Objective: Geriatric patients, especially those with dementia or in a delirious state, do not accept conventional contact-based monitoring. Therefore, we propose to measure heart rate (HR) and heart rate variability (HRV) of geriatric patients in a noncontact and unobtrusive way using photoplethysmography imaging (PPGI). Methods: PPGI video sequences were recorded from 10 geriatric patients and 10 healthy elderly people using a monochrome camera operating in the near-infrared spectrum and a colour camera operating in the visible spectrum. PPGI waveforms were extracted from both cameras using superpixel-based regions of interests (ROI). A classifier based on bagged trees was trained to automatically select artefact-free ROIs for HR estimation. HRV was calculated in the time-domain and frequency-domain. Results: an RMSE of 1.03 bpm and a correlation of 0.8 with the reference was achieved using the NIR camera for HR estimation. Using the RGB camera, RMSE and correlation improved to 0.48 bpm and 0.95, respectively. Correlation for HRV in the frequency-domain (LF/HF-ratio) was 0.50 using the NIR camera and 0.70 using the RGB camera. Conclusion: We were able to demonstrate that PPGI is very suitable to measure HR and HRV in geriatric patients. We strongly believe that PPGI will become clinically relevant in monitoring of geriatric patients. Significance: we are the first group to measure both HR and HRV in awake geriatric patients using PPGI. Moreover, we systematically evaluate the effects of the spectrum (near-infrared vs. visible), ROI, and additional motion artefact reduction algorithms on the accuracy of estimated HR and HRV.

中文翻译：

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使用光电体积描记法成像非接触式监测老年患者的心率和心率变异性


目的：老年患者，特别是患有痴呆症或处于神志不清状态的患者，不接受传统的接触式监测。因此，我们建议使用光电体积描记成像（PPGI）以非接触和不引人注目的方式测量老年患者的心率（HR）和心率变异性（HRV）。方法：使用在近红外光谱下工作的单色摄像机和在可见光谱下工作的彩色摄像机记录 10 名老年患者和 10 名健康老年人的 PPGI 视频序列。使用基于超像素的感兴趣区域 (ROI) 从两台相机中提取 PPGI 波形。基于袋装树的分类器经过训练，可以自动选择无伪影的 ROI 进行 HR 估计。 HRV 在时域和频域中计算。结果：使用 NIR 相机进行 HR 估计时，RMSE 为 1.03 bpm，与参考值的相关性为 0.8。使用 RGB 相机，RMSE 和相关性分别提高到 0.48 bpm 和 0.95。使用 NIR 相机时 HRV 频域相关性（LF/HF 比）为 0.50，使用 RGB 相机时为 0.70。结论：我们能够证明 PPGI 非常适合测量老年患者的 HR 和 HRV。我们坚信 PPGI 将在老年患者的监测方面具有临床意义。意义：我们是第一组使用 PPGI 测量清醒老年患者的 HR 和 HRV。此外，我们系统地评估了光谱（近红外与可见光）、ROI 和其他运动伪影减少算法对估计 HR 和 HRV 准确性的影响。