifies blood flowing through the blood circuit, a blood pump <NUM>, an air-trap chamber <NUM> connected to the arterial blood circuit <NUM>, an air-trap chamber <NUM> connected to the venous blood circuit <NUM>, a bubble detection unit <NUM>, a blood identifier <NUM>, an upstream bubble-detecting unit <NUM>, and a control unit E.

The arterial blood circuit <NUM> is provided with an arterial puncture needle a connected to a distal end thereof through a connector c. The blood pump <NUM>, which is of a peristaltic type, and the air-trap chamber <NUM> are provided at respective halfway positions of the arterial blood circuit <NUM>. The venous blood circuit <NUM> is provided with a venous puncture needle b connected to a distal end thereof through a connector d. The upstream bubble-detecting unit <NUM> and the air-trap chamber <NUM> are provided at respective halfway positions of the venous blood circuit <NUM>. Furthermore, the arterial blood circuit <NUM> and the venous blood circuit <NUM> are provided on respective distal sides thereof (near the respective connectors c and d) with respective tube clamps V1 and V2, which are capable of closing or opening respective flow routes. The tube clamps V1 and V2 may be replaced with other flow-route-closing mechanisms (such as electromagnetic valves or pinch valves).

When the blood pump <NUM> is activated while a patient is punctured with the arterial puncture needle a and the venous puncture needle b, the patient's blood flows through the arterial blood circuit <NUM> and reaches the dialyzer <NUM>, where the blood is purified. Then, the blood flows through the venous blood circuit <NUM> and returns into the patient's body. That is, blood purification treatment is performed by purifying the patient's blood with the dialyzer <NUM> while causing the blood to extracorporeally circulate through the blood circuit from the distal end of the arterial blood circuit <NUM> to the distal end of the venous blood circuit <NUM>. In this specification, the side of the puncture needle for blood removal (blood collection) is referred to as the "arterial" side, and the side of the puncture needle for blood return is referred to as the "venous" side. The "arterial" side and the "venous" side are not defined in accordance with which of the artery and the vein is to be the object of puncture.

The bubble detection unit <NUM> is attached to a distal portion of the venous blood circuit <NUM> (on a side nearer to the dialyzer <NUM> with respect to the tube clamp V2). The bubble detection unit <NUM> is a sensor capable of detecting bubbles contained in liquid flowing there. During the blood purification treatment, if any bubbles are detected by the bubble detection unit <NUM> while the patient's blood is extracorporeally circulating through the blood circuit, the tube clamp V2 closes the flow route, whereby the bubbles are prevented from reaching the patient's body.

The blood identifier <NUM> is attached to the distal portion of the venous blood circuit <NUM> (on a side nearer to the connector d with respect to the tube clamp V2). The blood identifier <NUM> is a sensor capable of identifying whether the liquid flowing there is blood. Before the blood purification treatment is started, whether blood has been substituted for a priming solution can be identified by the blood identifier <NUM>. When the blood purification treatment is ended and before the blood in the blood circuit is returned to the patient, whether the substitution solution has been substituted for the blood can be identified by the blood identifier <NUM>.

The blood pump <NUM>, provided to the arterial blood circuit <NUM>, is capable of delivering liquid, such as blood or the priming solution, within the blood circuit by squeezing a squeezable tube in the lengthwise direction. The squeezable tube is connected to the arterial blood circuit <NUM>. Specifically, the blood pump <NUM> is configured to squeeze the squeezable tube in the lengthwise direction while compressing the squeezable tube in the radial direction by using a squeezing unit (rollers), thereby causing the liquid thereinside to flow in the direction of rotation of the squeezing unit (rollers).

The air-trap chamber <NUM> is provided between the blood pump <NUM> and the dialyzer <NUM> in the arterial blood circuit <NUM>. As the liquid flows through the arterial blood circuit <NUM>, a liquid layer is formed on the lower side of the air-trap chamber <NUM> while an air layer is formed on the upper side of the air-trap chamber <NUM>. Thus, bubbles contained in the liquid can be trapped in the air layer for bubble removal. The air-trap chamber <NUM> is provided between the upstream bubble-detecting unit <NUM> and the bubble detection unit <NUM> in the venous blood circuit <NUM>. As the liquid flows through the venous blood circuit <NUM>, a liquid layer is formed on the lower side of the air-trap chamber <NUM> while an air layer is formed on the upper side of the air-trap chamber <NUM>. Thus, bubbles contained in the liquid can be trapped in the air layer for bubble removal.

