APPARATUS FOR HEATING AND MAINTAINING TEMPERATURE CONTROL OF CONTINUOUS AMBULATORY PERITONEAL DIALYSIS (CAPD) FLUID

Abstract: A continuous ambulatory CAPD body fluid heating and temperature control apparatus comprising regulated power supply means (10) and a heating element (5) connectable thereto, temperature sensing means (4) located in said element and controlling the power supply to the element (5) to maintain the temperature of the fluid at a preselected level.

Description: Apparatus for heating and maintaining temperature control of continuous ambulatory peritoneal dialysis (CAPD) fluid The present invention relates to apparatus for heating and maintaining temperature control of CAPD fluid. Patients who require CAPD have considerable problems in that the temperature of the fluid dialysate is often at a different temperature from normal body temperature (37°C - 38°C). Such temperature differences are not only uncomfortable, but in very cold or very warm weather large temperature deviations may occur which can be very dangerous upsetting the body's own thermal regulatory system and could even result in death. There is a known, system (as shown in Fig. 1) for warming bags which comprises a box-container which is divided into an upper andalower compartment by a perspex sheet with circular holes therein. In the lower compartment are two mains-power light-bulbs. The bag ' is placed- in the upper compartment and the lid placed thereon. When the light-bulbs are switched on to mains supply, the bulbs illuminate and heat is radiated from the bulbs to the fluid bag in the upper compartment. With the types of fluid bag used, it happens not infrequen- tly that there is leakage of fluid from the bag. In the case of the prior art if such leakage fluid contacted the light-bulbs they would explode. Furthermore if such a mains supply is used there is a danger of patient elec¬ trocution with this type of equipment. Additional disadvantages of this known system are that there is no control of the bag fluid temperature, the box is uninsula¬ ted and so considerable energy is wasted and the radiant heating from bulbs is inefficient and requires a relatively long time to heat the bag fluid up to body temperature. An object of the present invention is to obviate or to mitigate the abovesaid disadvantages. According to the present invention there is provided a continuous ambulatory CAPD body fluid heating and temperature control apparatus comprising, regulated power supply means and a heating element connectable thereto, temperature sensing means located in said element and controlling the power supply to the element to maintain the temperature of the fluid at a preselected level. Preferably, the apparatus includes timing control means connectable to the power supply means for permitting the bag to be heated within predetermined times. Preferably also, the temperature sensing means is a bimetallic switch. Preferably also, the heating element is aluminium foil covered in a thermally conductive electrically insulating material. Preferably also, the voltage applied to the heating element is 8-10 volts d.c. Preferably also, the timing control means includes a microprocessor, the microprocessor controls the operation of the apparatus in accordance with a pre¬ determined program. Preferably also, the heating element includes indicating means, said indicating means providing a signal when said heating element receives electrical power. Preferably also, the timing control means includes a real-time clock, controlled by said microprocessor. Preferably also, the timing control means includes audio and/or visual alarm means connected thereto. Preferably also, the timing control means includes a rechargeable battery. Preferably also, the heating element is connectable to a 12 v d.c. power supply. OM? Preferably also, the heating element is located in a plastic sheet, the said sheet being locatable on a thermally insulated portable bag container. Preferably also, the timing control means includes a mains output whereby electrical appliances can be connected to and driven therefrom. Preferably also, said microprocessor is programmed so as to be able to override normal temperature regulation to provide a rapid temperature rise. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:- Fig. 1 is a schematic diagram of a known CAPD bag heating device; Fig. 2 is a photograph showing the dialysis fluid bag in a portable case; and Fig. 3 is a block diagram of the apparatus according to the present invention. Referring now to Fig. 1 of the drawings a portable case 1 having insulated walls 2 contains a plastic bag 3 filled with dialysis fluid. The case 1 contains a plastic sheet 4 in which a convoluted aluminium foil heating element 5 is located. The aluminium foil heating element 5 is connected to power supply terminals 6. A bimetallic switch 7 is connected in series with the heating element 5. An indicator in the form of an LED (light emitting diode) 8 in series with a resistor 9 is connected across the heating element 5 and indicates when the bimetallic switch 7 is closed and is taking current. The terminals 6 of the heating element 5 are connectable -to an output 10a of a regulator power supply 10. The heating element 5 is also connectable to a 12 v d.c. supply (not shown in the interests of clarity) in the absence of the regulated power supply 10. The regulated power supply 10 is connectable to mains supply and provides a first regulated output 10a between 8-10 v d.c. and a second regulated output 10b c.'.?ι fa : which feeds a programmable timing controller 11. The second regulated output is typically 5 v. The programm¬ able timing controller 11 contains a microprocessor (not shown) which controls the operation of the apparatus under the directions of a program stored in its memory. A real-time clock 12 is connected to the controller 11. The time on the real-time clock 12 can also be preset. An audio alarm 13 and/or a visual alarm 14 are connected to the controller 11 and may be actuated when the time or temperature exceed preset limits. The controller 11 also has a rechargeable battery 15 connected thereto, the rechargeable battery 15 providing power to the clock 12 and alarms 13, 14 in the absence of power from the regulated power suppl 10b. The controller 11 also has an output socket 16 through which mains power may be provided to electrical appliances. In use, the bag is inserted into the carrying case 1 as shown in Fig. 2 and power switched on. The bimetallic switch 7, which is set to open about 38 C, remains closed and current is fed through the heating element 5, and the LED is illuminated. Heat is produced in the element 5 by resistive heating and is transferred via the plastic sheet 4 and the plastic bag cover 3 to the fluid by thermal conduction. When the temperature of the bag reaches about 37-38°C the bimetallic switch 4 opens stopping current flow to the heating element 5 and the LED 8 goes out. The bimetallic switch 7 constantly makes and breaks to regulate the temperature of the fluid in the bag at about 37°C - 38°C. The program controller 11 has a 24 hour clock which permits the apparatus to operate over a number of time intervals (typically 4-6) in any 24 hour cycle. The start and finish of each time interval can be programmed via the microprocessor by the user with the assistance of the real-time clock 12. To enable the patient to have control over the time- intervals the rechargeable battery provides power when the mains supply is disconnected. The heating, temperature and time control may be powered from a 12 v d.c. supply such as in a car. The alarms 13, 14 may operate if the required fluid temperature is not being achieved or if a time interval occurs during which the heating element 5 is not connected to the power supply 7. The apparatus includes the facility to override the above heating and temperature regulation control; a four position heat control switch is provided which allows the temperature of fluid in the bag 3 to be raised to body temperature over 30 mins, 1, 2 and 4 hours. This permits rapid warm-up which is particularly beneficial when the ambient temperature is considerably less than body temperature. Advantages of the present invention include, patient safety is considerably improved over known devices and the risk of electrocution is mitigated by using a very- low d.c. voltage to supply the heating element, the fluid temperature is controlled thus increasing patient safety and comfort; insulation of the bag carrier provides efficient use of power and transfer of heat to the dialysis fluid bag, thermal conduction also gives improved efficiency, and the rapid start-up override facility provides rapid heating of the fluid in cold weather. The heating and control system as hereinbefore described is designed for use with the 'Improved Continuous Peritoneal Dialysis System' which is the subject of co-pending British Patent Application No. 8133663 filed 7th November, 1981. OMPI

