Nemotece spremljanje delovanja srca z opticnim senzorjem v postelji

Abstract

Background: Demographic trends suggest that by 2050 approximately 11 % of the world population will be 80 or older. If a fast increase of chronic diseases is also considered, it becomes clear the present healthcare capacities wont be enough. The elderly and people with limited abilities must be assisted in their home environment and, thus, reduce needs for hospitalization and institutionalization. Todays computer and communication technologies provide dierent smart devices, which is a core of emerging intensication of homecare services, in particular remote and unobtrusive monitoring of human functional-health parameters.

Methods: Telemetric methods for human health monitoring have been available for a long time, but their wide implementation is hindered by the necessary manual interventions when preparing and controlling a measuring session and transmitting the data. These facts encouraged a research at the Faculty of Electrical Engineering and Computer Science in Maribor aiming at an entirely automated and unobtrusive device for monitoring the cardiac activity, such as ballistocardiogram and phonocardiogram.

The monitoring device comprises a combination of low-cost electronic and optical components. An embedded computer runs advanced algorithms for processing the optical signals.

The sensors core consists of a plastic optical ber which is illuminated by coherent light of a laser diode. Any external mechanical or acoustic inuence on the optical ber results in an interference spackle pattern at the bers exit face. Speckle-pattern changes are saved as a sequence of images. A computer program detects the changes and transforms them into a signal whose dynamics is proportional to external forces pressing against the optical ber. Finally, this signal is ltered in the frequency band that corresponds to the range of heart rate in order to detect individual heartbeats, heart rate, and possible arrhythmias.

Results: Developed heartbeat monitor has been tested in laboratory conditions by ve young, healthy subjects lying supine on a mattress with embedded optical ber. Statistical analysis conrmed the proposed device and heartbeat detection algorithms are highly efficient with sensitivity of 98.4 1.1 % and precision of 98,2 2 %.

Conclusions: Proposed approach for unobtrusive heartbeat detection is based on optical speckle interferometry. The sensor used is extremely efficient in reacting to tiniest vibrations and sounds caused by the heart, even indirectly through a mattress. Our future research focuses on improving the sensors and detection methods robustness in order to achieve reliable validation in aggravated dwelling and clinical environments.