APPARATUS FOR EXTRACORPOREAL TREATMENT OF BLOOD
An apparatus for extracorporeal treatment of blood (1) comprising a filtration unit (2), a blood withdrawal line (6), a blood return line (7), an effluent fluid line (13), a pre and/or post-dilution fluid line (15, 25) connected to the blood withdrawal line, and a dialysis fluid line. Pumps (17, 18, 21, 22, 27) act on the fluid lines for regulating the flow of fluid. A control unit (10) is configured to periodically calculate a new value for the patient fluid removal rate to be imposed on an ultrafiltration actuator in order to keep a predefined patient fluid removal rate across a reference time interval irrespective of machine down times.
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The present invention relates to an apparatus for extracorporeal treatment of blood.
Extracorporeal blood treatment involves removing blood from a patient, treating the blood externally to the patient, and returning the treated blood to the patient. Extracorporeal blood treatment is typically used to extract undesirable matter or molecules from the patient's blood and add desirable matter or molecules to the blood. Extracorporeal blood treatment is used with patients unable to effectively remove matter from their blood, such as when a patient has suffered temporary or permanent kidney failure. These patients and other patients may undergo extracorporeal blood treatment to add or remove matter to their blood, to maintain an acid/base balance or to remove excess body fluids, for example.
Extracorporeal blood treatment is typically accomplished by removing the blood from the patient in e.g. a continuous flow, introducing the blood into a primary chamber, also referred to as blood chamber, of a filtration unit (such as a dialyzer or an hemofilter) where the blood is allowed to flow past a semipermeable membrane. The semipermeable membrane selectively allows matter in the blood to cross the membrane from the primary chamber into a secondary chamber and also selectively allows matter in the secondary chamber to cross the membrane into the blood in the primary chamber, depending on the type of treatment.
A number of different types of extracorporeal blood treatments may be performed. In an ultrafiltration (UF) treatment, undesirable matter is removed from the blood by convection across the membrane into the secondary chamber. In a hemofiltration (HF) treatment, the blood flows past the semipermeable membrane as in UF and desirable matter is added to the blood, typically by dispensing a fluid into the blood either before and/or after it passes through the filtration unit and before it is returned to the patient. In a hemodialysis (HD) treatment, a secondary fluid containing desirable matter is introduced into the secondary chamber of the filtration unit. Undesirable matter from the blood crosses the semipermeable membrane into the secondary fluid and desirable matter from the secondary fluid may cross the membrane into the blood. In a hemodiafiltration (HDF) treatment, blood and secondary fluid exchange matter as in HD, and, in addition, matter is added to the blood, typically by dispensing a fluid into the treated blood before its return to the patient as in HF.
Specific blood treatment apparatus have been developed for the treatment of acute patients mainly because:
-
- it is not known how long these patients will suffer from kidney insufficiency; thus, the total treatment time is a priori unknown and, as such, it may not be used as setup parameter;
- in fact, intensive care apparatus used for treating acute patient are designed to request flow rate information as setup parameters;
- moreover, acute patients need relatively long treatment sessions, typically lasting several days, during which the blood treatment apparatus is a master piece of the patient fluid balance management, allowing for accurate balancing of the multiple infusions generally present (drugs, fluids, nutrition);
- furthermore, acute patients often need to be treated in emergency situations, thus apparatus for acute treatment shall be characterized by easy and safe set up procedures.
In this situation, blood treatment apparatus have been developed presenting infusion lines for supplying fluid upstream or downstream the filtration unit, a fresh dialysis liquid line for supplying liquid to the dialysate chamber of the filtration unit, and a waste line receiving spent dialysis fluid and ultrafiltered fluid from filtration unit. In correspondence of each of the above lines, means for generating a flow rate is acting, such as a peristaltic pump which is rotated under the supervision of a control unit. Moreover, fluid containers supply fluid to the infusion lines and to the dialysate line, while a waste container or a waste handling system receives the spent liquid from the waste line. Typically, scales are used to weigh the fluid containers and to provide signals used by the control unit to control the pumps or other actuators on the fluid lines so that the apparatus achieves the fluid removal rate set by the user, and—depending upon the apparatus—any other rates through each line. In more sophisticated solutions, each of the above lines receives fluid from a respective container which, in use, is associated to a respective scale and cooperates with a respective pump. A user interface allows an operator entering the patient fluid removal rate and the fluid flow rates of each of the substitution lines and dialysate line such that the apparatus is capable of continuously keep under control the amount of fluid infused, the amount of fluid flowing through the dialysate line and the fluid loss rate.
Although the above solution results in efficient apparatus able to perform all necessary treatments and to accurately control the flows, the applicant has found ways to further improve known blood treatment apparatuses.
It is an object of the present invention to render available a blood treatment apparatus suitable for intensive care applications which may be automatically able to account for down times or interruption in the treatment delivery.
More in detail, it is an object of the invention an apparatus which is able to take into account the effective portions of the treatment procedure, adapting certain set-up parameters to account for machine stops, therapy delivery interruptions, machine downtimes.
An auxiliary object is an apparatus able to control patient fluid removal rate across long treatments, without compromising the operating philosophy of an intensive care apparatus.
Another object is an apparatus capable of operating in a safe manner.
Another object is to automatically ascertain whether certain prescription targets cannot be achieved and inform the operator accordingly.
SUMMARYAt least one of the above objects is substantially reached by an apparatus according to one or more of the appended claims.
Apparatus and processes for the extracorporeal treatment of blood according to aspects of the invention are here below described.
A 1st aspect relates to an apparatus for extracorporeal treatment of blood comprising:
- a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semi-permeable membrane (5); a blood withdrawal line (6) connected to an inlet of the primary chamber (3), and a blood return line (7) connected to an outlet of the primary chamber (4) said blood lines being designed to be connected to a patient cardiovascular system; a blood pump (11) for controlling the flow of blood through the blood lines (6, 7); an effluent fluid line (13) connected to an outlet of the secondary chamber (4); an ultrafiltration actuator connected to the effluent fluid line (13) and configured to cause a transfer of fluid from the primary (3) to the secondary chamber (4), and a control unit (10) configured to control the ultrafiltration actuator based on a set value (Qpfr
— set) for patient fluid removal rate, said set value (Qpfr— set) being a desired value for the rate of fluid removal from the patient, wherein the control unit (10) is configured to execute at check points (Ti) during patient treatment a control procedure comprising:- receiving one check information selected in the group of:
- a value of fluid removed from the patient (Vpfr
— removed; Vpfr(0)) over a time period (Ti-Tretro to Ti) preceding a check point (Ti), - an effective time portion, of said time period (Ti-Tretro to Ti) preceding a check point (Ti), during which said ultrafiltration actuator is operated,
- a down time portion, of said time period (Ti-Tretro to Ti) preceding a check point (Ti), during which said ultrafiltration actuator is not operated,
- a value of fluid removed from the patient (Vpfr
- calculating an updated value (Qpfr
— new) for said fluid removal rate (Qpfr) as a function of said set value for a fluid removal rate (Qpfr— set) and of said check information.