The air-trap chamber <NUM> according to the present embodiment is provided with an overflow line Lc. The overflow line Lc extends from the top of the air-trap chamber <NUM> with a distal end thereof being open to the atmosphere. The overflow line Lc allows the liquid (the priming solution) overflowing from the air-trap chamber <NUM> to be discharged to the outside. The overflow line Lc is provided with an electromagnetic valve V3, which is capable of closing or opening a flow route of the overflow line Lc at an arbitrary timing.

The dialyzer <NUM> has, in a housing thereof, a blood inlet 3a (a blood introduction port), a blood outlet 3b (a blood delivery port), a dialysate inlet 3c (an inlet of a dialysate flow route: a dialysate introduction port), and a dialysate outlet 3d (an outlet of the dialysate flow route: a dialysate delivery port). The blood inlet 3a is connected to the proximal end of the arterial blood circuit <NUM>. The blood outlet 3b is connected to the proximal end of the venous blood circuit <NUM>. The dialysate inlet 3c and the dialysate outlet 3d are connected to a dialysate introduction line La and a dialysate drain line Lb, respectively, extending from a dialysis-apparatus body.

The dialyzer <NUM> houses a plurality of hollow fibers (not illustrated). The hollow fibers form blood purification membranes for purifying the blood. The blood purification membranes in the dialyzer <NUM> define blood flow routes (each extending between the blood inlet 3a and the blood outlet 3b) through which the patient's blood flows and dialysate flow routes (each extending between the dialysate inlet 3c and the dialysate outlet 3d) through which dialysate flows. The hollow fibers forming the blood purification membranes each have a number of microscopic holes (pores) extending therethrough from the outer peripheral surface to the inner peripheral surface, thereby forming a hollow fiber membrane. Impurities and the like contained in the blood are allowed to permeate through the hollow fiber membranes into the dialysate.

A duplex pump <NUM> is provided over the dialysate introduction line La and the dialysate drain line Lb in the dialysis-apparatus body. The dialysate drain line Lb is provided with a bypass line that bypasses the duplex pump <NUM>. The bypass line is provided with an ultrafiltration pump <NUM> for removing water from the patient's blood flowing in the dialyzer <NUM>. One end of the dialysate introduction line La is connected to the dialyzer <NUM> (the dialysate inlet 3c), and the other end is connected to a dialysate supply device (not illustrated) that prepares a dialysate at a predetermined concentration. One end of the dialysate drain line Lb is connected to the dialyzer <NUM> (the dialysate outlet 3d), and the other end is connected to a drainage unit, not illustrated. The dialysate supplied from the dialysate supply device flows through the dialysate introduction line La into the dialyzer <NUM>, and further flows through the dialysate drain line Lb into the drainage unit.

The present embodiment employs the upstream bubble-detecting unit <NUM> attached to a position of the blood circuit (the venous blood circuit <NUM>) on the upstream side with respect to the air-trap chamber <NUM> and that detects bubbles contained in the liquid, such as blood, flowing in the venous blood circuit <NUM>; and the control unit E that reduces the flow rate of the liquid flowing into the air-trap chamber <NUM> by reducing the driving speed of the blood pump <NUM> if any bubbles are detected by the upstream bubble-detecting unit <NUM>.

As with the bubble detection unit <NUM>, the upstream bubble-detecting unit <NUM> is a sensor capable of detecting bubbles contained in liquid and includes, for example, a pair of ultrasonic vibrators (an oscillating device and a receiving device) formed of piezoelectric devices. Specifically, the upstream bubble-detecting unit <NUM> (as well as the bubble detection unit <NUM>) is capable of emitting ultrasonic waves from the ultrasonic vibrator as the oscillating device toward a flexible tube forming the blood circuit (the venous blood circuit <NUM>), and is also capable of receiving the thus generated vibration by an ultrasonic receiver as the receiving device. The ultrasonic receiver having received the vibration generates a voltage that changes with the vibration received. The ultrasonic receiver is capable of detecting the flow of bubbles in the liquid by a fact that the detected voltage has exceeded a predetermined threshold.

