This article aims to provide simple general information about the process of hemodialysis and peritoneal dialysis, focusing in particular on the operation of the hydraulic circuit of a dialysis machine.
Below is a brief summary:
The kidneys are even parenchymatous secretory organs and together with the urinary tract form the urinary system.
The main task of the kidneys in an unaffected individual is to maintain the correct electrolyte balance in the body and to ensure the constant purification of the blood everyday by means of their functional units, the nephrons. When the kidneys are no longer able to work normally (in case of renal failure), in particular when the functionality of the patient is compromised by 85-90%, it is necessary to resort to dialysis, a treatment that partially replaces their functions.
There are two main types of dialysis treatment:
• This technique involves the permanent application of a catheter to the patient's abdomen to reach the inside of the peritoneal cavity. A liquid (dialysis fluid), composed of salts and glucose, is introduced through the catheter. The peritoneal membrane, in turn in contact with the dialysis fluid, works as an osmosis filter, allowing the exchange of electrolytes and the elimination of toxins. After the period of contact, the liquid is discarded and replaced with a new dialyzer for a number of cycles that normally cover about 8 hours of session
• It usually takes place at the patient's home, preferably during the night
• Its efficiency is limited by the filtering capacity of the peritoneal membrane
• The technique consists in connecting the patient, through vascular access, to a circuit that aspirates the blood through a pump and pushes it into a special filter that works as an artificial kidney allowing the transition of waste from the blood to the dialysis liquid; once passed the filter, the purified blood returns to the patient's body through a second cannula inserted, generally, in the same arm
• This type of procedure takes about four hours and is performed three times a week in hospitals or specialized centers
• The removal of uremic toxins through hemodialysis is particularly efficient even for patients at a stage of the total loss of kidney function
In a hemodialysis machine, there are two circuits: the blood circuit is intended to make the patient's blood circulate through the extracorporeal circulation lines; the hydraulic circuit is intended to manage the dialysis fluid.
The hydraulic circuit contemplates a series of pumps whose functions are mainly:
• Pressure pump - the supplying of the dialyzer to the filter (dialyzer)
• Discharge pump - the removal of the waste dialyzed solution from the dialyzer
• Degassing pump - the removing of air bubbles from the solution
• Concentrate pump - the accurate dispensing of electrolytes into the fluid stream in order to achieve and maintain constant prescription concentrations
The pumps operate throughout the dialysis cycle with fluid at a temperature of 38° C to prevent thermal shock to the patient, and their quiet operation is an essential element in making treatment as comfortable as possible. Dialysis machines are disinfected after use - typically with citric acid and temperatures of 95°- 120°C for at least 20 minutes (depending on the machine). Stable performance, maintenance of vacuum, and differential pressures are critical to the operation of the process.
Fluid-o-Tech pumps, valves, and sensors can precisely and safely manage fluids within dialysis systems.
Fluid-o-Tech is a world leader in the design and manufacture of positive displacement pumps and fluidic solutions for the medical industry, and by working alongside customers with commitment and passion, offers technical solutions for all those devices where hydraulic parameters are critical to safety and performance requirements.
Among the most popular devices for dialysis machines, there are external gear pumps. This type of pump uses two identical gears side by side, where one gear driven by a motor in turn drives the other gear. For convenience, these gears are referred to as the "motor" and "driven" gears, respectively.
Fluid transport is accomplished by trapping small volumes of fluid between the gear teeth and the outer wall of the housing and moving it from the inlet side to the outlet side. In the lines along which the teeth mate, the fluid is unable to flow and is therefore pushed toward the outlet. External gear pumps are commonly used in applications where it is required to pressurize or dose fluids with high precision and very low-pressure fluctuations. For this reason, they are used in the medical sector and in particular in hemodialysis machines.
Among the advantages of external gear pumps that make them suitable for application in the world of health technology, we also find an excellent priming capacity, compatibility with wide temperature variations (an important feature if we think of those reached during the washing after the treatment), and a compact size.
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