- receiving one check information selected in the group of:
In a 2nd aspect according to the 1st aspect, the control procedure further comprises, after calculation of said updated value (Qpfr
In a 3rd aspect according to any one of 1stor 2nd aspect, the control procedure further comprises controlling the ultrafiltration actuator, after the check point and until either a subsequent check point as a function of said updated value (Qpfr
In a 4th aspect according to any one of 1stor 2nd or 3rd aspect the control unit (10) is configured for re-executing said control procedure at a plurality of check points (Ti) during patient treatment, said plurality of check points being one or more in the group of:
-
- check points at regular intervals,
- periodic check points,
- check points triggered by specific setting of a new set value (Qpfr
— set) for patient fluid removal rate, - check points triggered by a stop in the ultrafiltration actuator,
- check points triggered by each time a flow rate setting is changed.
In a 5th aspect according to any one of the preceding aspects, the control procedure comprises:
-
- determining a value of the fluid removed from the patient (Vpfr
— removed) over a time period (Tretro) preceding a check point (Ti); - determining a value of fluid to be removed from the patient (Vpfr
— need)over a time period (Tprosp) following the check point (Ti) in order to achieve the set value (Qpfr— set) for fluid removal rate (Qpfr) over the sum of the time period (Tretro) preceding check point (Ti) and of the time period (Tprosp) following the check point (Ti); - calculating the updated value (Qpfr
— new) for said fluid removal rate (Qpfr) based on said set value for a fluid removal rate (Qpfr— set), on said value of fluid to be removed from the patient (Vpfr— need)over the time period (Tprosp) following the check point (Ti) and on the duration the time period (Tprosp) following the check point (Ti).
- determining a value of the fluid removed from the patient (Vpfr
In a 6th aspect according to any one of the preceding aspects, the control procedure comprises calculating the updated value (Qpfr
Qpfr
where:
-
- Qpfr
— set is the set value for fluid removal rate;
- Qpfr
Vpfr
-
- Tretro is a time period preceding check point (Ti);
- Tprosp is a time period following the check point (Ti);
- (Tretro+Tprosp) is the sum of the time period (Tretro) preceding check point (Ti) and of the time period (Tprosp) following the check point (Ti).
In a 7th aspect according to any one of the preceding aspects, each reference time interval (ΔT) is of prefixed duration, beginning at prefixed start times (T00; T00+ΔT; . . . ; T00+k·ΔT) and ending at prefixed ending times (T00+ΔT; T00+2ΔT; . . . ; T00+(k+1)·ΔT).
In a 8th aspect according to the 7th aspect the control procedure comprises calculating the updated value (Qpfr
Qpfr
or
Qpfr
where:
-
- Qpfr
— set is the set value for fluid removal rate; - Vpfr(0) is the value of the fluid removed from the patient over time window running from (T00+k·ΔT) to check point (Ti);
- Vpfr(k−1) is the value of the fluid removed from the patient over time window running from (T00+(k−1)·ΔT) to (T00+k·ΔT);
- [(T00+(k+1)·ΔT)−Ti] is the duration of time period following the check point (Ti);
- ΔT is the reference time interval.
- Qpfr
In a 9th aspect according to any one of the preceding aspects, the control procedure comprises:
-
- determining an effective portion (Teff) of said the time period (Tprosp; [T00+(k+1)·ΔT)−Ti]) following the check point (Ti), during which it is forecasted that the ultrafiltration actuator will be actually pulling fluid from the primary into the secondary chamber (4);
- calculating the updated value (Qpfr
— new) for said fluid removal rate (Qpfr) using said effective portion (Teff) in place of the duration the time period following the check point (Ti).
In a 10th aspect according to any one of the preceding aspects the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity linked to the number of bag changes expected in the next time period.
In a 11th aspect according to any one of the preceding aspects the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity linked to down times caused by alarm conditions.
In a 12th aspect according to any one of the preceding aspects from the 5th to the 11th the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity 11 linked to down times caused by alarm conditions if the duration of the time period (Tprosp) following the check point (Ti) is greater than a prefixed duration, such as grater than 30 mins or grater than 60 mins.
In a 13th aspect according to any one of the preceding aspects, the control unit is configured for receiving the set value (Qpfr
In a 14th aspect according to any one of the preceding aspects, the apparatus further comprises a user interface (12) connected to the control unit (10), said control unit being configured to execute the following before executing the control procedure:
-
- display on the user interface an indicium prompting a user to select a set value (Qpfr
— set) for the patient fluid removal rate (Qpfr). - detect entry by the user of the set value (Qpfr
— set) for the patient fluid removal rate (Qpfr), - receive the entered set value (Qpfr
— set) for the patient fluid removal rate (Qpfr).
- display on the user interface an indicium prompting a user to select a set value (Qpfr
In a 15th aspect according to any one of the preceding aspects, the apparatus further comprises a pre-dilution fluid line (15) connected to the blood withdrawal line and a pre-dilution pump (18) connected to the control unit (10) and acting on the pre-dilution line for regulating the flow through said pre-dilution fluid.
In a 16th aspect according to any one of the preceding aspects, the apparatus further comprises a post-dilution fluid line (25) connected to the blood return line and a post-dilution pump (27) connected to the control unit (10) and acting on the post-dilution line for regulating the flow through said post-dilution fluid line.
In a 17th aspect according to any one of the preceding aspects, the apparatus further comprises a dialysis fluid line (19) connected to the inlet of the secondary chamber and a dialysis fluid pump (21) connected to the control unit (10) and acting on the dialysis liquid line for regulating the flow through said dialysis fluid line.
In a 18th aspect according to any one of the preceding aspects, the apparatus further comprises a pre-blood pump infusion line (22) connected to the blood withdrawal line in a region of this latter which is positioned in use upstream the blood pump, a pre-blood infusion pump (24) connected to the control unit (10) and acting on the pre-blood pump infusion line for regulating the flow through said pre-blood pump infusion line.
In a 19th aspect according to any one of the preceding aspects from the 15th to the 18th said control unit is configured to receive set values for one or more fluid flow rates selected in the group including a fluid flow rate (Qeff) through the effluent line (13), a fluid flow rate (Qrep, Qpbp) through the infusion fluid line (15, 22, 25), a fluid flow rate (Qdial) through the dialysis liquid fluid line (19), in addition to said fluid removal rate (Qpfr) from the patient and to control said pumps and said actuator based on the set values for said one or more fluid flow rates and for said fluid removal rate (Qpfr) from the patient.