Specifically, the upstream bubble-detecting unit <NUM> is provided at a position on the upstream side with respect to the air-trap chamber <NUM> (a position on the upstream side of the flow of the extracorporeally circulating blood and between the air-trap chamber <NUM> and the dialyzer <NUM>). The upstream bubble-detecting unit <NUM> is capable of transmitting, at the detection of any bubbles, a predetermined detection signal to the control unit E before the bubbles reach the air-trap chamber <NUM>. The control unit E is a microcomputer or the like and is electrically connected to the upstream bubble-detecting unit <NUM> and to the blood pump <NUM>, thereby being capable of transmitting and receiving predetermined signals.

If the control unit E according to the present embodiment has identified the detection of any bubbles by receiving the predetermined detection signal from the upstream bubble-detecting unit <NUM>, the control unit E transmits a predetermined control signal to the blood pump <NUM>, so that the driving speed of the blood pump <NUM> can be reduced to a preset level. Thus, the flow rate of the blood flowing in the blood circuit can be reduced, and the flow velocity of the bubbles detected by the upstream bubble-detecting unit <NUM> and flowing toward the air-trap chamber <NUM> can be reduced. Therefore, bubbles can be trapped assuredly in the air-trap chamber <NUM>.

At the elapse of a predetermined time period after the flow rate of the blood (liquid) flowing into the air-trap chamber <NUM> is reduced, the control unit E according to the present embodiment resets the driving speed of the blood pump <NUM> to an initial driving speed, so that a preset flow rate of the blood (liquid) (a normal flow rate that is set before or during the blood purification treatment) is resumed. Thus, after bubbles are trapped in the air-trap chamber <NUM> with the elapse of the predetermined time period, the preset flow rate can be resumed automatically.

In the present embodiment, the upstream bubble-detecting unit <NUM> is provided on the upstream side with respect to the air-trap chamber <NUM> connected to the venous blood circuit <NUM>. However, as illustrated in <FIG>, for example, an upstream bubble-detecting unit <NUM>' (having the same configuration and the same function as the upstream bubble-detecting unit <NUM>) may be provided on the upstream side with respect to the air-trap chamber <NUM> connected to the arterial blood circuit <NUM> (at a position between the blood pump <NUM> and the air-trap chamber <NUM>), so that the flow rate of the liquid flowing into the air-trap chamber <NUM> is reduced by reducing the driving speed of the blood pump <NUM> at the detection of any bubbles by the upstream bubble-detecting unit <NUM>'.

The distance between the upstream bubble-detecting unit (<NUM>, <NUM>') and the air-trap chamber (<NUM>, <NUM>) is calculable as follows. The length of travel of bubbles in the liquid flowing through the blood circuit is calculable in accordance with the following mathematical expression: <NUM> × (preset blood flow rate (initial blood flow rate) of blood pump <NUM> × time period from detection of bubbles by upstream bubble-detecting unit (<NUM>, <NUM>') until start of low-speed driving of blood pump <NUM> + blood flow rate after reduction of driving speed of blood pump <NUM> × time period of low-speed driving of blood pump <NUM>)/3π(inside diameter of tube forming blood circuit)<NUM>.

Assuming that the time period from the detection of bubbles by the upstream bubble-detecting unit (<NUM>, <NUM>') until the start of low-speed driving of the blood pump <NUM> is <NUM> (sec); the blood flow rate during the low-speed driving is <NUM> (mL/min); and the time period of the low-speed driving of the blood pump <NUM> is <NUM> (sec), a table illustrated in <FIG> can be obtained in accordance with the above mathematical expression. According to the table, for example, in a case where the blood circuit is formed of a tube having an inside diameter of <NUM> (mm) and the blood flow rate (the initial blood flow rate) is set to <NUM> (mL/min), bubbles travel by <NUM> (mm). Therefore, the distance between the upstream bubble-detecting unit (<NUM>, <NUM>') and the air-trap chamber (<NUM>, <NUM>) needs to be <NUM> (mm) or greater.

