DE2607022A1 - Haemodiafiltration with controlled substitution soln. - using difference in arterial and venous flow rates as variable - Google Patents

Abstract

A control circuit for regulating the feed of substitution soln. in haemodiafiltration equipment is intended for balancing the flow rate of the substitution soln. to the extn. rate of the filtrate from the patient; the substitution flow rate may be either equal to or less than the removal flow rate. The control variable used for the control circuit is the difference between the flow rate in the arterial and venose tube systems in the haemodiafiltration appts. Pref., this difference can be freely selected to various desired values, to enable the balancing to be carried out. Continuous measurement can be obtd. without difficulty enabling accurate balancing of the flow rates to be achieved.

Description

DESCRIPTION

Title control circuit for the addition of substitution solution for hemodiailtration devices, Field of application The invention relates to a Fegelkreis which continuously controls the addition of the substitution solution during the duration of the hemodiafiltration.

Purpose In hemodiafiltration it is necessary that the patient Volume of liquid withdrawn as ultrafiltrate by a suitable substitution solution to replace. To during the duration of the hemodiafiltration process serious Avoid balance disturbances (differential volume: ultrafiltrate / substitution solution), the addition of the substitution solution must be continuous according to the amount of produced ultrafiltrate volume. Furthermore, the possibility must be given be, during the entire duration of the hemodiafiltration process a predetermined, constant negativity (ultrafiltration volume> substitution solution volume ) to reach.

State of the art Hemodiafiltration is a new type of dialysis process (Artificial kidney "), which has been in clinical trials on terminal kidney patients since 1971/72 Patient is located.

The diafiltration devices used so far are Erototypes, which are composed of components of conventional dialysis machines, The good clinical results and the relatively simple practical implementation the hemodiafiltration leave this dialysis method as a future-oriented treatment method recognize, so that the development is clinically useful, easier to operate Hemodiafiltration devices from the existing erototypes are sought.

Criticism of the Prior Art Among those in clinical use The volume balancing of the ultrafiltrate / substitution solution is carried out using prototypes the continuously determined patient weight with the help of a bed scale. the Control of the addition of substitution solution is the responsibility of a permanently present nurse. The hemodiafiltration devices located in the flaning stage are automated of the addition of substitution solution aimed at carrying out the hemodiafiltration to make it independent of the constant presence of a caregiver. As a rule Input measured variable for the required control loop to control the addition of substitution solution the ultrafiltrate is used in the devices under development, whereby Fa. Gambro / Lund - Sweden its volume (official communication), Fa. Cobe / Denver - USA its flow volume / time (# Flow) (inspection of the planned Device structure) is used as the measured variable. (Further hemodiafiltration devices see as far as we know not in planning). The use of the ultrafiltrate as an object The measurement in the aforementioned form assumes an absolute degassing of the hemodiafiltration obtained, c h a u m i g e n ultrafiltrates ahead, which on the one hand a considerable requires technical effort, on the other hand not yet fully satisfactory is resolved.

The object of the invention is to provide a for the necessary control loop to find the required measurement values that are a continuous measurement easily accessible and nevertheless suitable for an exact balancing.

Solution This object is achieved according to the invention in that it is used as a controlled variable of the control loop for controlling the addition of substitution solution, the difference in Flow volumes / time in the arterial and venous tube system of the hemodiafiltration device is used.

Further embodiment of the invention The control loop constructed in this way makes it possible es, a previously determinable difference in flow volumes / time between arterial and venous tube system of the hemodiafiltration device by acting on the Actuator (addition of substitution solution) But the entire period of the hemodiafiltration process to be adhered to and thus a negative balance (arterial outflow> venous influence - to achieve corresponding ultrafiltration volume> substitution solution volume).

Achievable advantages The hemodiafiltration devices currently being planned Technically complex degassing of the ultrafiltrate is not necessary. The measurement of flow volumes / Time in hose systems (e.g. using an ultrasonic flow meter) is technically solved and with the appropriate arrangement, choice of hose diameter and size of the measuring field etc.) can be carried out with sufficient accuracy, especially as the required measuring range is narrowly limited. Based on the measurement of the flow volume / time in venous tube system, one of the possible operating errors can be recognized immediately : When the substitution solution is used up, the required flow volume can be used / Time in the venous tube system cannot be reached. By eliminating degassing of the ultrafiltrate can reduce the weight and size of the hemodiafiltration device can be achieved, especially with regard to the use of the product as a home dialysis machine (Placement in the patient's home) is significant.

Description of the exemplary embodiments Fig. 1 shows the schematic Construction of a hemodiafiltration device, but not in this context details of interest are dispensed with.

To understand a brief description of the functional sequence: With Help the blood puspu (Pß) gets blood But the arterial tube system (AS) from the patient (p) conveyed through the dialysis plate (DP); in the Dialysis plate (DP) is transferred to the blood through a suitable membrane with the help of a transmembrane The ultrafiltrate (U) is squeezed out under pressure. That reduced by the amount of ultrafiltrate Blood is returned to the patient (P) via the venous tube system (VS), the amount of ultrafiltrate withdrawn (or part of it by a suitable Substitution solution (S) is replaced. The controlled addition of the substitution solution (S) takes place via the substitution solution pump (PS).

FIG. 2 shows the structure of the control loop on the one in FIG. 1 schematically illustrated kfaemodiafiltration device. The flow volumes / Time using two flow meters in the arterial (iA) and venous tube system (FV). (With a suitable blood pump (PB), FA can be omitted, since the flow rate / time equals the flow volume / Time can be set and thus the difference in flow rate / time of Pb and the flow volume / time in the venous tube system are taken as the controlled variable can be.) The difference in flow volumes / time in the arterial and venous Hose system (# FA-FV) enters the control loop as a controlled variable and controls as Actuator the substitution solution pump (P).

s Example 1: # FA-FV is selected with Oml / min; so must the delivery rate the pump PS of substitution solution / time equal to the amount of ultrafiltrate / time, in order to achieve identical flow volumes at FA and FV.

Example 2: # FA-FV is selected with a ml / min. To the chosen difference the flow volume / time to reach the pump delivery rate of the pump PS by a ml / min below the amount of ultrafiltrate generated per minute.

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Claims (1)

P A T E N T A N S P R Ü C H E Generic term 18 control loop for the controlled Addition of substitution solution to hemodiafiltration devices with the option of balancing. Identifying part: characterized as the controlled variable of the control loop for controlling the addition of substitution solution, the difference in Flow volumes / time in the arterial and venous tube system of the hemodiafiltration device is used. Preamble of dependent claim 2. Control loop according to claim 1. Characteristic part of the sub-claim: characterized, that a difference in flow volumes / time between arterial and venous Hose system is freely selectable, with a balancing by acting on the actuator becomes possible.