Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Patent
1996-02-22
1998-03-31
Buiz, Michael
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
A61M 100
Patent
active
057332576
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a method for calibrating a pump segment used in a peristaltic pump and a device adapted for carrying out the method.
The invention is intended to be used within the medical field and particularly in connection with hemodialysis, hemodiafiltration and hemofiltration. It is however clear for the skilled person that the invention has many other fields of application, e.g. dialysis in general.
PRIOR ART
It is well known that the flow rate obtained from a peristaltic pump depends on many factors such as pump speed, elasticity and diameter of the pump segment and the pressure upstreams and downstreams of the pump.
When such a peristaltic pump is used in connection with a dialysis machine, such as GAMBRO AK100, including a peristaltic pump, the flow through the peristaltic pump is calculated as being proportional to the revolution rate of the pump. To obtain the flow rate, the revolution rate is multiplied by a calibration factor which is dependent on inter alia the inner diameter of the pump segment used. This can lead to substantial errors in the fluid flow as presented on a display of the dialysis machine. This is especially true at larger flows, where the pressure upstreams of the pump can be very low.
The above mentioned dialysis machine, GAMBRO AK 100, includes an option to include a pressure meter just upstreams of the peristaltic pump instead of a pressure monitoring arrangement which otherwise is standard.
GAMBRO AK 100 machine is further provided with a safety coupling, to which the dialysis fluid tubes are connected during cleaning of the dialysis fluid circuit in the monitor. As will appear below, such a safety coupling can advantageously be used when carrying out the present invention. Examples of such safety couplings are described in U.S. Pat. Nos. 4,122,010 and 4,728,496. Moreover, U.S. Pat. No. 4,762,618 describes further components which can be included in the device according to the present invention.
WO 91/09229 discloses a peristaltic pump, in which the pumping action is adjusted in dependence of the outer diameter of the tubing after a certain time period. The motor speed is adjusted for maintaining an approximately constant flow rate of infusion.
A peristaltic pump of the dialysis machine GAMBRO AK 100 is provided with a pump segment included in a set of tubings, which is exchanged at each treatment. During one treatment, a patient is connected to the set of tubings by a fistula needle. The blood of the patient is taken out into an extracorporeal circuit and passes the pump segment of the peristaltic pump.
Such set of tubings are made of inexpensive PVC-material. Thus, the diameter of the pump segment can vary considerably, due to manufacturing tolerances. Moreover, a pump segment having the same outer diameter can have different inner diameter, due to different wall thickness. Still further, a pump segment having the same internal diameter can have different flow resistance, due to different inner surface roughness or other dimension alterations.
In order to take account for pump segments having different properties, it is necessary to calibrate the peristaltic pump for each new pump segment used. This will mean that the peristaltic pump will need to be recalibrated for each treatment.
Before each treatment, the set of tubings and the dialyzer are primed with a sterile priming solution. Moreover, the part of the dialyzer being connected to the dialysis solution is primed with ordinary dialysis solution and a transmembrane pressure is supplied for testing the dialyzer.
DISCLOSE OF THE INVENTION
According to the present invention there is provided a method of calibrating a peristaltic pump intended to be used in connection with a medical machine comprising an internal fluid flow meter. The peristaltic pump includes a replaceable pump segment and propelling means for advancing a fluid or liquid inside the pump segment. According to the invention, the method comprises introducing a fluid to said pump segment, when placed in position in
REFERENCES:
patent: 4797655 (1989-01-01), Orndal et al.
patent: 5057278 (1991-10-01), Maxwell et al.
patent: 5372709 (1994-12-01), Hood
Buiz Michael
Gambro AB
Mendez Manuel
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