Now, a control process according to the present embodiment will be described with reference to a flow chart illustrated in <FIG>.

First, the patient is punctured with the arterial puncture needle a and the venous puncture needle b, and the blood pump <NUM> is activated, whereby blood purification treatment is started by causing the patient's blood to extracorporeally circulate through the blood circuit (S1). Then, in S2, whether any bubbles have been detected by the upstream bubble-detecting unit <NUM> is checked. If it is judged that bubbles have been detected, the process proceeds to S3, where the low-speed driving of the blood pump <NUM> is started (the driving speed is reduced to a level lower than the initial driving speed), whereby the flow rate of the blood flowing into the air-trap chamber <NUM> is reduced.

Subsequently, whether a predetermined time period has elapsed is checked (S4). If it is judged that the predetermined time period has elapsed, the process proceeds to S5, where the normal driving (the initial driving speed) of the blood pump <NUM> is resumed. Then, whether the blood purification treatment has ended is checked in S6. If it is judged that the treatment has not ended, the process returns to S2, where whether any bubbles have been detected is checked again, and the subsequent steps of the control process are performed. On the other hand, if it is judged in S6 that the blood purification treatment has ended, the control process is ended.

According to the present embodiment, the blood purification apparatus includes the upstream bubble-detecting unit (<NUM>, <NUM>') attached to a position of the blood circuit on the upstream side with respect to the air-trap chamber (<NUM>, <NUM>) and that detects bubbles contained in the liquid flowing in the blood circuit. Furthermore, the flow rate of the liquid flowing into the air-trap chamber (<NUM>, <NUM>) is reduced at the detection of any bubbles by the upstream bubble-detecting unit (<NUM>, <NUM>'). Therefore, bubbles including relatively small ones can be trapped assuredly in the air-trap chamber (<NUM>, <NUM>) having a reduced capacity. Furthermore, the reduction in treatment efficiency can be suppressed more than in a case where the flow rate of the liquid is constantly low.

Furthermore, according to the present embodiment, the flow rate of the liquid flowing into the air-trap chamber (<NUM>, <NUM>) is reduced by reducing the driving speed of the blood pump <NUM> at the detection of any bubbles by the upstream bubble-detecting unit (<NUM>, <NUM>'). Therefore, bubbles can be trapped assuredly by controlling the driving speed of the blood pump <NUM>. Hence, no additional components are necessary. Furthermore, the preset flow rate of the liquid is resumed at the elapse of a predetermined time period after the flow rate of the liquid flowing into the air-trap chamber (<NUM>, <NUM>) is reduced. Therefore, after bubbles are trapped in the air-trap chamber, the flow rate of the liquid flowing in the blood circuit can be reset automatically.

Now, a blood purification apparatus according to a second embodiment of the present invention will be described.

As with the case of the first embodiment, the blood purification apparatus according to the present embodiment is a dialysis apparatus intended for dialysis treatment and basically includes, as illustrated in <FIG>, a blood circuit including an arterial blood circuit <NUM> and a venous blood circuit <NUM>, a dialyzer <NUM> (a blood purifier) connected to a proximal end of the arterial blood circuit <NUM> and to a proximal end of the venous blood circuit <NUM> and that purifies blood flowing through the blood circuit, a blood pump <NUM>, an air-trap chamber <NUM> connected to the arterial blood circuit <NUM>, an air-trap chamber <NUM> connected to the venous blood circuit <NUM>, a bubble detection unit <NUM>, a blood identifier <NUM>, an upstream bubble-detecting unit <NUM>, a narrowing unit <NUM>, and a control unit E. Elements that are the same as those described in the first embodiment are denoted by corresponding ones of the reference numerals, and detailed description of those elements is omitted.

The narrowing unit <NUM> is provided at a position of the blood circuit (in the present embodiment, the venous blood circuit <NUM>) between the air-trap chamber <NUM> and the upstream bubble-detecting unit <NUM> and is capable of reducing the flow rate of the liquid by pinching and thus narrowing the flow route of the blood circuit. The narrowing unit <NUM> is, for example, a solenoid clamp or the like. The control unit E reduces the flow rate of the liquid flowing into the air-trap chamber <NUM> by activating the narrowing unit <NUM> to narrow the flow route at the detection of any bubbles by the upstream bubble-detecting unit <NUM>.

