with reference to fig1 , 1 denotes in its entirety an extracorporeal blood treatment apparatus , which in the specific case comprises a hemodiafiltration apparatus . the extracorporeal blood treatment apparatus can comprise any one of the hemodialysis or hemo ( dia ) filtration apparatus of the known art . 2 denotes a blood treatment device ( hemodialyser ) having a blood chamber 3 and a fluid chamber 4 which are separated from one another by a semipermeable membrane 5 . 6 denotes an extracorporeal blood circuit connected to the blood chamber 3 in order to transport blood from an individual 7 to the blood chamber 3 and to return the blood from the blood chamber 3 to the individual 7 . the blood circuit 6 comprises a removal line 8 ( arterial line ) and a return line 9 ( venous line ). the removal line 8 and the return line 9 can comprise any one of the arterial and venous lines known in the prior art and used in a hemodialysis or hemo ( dia ) filtration apparatus . in particular the removal line 8 and the return line 9 can be provided with and / or connected to various sensors and actuators of known type ( for example pressure sensors , blood presence sensors or patient sensors , liquid level sensors , air presence sensors , blood transport pumps , infusion liquid transport pumps , automatic check valves , liquid level regulation devices , etc .) for control and monitoring of the circuit , and to various devices of known type ( gas - liquid separating devices , access sites for removal / injection , manual clamps , service lines , etc .) for performing various operations on the circuit . 10 denotes in particular a sensor predisposed in the extracorporeal blood circuit ( in the specific case in the removal line 8 ) for emitting at least a signal indicating the change in hematic volume of the individual subjected to extracorporeal blood treatment . the sensor 8 , of known type , can emit for example an optical or acoustic signal . in the specific case the hematic volume 8 change sensor 8 comprises a hematocrit sensor . the signals emitted by the hematocrit sensor during the treatment are used in a known way for determining the change in hematic volume of the individual 7 . the apparatus 1 comprises a weight loss system for actuating the weight loss of the individual during the extracorporeal blood treatment . in the specific case the weight loss system comprises a discharge line 11 connected to an outlet of the fluid chamber 4 for removing a discharge liquid from the chamber and sending it to a drainage 12 . 13 denotes a discharge pump for moving the discharge liquid . 14 denotes a sensor configured for emitting at least a signal indicating the weight loss of the individual subjected to the extracorporeal blood treatment . in the specific case the sensor 14 comprises any one of the known - type sensor means used for detecting the weight loss of a patient in an ultrafiltration , a hemodialysis or a hemodiafiltration apparatus . in the specific case , in which the apparatus 1 is a hemodiafiltration apparatus , the sensor 14 can comprise , for example , the following systems of known type : a system of two flow - meters ( one upstream and one downstream of the hemodiafilter ), or a differential flow - meter , or a system of balances , or a system of control of the filling to predetermined volumes , or an ultrafiltration flow - rate sensor in the ambit of a fluid balancing system with variable - volume chambers , or other systems of known type . the hemodiafiltration apparatus comprises a supply system for supplying a treatment fluid of a predetermined composition to the fluid chamber 4 . the supply system can comprise any one of the supply systems of known type used for supplying a dialysis fluid and / or a substituting fluid in a hemodialysis apparatus or hemo ( dia ) filtration apparatus ( for example of a type with in - line preparation of the treatment fluid starting from water and concentrates or of the type which is sourced from a batch ). in the specific case the supply system comprises a supply line 15 connected to an inlet of the fluid chamber 4 , a source 16 of the treatment fluid ( batch - type or in - line preparation type ) and a supply pump 17 . the sensor 14 in this case will be connected to the supply line 15 in order to take account , in determining the weight loss of the individual , also of the treatment fluid flow , in particular the dialysis fluid which enters the fluid chamber 4 and / or the substitution fluid infused into the extracorporeal circuit 6 . in the specific case the source 16 comprises a device for in - line preparation of a treatment fluid with a predetermined concentration . the preparation device can comprise any one of the devices of known type used for this aim in a hemodialysis or hemo ( dia ) filtration machine . in particular the preparation device can prepare the treatment fluid starting from water and concentrates by means of the use of one or more electrical conductivity sensors for determining , in a known way , the composition of the prepared fluid . the structure and functioning of the treatment fluid preparation device is known and will therefore not be further explained herein . in use , the hemodiafiltration apparatus operates , in a known way , to effect a predetermined weight loss in the individual , giving rise to an ultrafiltration device for ultrafiltering liquid from the blood chamber 3 to the fluid chamber 4 through the semipermeable membrane 5 . in particular the ultrafiltration is performed thanks to the pressure difference on the two sides of the membrane 5 ( transmembrane pressure ) and the consequent convective transport of liquid generated by the discharge pump 13 which enables a pressure to be obtained in the fluid chamber 4 that is lower than the pressure in the blood chamber 3 . the ultrafiltration means are substantially of known type and thus do not require further explanation . it is also possible to use any other known method of ultrafiltration . the hemodiafiltration apparatus comprises an infusion device for infusing liquid into the extracorporeal circuit . in the specific case the