In a 20th aspect according to any one of the preceding aspects from the 15th to the 18th, the apparatus further comprises a syringe pump connected to the blood withdrawal line and/or a syringe pump connected to the blood return line said control unit is configured to receive set values for the fluid flow rates through the syringe pump or syringe pumps and to control said infusion pumps, said dialysis pump and said ultrafiltration actuator based on the set values for said one or more fluid flow rates, for said fluid removal rate (Qpfr) from the patient, and on the set flow rates for the syringe pumps. In practice each line is controlled based on the respective set flow rate, except for the effluent line where the ultrafiltration actuator (e.g. a pump) is controlled based on the Qeff calculated using formulas (1), (2) or (3) described below in the detailed description, adopting Qpfr
In a 21st aspect according to any one of the preceding aspects the control procedure comprises requesting the user, optionally via the user interface, to confirm that the calculated updated value (Qpfr
In a 22nd aspect according to any one of the preceding aspects the control procedure comprises comparing the calculated updated value (Qpfr
In a 23rd aspect according to any one of the preceding aspects the control procedure comprises executing one or more of the following safety checks:
-
- comparing the ratio between the calculated updated value and the set value for the patient fluid removal rate with a first boundary condition (typically to ±30%),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate with a second boundary condition (typically by ±100 ml/h),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate as a function of patient body weight with a third boundary condition (typically by 0.1 ml/min/kg),
- wherein the control procedure comprises verifying that a prefixed number, optionally all, of said checks is positively passed before using the update value for controlling the ultrafiltration actuator,
- optionally wherein said control unit is configured for allowing setting of one or more of said boundary conditions.
In a 24th aspect according to any one of the preceding aspects the ultrafiltration actuator comprises a waste pump (17) acting on the effluent conduit (13), this latter leading to a waste container (14) configured for collecting fluid extracted from the secondary chamber (4);
- at least one sensor (33) being associated to the waste container and being communicatively connected to the control unit, wherein the sensor is configured to:
- determine the weight or the volume of the fluid in said waste container and
- generate corresponding measurement signals (Wi) for the control unit, and wherein the control unit (10) is configured to calculate the actual quantity of fluid removed from the patient (Vpfr) over the reference time interval based at least on said measurement signals (Wi) coming from the sensor.
In a 25th aspect according to the preceding aspect, the apparatus comprises one or more of the following containers:
- a pre-dilution fluid container connected to the pre-dilution line (15),
- a post-dilution fluid container connected to the post-dilution fluid line (25),
- a dialysis fluid container connected to the dialysis fluid line (19),
- a pre-blood pump infusion fluid container connected to the pre-blood pump infusion (22) line,
- a respective weighing sensor (34, 37, 35, 36) associated to each one of the above fluid containers and connected to the control unit (10),
- wherein said control unit is configured to receive set values for one or more fluid flow rates selected in the group including a fluid flow rate (Qeff) through the effluent line (13), a fluid flow rate (Qrep, Qpbp) through the infusion fluid line (15, 21, 25), a fluid flow rate (Qdial) through the dialysis liquid fluid line (27), in addition to said fluid removal rate (Qpfr) from the patient, weigh signals (Wi) from said weighing sensors and to control said pumps and said actuator based on said weight signals, the set values for said one or more fluid flow rates and for said fluid removal rate (Qpfr) from the patient.
In a 26th aspect according to the preceding aspect, the apparatus comprises the following containers:
- a pre-dilution fluid container connected to the pre-dilution line (15),
- a post-dilution fluid container connected to the post-dilution fluid line (25),
- a dialysis fluid container connected to the dialysis fluid line (19),
- a respective weighing sensor associated to each one of the above fluid containers and connected to the control unit (10),
- wherein said control unit is configured to receive set values for a fluid flow rate (Qeff) through the effluent line (13), a fluid flow rate (Qrep) through the infusion fluid line, a fluid flow rate (Qdial) through the dialysis liquid fluid line, in addition to said fluid removal rate (Qpfr) from the patient, weigh signals (Wi) from said weighing sensors and
- to control said pumps and said actuator based on said weight signals, the set values for said fluid flow rates and for said fluid removal rate (Qpfr) from the patient.
A 27th aspect relates to a process for controlling an apparatus for extracorporeal treatment of blood, the apparatus being of the type comprising: a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semi-permeable membrane (5); a blood withdrawal line (6) connected to an inlet of the primary chamber (3), and a blood return line (7) connected to an outlet of the primary chamber (4) said blood lines being designed to be connected to a patient cardiovascular system; a blood pump (11) for controlling the flow of blood through the blood lines (6, 7); an effluent fluid line (13) connected to an outlet of the secondary chamber (4); an ultrafiltration actuator connected to the effluent fluid line (13) and configured to cause a transfer of fluid from the primary (3) to the secondary chamber (4). The process, which may for instance be executed by a control unit, includes the steps of:
-
- controlling the ultrafiltration actuator based on a set value (Qpfr
— set) for patient fluid removal rate, said set value (Qpfr— set) being a desired value for the rate of fluid removal from the patient, - executing at check points (Ti) during patient treatment a control procedure comprising:
- receiving one check information selected in the group of:
- a value of fluid removed from the patient (Vpfr
— removed; Vpfr(0)) over a time period (Ti-Tretro to Ti) preceding a check point (Ti), - an effective time portion, of said time period (Ti-Tretro to Ti) preceding a check point (Ti), during which said ultrafiltration actuator is operated,
- a down time portion, of said time period (Ti-Tretro to Ti) preceding a check point (Ti), during which said ultrafiltration actuator is not operated,
- a value of fluid removed from the patient (Vpfr
- receiving one check information selected in the group of:
- calculating an updated value (Qpfr
— new) for said fluid removal rate (Qpfr) as a function of said set value for a fluid removal rate (Qpfr— set) and of said check information.
- controlling the ultrafiltration actuator based on a set value (Qpfr
In a 28th aspect according to the 27th aspect, the control procedure further comprises, after calculation of said updated value (Qpfr
In a 29th aspect according to any one of the preceding 2 aspects, the control procedure further comprises controlling the ultrafiltration actuator, after the check point and until either a subsequent check point as a function of said updated value (Qpfr
In a 30th aspect according to any one of the preceding 3 aspects comprising re-executing said control procedure at a plurality of check points (Ti) during patient treatment, said plurality of check points being one or more in the group of:
-
- check points at regular intervals,
- periodic check points,
- check points triggered by specific setting of a new set value (Qpfr
— set) for patient fluid removal rate, - check points triggered by a stop in the ultrafiltration actuator,
- check points triggered by each time a flow rate setting is changed.
In a 31st aspect according to any one of the preceding 4 aspects, the control procedure comprises:
-
- determining a value of the fluid removed from the patient (Vpfr
— removed) over a time period (Tretro) preceding a check point (Ti); - determining a value of fluid to be removed from the patient (Vpfr
— need) over a time period (Tprosp) following the check point (Ti) in order to achieve the set value (Qpfr— set) for fluid removal rate (Qpfr) over the sum of the time period (Tretro) preceding check point (Ti) and of the time period (Tprosp) following the check point (Ti); - calculating the updated value (Qpfr
— new) for said fluid removal rate (Qpfr) based on said set value for a fluid removal rate (Qpfr— set), on said value of fluid to be removed from the patient (Vpfr— need) over the time period (Tprosp) following the check point (Ti) and on the duration the time period (Tprosp) following the check point (Ti).
