Laboratory of Integrative Physiology, Department of Neuroscience, Università di Torino, Torino, Italy.
Mathematical Biology and Physiology, Department of Electronics and Telecommunications, Politecnico di Torino, Torino, Italy.
J Ultrasound Med. 2022 Sep;41(9):2247-2258. doi: 10.1002/jum.15909. Epub 2021 Dec 8.
Inferior vena cava (IVC) pulsatility quantified by the Caval Index (CI) is characterized by poor reliability, also due to the irregular magnitude of spontaneous respiratory activity generating the major pulsatile component. The aim of this study was to test whether the IVC cardiac oscillatory component could provide a more stable index (Cardiac CI-CCI) compared to CI or respiratory CI (RCI).
Nine healthy volunteers underwent long-term monitoring in supine position of IVC, followed by 3 minutes passive leg raising (PLR). CI, RCI, and CCI were extracted from video recordings by automated edge-tracking and CCI was averaged over each respiratory cycle (aCCI). Cardiac output (CO), mean arterial pressure (MAP) and heart rate (HR) were also recorded during baseline (1 minutes prior to PLR) and PLR (first minute).
In response to PLR, all IVC indices decreased (P < .01), CO increased by 4 ± 4% (P = .055) while HR and MAP did not vary. The Coefficient of Variation (CoV) of aCCI (13 ± 5%) was lower than that of CI (17 ± 5%, P < .01), RCI (26 ± 7%, P < .001) and CCI (25 ± 7%, P < .001). The mutual correlations in time of the indices were 0.81 (CI-RCI), 0.49 (CI-aCCI) and 0.2 (RCI-aCCI).
Long-term IVC monitoring by automated edge-tracking allowed us to evidence that 1) respiratory and averaged cardiac pulsatility components are uncorrelated and thus carry different information and 2) the new index aCCI, exhibiting the lowest CoV while maintaining good sensitivity to blood volume changes, may overcome the poor reliability of CI and RCI.
下腔静脉（IVC）搏动性通过 Caval 指数（CI）来量化，其特点是可靠性差，这也是由于自发呼吸活动的不规则幅度产生主要搏动分量所致。本研究旨在测试 IVC 心搏震荡分量是否可以提供比 CI 或呼吸 CI（RCI）更稳定的指数（心脏 CI-CCI）。
9 名健康志愿者在仰卧位接受 IVC 的长期监测，然后进行 3 分钟被动抬腿（PLR）。通过自动边缘跟踪从视频记录中提取 CI、RCI 和 CCI，CCI 是通过对每个呼吸周期进行平均（aCCI）得到的。在 PLR（PLR 前 1 分钟）和 PLR 期间（第 1 分钟）还记录心输出量（CO）、平均动脉压（MAP）和心率（HR）。
在 PLR 期间，所有 IVC 指数均降低（P<0.01），CO 增加 4±4%（P=0.055），而 HR 和 MAP 没有变化。aCCI 的变异系数（CV）（13±5%）低于 CI（17±5%，P<0.01）、RCI（26±7%，P<0.001）和 CCI（25±7%，P<0.001）。指数的时间相关性分别为 0.81（CI-RCI）、0.49（CI-aCCI）和 0.2（RCI-aCCI）。
通过自动边缘跟踪对 IVC 进行长期监测使我们能够证明：1）呼吸和平均心搏震荡分量不相关，因此携带不同的信息；2）新指数 aCCI 显示出最低的 CV，同时保持对血容量变化的良好敏感性，可能克服 CI 和 RCI 的可靠性差。
