New Technology Offers a Window into Lungs

PLYMOUTH, MI -- Freudenberg and Swisstom AG developed an innovative system that combines electrical impedance tomography (EIT) with an electrode belt for the real-time monitoring of the human lungs. The SensorBelt is positioned around the patient's chest and provides something that was not possible before – a window into the lungs.

Every year, almost 50 million patients throughout the world are placed on ventilators, whether in operating rooms or in intensive care units. 15 percent of those patients in the intensive care unit suffer acute respiratory failure, and 39 percent of them die. In the US, more patients die from accurate respiratory failure than from breast cancer. The SensorBelt offers a remedy. Positioned around the patient's chest, it allows for real-time lung performance monitoring.

Medical technology solutions have a long tradition and enjoy high priority at Freudenberg. "A world population that is both ageing and growing will have considerable impact on the health market," says Dr. Mohsen Sohi, Speaker of the Board of Management of the Freudenberg Group. "We can play a key contribution in this field with our materials competence and our product solutions."

Optimum respiratory therapy saves lives. It is important to monitor the effects of ventilation on the fragile tissue of the lungs. This is where the EIT system with the SensorBelt comes into play. The sensors use the principle of electrical impedance tomography without x-rays. Alternating current flows through the patient's body creating voltages on the surface of the body. These voltages change rhythmically as the patient breathes. The sensors in the SensorBelt pick up these very small changes in voltage, and a computer uses the measurements to create real-time images of the lungs.

"This is a considerable benefit to intensive care medicine," Dr. Christian Karagiannidis, senior pneumologist at the Cologne-Merheim Lung Hospital, explains. He has already tested the product in practice. In contrast to the large remote CT scanners which deliver static images of lung structures, the small bedside EIT system with the SensorBelt allows continuous monitoring of the patient's lung function without negative effects of radiation. "Especially with seriously ill patients, continuous monitoring allows us to optimize mechanical ventilation and to recognize any pathological changes very rapidly," Karagiannidis reports.

Freudenberg Business Groups enmech and Freudenberg Nonwovens contributed their expertise in the fields of flexible circuit boards and skin-friendly nonwovens.

To ensure contact between the electronic systems and the patient's skin at all times even under the difficult conditions of intensive care units, the electrode belt must fit the patient like a second skin. A tight fit is ensured by the flexible circuit boards from enmech on which the 32 sensors are installed. The skin-friendly outer fabric is provided by Freudenberg Nonwovens. It protects both the body and the electronic systems against environmental effects.

This nonwoven material consists of very fine polyurethane threads, a backing material that is also used for wound dressings. These threads can be spun to form a very tight fabric that still remains breathable and elastic. "We had to find a material that was flexible and would adapt well to the patient's body while remaining stable and retaining its shape even after having been exposed to body fluids and warmth and after opening and closing it for several times," Katja Herbrand, area sales manager medical Europe at Freudenberg Nonwovens, reports.

The circuit boards for the SensorBelt are supplied by enmech. This Freudenberg company was selected because it is "in a position to produce flexible circuit boards with a length of over one meter and to equip them with electronic components such as our EIT Chip. At the same time, these circuit boards have to comply with the highest possible quality standards," explains Dr. Stephan Bohm, chief medical officer of Swisstom AG. Different-sized circuit boards are required for different body girths. enmech produces these circuit boards and also equips them with the electronic components required. "This reduces electrical interfaces and eliminates the need for complex electrode cabling," explains Christophe Luciani, managing director of enmech.

Quality is the top priority in the production process for the SensorBelt. The quality of brazed joints is ensured by 100% automatic optical inspection (AOI). An individually adapted electric end-of-line (EOL) test ensures that the electronic systems function properly. The most stringent hygiene requirements apply to the integration of the flexible circuit board with the electrodes into the non-woven fabric.

The EIT system with the SensorBelt may prove to be a life-saver for many patients. "The system has already been tested at various hospitals throughout the world and the feedback has been extremely positive," says Bohm. The Swisstom system provides measured data and images of unprecedented quality, without any side effects or negative impact on the patient.

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