- determining a value of the fluid removed from the patient (Vpfr
In a 32nd aspect according to any one of the preceding 5 aspects, the control procedure comprises calculating the updated value (Qpfr
Qpfr
where:
-
- Qpfr
— set is the set value for fluid removal rate; - Vpfr
— removed is the value of the fluid removed from the patient over time period (Tretro) preceding a check point (Ti); - Tretro is a time period preceding check point (Ti);
- Tprosp is a time period following the check point (Ti);
- (Tretro+Tprosp) is the sum of the time period (Tretro) preceding check point (Ti) and of the time period (Tprosp) following the check point (Ti).
- Qpfr
In a 33rd aspect according to any one of the preceding 6 aspects, each reference time interval (ΔT) is of prefixed duration, beginning at prefixed start times (T00; T00+ΔT; . . . ; T00+k·ΔT) and ending at prefixed ending times (T00+ΔT; T00+2ΔT; . . . ; T00+(k+1)·ΔT).
In a 34th aspect according to the preceding aspect the control procedure comprises calculating the updated value (Qpfr
Qpfr
or
Qpfr
where:
-
- Qpfr
— set is the set value for fluid removal rate; - Vpfr(0) is the value of the fluid removed from the patient over time window running from (T00+k·ΔT) to check point (Ti);
- Vpfr(k−1) is the value of the fluid removed from the patient over time window running from (T00+(k−1)·ΔT) to (T00+k·ΔT);
- [(T00+(k+1)·ΔT)−Ti] is the duration of time period following the check point (Ti);
- ΔT is the reference time interval.
- Qpfr
In a 35th aspect according to any one of the preceding 8 aspects, the control procedure comprises:
-
- determining an effective portion (Teff) of said the time period (Tprosp; [T00+(k+1)·ΔT)−Ti]) following the check point (Ti), during which it is forecasted that the ultrafiltration actuator will be actually pulling fluid from the primary into the secondary chamber (4);
- calculating the updated value (Qpfr
— new) for said fluid removal rate (Qpfr) using said effective portion (Teff) in place of the duration the time period following the check point (Ti).
In a 36th aspect according to any one of the preceding 9 aspects the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity linked to the number of bag changes expected in the next time period.
In a 37th aspect according to any one of the preceding 10 aspects the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity linked to down times caused by alarm conditions.
In a 38th aspect according to any one of the preceding 7 aspects the effective portion (Teff) is calculated reducing the duration of said the time period following check point (Ti) by a quantity 11 linked to down times caused by alarm conditions if the duration of the time period (Tprosp) following the check point (Ti) is greater than a prefixed duration, such as grater than 30 mins or grater than 60 mins.
In a 39th aspect according to any one of the preceding aspects, the process includes receiving the set value (Qpfr
In a 40th aspect according to any one of the preceding 13 aspects, the process comprises executing the following steps before executing the control procedure:
-
- display on a user interface an indicium prompting a user to select a set value (Qpfr
— set) for the patient fluid removal rate (Qpfr), - detect entry by the user of the set value (Qpfr
— set) for the patient fluid removal rate (Qpfr), - receive the entered set value (Qpfr
— set) for the patient fluid removal rate (Qpfr).
- display on a user interface an indicium prompting a user to select a set value (Qpfr
In a 41th aspect according to any one of the preceding 14 aspects, the apparatus is of the type disclosed in any one of aspects from the 15th to the 20th.
In a 42nd aspect according to any one of the preceding 15 aspects the control procedure comprises comparing the calculated updated value (Qpfr
In a 43rd aspect according to any one of the preceding 16 aspects the control procedure comprises executing one or more of the following safety checks:
-
- comparing the ratio between the calculated updated value and the set value for the patient fluid removal rate with a first boundary condition (typically to ±30%),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate with a second boundary condition (typically by ±100 ml/h),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate as a function of patient body weight with a third boundary condition (typically by 0.1 ml/min/kg),
wherein the control procedure comprises verifying that a prefixed number, optionally all, of said checks is positively passed before using the update value for controlling the ultrafiltration actuator.
In a 44th aspect according to any one of the preceding aspects the ultrafiltration actuator comprises a waste pump (17) acting on the effluent conduit (13), this latter leading to a waste container (14) configured for collecting fluid extracted from the secondary chamber (4);
- at least one sensor (33) being associated to the waste container and being communicatively connected to the control unit, wherein the sensor is configured to:
- determine the weight or the volume of the fluid in said waste container and
- generate corresponding measurement signals (Wi) for the control unit, and wherein the process comprises the step of calculating the actual quantity of fluid removed from the patient (Vpfr) over the reference time interval based at least on said measurement signals (Wi) coming from the sensor.
In a 45th aspect according to the preceding aspect, the apparatus comprises one or more of the following containers:
- a pre-dilution fluid container connected to the pre-dilution line (15),
- a post-dilution fluid container connected to the post-dilution fluid line (25),
- a dialysis fluid container connected to the dialysis fluid line (19),
- a pre-blood pump infusion fluid container connected to the pre-blood pump infusion (22) line,
- a respective weighing sensor (34, 37, 35, 36) associated to each one of the above fluid containers and connected to the control unit (10),
- wherein said process comprises receiving set values for one or more fluid flow rates selected in the group including a fluid flow rate (Qeff) through the effluent line (13), a fluid flow rate (Qrep, Qpbp) through the infusion fluid line (15, 21, 25), a fluid flow rate (Qdial) through the dialysis liquid fluid line (27), in addition to said fluid removal rate (Qpfr) from the patient, weigh signals (Wi) from said weighing sensors and to control said pumps and said actuator based on said weight signals, the set values for said one or more fluid flow rates and for said fluid removal rate (Qpfr) from the patient.
In a 46th aspect a data carrier including instructions executable by a control unit of a blood treatment (for instance of the blood treatment device of any one of aspects from 1st to 26th apparatus) is provided. The instructions are configured such that, when executed by the control unit, they cause execution of the process according to any one of the preceding aspects from 27th to 45th.
In a 47TH aspect according to the preceding aspect the data carrier may be any support suitable for storing data, such as by way of non-limiting example: a RAM, a ROM, an EPROM, an optical or a magnetic disc, an electromagnetic wave, a mass memory storage device such as an Hard Disk or a flash memory bank.