infusion device comprises an infusion line 18 and an infusion pump 19 for the movement of the infusion fluid . in the specific case the infusion line 18 is connected in a branch relation with the supply line 15 via a branching point arranged downstream of the sensor 14 . the infusion line can be connected to an infusion fluid batch source . in the specific case the infusion line 18 is connected to the return line 9 ( post - dilution ), even though it would be possible to have , additionally or alternatively to the line 18 , an infusion line , not illustrated , connected to the removal line 8 ( pre - dilution ). the extracorporeal blood treatment apparatus comprises a control unit 20 configured to receive the relative blood and weight volume variation signals during the extracorporeal blood treatment . the control unit is configured to receive an effective weight value for the patient , a desired weight loss value for the patient , and is configured to determine at least a desired value of an individual &# 39 ; s parameter ( in particular the change in hematic volume desired at the end of the treatment ) on the basis of the effective weight value and the desired weight loss , and is also configured to control the weight loss system ( in particular ultrafiltation and / or infusion and / or supply of dialysis fluid ) from the above signal of hematic volume change and the desired value of a parameter of the individual . the control unit is configured to determine a plurality of desired values of the individual &# 39 ; s parameter according to the treatment time ( for example a desired profile of the hematic volume change during the course of treatment ) on the basis of the desired value of the individual &# 39 ; s parameter , which in particular might comprise an objective value of the individual &# 39 ; s parameter ( for example the change in the individual &# 39 ; s hematic volume ) which it is desired to obtain at the end of the treatment . the above - mentioned operation of determining at least a desired value of an individual &# 39 ; s parameter might comprise the sub - operations of receiving ( for example by entering a value via a user interface ) a desired value of a second parameter of an individual ( the second parameter being , for example the refilling index or another parameter which is a function of the individual &# 39 ; s parameter , the above - cited effect weight value and the desired weight - loss value ) and calculating the desired value of the individual &# 39 ; s parameter ( change in hematic volume ) on the basis of the previously - received desired value of the second parameter of the individual ( refilling index ). the second parameter of the individual can comprise a relation between the relative change in hematic volume and the relative weight loss , where the relative weight loss comprises a relation between a desired weight loss and an effective weight of the patient . in particular , as mentioned , the second parameter of the individual might comprise a refilling index ri as follows : where δbv % is the relative change in hematic volume , i . e . the change in hematic volume in relation to the total hematic volume , and wl % is the relative weight loss , i . e . the weight loss in relation to the total weight of the individual or the weight of the bodily water of the individual . the control unit can further be configured to receive a minimum threshold value and / or a maximum threshold value of acceptability for the second parameter of the individual . in the specific case in which the second parameter of the individual is the refilling index , the minimum threshold value might be comprised between 0 . 5 and 1 . 1 , while the maximum threshold value might be between 1 . 2 and 2 . 5 . the control unit can be further configured to receive a range of acceptable values for the second parameter of the individual . in the specific case in which the second parameter of the individual is the refilling index , the range of acceptable values might be from 0 . 5 to 2 . 5 , or from 0 . 5 to 2 . 0 , or from 0 . 7 to 1 . 5 , or from 0 . 75 to 1 . 3 . the above effective weight value of the individual might comprise a value selected from among the total body weight of the individual before or after the treatment and the weight of the bodily water of the individual before or after the treatment . the control unit might also be configured for controlling the ultrafiltration device on the basis of the signal of change in hematic volume and the desired value of a parameter of the individual . the control unit might also be configured for controlling the infusion device on the basis of the hematic volume change signal and the desired value of a parameter of the individual . further , the control unit might also be configured for controlling the treatment fluid supply system ( in particular the composition of the fluid via concentration / conductivity measurements ) on the basis of the above - mentioned hematic volume change signal and the desired value of a parameter of the individual . the control unit might operate the automatic control of the weight loss ( plasmatic ultrafiltration and / or infusion fluid supply / substitution and / or supply of dialysis fluid ) as described in italian patents it 1252601 and it 1276468 , on the basis of the detection of the hematic volume change , the weight loss and the conductivity of the dialysate , taking however into account the fact that in this case the objective value of the hematic volume change ( particularly at the end of treatment ) is obtained starting from the effective value of the patient &# 39 ; s weight ( wet / dry , before / after the treatment ). in this case in particular the desired profile for the hematic volume change according to treatment time is obtained as described in the above - mentioned patents it 1252601 and it 1276468 , but using as a reference point the objective value of the hematic volume change ( especially the value at end of treatment ) obtained starting from the effective weight value of the patient . let us suppose that for a certain patient it has been ascertained that on the basis of dialytic treatments undertaken previously and the consequent physiological reactions , an optimal value for the refilling index is 1 . 