Study on the secretion rate measurement in thoracic drainage device

Modern thoracic drainage devices provide excess secretions  suction in the pleural space and thus help to keep the necessary vacuum upright. The application of a thoracic drainage is the standard treatment for a pneumothorax. Depending on the cause of the pneumothorax, the secreation rate may allow conclusions on the disease progress. In particular, in the field of open-heart surgery, the secretion rate is an important indicator of the patient's recovery and must be monitored closely. Typical chest drainage devices collect the secretion into Containers with readable scales. The quantities are determined by the staff at given intervals, and the secretion rates are determined accordingly.

A well-known manufacturer of such devices commissioned CogniMed to develop a concept for an automatic secretion rate measurement.


The aim is to show the secretion rate in the operating unit of the thorax device and to be able to hook it up for example with the nurse call. It was decided to use the weight of the collected secrete as a metrological basis for the determination of the secretion rate. The essential evaluation criterion was the update effort caused by the integration of the secretion rate measurement into the device.

The definition of the metrological characteristics was done quickly. Only the abundance of potential measurement errors sources presented a conceptual problem. How to conceptually decouple tensile forces acting through hoses and pipes on the secretion container from the weight result? Finally, a prediction filter associated with the tare function was a promising approach to solving this problem. For wireless transmission of the measured data a number of possibilities (optical, via BT, via NFC, proprietary) were discussed and evaluated in the context of this specific application. CogniMeds experience in the field of wireless data transmission proved very beneficial. Finally, a wireless energy Transmission was also proposed, so that the secretion rate measurement could be supplied with no electric connection lines from the appliance.

Remains to be seen what of these ideas will be found in the next unit of the manufacturer...