Specifically, if the control unit E according to the present embodiment has identified the detection of any bubbles by receiving a predetermined detection signal from the upstream bubble-detecting unit <NUM>, the control unit E transmits a predetermined control signal to the narrowing unit <NUM>, so that the flow route can be narrowed. Thus, the flow rate of the blood flowing in the blood circuit can be reduced, and the flow velocity of the bubbles detected by the upstream bubble-detecting unit <NUM> and flowing toward the air-trap chamber <NUM> can be reduced. Therefore, bubbles can be trapped assuredly in the air-trap chamber <NUM>.

Furthermore, at the elapse of a predetermined time period after the flow rate of the blood (liquid) flowing into the air-trap chamber <NUM> is reduced, the control unit E according to the present embodiment resets the flow rate of the blood (liquid), so that a preset flow rate (a normal flow rate that is set before or during the blood purification treatment) is resumed. Thus, after bubbles are trapped in the air-trap chamber <NUM> with the elapse of the predetermined time period, the preset flow rate can be resumed automatically.

First, the patient is punctured with the arterial puncture needle a and the venous puncture needle b, and the blood pump <NUM> is activated, whereby blood purification treatment is started by causing the patient's blood to extracorporeally circulate through the blood circuit (S1). Then, in S2, whether any bubbles have been detected by the upstream bubble-detecting unit <NUM> is checked. If it is judged that bubbles have been detected, the process proceeds to S3, where the narrowing unit <NUM> is activated to reduce the flow rate of the blood flowing into the air-trap chamber <NUM>.

Subsequently, whether a predetermined time period has elapsed is checked (S4). If it is judged that the predetermined time period has elapsed, the process proceeds to S5, where the narrowing of the flow route by the narrowing unit <NUM> is disabled, and the normal blood flow rate (the initial blood flow rate) is resumed. Then, whether the blood purification treatment has ended is checked in S6. If it is judged that the treatment has not ended, the process returns to S2, where whether any bubbles have been detected is checked again, and the subsequent steps of the control process are performed. On the other hand, if it is judged in S6 that the blood purification treatment has ended, the control process is ended.

According to the present embodiment, the blood purification apparatus includes the upstream bubble-detecting unit <NUM> attached to a position of the blood circuit on the upstream side with respect to the air-trap chamber <NUM> and that detects bubbles contained in the liquid flowing in the blood circuit. Furthermore, the flow rate of the liquid flowing into the air-trap chamber <NUM> is reduced at the detection of any bubbles by the upstream bubble-detecting unit <NUM>. Therefore, bubbles including relatively small ones can be trapped assuredly in the air-trap chamber <NUM> having a reduced capacity. Furthermore, the reduction in treatment efficiency can be suppressed more than in a case where the flow rate of the liquid is constantly low.

Furthermore, according to the present embodiment, the blood purification apparatus includes the narrowing unit <NUM> provided at a position of the blood circuit between the air-trap chamber <NUM> and the upstream bubble-detecting unit <NUM> and that is capable of reducing the flow rate of the liquid by narrowing the flow route of the blood circuit. Furthermore, the flow rate of the liquid flowing into the air-trap chamber <NUM> is reduced by activating the narrowing unit <NUM> to narrow the flow route at the detection of any bubbles by the upstream bubble-detecting unit <NUM>. Therefore, bubbles can be trapped assuredly without changing the driving speed of the blood pump <NUM> but by activating the narrowing unit <NUM>.

Furthermore, the preset flow rate of the liquid is resumed by disabling the narrowing by the narrowing unit <NUM> at the elapse of a predetermined time period after the flow rate of the liquid flowing into the air-trap chamber <NUM> is reduced. Therefore, after bubbles are trapped in the air-trap chamber <NUM>, the flow rate of the liquid flowing in the blood circuit can be reset automatically. The upstream bubble-detecting unit <NUM> and the narrowing unit <NUM> according to the present embodiment are provided on the upstream side with respect to the air-trap chamber <NUM> connected to the venous blood circuit <NUM>. Instead or in addition, an upstream bubble-detecting unit <NUM> and a narrowing unit <NUM> may be provided on the upstream side with respect to the air-trap chamber <NUM> connected to the arterial blood circuit <NUM>.