Aspects of the invention are shown in the attached drawings, which are provided by way of non-limiting example, wherein:
In fact, the apparatus 1 comprises a filtration unit 2 having a primary chamber 3 and a secondary chamber 4 separated by a semi-permeable membrane 5; depending upon the treatment, the membrane of the filtration unit may be selected to have different properties and performances. A blood withdrawal line 6 is connected to an inlet of the primary chamber 3, and a blood return line 7 is connected to an outlet of the primary chamber 3. In use, the blood withdrawal line 6 and the blood return line 7 are connected to a needle or to a catheter or other access device (not shown) which is then placed in fluid communication with the patient vascular system, such that blood can be withdrawn through the blood withdrawal line, flown through the primary chamber and then returned to the patient's vascular system through the blood return line. An air separator, such as a bubble trap 8 may be present on the blood return line; moreover, a safety clamp 9 controlled by a control unit 10 may be present on the blood return line downstream the bubble trap 8. A bubble sensor 8a, for instance associated to the bubble trap 8 or coupled to a portion of the line 7 between bubble trap 8 and clamp 9 may be present: if present, the bubble sensor is connected to the control unit 10 and sends to the control unit signals for the control unit to cause closure of the clamp 9 in case one or more bubbles above certain safety thresholds are detected. As shown in
The dialysis fluid pump 21, the infusion fluid pump 15 and the effluent fluid pump 17 are operatively connected to the control unit 10 which controls the pumps as it will be in detail disclosed herein below. The control unit 10 is also connected to the user interface 12, for instance a graphic user interface, which receives operator's inputs and displays the apparatus outputs. For instance, the graphic user interface 12 may include a touch screen, a display screen and hard keys for entering user's inputs or a combination thereof.
The embodiment of
The apparatus of
A third embodiment is shown in
In each one of the above described embodiments an ultrafiltration actuator, comprising the effluent fluid pump 17, is inserted into the effluent fluid line 13 and configured to cause a transfer of fluid from the primary 3 to the secondary chamber 4; in practice, in the embodiment of
In order to measure the quantity of fluid delivered or collected in each container, appropriate sensors are used. For instance, referring to
From a structural point of view one or more, all containers 14, 16, 20, 23 may be disposable plastic containers, for instance bags which are hang on a support carried by the respective scale. All lines and the filtration unit may also be plastic disposable components which may be mounted at the beginning of the treatment session and then disposed of at the end of the treatment session. Pumps, e.g. peristaltic pumps, have been described as means for regulating fluid flow through each of the lines; however it should be noted that other flow regulating means could alternatively be adopted such as for example valves or combinations of valves and pumps. The scales may comprise piezoelectric sensors, or strain gauges, or spring sensors, or any other type of transducer able to sense forces applied thereon. Although the examples in the figures show use of scales for determining the amount of fluid in the respective containers and for allowing calculation of the respective flow rates through the various lines, it should be noted that volumetric sensors for determining flow rates or combinations of mass and volumetric sensors may alternatively be adopted.
OperationReference is made by way of non limiting example to the flowchart of
Qeff
Note that in case there is a pre-blood pump infusion line either the user shall enter a set value Qpbp
Qeff
Of course, in case there is no infusion line and no dialysis line then equation (2) becomes:
Qeff
Then, the control unit uses the calculated Qeff
The control unit 10 is also configured to execute at check points Ti (step 103) during patient treatment a control procedure comprising the steps 104, 105 and 106 as schematically shown in the flow chart of
The control unit 10 may be configured for re-executing the control procedure at a plurality of check points Ti during patient treatment: various criteria may be adopted to identify the check points Ti. For instance the control procedure may be repeated at periodic check points or at check points separated by time intervals following a prescribed rule (i.e. the time intervals between consecutive check points may not be all equal but nevertheless follow a prescribed rule). According to a further alternative the control procedure may be activated at check points triggered by specific events, such as a downtime of the machine due to a bag change or other reason, setting of a new set value Qpfr
Going now into the details of the exemplifying embodiment of
Step 104: receiving one check information selected in the group of:
-
- a. a value of fluid removed from the patient over a time period preceding a check point
Ti; this value may be calculated or measured by the scale or scales.
-
- b. an effective time portion, of said time period preceding a check point, during which said ultrafiltration actuator is operated; this value may be measured by the apparatus taking detecting all intervals when the machine or the treatment is stopped, e.g. due to an alarm or due to a bag change or due to a change of the disposable set or due to other reasons.
- c. a down time portion, of said time period preceding a check point Ti, during which said ultrafiltration actuator is not operated; this value may be measured by the apparatus taking detecting all intervals when the machine or the treatment is stopped, e.g. due to an alarm or due to a bag change or due to a change of the disposable set or due to other reasons.
Step 105: calculating an updated value Qpfr
Steps 106: after calculation of said updated value Qpfr
At step 102 the control unit controls the ultrafiltration actuator (and the other pumps if present as above described in connection with step 102) as a function of said new Qeff and therefore as a function of the updated value Qpfr
The control with the updated value may start immediately after the check point and last until a subsequent check point.
Here below some implementing examples are provided in order to exemplify the operation of apparatuses according to the invention. In below examples it is assumed that the set patient fluid flow rate Qpfr
In this embodiment, the control procedure comprises:
-
- determining a value of the fluid removed from the patient Vpfr
— removed over a time period Tretro preceding a check point Ti; - determining a value of fluid to be removed from the patient Vpfr
— need over a time period Tprosp following the check point Ti in order to achieve the set value Qpfr— set for fluid removal rate Qpfr over the sum of the time period Tretro preceding check point Ti and of the time period Tprosp following the check point (Ti); inFIG. 5 , Tretro is equal to Tprosp: although this may be a preferred option, it should be noted that Tretro may also be different from Tprosp. - calculating the updated value Qpfr
— new for said fluid removal rate Qpfr based on the set value for a fluid removal rate Qpfr— set, on the value of fluid to be removed from the patient Vpfr— need over the time period Tprosp following the check point (Ti) and on the duration the time period Tprosp following the check point Ti.
- determining a value of the fluid removed from the patient Vpfr
For example the following formula may be adopted for the calculation of Qpfr
Qpfr
where:
-
- Qpfr
— set is the set value for fluid removal rate; - Vpfr
— removed is the value of the fluid removed from the patient over time period Tretro preceding a check point Ti; - Tretro is a time period preceding check point Ti;
- Tprosp is a time period following the check point Ti;
- (Tretro+Tprosp) is the reference time interval which is the sum of the time period Tretro preceding check point Ti and of the time period Tprosp following the check point Ti.
- Qpfr
The ‘check point’ Ti, when instantaneous Qpfr
-
- after each treatment interruption (down time),
- on a periodic basis,
- each time the a flow rate setting is changed,
- by time Ti+Tprosp.
In the context of patient fluid removal management, relevant values for Tretro and Tprosp may be in the range of 1 to 6-8 hours.
