ECsens, CITIC-UGR, Department of Electronics and Computer Technology, University of Granada, 18071 Granada, Spain.
Sensors (Basel). 2022 May 28;22(11):4112. doi: 10.3390/s22114112.
In this work, we present a ballistocardiographic (BCG) system for the determination of heart and breath rates and activity of a user lying in bed. Our primary goal was to simplify the analog and digital processing usually required in these kinds of systems while retaining high performance. A novel sensing approach is proposed consisting of a white LED facing a digital light detector. This detector provides precise measurements of the variations of the light intensity of the incident light due to the vibrations of the bed produced by the subject's breathing, heartbeat, or activity. Four small springs, acting as a bandpass filter, connect the boards where the LED and the detector are mounted. Owing to the mechanical bandpass filtering caused by the compressed springs, the proposed system generates a BCG signal that reflects the main frequencies of the heartbeat, breathing, and movement of the lying subject. Without requiring any analog signal processing, this device continuously transmits the measurements to a microcontroller through a two-wire communication protocol, where they are processed to provide an estimation of the parameters of interest in configurable time intervals. The final information of interest is wirelessly sent to the user's smartphone by means of a Bluetooth connection. For evaluation purposes, the proposed system has been compared with typical BCG systems showing excellent performance for different subject positions. Moreover, applied postprocessing methods have shown good behavior for information separation from a single-channel signal. Therefore, the determination of the heart rate, breathing rate, and activity of the patient is achieved through a highly simplified signal processing without any need for analog signal conditioning.
在这项工作中，我们提出了一种用于确定躺在床上的用户的心率、呼吸率和活动的心动描记（BCG）系统。我们的主要目标是简化这些系统通常需要的模拟和数字处理，同时保持高性能。提出了一种新颖的传感方法，该方法由一个面向数字光探测器的白色 LED 组成。该探测器通过检测由于主体呼吸、心跳或活动引起的床的振动而导致的入射光强度的变化，提供精确的测量。四个小弹簧作为带通滤波器，连接安装 LED 和探测器的电路板。由于压缩弹簧引起的机械带通滤波，所提出的系统产生了一个 BCG 信号，该信号反映了躺着的主体的心跳、呼吸和运动的主要频率。该设备无需任何模拟信号处理，即可通过二线通信协议将测量值连续传输到微控制器，在微控制器中，它们被处理以在可配置的时间间隔内提供感兴趣参数的估计值。最终的感兴趣信息通过蓝牙连接无线发送到用户的智能手机。为了评估目的，将所提出的系统与典型的 BCG 系统进行了比较，结果表明，对于不同的主体位置，该系统具有出色的性能。此外，应用的后处理方法表明，从单通道信号中分离信息的效果良好。因此，通过高度简化的信号处理而无需任何模拟信号调理，即可实现心率、呼吸率和患者活动的确定。
