Abstract
This paper introduces an automatic non-contact monitoring method based on the synchronous evaluation of a 3D time-of-flight (ToF) camera and a microwave interferometric radar sensor for measuring the respiratory rate of neonates. The current monitoring on the Neonatal Intensive Care Unit (NICU) has several issues which can cause pressure marks, skin irritations and eczema. To minimize these risks, a non-contact system made up of a 3D time-of-flight camera and a microwave interferometric radar sensor is presented. The 3D time-of-flight camera delivers 3D point clouds which can be used to calculate the change in distance of the moving chest and from it the respiratory rate. The disadvantage of the ToF camera is that the heartbeat cannot be determined. The microwave interferometric radar sensor determines the change in displacement caused by the respiration and is even capable of measuring the small superimposed movements due to the heartbeat. The radar sensor is very sensitive towards movement artifacts due to, e.g., the baby moving its arms. To allow a robust vital parameter detection the data of both sensors was evaluated synchronously. In this publication, we focus on the first step: determining the respiratory rate. After all processing steps, the respiratory rate determined by the radar sensor was compared to the value received from the 3D time-of-flight camera. The method was validated against our gold standard: a self-developed neonatal simulation system which can simulate different breathing patterns. In this paper, we show that we are the first to determine the respiratory rate by evaluating the data of an interferometric microwave radar sensor and a ToF camera synchronously. Our system delivers very precise breaths per minute (BPM) values within the norm range of 20–60 BPM with a maximum difference of 3 BPM (for the ToF camera itself at 30 BPM in normal mode). Especially in lower respiratory rate regions, i.e., 5 and 10 BPM, the synchronous evaluation is required to compensate the drawbacks of the ToF camera. In the norm range, the ToF camera performs slightly better than the radar sensor.
Highlights
We found that ToF cameras and microwave interferometric radar sensors based on Continuous Wave (CW) show many advantages
We prove that we are the first to evaluate the data of a microwave interferometric radar sensor and a ToF camera synchronously for determining the respiratory rate
We showed that it is possible to evaluate the data of a radar sensor and a ToF camera synchronously and that the respiratory rate detection is very precise compared to our gold standard
Summary
Preterm neonates on the Neonatal Intensive Care Unit (NICU) require continuous monitoring of their vital parameters such as heart and respiratory rate and the core temperature in order to allow an accurate assessment of their health status. When monitoring the respiratory rate, measurements are taken via electrocardiogram (ECG) electrodes (impedance pneumography), pulse oximeter, transcapnodes or even the ventilator itself. All of these methods involve direct contact with the baby’s skin and are cable-based. The cable connection makes the handling of the baby more difficult, i.e., when weighing, changing the diapers and during cleaning. To increase the comfort of the baby, minimize the current risks and make the handling of the baby easier, a non-contact respiratory monitoring approach is developed
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