Applying the above algorithm to the apparatus of
-
- the operator initially sets a Qpfr
— set=100 ml/h, - Tretro and Tprosp both equal to 4 h,
- the fluid actually removed Vpfr
— removed from the patient as measured by scale 33 (in case the apparatuses ofFIGS. 1 and 2 would be used then information from all scales would be received by the control unit) over time period Tretro=4 h preceding check point T1 is Vpfr— removed=390 ml,
then applying formula (4) above:
- the operator initially sets a Qpfr
Qpfr
Thus, the control unit 10 will control the pump 17 based on the new calculated value of 102.5 ml/h during the 4 h following the first check point.
EXAMPLE 2In this case, the procedure aims at achieving the most accurate Patient Fluid Removal over predefined time periods. In this example, periods of constant duration ΔT are prefixed, beginning at a prefixed time T00:
T00; T00+ΔT; . . . ; T00+k·ΔT
and ending at prefixed ending times
T00+ΔT; T00+2ΔT; . . . ; T00+(k+1)·ΔT.
In this variant, the control unit 10 aims at delivering the exact patient fluid removal prescription over predefined time windows, such as matching with staff shifts or simply ‘round hours’ (13:00, 14:00, 15:00 . . . ).
The ‘check point’ Ti when instantaneous Qpfr
-
- at each treatment interruption (down time),
- at each time a flow rate setting is changed,
- at each predefined time window limit (T00+k.T),
According to this variant, the control procedure comprises calculating the updated value Qpfr
Qpfr
or according to the formula (which takes into account the volume of fluid removed in a further time window):
Qpfr
where:
- Qpfr
— set is the set value for fluid removal rate; - Vpfr(0) is the value of fluid removed from patient over time window running from (T00+k·ΔT) to check point (Ti);
- Vpfr(k−1 ) is the value of fluid removed from patient over time window running from (T00+(k−1)·ΔT) to (T00+k·ΔT);
- [(T00+(k+1)·ΔT)−Ti] is the duration of time period following the check point (Ti);
- ΔT is the duration of the reference time interval.
Note:
Formula 5 is equivalent to formula 4 with:
Tretro+Tprosp=ΔT
Tprosp=(T00+(k+1)·ΔT)−Ti
Formula 6 is equivalent to formula 4 with:
Tretro+Tprosp=2ΔT
Tprosp=(T00+(k+1)·ΔT)−T,
Applying the above algorithm to the apparatus of
-
- the operator initially sets a Qpfr
— set=100 ml/h; - Predefined time windows: 0:00; 4:00; 8:00; 12:00; 16:00; 20:00;
- Check time Ti: 10:30,
- the fluid actually removed over [4:00; 8:00] as measured by scale 33 (of course in case the apparatuses of
FIGS. 1 and 2 would be used then information from all scales would be received by the control unit) is Vpfr(k−1)=396 ml; - the fluid actually removed over [4:00; 10:30] as measured by scale 33 (of course in case the apparatuses of
FIGS. 1 and 2 would be used then information from all scales would be received by the control unit) is Vpfr(0)=245 ml,
then applying formula (6) above:
- the operator initially sets a Qpfr
Qpfr
Thus, the control unit 10 will control the pump 17 based on the new calculated value of 106.0 ml/h during the 1.5 h following the check point at 10.30 in order to achieve the desired patient fluid removal by 12.00.
Anticipation of Down TimesPerformance of the previous algorithms may be further enhanced when anticipating ‘future’ down times.
Several types of down-times may be estimated:
-
- related to bag management: flow rate and bag volume data available to the system allow anticipating the number of bag changes which will occur over the period of interest; corresponding down time of the ultrafiltration actuator may then be derived using an assumption of the time used for changing a bag; such an estimate may derive from general statistical data or statistics more specific to the system in use and the local handling processes;
- related to alarms: a simple alarm down time coefficient may be applied to estimate for the down times related to alarms interrupting the ultrafiltration actuator. Again such a coefficient may be built in the system or derived from statistics specific on the system in use.
By calculating the impact of the above down times it is possible to account for the effective portion Teff of the time period after check time Ti during which it is forecasted that the ultrafiltration actuator will be actually pulling fluid from the primary into the secondary chamber 4. This allows further correcting the value of the new calculated patient fluid removal rate.
In practice, the control procedure described above may comprises a step of determining an effective portion Teff of said the time period Tprosp or (T00+(k+1)·ΔT)−Ti following the check point Ti. Then, the updated value Qpfr
The following example is similar to Example 2 (reference is made to
Applying algorithm (6) to the apparatus of
-
- the operator initially sets a Qpfr
— set=100 ml/h; - Predefined time windows: 0:00; 4:00; 8:00; 12:00; 16:00; 20:00;
- Check time Ti: 10:30,
- the fluid actually removed over [4:00; 8:00] as measured by scale 33 is Vpfr(k−1)=396 ml;
- the fluid actually removed over [4:00; 10:30] as measured by scale 33 is Vpfr(0)=245 ml;
- Number of bag changes planned over [10:30; 12:00]: Nchange
— bag=2; - Mean time for changing a bag: Tchange
— bag=100 s; - Alarm down time coefficient: Kalarm=1.7%,
- the operator initially sets a Qpfr
Thus, the effective run time of ‘prospective’ time window [10:30; 12:00] is:
Teff=1.5−0.017·1.5−2·(100/3600)=1.42 h
It should be noted that in calculating Teff, where Tprosp becomes small (e.g. <30 minutes) the predictive term due to alarms may be ignored.
Then applying formula (6) using the calculated Teff:
Qpfr
Thus, the control unit 10 will control the pump 17 based on the new calculated value of 112.1 ml/h during the 1.5 h following the check point at 10.30 in order achieve the most accurate delivery of the desired patient fluid removal over the time periods [4:00; 8:00] and [8:00; 12:00]. According to the criteria used for deciding on check points, this flow rate will be further adjusted at least twice before the current time period [8:00; 12:00] is elapsed (2 planned bag changes).
EXAMPLE 4In this case, and as in example 2, the procedure aims at achieving the most accurate Patient Fluid Removal over predefined time periods. However, in this example, the time periods are defined around the clock and may be of different durations.
N clock times between 0:00 and 24:00 (T1, T2, . . . Tk, . . . TN) define N time periods [Tk, Tk+1] (for k=1 to N and TN+1=T1).
In this variant, the control unit 10 aims at delivering the exact patient fluid removal prescription over each predefined time window, such as matching with staff shifts.
The ‘check point’ Ti when instantaneous Qpfr
-
- at each treatment interruption (down time),
- at each time a flow rate setting is changed,
- at each predefined clock time Tk.
