Nuremberg Institute of Technology, 90489 Nürnberg, Germany.
Institute of High-Frequency Technology, Hamburg University of Technology, 21073 Hamburg, Germany.
Sensors (Basel). 2021 Apr 23;21(9):2959. doi: 10.3390/s21092959.
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 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.
本文提出了一种基于 3D 飞行时间（ToF）相机和微波干涉雷达传感器同步评估的自动非接触式监测方法，用于测量新生儿的呼吸频率。目前在新生儿重症监护病房（NICU）的监测存在一些问题，可能会导致压痕、皮肤刺激和湿疹。为了最大限度地降低这些风险，提出了一种由 3D 飞行时间相机和微波干涉雷达传感器组成的非接触式系统。3D 飞行时间相机提供 3D 点云，可用于计算移动胸部的距离变化，并从中计算出呼吸频率。ToF 相机的缺点是无法确定心跳。微波干涉雷达传感器测量呼吸引起的位移变化，甚至能够测量由于心跳引起的小叠加运动。由于婴儿移动手臂等原因，雷达传感器对运动伪影非常敏感。为了实现稳健的生命参数检测，同步评估了两个传感器的数据。在本出版物中，我们专注于第一步：确定呼吸频率。经过所有处理步骤后，将雷达传感器确定的呼吸频率与从 3D 飞行时间相机接收到的数值进行比较。该方法已通过我们的黄金标准进行了验证：一个自行开发的新生儿模拟系统，可以模拟不同的呼吸模式。在本文中，我们表明，我们是第一个通过同步评估干涉式微波雷达传感器和 ToF 相机的数据来确定呼吸频率的人。我们的系统在 20-60 BPM 的正常范围内提供非常精确的每分钟呼吸次数（BPM）值，最大差异为 3 BPM（对于 30 BPM 的 ToF 相机）。特别是在较低的呼吸率区域，即 5 和 10 BPM，需要同步评估来补偿 ToF 相机的缺点。在正常范围内，ToF 相机的性能略优于雷达传感器。