0 , which is therefore used as a setting value : this value is entered by the operator as a setting value for the treatment , using the user interface of the apparatus . the operator further enters a weight value for the patient , for example by using the user interface of the apparatus . this value can be the weight of the patient before treatment ( known as the wet weight ) or the patient &# 39 ; s weight after the treatment ( known as the dry weight ), or it can be the weight of the patient &# 39 ; s bodily water ( before or after the treatment ). the weight of the bodily water is calculable , as is known , as a function of the total weight of the patient , for example via a proportionality factor ( sometimes known as the bodily weight distribution volume ) which is normally considered to be between 50 % and 60 %, for example 55 %. thus , supposing for example that the dry weight of the patient ( at end of treatment ) is 80 kg , the weight of the bodily water at end of treatment can be calculated at 80 * 0 . 55 = 44 kg . the operator further enters the total body weight loss of the patient ( for example 4 . 5 kg ). this value too is entered as a setting value via the apparatus user interface . the control unit can thus calculate the percentage weight loss , i . e . the total weight loss normalised on the basis of the total weight ( of the bodily water ): the percentage weight loss can also be normalised on the basis of the total weight of the patient before or after treatment or the weight of the bodily water before treatment . the percentage variation of the hematic volume ( i . e . the variation in hematic volume normalised on the basis of the initial hematic volume ) which it is desired to obtain at the end of treatment is thus calculated on the basis of the percentage weight loss and the preset value of the refilling index according to the following formula : this value for δbv % is a desired value , i . e . the value of the percentage variation of the hematic volume which it is desired to obtain at the end of treatment . starting from the desired value δbv % a desired profile is calculated for the percentage variation of the hematic volume during the course of the treatment . it is evident that the initial value of δbv % will be 0 . this calculation of the profile can be performed using known methods , such as for example the one used in the hemocontrol ® control system of the integra ® dialysis machine . the determination of the desired profile for a certain patient can be performed , for example , by analysing the effective profile for that patient for a certain number of treatments . once the desired profile of the relative hematic volume change δbv % has been defined and stored by the control unit , the treatment can begin and proceed in a known way so that the relative variation in hematic volume which is effectively measured for the patient during the course of treatment follows the desired profile , at least within predetermined upper and lower limits . the control system for reaching this objective can be , as mentioned , of known type , for example a control system operating on the amount of weight loss of the patient and / or the conductivity of the dialysis fluid and / or the amount of the infusion liquid . the control system can comprise , for example , the system described in italian patent it 1252601 ( which is incorporated herein for the sake of reference ) or the hemocontrol ® used in integra ® dialysis machines . the individual &# 39 ; s weight can comprise , for example , the total body weight or the bodily water weight or another weight . the individual &# 39 ; s weight can comprise a weight considered wet or dry , or in another way . the control unit can be configured to receive the effective value of the individual &# 39 ; s weight which will be used as input directly from outside . the determination of the weight can also be performed ( possibly also by the control unit of the treatment apparatus ) by any one of the formulas of known type usable for this purpose , such as for example the formulas for the determination of the total bodily water volume ( watson &# 39 ; s formula , hume - weyer &# 39 ; s formula , mellits - cheek &# 39 ; s formula , etc .). the control unit , for example , can receive in input data relating to the patient to be subjected to the treatment ( for example sex , age , height , total weight etc ) and this data , via the use of one of the stored known formulas , can be configured to determine in outlet the total bodily water volume . it is also possible for the control unit to be configured to determine the weight of the individual in real - time , for example in a period of time at the start of treatment , on the basis of reading made by the sensors of the treatment apparatus or by external sensors applied to the individual and connected to the control unit of the apparatus . it is therefore possible for the individual &# 39 ; s weight value not necessarily to be introduced as input from the outside ( for example by an operator or by means of an identification system of the individual ) but to be calculated directly in - line , in particular with the individual connected to the treatment apparatus , using a mathematical model and values measured in - line .
an extracorporeal blood treatment apparatus comprises a sensor for emitting a signal indicating a change of hematic volume of an individual subjected to a treatment and a weight loss system for actuating the individual &# 39 ; s weight loss . a control unit receives an effective weight value of the individual and a desired weight loss value and from these values determines a desired value of a change in hematic volume at end of treatment . the weight loss system is controlled on a basis of the hematic volume change signal and the desired value of the hematic volume change . the apparatus enables automatic control of a dialysis operation while preventing some complications arising from hypotension .