Hemodialysis Machine Process Elements and Operate
1. FUNCTION OF THE KIDNEYS
The principle operate of the kidneys is to kind urine out of blood plasma, which principally consists of two processes,
(i) The elimination of waste merchandise from blood plasma
(ii) The regulation of the composition of blood plasma
The human physique has two kidneys which lie at the back of the stomach cavity slightly below the diaphragm, every kidney include about one million particular person models, these tiny models are known as ‘nephrons’.
The kidney work solely on plasma, every substance in plasma is dealt with in a attribute method by the nephron, involving specific combos of filtration, re-absorption and secretion.
The whole blood stream by way of the kidneys as about 1200 ml/min. Kidneys additionally play an essential position in sustaining the acid-base steadiness.
1.2 ARTIFICIAL KIDNEY
Remedy with a mechanical machine like the unreal accumulation of waste merchandise and water and thus the blood concentrations of the poisonous substances are returned to regular ranges. By successfully eradicating these supplies from the blood, the dialyzer quickly replaces the operate of the pure kidneys and is ready to preserve the affected person near regular situation. Dialyzing unit operates outdoors the affected person’s personal physique.
The dialyzing membrane has perforations that are extraordinarily small and are invisible to the bare eye. The perforations within the dialysis membrane have a median diameter of fifty Å with an estimated vary of 30 Å to 90 Å.
The bogus kidney is thus merely a membrane separation machine that serves as a mass exchanger throughout medical use. It’s unable to carry out any of the artificial or metabolic operate of the conventional kidney and, due to this fact, can not appropriate abnormalities that consequence from the lack of these features.
1.3 HAEMODIALYSIS MACHINE
A haemodialysis machine is used for the manufacturing of heat dialysate which is then circulated by way of an exterior dialyzer meeting. It additionally controls the biking of the blood from the affected person by way of the unreal kidney (dialyzer) and again to the affected person. It repeatedly displays and controls all essential parameters.
The haemodialysis machine performs 5 fundamental features,
– Mixes the dialysate
– Screens the dialysate
– Pumps the blood and controls administration
– Screens the blood for the presence of air and drip chamber stress
– Screens the ultra-filtration
Block Diagram of Hemodialysis Machine
Mixing great amount of dialysate from dry chemical compounds is time consuming and laborious. Water and focus pumps have been pushed by one shaft from the identical motor delivering a hard and fast ratio of water and focus right into a mixing chamber, fastened proportion of water (piston) and focus (shaft) from totally different chambers. The proportion system might be of the fastened ratio or variable ratio sort.
Dialysate Temperature Management and Measurement
The dialysis is often performed on the physique temperature. The temperature of the dialysate is, due to this fact, monitored and managed earlier than it’s provided to the dialyzer.
Two sorts of circuits can be utilized for effecting management of temperature:
(i) A bi-metallic thermostat which might join or disconnect provide to the heater coil relying upon the temperature of the dialysate.
(ii) A very digital single-term proportional controller which makes use of a thermistor for sensing the temperature and a triac for management of energy to the heater.
Within the fashionable microprocessor-based haemodialysis machine, A twin ingredient heater meeting, which has a 150W and a 300W ingredient, is used to deliver the fluid as much as and to take care of the working temperature. When the fluid temperature rises to inside 2.5℃ of the preset temperature (between 35 ℃ to 39℃ ), the 300W heater is turned off and the 150W heater is used to take care of the set temperature (Fig1.3)
(Fig 1.3) Temperature monitor and management circuit utilizing a number of heaters
The stream is measured utilizing a flow-thru transducer which produces a exact variety of pulses per unit of stream (26,000 / liter or 108 pulses / seconds at 250 ml / min).
The conductivity monitored by a conducting cell, to confirm the accuracy of proportioning. The conductivity of the dialysate modifications by about 2% for each 1℃ change in temperature.
Dialysate Stress Management and Measurement
Unfavourable stress upon the dialysate is created by the effluent pump. The effluent pump is a hard and fast stream.
Stress adjustment mustn’t produce any vital change within the stream charge. The stress is measured by a pressure gauge transducer linked instantly downstream of the dialysate return facet. Pressures inside the vary 0 to 400 mmHg are typically made accessible and any worth will be adjusted on this vary.
|Constituent||Focus (mEq/l) (g/l)|
Desk: Composition of Dialysate
Venous Stress Measurement
Venous stress is often measured on the bubble lure. A size of tubing connects the lure to a small plastic housing to which a pressure gauge transducer is hooked up.
For max accuracy, the sensor connection ought to be maintained in the identical altitude throughout dialysis.
Blood Leak Detector
In a dialysis machine, a skinny membrane separates the affected person’s blood from the dialysate. Usually, the stress on the blood facet of the membrane is maintained at a a lot larger stage than the stress on the dialysate facet. That is crucial to reduce the time required for the dialysis process.
The ultra-filtrate monitor circuit is used to watch the quantity of fluid faraway from the affected person and along side the unfavorable stress, to manage the speed at which it’s eliminated.
UF Price (L/hr)= Complete fluid elimination Required (liters) / Complete fluid elimination Required (liters)
The stream is measured with a stream meter which contains a chrome steel float. The stream charge is fastened at a standard 500 ml/min. It’s positioned downstream of the dialyzer, it’s doable to watch a big blood-to-dialysate.
Effluent pumps can be found in a number of design configurations. The extra widespread varieties are: the diaphragm sort, gear sort and magnetically coupled.
The blood pump utilized in dialysis machine is often of the peristaltic sort. It’s designed to present blood stream at a charge of fifty to 350 ml/min.
Air embolism is a severe hazard in dialysis. Air could also be sucked in on account of insufficient stream within the line within the pumped dialysis system. The extent of blood within the venous return bubble lure could also be monitored by a photo-electric cell.
These pumps are often of the plastic syringe sort, having a capability of 30cc. The supply of heparin from the pump is calibrated in cm/h. The pump is pushed by a stepper motor.
Blood Stress Monitor
The blood stress monitor circuit is used to watch the arterial and venous blood pressures. Two separate stress transducers of the pressure gauge sort are used for this goal.
The guts of the pc system is a microprocessor. The microprocessor operates with a clock frequency of 1 MHz or larger. This system is saved in EPROM with a complete capability of round 24 Okay bytes. The system features a RAM circuit (2 Okay × 8 bits reminiscence) powered by a inbuilt battery.
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