Hemodialysis is an essential and routine medical treatment for which safety has become a clinical priority. Therefore the process requires a chain of interventions to ensure maximum patient safety. Dialysis machines combine a variety of sensors for the monitoring of pressure, flow and liquid level as well as for detecting leaks and air in the tubing system.
Hemodialysis is a blood purification procedure used for acute kidney failure and has been widely used as a routine treatment since the late 1960s. Along with kidney transplantation, it is the most important renal replacement therapy for chronic kidney failure. In a broader sense, the term dialysis describes the exchange of substances across a semipermeable membrane known as diffusion - a transfer of molecules dissolved in the blood or plasma into the weakly concentrated dialysis solution.
The Extracorporeal Blood Circulation During the Dialysis Procedure
As an extracorporeal circuit, the dialysis machine substitutes a kidney‘s function during treatment. The patient‘s blood is redirected from the intracorporeal to the extracorporeal circuit. The actual diffusion between blood and dialysis fluid is processed in the dialyzer in which a biocompatible polymer membrane separates the two fluids from each other. Finally, toxins and/or water are removed from the blood through the membrane, or filter, as the membrane is often named.
During the process of blood transfer from the human body to the dialysis machine and back, as well as during membrane diffusion itself, there are numerous critical parameters to be monitored and controlled. For patient safety reasons, blood circulation is continuously observed with regard to the presence of air bubbles as they may result in life-threatening air embolisms. Membrane defects in the dialyzer, in turn, can accidentally cause blood loss through the separated dialysate. For this reason, the dialysate discharge tube is constantly monitored for blood leaks.
Non-Invasive SONOCHECK® ABD Air Bubble Sensors Used in Hemodialysis
SONOCKECK ABD air bubble sensors are widely used in dialysis machines for hemodialysis. They are applied for fast and safe air bubble detection in the venous path of the extracorporeal blood circulation. By squeezing the tube into the measuring channel of the sensor, simple tube handling is guaranteed. This enables dry coupling with no need for any additional closing mechanisms. The sophisticated sensor design also ensures easy single-handed operation and a smooth cleaning process. The air detector itself is integrated into the front panel of the dialysis machine and acts as the last safety component before returning the blood to the patient.
Ultimate Patient Safety by Use of Air Bubble Sensors
Based on quality regulations requiring overall patient safety, a simple and intuitive handling as well as a faultless operation at any time, SONOTEC engineers have developed the sophisticated SONOCHECK ABD05 sensor family. The sensor detects air bubbles reliably, but ignores harmless microbubbles. An additional optional optical sensor module acts as an initialization switch to start the actual dialysis treatment after the rinsing process.
Since the acoustic transmission through the tube strongly depends on ambient conditions during treatment, the sensor is programmed to constantly adapt to these changes without compromising patient safety. Bubbles are reliably detected from a certain predefined size onwards, with no influences caused by the tube setting, ambient humidity, temperature change, or a potential tubing shift. The built-in microcontroller allows smart and dynamic adaption of the ultrasonic properties to ensure reproducible results. A patented algorithm dynamically adjusts the sensor to guarantee constant bubble sensitivity. Thus, the sensor does not need to be calibrated.
SONOCHECK® ABD05 Bubble Sensor With Modern Fail-Safe Safety Architecture
Within the SONOCHECK ABD05 security architecture, redundancy has been deemed unnecessary since all components meet the high requirements of “fail-safe” and run extensive self-check routines during operation. “Fail-safe” ensures that there is no need for the machine to actively trigger bubble simulations. This allows the bubble detection sensor to keep performing without technically caused interruptions and to react to error messages in less than 0.2 seconds. For this purpose, the air bubble detector periodically sends measured values as status reports as well as predefined messages for bubble activity and error codes as alarm settings.
With its unique safety concept, the SONOCHECK ABD05 air bubble sensor has been implemented by numerous medical device manufacturers and is verified by their renowned regulatory authorities. Today, the bubble detector is used worldwide in all major medical technology markets.
BLD Blood Leak Sensors Detect the Smallest Traces of Blood in Dialysis Fluids and Prevent Extracorporeal Blood Loss
An undetected membrane rupture in the dialyzer can lead to unwanted blood loss of the patient during dialysis treatment. For this reason, the discharged dialysate is continuously examined for blood traces. This task is performed by panchromatic optical blood leak sensors that non-invasively detect for red colorations in the dialysate.
With a wavelength adapted to the transmittance of blood, the blood leak detector BLD meets the international standard IEC 60601-2-16:2018 for electronic medical devices. The sensor reliably detects 0.35 ml/min of blood at a hematocrit level of 32 % at a specified flow rate. If the sensor identifies blood in the dialysate, an error message is triggered on suspicion of membrane defects. Depending on treatment progression, either the blood pump is stopped, the venous clamp activated, or the ultrafiltration rate (UF rate) is reduced to a minimum.