瞬時脈率變異度於輸液治療反應性之量化評估：探討無心血管疾病者之靜脈回流變化

Abstract

血液動力學是人類生理上維持生命的重要機轉之一，當不穩定的血液動力反應時，易產生休克情形，臨床上對此多採輸液方式來進行調控(簡稱輸液治療)，所以預測病患對輸液治療之反應就更顯重要。臨床上有許多慣用指標來預測此一反應，偵測標的大都為輸液後心輸出量的變化幅度，且皆基於時域訊號之變化程度來進行計算，此法雖可獲得立即性反應資訊，也可隨時變的血液動力反應而產生非穩態之變異，導致非穩定的評估指標。 瞬時脈率變異度(Instantaneous pulse rate variability，簡稱iPRV)為一種計算脈波訊號的瞬時頻率，提供心血管調控訊息的創新性方法，由於採取經驗法則分式來解構訊號，因此，對應到頻譜上可突破0.5赫茲(此為心率變異度之限制)，研究進一步指出，非常高頻區(Very high frequency band, 0.4-0.8赫茲，簡稱VHF)可呈現週邊血管調控機轉。本研究係利用iPRV分析脈波訊號，預期VHF可成為評估心輸出量的指標。 為此，提出一個心回流量變化的實驗，藉由不同姿勢所造成的心回流量變化來對應VHF之變化情形，如傾斜床實驗可在短時間內減少心回流量，以及被動抬腳實驗則模擬輸液狀態，可增加受測者心回流量。在IRB同意下進行30位健康受測者實驗，數據結果顯示(最後26位檢覈通過)，在HRV中的VHF在不同姿勢下並無明顯變化；相對於此，實驗預期產生的心回流量變化，可於iPRV的VHF觀察到相應的變化性，如此可知，iPRV可視為心輸出量之評估指標選項之一，並且也有潛力成為預測輸液治療反應性的評估方式。

Hemodynamically unstable patient leads to be in shock generally. As fluid therapy is primary treatment for shock, fluid responsiveness (FR) of patient should be evaluated before volume expansion. Conventional methods predict FR by analyzing variation of blood pressure signal in time domain for acquiring cardiac output change after volume expansion. However, nonstationary problem exists in time domain which make it difficult to provide stable index for FR. Previous study showed that instantaneous pulse rate variability (iPRV) is a cardiovascular assessment in frequency domain by using instantaneous frequency estimation method. Furthermore, iPRV used ensemble empirical mode decomposition (EEMD), which could solve nonstationary problem, to break frequency limitation in power spectrum of heart rate variability (HRV). Also, iPRV provides a new indication in very high frequency (VHF) range (0.4-0.8Hz) of spectrum for peripheral responses. The aim of this study was to verify the ability of iPRV to indicate VHF for cardiac output assessment. It was thought that propose an experiment of change in venous return to examine the reliability of VHF to assess cardiac output. The experiment included head-up tilt (HUT) which induced blood pooling in the legs and passive leg raising (PLR) which induces a translocation of venous blood. Thirty healthy participants participated this study but only had twenty-six inclusive participants who are no uncontrollable distortion in acquired data, and the experiment was approved by institutional review board of Tungs’ Taichung Metro Harbor Hospital. The result showed that normalized power of VHF in HRV was small and no corresponding variation in different postures, conversely, normalized power of VHF in iPRV presented relative trend with different venous return changes. Overall, iPRV provides a novel cardiac output assessment in frequency domain and is potential to evaluate FR.