According to this variant, the control procedure comprises calculating the updated value Qpfr
Qpfr
where:
- Qpfr
— set is the set value for fluid removal rate; - Vpfr(0) is the value of fluid removed from patient over time window running from clock time Tk to check point (Ti);
- Tk+1−Tk matches with Tretro+Tprosp;
- Tk+1−Ti matches with Tprosp;
Applying the above algorithm (again refer to
-
- the operator initially sets a Qpfr
— set=100 ml/h; - Predefined clock times: 6:00; 13:00; 20:00;
- Check time Ti: 11:12;
- The fluid actually removed over [6:00; 11:12] as measured by scale 33 (of course in case the apparatuses of
FIGS. 1 and 2 would be used then information from all scales would be received by the control unit) is Vpfr(k−1)=508 ml; - No bag change expected before next predefined clock time T2=13:00;
- Mean time for changing a bag: Tchange
— bag=100 s; - Alarm down time coefficient: Kalarm=1.5%, the effective run time Teff of ‘prospective’ time window [11:12; 13:00] is:
- the operator initially sets a Qpfr
Teff=(13.0−11.2)−0.015·.(13.0−11.2)−0. (100/3600)=1.773 h
Then, applying formula (7) above:
Qpfr
Thus, the control unit 10 will control the pump 17 based on the new calculated value of 108.3 ml/h from the 11:12 check point in order to achieve the desired patient fluid removal by 13.00.
Safety FeaturesThe apparatus described above may include one or more of the following safety features.
For instance safety features below disclosed may play an important role after a therapy interruption of several tens of minutes, e.g. change of the disposable tubing or substitution of filter set associated with the apparatus, temporary patient disconnection due to any reason. These situations may lead to relatively high Qpfr_new values which if actuated with no safety checks might lead to problems for the treated patient.
The control procedure executed by the control unit 10 may include a step of requesting the user, for instance via the user interface 12, to confirm that the calculated updated value Qpfr
The control procedure may also include comparing the calculated updated value Qpfr
The control procedure may comprise executing one or more of the following further safety checks:
-
- comparing the ratio between the calculated updated value and the set value for the patient fluid removal rate with a first boundary condition (typically to ±30%),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate with a second boundary condition (typically by ±100 ml/h),
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate as a function of patient body weight with a third boundary condition (typically by 0.1 ml/min/kg).
If a prefixed number of said checks is positively passed, for instance if all checks are passed, the update value Qpfr
Note that the control unit is may also be configured for allowing setting of one or more boundary conditions in order to customize the apparatus to specific needs or patients.
Control UnitAs already indicated the apparatus according to the invention makes use of at least one control unit. This control unit may comprise a digital processor (CPU) with memory (or memories), an analogical type circuit, or a combination of one or more digital processing units with one or more analogical processing circuits. In the present description and in the claims it is indicated that the control unit is “configured” or “programmed” to execute certain steps: this may be achieved in practice by any means which allow configuring or programming the control unit. For instance, in case of a control unit comprising one or more CPUs, one or more programs are stored in an appropriate memory: the program or programs containing instructions which, when executed by the control unit, cause the control unit to execute the steps described or claimed in connection with the control unit. Alternatively, if the control unit is of an analogical type, then the circuitry of the control unit is designed to include circuitry configured, in use, to process electric signals such as to execute the control unit steps herein disclosed.
Claims
1-26. (canceled)
27. A process of controlling an apparatus for extracorporeal treatment of blood, the apparatus being of the type comprising: a filtration unit having a primary chamber and a secondary chamber separated by a semi-permeable membrane; a blood withdrawal line connected to an inlet of the primary chamber, and a blood return line connected to an outlet of the primary chamber said blood lines being designed to be connected to a patient cardiovascular system; a blood pump for controlling the flow of blood through the blood lines; an effluent fluid line connected to an outlet of the secondary chamber; an ultrafiltration actuator connected to the effluent fluid line and configured to cause a transfer of fluid from the primary to the secondary chamber, and
- a control unit configured to execute a control procedure comprising: controlling the ultrafiltration actuator based on a set value for patient fluid removal rate, said set value being a desired value for the rate of fluid removal from the patient, executing at check points during patient treatment a control procedure comprising: receiving one check information selected in the group of: a value of fluid removed from the patient over a time period preceding a check point, an effective time portion, of a time period preceding a check point, during which said ultrafiltration actuator is operated, a down time portion, of a time period preceding a check point, during which said ultrafiltration actuator is not operated, calculating an updated value for said fluid removal rate as a function of said set value for a fluid removal rate and of said check information.
28. A process according to claim 27 wherein the control procedure further comprises, after calculation of said updated value, controlling the ultrafiltration actuator after the check point as a function of said updated value for the fluid removal rate.
29. (canceled)
30. A process according to claim 27, wherein the control procedure comprises re-executing said control procedure at a plurality of check points during patient treatment, said plurality of check points comprising one or more in the group of:
- check points at regular intervals,
- periodic check points,
- check points triggered by specific setting of a new set value for patient fluid removal rate,
- check points triggered by a stop in the ultrafiltration actuator,
- check points triggered by each time a flow rate setting is changed.
31. A process according to claim 27 wherein the control procedure comprises:
- determining a value of the fluid removed from the patient over a time period preceding a check point;
- determining a value of fluid to be removed from the patient over a time period following the check point in order to achieve the set value for fluid removal rate over the sum of the time period preceding check point and of the time period following the check point;
- calculating the updated value for said fluid removal rate based on said set value for a fluid removal rate, on said value of fluid to be removed from the patient over the time period following the check point and on the duration the time period following the check point.
32. A process according to claim 31 wherein the control procedure comprises calculating the updated value for said fluid removal rate at check point according to the formula: where:
- Qpfr—new=[(Tretro+Tprosp)·Qpfr—setVpfr—removed]/Tprosp
- Qpfr—new is the calculated updated value for said fluid removal rate;
- Qpfr—set is the set value for fluid removal rate;
- Vpfr—removed is the value of the fluid removed from the patient over time period Tretro preceding a check point;
- Tretro is a time period preceding the check point;
- Tprosp is a time period following the check point;
- (Tretro+Tprosp) is the sum of the time period (Tretro) preceding the check point and of the time period (Tprosp) following the check point.
33. (canceled)
34. A process according to claim 27 wherein the control procedure comprises calculating the updated value for said fluid removal rate at a check point comprised between a start time and an end time according to the formula: or where:
- Qpfr—new=(ΔT·Qpfr—set−Vpfr(0))/[(T00+(k+1)·ΔT)−Ti]
- Qpfr—new=(2·ΔT·Qpfr—set−Vpfr(0)−Vpfr(k−1))/[(T00+(k+1)·ΔT)−Ti]
- Qpfr—new is the updated value for fluid removal rate;
- Qpfr—set is the set value for fluid removal rate;
- (T00+k·ΔT) is the start time;
- T00+(k+1)·ΔT is the end time;
- Ti is the check point;
- Vpfr(0) is the value of the fluid removed from the patient over time window running from start time (T00+k·ΔT) to check point (Ti);
- Vpfr(k-1) is the value of the fluid removed from the patient over time window running from start time (T00+(k−1)·ΔT) to end time (T00+k·ΔT);
- [(T00+(k+1)·ΔT)−Ti] is the duration of time period following the check point (T1);
- ΔT is a reference time interval of prefixed duration.