The first and second embodiments each concern the trapping of bubbles during the blood purification treatment. The present invention is also applicable to the trapping of bubbles at the time of, for example, priming performed before the treatment. First, a case where the present invention is applied to a blood purification apparatus capable of performing pre-substitution (substitution for the blood that is yet to be purified by the dialyzer <NUM>) will be described.

As illustrated in <FIG> and <FIG>, the blood purification apparatus includes a substitution line Ld connecting the dialysate introduction line La and the air-trap chamber <NUM> connected to the arterial blood circuit <NUM> to each other, so that the dialysate in the dialysate introduction line La can be introduced into the blood circuit and be used as a substitution solution and as a priming solution.

To perform priming with the above blood purification apparatus, as illustrated in <FIG>, the connector c at the distal end of the arterial blood circuit <NUM> and the connector d at the distal end of the venous blood circuit <NUM> are connected to each other to form a closed circuit. Then, a substitution pump <NUM> is activated, and the blood pump <NUM> is rotated reversely (driven such that the liquid is delivered in the direction opposite to the direction for the blood purification treatment). Thus, some of the dialysate as the priming solution introduced into the blood circuit through the substitution line Ld flows toward the dialyzer <NUM>, while the rest of the dialysate flows toward the connection between the distal end of the arterial blood circuit <NUM> and the distal end of the venous blood circuit <NUM>. Then, the two flows of the dialysate merge at the air-trap chamber <NUM>, and the merged dialysate is discharged from the overflow line Lc. In this process, a liquid layer and an air layer are formed in the air-trap chamber <NUM>, and bubbles and an excessive portion of the dialysate are discharged from the overflow line Lc.

Subsequently, as illustrated in <FIG>, while the substitution pump <NUM> is kept activated, the blood pump <NUM> is rotated normally (driven such that the liquid is delivered in the direction for the blood purification treatment). Thus, the dialysate as the priming solution introduced into the blood circuit through the substitution line Ld flows through the blood circuit in the direction indicated by arrows illustrated in the drawing. In this process, the control unit E reduces the flow rate of the priming solution (the dialysate) flowing into the air-trap chamber <NUM> by reducing the respective driving speeds of the blood pump <NUM> and the substitution pump <NUM> at the detection of any bubbles by the upstream bubble-detecting unit <NUM>, so that residual bubbles can be trapped assuredly in the air-trap chamber <NUM>.

Now, a case where the present invention is applied to a blood purification apparatus capable of performing post-substitution (substitution for the blood that has been purified by the dialyzer <NUM>) will be described. As illustrated in <FIG> and <FIG>, the blood purification apparatus includes a substitution line Ld connecting the dialysate introduction line La and the venous blood circuit <NUM> (a position between the dialyzer <NUM> and the upstream bubble-detecting unit <NUM>) to each other, so that the dialysate in the dialysate introduction line La can be introduced into the blood circuit and be used as a substitution solution and as a priming solution.

To perform priming with the above blood purification apparatus, as illustrated in <FIG>, the connector c at the distal end of the arterial blood circuit <NUM> and the connector d at the distal end of the venous blood circuit <NUM> are connected to each other to form a closed circuit. Then, the substitution pump <NUM> is activated, and the blood pump <NUM> is rotated normally (driven such that the liquid is delivered in the direction for the blood purification treatment). Thus, the dialysate as the priming solution introduced into the blood circuit through the substitution line Ld flows through the blood circuit in the direction indicated by arrows illustrated in the drawing, and bubbles and an excessive portion of the dialysate are discharged from the overflow line Lc.

