Reliable stroke measurement during chest compressions
Medical Engineering applications Medical Engineering particularly high demands on reliability, precision, and robustness. A striking example is a mobile device for automated chest compressions, in which a custom-made conductive plastic potentiometer from Novotechnik ensures highly accurate position detection—thereby making a crucial contribution to a safe and effective treatment process.
Why precise stroke measurement is so important during chest compressions
In the event of cardiac arrest, every second counts. Chest compressions ensure that the body continues to receive oxygen—ideally at a rate of 100 to 120 compressions per minute and a depth of 5 to 6 cm. Over extended periods, it is nearly impossible for emergency responders to maintain this pace consistently. Automated CPR devices play a crucial role in this situation.
To ensure safe operation, they must detect the exact position of the compression pad. This is because the chest changes constantly during treatment: it can yield, sink, or rise again due to ventilation. The displacement measurement must precisely compensate for these changes—even under high forces of up to 600 N.
The challenge: precision and reliability in a very confined space
This task requires a sensor that:
- measures very precisely
- is compact and can be integrated into the device's compact design
- operates reliably under changing, mobile operating conditions
- is designed with redundancy to ensure maximum security
The solution was found in the form of a linear-action plastic-cased potentiometer from Novotechnik.
The solution: A custom-designed, redundant position sensor
A specially adapted, mechanically and electrically redundant Leitplastik potentiometer was developed for the automated CPR device. Simply put, two potentiometers are mounted back-to-back using an aluminum profile and detect movement independently of one another.
Key features of this solution:
- High precision: measuring range 100 mm, repeatability better than 50 µm
- Extremely durable: service life of up to 100 million cycles – supported by precious metal abrasives
- Compact design: Ideal for the limited space in the upper section of the CPR device
- Enhanced security through redundancy: Two channels for maximum reliability
- Easy installation: The design allows for installation in front of the spindle system
The robust design of the drive springs also ensures reliable power transmission, even at high accelerations, such as those that can occur in mobile applications.
Reliability that matters
The sensor solution not only meets the high standards for accuracy and durability, but also supports the rigorous certification processes for medical devices. Detailed documentation and quality assurance processes further facilitated the approval process.
The result: a position sensor that operates reliably and safely in a life-saving device—and impressively demonstrates just how capable Novotechnik’s modern conductive plastic potentiometers can be in demanding applications.
