Abstract

In hospitals, continuous monitoring of vital parameters can provide valuable information about the course of a patient’s illness and allows early warning of emergencies. To enable such monitoring without restricting the patient’s freedom of movement and comfort, a radar system is attached under the mattress which consists of four individual radar modules to cover the entire width of the bed. Using radar, heartbeat and respiration can be measured without contact and through clothing. By processing the raw radar data, the presence of a patient can be determined and movements are categorized into the classes “bed exit”, “bed entry”, and “on bed movement”. Using this information, the vital parameters can be assessed in sections where the patient lies calmly in bed. In the first step, the presence and movement classification is demonstrated using recorded training and test data. Next, the radar was modified to perform vital sign measurements synchronized to a gold standard device. The evaluation of the individual radar modules shows that, regardless of the lying position of the test person, at least one of the radar modules delivers accurate results for continuous monitoring.

Highlights

  • Complications and sudden deterioration are often unexpected in hospitals

  • A system based on multiple radar modules for continuous in bed monitoring of vital sings was presented and compared to a gold standard reference device

  • The radar system was tailored for hospital beds and modified for a synchronization with the reference device

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Summary

Introduction

Complications and sudden deterioration are often unexpected in hospitals. In retrospective analyses of deaths in hospitals, less than 30% were expected and compensated by intensive care, and more than 70% occurred unexpectedly [1]. We present a signal processing method which can automatically detect sections in the raw data without artifact movements of the test person in order to achieve a reliable vital parameter detection in the remaining sections. This signal processing routine for the monitoring of freely moving patients is introduced and evaluated. Using this method, the raw data of the four 24 GHz. CW radar modules are divided into the four states: “Absence”, “resting”, “bed exit”,” bed entry”, and “on bed movement”. The performance of the individual modules at different lying positions using a synchronised gold standard device is examined

Measurement Setup and Protocol
Multi Radar System
Reference Device
Presence and Movement Classification
Vital Sign Evaluation
Radar Signal Processing
Section-Wise Displacement Signal Reconstruction
Respiration Signal Analysis
Heartbeat Signal Analysis
Results and Discussion
Vital Sign Extraction
Conclusions
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