Subsequently, as illustrated in <FIG>, while the substitution pump <NUM> is kept activated, the blood pump <NUM> is rotated reversely (driven such that the liquid is delivered in the direction opposite to the direction for the blood purification treatment). Thus, the dialysate as the priming solution introduced into the blood circuit through the substitution line Ld flows through the blood circuit in the direction indicated by arrows illustrated in the drawing. In this process, the control unit E reduces the flow rate of the priming solution (the dialysate) flowing into the air-trap chamber <NUM> by reducing the respective driving speeds of the blood pump <NUM> and the substitution pump <NUM> at the detection of any bubbles by the bubble detection unit <NUM> (in the present embodiment, the bubble detection unit <NUM> corresponds to the upstream bubble-detecting unit), so that residual bubbles can be trapped assuredly in the air-trap chamber <NUM>.

As described above, the upstream bubble-detecting unit varies with the direction in which the liquid flows through the blood circuit. If the present invention is applied to a case where the liquid (the priming solution) flows from the distal end (the connector d) of the venous blood circuit <NUM> toward the air-trap chamber <NUM> as illustrated in <FIG>, the bubble detection unit <NUM> provided on the upstream side with respect to the air-trap chamber <NUM> serves as the upstream bubble-detecting unit according to the present invention.

The blood purification apparatus includes the substitution pump <NUM> capable of performing substitution or priming by introducing the dialysate into the blood circuit. Furthermore, the driving speeds of the blood pump <NUM> and the substitution pump <NUM> are reduced at the detection of any bubbles by the upstream bubble-detecting unit <NUM> (the bubble detection unit <NUM>). Therefore, bubbles can be trapped assuredly by controlling the driving speeds of the blood pump <NUM> and the substitution pump <NUM>. Hence, no additional components are necessary.

While some embodiments have been described above, the present invention is not limited thereto. For example, if bubbles are to be trapped in the blood purification treatment as described in the first and second embodiments, the present invention may be applied not only to a case where bubbles are trapped at the time of priming as illustrated in <FIG> but also to another case (such as a blood-return process in which the blood in the blood circuit is returned to the patient after the blood purification treatment). Furthermore, the device for reducing the flow rate of the liquid flowing into the air-trap chamber (<NUM>, <NUM>) at the detection of any bubbles by the upstream bubble-detecting unit (<NUM>, <NUM>', <NUM>) is not limited to the blood pump <NUM> and the narrowing unit <NUM> and may be any other device that is capable of reducing the flow rate.

Furthermore, the flow rate of the liquid flowing through the blood circuit may be reduced arbitrarily by controlling the blood pump <NUM> or the narrowing unit <NUM> in accordance with the sizes or the flow velocity of the bubbles detected by the upstream bubble-detecting unit (<NUM>, <NUM>', <NUM>). While the above embodiments are each applied to a dialysis apparatus intended for dialysis treatment, the present invention may also be applied to an apparatus (such as a blood purification apparatus or a plasma adsorption apparatus intended for hemodiafiltration, hemofiltration, or AFBF) that is capable of purifying a patient's blood while causing the blood to extracorporeally circulate.

Claim 1:
A blood purification apparatus that includes
a blood circuit including an arterial blood circuit (<NUM>) and a venous blood circuit (<NUM>) and having a flow route that allows a patient's blood to extracorporeally circulate from a distal end of the arterial blood circuit (<NUM>) to a distal end of the venous blood circuit (<NUM>);
a blood purifier (<NUM>) connected to a proximal end of the arterial blood circuit (<NUM>) and to a proximal end of the venous blood circuit (<NUM>) and that purifies the blood flowing through the blood circuit;
an air-trap chamber (<NUM>, <NUM>) connected to the blood circuit and that is configured to trap bubbles contained in a liquid flowing in the flow route of the blood circuit; and
a blood pump (<NUM>) provided to the arterial blood circuit (<NUM>) and being capable of delivering the liquid within the blood circuit, and
an upstream bubble-detecting unit (<NUM>, <NUM>') attached to a position of the blood circuit on an upstream side with respect to the air-trap chamber (<NUM>, <NUM>) and that is configured to detect bubbles contained in the liquid flowing in the blood circuit;
characterized in that the blood purification apparatus further includes
a control unit (E) that upon detection of any bubbles by the upstream bubble-detecting unit (<NUM>, <NUM>') is configured to reduce a flow rate of the liquid flowing into the air-trap chamber (<NUM>, <NUM>).