Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
Physiol Meas. 2012 Oct;33(10):1643-60. doi: 10.1088/0967-3334/33/10/1643. Epub 2012 Sep 18.
Seismocardiography (SCG) is a non-invasive measurement of the vibrations of the chest caused by the heartbeat. SCG signals can be measured using a miniature accelerometer attached to the chest, and are thus well-suited for unobtrusive and long-term patient monitoring. Additionally, SCG contains information relating to both cardiovascular and respiratory systems. In this work, algorithms were developed for extracting three respiration-dependent features of the SCG signal: intensity modulation, timing interval changes within each heartbeat, and timing interval changes between successive heartbeats. Simultaneously with a reference respiration belt, SCG signals were measured from 20 healthy subjects and a respiration rate was estimated using each of the three SCG features and the reference signal. The agreement between each of the three accelerometer-derived respiration rate measurements was computed with respect to the respiration rate derived from the reference respiration belt. The respiration rate obtained from the intensity modulation in the SCG signal was found to be in closest agreement with the respiration rate obtained from the reference respiration belt: the bias was found to be 0.06 breaths per minute with a 95% confidence interval of -0.99 to 1.11 breaths per minute. The limits of agreement between the respiration rates estimated using SCG (intensity modulation) and the reference were within the clinically relevant ranges given in existing literature, demonstrating that SCG could be used for both cardiovascular and respiratory monitoring. Furthermore, phases of each of the three SCG parameters were investigated at four instances of a respiration cycle-start inspiration, peak inspiration, start expiration, and peak expiration-and during breath hold (apnea). The phases of the three SCG parameters observed during the respiration cycle were congruent with existing literature and physiologically expected trends.
心冲击图（SCG）是一种测量由心跳引起的胸部振动的非侵入性方法。可以使用附着在胸部的微型加速度计来测量 SCG 信号，因此非常适合进行不引人注目的长期患者监测。此外，SCG 包含与心血管和呼吸系统相关的信息。在这项工作中，开发了用于提取 SCG 信号的三个与呼吸相关的特征的算法：强度调制、每个心跳内的时间间隔变化以及连续心跳之间的时间间隔变化。同时使用参考呼吸带，从 20 名健康受试者测量 SCG 信号，并使用这三个 SCG 特征中的每一个和参考信号来估计呼吸率。分别计算了三种加速度计衍生的呼吸率测量值与参考呼吸带衍生的呼吸率之间的一致性。从 SCG 信号中的强度调制获得的呼吸率与从参考呼吸带获得的呼吸率最为一致：偏差为每分钟 0.06 次呼吸，95%置信区间为每分钟-0.99 至 1.11 次呼吸。使用 SCG（强度调制）估计的呼吸率与参考值之间的一致性界限在现有文献中给出的临床相关范围内，表明 SCG 可用于心血管和呼吸监测。此外，在呼吸周期的四个实例-起始吸气、峰值吸气、起始呼气和峰值呼气-以及呼吸暂停期间，研究了三个 SCG 参数中的每一个的相位。在呼吸周期中观察到的三个 SCG 参数的相位与现有文献和生理预期趋势一致。