Claims: Claims 1. A continuous ambulatory CAPD body fluid heating and temperature control apparatus comprising, regulated power supply means and a heating element connectable thereto, temperature sensing means located in said element and controlling the power supply to the element to maintain the temperature of the fluid at a preselected level. 2. Apparatus according to claim 1 which includes timing control means connectable to the power supply means for permitting the bag to be heated within predetermined times. 3. Apparatus according to claim 2 wherein the timing control means includes a microprocessor, the said micro¬ processor controlling the operation of the apparatus in accordance with a predetermined program. 4. Apparatus according to claim 3 wherein the timing • control means includes a real-time clock, controlled by said microprocessor. 5. Apparatus according to any one of claims 2 to 4, wherein the timing control means includes audio and/or visual alarm means connected thereto. 6. Apparatus according to claim 2 wherein the timing control means includes a rechargeable battery. 7. Apparatus according to claim 2 wherein the timing control means includes a mains output, whereby electrical appliances can be connected to and driven therefrom. 8. Apparatus according to claim 1 wherein the heating element includes indicating means, said indicating means providing a signal when said heating element receives electrical power. 9. Apparatus according to claim 1 or claim 8 wherein the heating element is connectable to a 12v d.c. power supply. 10. Apparatus according to claim 1 wherein the heating element is aluminium foil covered in a thermally conductiv electrically insulating material. 11. Apparatus according to claim 10 wherein the heating element is a convoluted aluminium foil contained in a plastic sheet. 12. Apparatus according to claim 11 wherein the plastic sheet is locatable on a thermally insulated portable bag container. 13. Apparatus according to any one of claims 10 to 12 wherein the voltage applied to the heating element is 8-10 volts d.c. 14. Apparatus according to claim 1 wherein the temparture sensing means is a bimetallic switch. 15. Apparatus according to claim 1 wherein the heating element includes indicating means providing a signal when said heating element receives electrical power. 16. Apparatus according to claim 3 wherein the icro- processor is programmed to provide for overriding normal temperature regulation to provide a rapid temperature rise. OMFI

Inventors: JUHASZ LAZSLO, JUHASZ, LAZSLO
Applicants: UNIV STRATHCLYDE, UNIVERSITY OF STRATHCLYDE
Application year: 1984
Main classification: A61M1
IPC codes: A61M1, A61M5, H05B3