35. A process according to claim 27 wherein the control procedure comprises:
- determining an effective portion of said the time period following the check point, during which it is forecasted that the ultrafiltration actuator will be actually pulling fluid from the primary into the secondary chamber;
- calculating the updated value for said fluid removal rate using said effective portion in place of the duration the time period following the check point.
36. A process according to claim 35 wherein the effective portion is calculated by reducing the duration of said the time period following check point by a quantity linked to one or more of:
- number of bag changes expected in the next time period;
- down times caused by alarm conditions;
- down times caused by alarm conditions if the duration of the time period following the check point is greater than a prefixed duration.
37-41. (canceled)
42. A process according to claim 27 wherein the control procedure comprises comparing the calculated updated value for said fluid removal rate against a maximum threshold value before using it for controlling the ultrafiltration actuator.
43. A process according to claim 27 wherein the control procedure comprises executing one or more of the following safety checks: wherein the control procedure comprises verifying that a prefixed number of said checks is positively passed before using the update value for controlling the ultrafiltration actuator.
- comparing the ratio between the calculated updated value and the set value for the patient fluid removal rate with a first boundary condition,
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate with a second boundary condition,
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate as a function of patient body weight with a third boundary condition,
44-47. (canceled)
48. An apparatus for extracorporeal treatment of blood comprising: an effluent fluid line connected to an outlet of the secondary chamber;
- a filtration unit having a primary chamber and a secondary chamber separated by a semi-permeable membrane;
- a blood withdrawal line connected to an inlet of the primary chamber, and a blood return line connected to an outlet of the primary chamber said blood lines being designed to be connected to a patient cardiovascular system;
- a blood pump for controlling the flow of blood through the blood lines;
- an ultrafiltration actuator connected to the effluent fluid line and configured to cause a transfer of fluid from the primary to the secondary chamber; and
- a control unit configured to control the ultrafiltration actuator based on a set value for patient fluid removal rate, said set value being a desired value for the rate of fluid removal from the patient, wherein the control unit is configured to execute at check points during patient treatment a control procedure comprising: receiving one check information selected in the group of: a value of fluid removed from the patient over a time period preceding a check point, an effective time portion, of a time period preceding a check point, during which said ultrafiltration actuator is operated, a down time portion, of a time period preceding a check point, during which said ultrafiltration actuator is not operated, calculating an updated value for said fluid removal rate as a function of said set value for a fluid removal rate and of said check information.
49. (canceled)
50. Apparatus according to claim 48 wherein the control procedure further comprises controlling the ultrafiltration actuator, after the check point and until a subsequent check point as a function of said updated value for the fluid removal rate.
51. Apparatus according to claim 48 wherein the control unit is configured for re-executing said control procedure at a plurality of check points during patient treatment, said plurality of check points comprising one or more in the group of:
- check points at regular intervals,
- periodic check points,
- check points triggered by specific setting of a new set value for patient fluid removal rate,
- check points triggered by a stop in the ultrafiltration actuator,
- check points triggered by each time a flow rate setting is changed.
52. The apparatus of claim 48 wherein the control procedure comprises:
- determining a value of the fluid removed from the patient over a time period preceding a check point;
- determining a value of fluid to be removed from the patient over a time period following the check point in order to achieve the set value for fluid removal rate over the sum of the time period preceding check point and of the time period following the check point;
- calculating the updated value for said fluid removal rate based on said set value for a fluid removal rate, on said value of fluid to be removed from the patient over the time period following the check point and on the duration the time period following the check point.
53. The apparatus of claim 52 wherein the control procedure comprises calculating the updated value for said fluid removal rate at check point according to the formula: where:
- Qpfr—new=[(Tretro+Tprosp)·Qpfr—set−Vpfr—removed]/Tprosp
- Qpfr—new is the calculated updated value for said fluid removal rate;
- Qpfr—set is the set value for fluid removal rate;
- Vpfr—removed is the value of the fluid removed from the patient over time period (Tretro) preceding a check point;
- Tretro is a time period preceding check point;
- Tprosp is a time period following the check point;
- (Tretro+Tprosp) is the sum of the time period (Tretro) preceding the check point and of the time period (Tprosp) following the check point.
54. (canceled)
55. The apparatus of claim 48 wherein the control procedure comprises calculating the updated value for said fluid removal rate at check point comprised between a start time and an end time according to the formula: or where:
- Qpfr—new=(ΔT·Qpfr—set−Vpfr(0))/[(T00+(k+1)·ΔT)−Ti]
- Qpfr—new=(2·ΔT·Qpfr—set−Vpfr(0)−Vpfr(k−1))/[(T00+(k+1)·ΔT)−Ti]
- Qpfr—new is the updated value for fluid removal rate;
- Qpfr—set is the set value for fluid removal rate;
- (T00+k·ΔT) is the start time;
- T00+(k+1)·ΔT is the end time;
- Ti is the check point;
- Vpfr(0) is the value of the fluid removed from the patient over time window running from start time (T00+k·ΔT) to check point (Ti);
- Vpfr(k−1) is the value of the fluid removed from the patient over time window running from start time (T00+(k−1)·ΔT) to end time (T00+k·ΔT);
- [(T00+(k+1)·ΔT)−Ti] is the duration of time period following the check point (Ti);
- ΔT is a reference time interval of prefixed duration.
56. The apparatus according to claim 48 wherein, the control procedure comprises:
- determining an effective portion of said the time period following the check point, during which it is forecasted that the ultrafiltration actuator will be actually pulling fluid from the primary into the secondary chamber;
- calculating the updated value for said fluid removal rate using said effective portion (Teff) in place of the duration the time period following the check point; wherein the effective portion is calculated reducing the duration of said the time period following the check point by a first quantity linked to the number of bag changes expected in the next time period and/or by a second quantity linked to down times caused by alarm conditions.
57-60. (canceled)
61. The apparatus according to claim 48 wherein the control procedure comprises:
- requesting the user, via a user interface, to confirm that the calculated updated value for said fluid removal rate is acceptable before using it for controlling the ultrafiltration actuator, and
- comparing the calculated updated value for said fluid removal rate against a maximum threshold value before using it for controlling the ultrafiltration actuator.
62. (canceled)
63. The apparatus according to claim 48 wherein the control procedure comprises executing one or more of the following safety checks: wherein the control procedure comprises verifying that a prefixed number of said checks is positively passed before using the update value for controlling the ultrafiltration actuator.
- comparing the ratio between the calculated updated value and the set value for the patient fluid removal rate with a first boundary condition,
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate with a second boundary condition,
- comparing the absolute difference between the calculated updated value and the set value for the patient fluid removal rate as a function of patient body weight with a third boundary condition,
64-65. (canceled)
Type: Application
Filed: Mar 22, 2013
Publication Date: Mar 5, 2015
Applicant: Gambro Lundia AB (Lund)
Inventor: Dominique Pouchoulin (Tramoyes)
Application Number: 14/388,295
International Classification: A61M 1/34 (20060101);