Unconstrained measurement of cardiorespiratory and body movind episodes for infant monitoring

我们提出了一种简单的测量呼吸频率(RR)、心率(HR)和身体运动次数的系统，用于婴儿健康监测。该系统由8个聚偏氟乙烯(PVDF)电缆传感器、一个变化放大器和带有CCD摄像单元的测量软件组成。电缆传感器水平高，分布在床面，电缆间距离约8厘米，覆盖上半身。传感器通过呼吸活动检测胸腔移位，通过心跳检测弹道运动。系统软件根据相应输出功率谱密度的幅度搜索用于测量呼吸和心跳的最佳传感器。专门构造的FIR数字滤波器提取由呼吸和心脏动作引起的信号。然后，滤波后的心脏信号通过一个全整流积分滤波器。对滤波信号的自相关函数(ACF)进行计算和微分，以检测各个ACF中的峰值。如果受试者改变了姿势，该软件就会通过一个ccd摄像头捕捉到带有时间戳的身体位置的图像，并调用例程进行最佳传感器选择。为了验证该方法的有效性，将该监护仪测得的HR和RR与呼吸流量和心电波同时测得的心率和RR进行了比较。在大多数情况下，系统成功地实时提取了呼吸和心脏动作。平均心率和RR的个体误差均小于10%。实验结果表明，该系统适用于家庭或医院的联合长期监护。

We proposed a simple system for measuring respiratory rate (RR), heart rate (HR), and body moving episodes for infant health monitoring. The system consists of eight polyvinylidene fluoride (PVDF) cable sensor, a change amplifier, and measuring software with CCD camera unit. The cable sensors were horizontall distributed to the bed surface with an inter-cable distance of about 8-cm, covering the upper half of the body. The sensors detect thorax displacement by respiratory activity and ballistic movement by heartbeat. The system software searches the optimal sensors for measuring respiration and heartbeat based on the amplitude of the power spectral density of the respective outputs. The FIR digital filters that were specifically constructed extract the signals caused by respiratory and cardiac actions. The filtered cardiac signal was then passed through a full rectified integrate filter. The autocorrelation functions (ACFs) of the filtered signals were computed and differentiated to detect the peaks in the respective ACFs. If a subject changes a posture, the software captures the image of the body position with a time stamp by a CCD camera and calls the routine for the optimal sensor seletion. To demonstrate the validity of this method, HR and RR obtained by this monitor were compared with those measured simultaneously with respiratory flow and ECG wave. In most cases, the system successfully extracted the respiratory and cardiac action on a real-time basis. The individual errors of average HR and RR were less than 10%. These experimental results demonstrate that the proposed system is feasible for the combined long-term monitoring at home or hospital.