gms | German Medical Science

Objective: Non-invasive ICP-monitoring offers new possibilities in keeping a number of pathologic brain conditions under surveillance that would may otherwise not be amenable to clinical assessment. We investigated a new technology that uses acoustic signals which are transmitted through the head via earphones and compared the ICP values from this non-invasive data with those that were recorded by simultaneous invasive recordings on our ICU.

Method: The system uses a transmitting sensor in an acoustic earphone placed in the subject’s ear. The earphone generates an acoustic signal in a fixed low frequency. A receiving sensor is placed in the subject’s contralateral ear and picks up the acoustic signal after its propagation through the head. The received signal is then converted from analog to digital and processed by a mathematical algorithm that uses several methods of signal processing to calculate the ICP after filtering out artifacts and external noise. Using this technology, we recorded and processed data from 15 patients who also were on continuous invasive ICP monitoring by means of external ventricular catheters.

Results: Our method of non-invasive ICP monitoring was feasible in all patients. We found a discrepancy of 5 mmHg in 85% and 4mmHg in 72% of the signals between the recorded non-invasive ICP signals and the invasive recording.

Conclusions: Our results show that our non-invasive ICP monitoring technology is a feasible and promising method, with the added advantage of application in situations where invasive monitoring is not possible. However, further improvements in hardware and signal processing are needed to make this system reliable for clinical use.