Apparatus for extracorporeal treatment of blood

Abstract

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.

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:
     Q   pfr     —     new =[( T   retro   +T   prosp )· Q   pfr     —     set   V   pfr     —     removed   ]/T   prosp  
 
 
       where:
 Q pfr     —     new  is the calculated updated value for said fluid removal rate; 
 Q pfr     —     set  is the set value for fluid removal rate; 
 V pfr     —     removed  is the value of the fluid removed from the patient over time period T retro  preceding a check point; 
 T retro  is a time period preceding the check point; 
 T prosp  is a time period following the check point; 
 (T retro +T prosp ) is the sum of the time period (T retro ) preceding the check point and of the time period (T prosp ) 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:
     Q   pfr     —     new =(Δ T·Q   pfr     —     set   −V   pfr(0) )/[( T   00 +( k+ 1)·Δ T )− T   i ]
 
 
       or
     Q   pfr     —     new =(2 ·ΔT·Q   pfr     —     set   −V   pfr(0)   −V   pfr(k−1) )/[( T   00 +( k+ 1)·Δ T )−T i ]
 
 
       where:
 Q pfr     —     new  is the updated value for fluid removal rate; 
 Q pfr     —     set  is the set value for fluid removal rate; 
 (T 00 +k·ΔT) is the start time; 
 T 00 +(k+1)·ΔT is the end time; 
 T i  is the check point; 
 V pfr(0)  is the value of the fluid removed from the patient over time window running from start time (T 00 +k·ΔT) to check point (T i ); 
 V pfr(k-1)  is the value of the fluid removed from the patient over time window running from start time (T 00 +(k−1)·ΔT) to end time (T 00 +k·ΔT); 
 [(T 00 +(k+1)·ΔT)−T i ] is the duration of time period following the check point (T 1 ); 
 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:
 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, 
 
       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. 
     
     
         44 - 47 . (canceled) 
     
     
         48 . An apparatus for extracorporeal treatment of blood 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 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:
     Q   pfr     —     new =[( T   retro   +T   prosp )· Q   pfr     —     set   −V   pfr     —     removed   ]/T   prosp  
 
 
       where:
 Q pfr     —     new  is the calculated updated value for said fluid removal rate; 
 Q pfr     —     set  is the set value for fluid removal rate; 
 V pfr     —     removed  is the value of the fluid removed from the patient over time period (T retro ) preceding a check point; 
 T retro  is a time period preceding check point; 
 T prosp  is a time period following the check point; 
 (T retro +T prosp ) is the sum of the time period (T retro ) preceding the check point and of the time period (T prosp ) 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:
     Q   pfr     —     new =(Δ T·Q   pfr     —     set   −V   pfr(0) )/[( T   00 +( k +1)·Δ T )− T   i ]
 
 
       or
     Q   pfr     —     new =(2 ·ΔT·Q   pfr     —     set   −V   pfr(0)   −V   pfr(k−1) )/[( T   00 +( k +1)·Δ T )− T   i ]
 
 
       where:
 Q pfr     —     new  is the updated value for fluid removal rate; 
 Q pfr     —     set  is the set value for fluid removal rate; 
 (T 00 +k·ΔT) is the start time; 
 T 00 +(k+1)·ΔT is the end time; 
 T i  is the check point; 
 V pfr(0)  is the value of the fluid removed from the patient over time window running from start time (T 00 +k·ΔT) to check point (T i ); 
 V pfr(k−1)  is the value of the fluid removed from the patient over time window running from start time (T 00 +(k−1)·ΔT) to end time (T 00 +k·ΔT); 
 [(T 00 +(k+1)·ΔT)−T i ] is the duration of time period following the check point (T i ); 
 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 (T eff ) 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:
 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, 
 
       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. 
     
     
         64 - 65 . (canceled)