Pressure Sensors in Medical Applications
Pressure sensors are pressure sensing devices, that can be applied in a wide variety of applications. Their measurement principle is based on the piezoelectric effect that transforms a pressure signal into an electric signal. Since pressure is also correlated with the flow rate in the mechanics of liquid and gaseous media, pressure sensors are indispensable components in flow measurement systems that enable reliable and accurate flow-rate control. The measured pressure range of our pressure sensors is a few millibars to a few bars. Pressure sensors can therefore be used as flow switches, that monitor the flow rate and notify a measuring device or a system that a predefined flow threshold has been reached. That is especially important in life-saving medical applications where accuracy is essential. Pressure sensors can form, for example, a part of medical ventilators, dialysis systems, infusion pumps, to name just a few. In this document, we focus on the function that pressure sensors have in ECMO devices.
The purpose of ECMO systems is to provide a sufficiently oxygenated blood flow through the body in case that the heart or lungs of a patient are not capable to perform that. If the patient’s lungs are impaired, the system is called Veno-Venus ECMO and if the patient’s heart function is weakened, the system is called Veno-Arterial ECMO. The blood flow is pushed through the patient’s body by a circulating pump, which provides sufficiently oxygenated blood to the tissues and takes deoxygenated blood from the body. The blood is being pumped through an oxygenation membrane that enriches it with oxygen and then through a heat exchanger to warm it to the adequate body temperature. The blood stream is enabled by special cannulas, inserted in the heart to provide the required blood flow.
HYB pressure Sensors
Extracorporeal membrane oxygenation (ECMO) models
- ‘Full optional’ ECMO model: consists of a bladder in the venous line, a roller pump, an oxygenator, a bubble sensor and a heat exchanger.
- Basic ECMO circuit: consists of a simple tubing circuit and a centrifugal pump. The number of connectors is minimized. There are no pressure transducers in the circuit.
- A ‘homemade’ continuous veno-venous ultrafiltration circuit with a haemofilter in the circuit.
ECMO is a lifesaving system, but quite an expensive one regarding financial, technical and human perspective.
Current Practice
The current procedure is to basically guess the pressure at the catheter from the pressure value of the gauge transducer, located at1-4 feet (30.5 to 122 cm) below the patient in a vertical direction. In order to change the pressure at the gauge transducer or to adjust the flow rate, medical staff changes the height of the patient (if blood pressure and oxygenation parameters allow that).
In order to improve the procedure mentioned above, a new, venous pressure transducer was implemented in the system at the same level as the patient. The purpose is to induce the required pressure.
Sensors
ECMO System should function very precisely therefore several control mechanisms are required. The control mechanisms are based on various sensors, that ensure the necessary blood flow rates, the temperature and the level of oxygen saturation.
One of the very important sensors in the ECMO system are also pressure transducers, responsible for ensuring the adequate blood flow rate. The following list of pressure transducers gives you a brief idea where in the ECMO circuit they are most commonly located.
- Pre-Oxygenation Membrane Pressure (Standard Nation Wide)
A sensor placed before the oxygenation membrane checks if oxygenator works properly - Post-Oxygenation Membrane Pressure (Standard Nation Wide)
A sensor after the oxygenation membrane checks if there is an adequate flow into the patient - Return Pressure before Pump (Standard Nation Wide)
A sensor before a pump checks the return blood flow from a patient
HYB Pressure Sensors in Devices
According to the description, given so far, it is crucial that the pressure and the airflow are regulated very reliably and accurately. Based on the vast experience that HYB has gained during the past 50 years of being present as a quality company on the market of pressure sensors, we can provide custom-made reliable solutions that can be integrated into your system. The relatively small size of the company enables us the flexibility that is essential in the custom-made solutions. On the scheme above you can see an example of HYB pressure sensors application in a NPPV system.
Pressure Sensor Series Recommendation
At HYB company we have experienced the biggest market success with our HYB 3000 series, HYB 4000 series, and HYB 8000 series of pressure sensors. These, state-of-the-art piezoresistive temperature-compensated MEMS pressure sensors can deliver analog, digital or combined output signal. Our pressure sensors are also capable of air temperature adaptation, which enables higher patient comfort.
Features of Pressure Sensors Series
Features of each pressure sensors series can be found in the Data Sheets of each sensor type.
If you have any questions or special requests, don’t hesitate to contact our customer support at: inquiry@hyb.si and we will be glad to customize our equipment to your system or device.
