應用瞬時脈率變異度於 未成年人之自體調節探討

Abstract

體溫是人類生理機轉中相當重要的自體調節指標，亦是一般診所中判定病徵的要項之一。下視丘為體溫調節中樞，透過自律神經系統(Autonomic nervous system，ANS)來調控身體各處升降溫之機轉。一般在發燒時會產生周邊血管收縮、體溫上升、心跳加快、交感神經興奮、偶爾血壓增加等等諸多的生理反應，因此觀察ANS中交感與副交感神經系統與體溫之間的變化就顯得重要。臨床上使用非侵入量測心率變異程度，觀察ANS活性變化，在特定條件下(平躺狀態或傾斜床實驗)亦能使用脈率變異度協助評估。然受限於心跳週期的時間尺度，頻譜圖顯示有所限制。為能突破此限制，瞬時脈率變異度(Instantaneous pulse rate variability，iPRV)被提出，此法應用經驗模態分解來進行脈波訊號(photoplethysmography， PPG)前處理，解構出特定頻帶的內生性特徵函數(Intrinsic mode function)後再計算瞬時週期(Instantaneous period)，成功地突破時間尺度的限制，得到更高解析的資訊。 本研究在國立交通大學人體與行為研究倫理委員會(Research Ethics Committee for Human Subject Protection， NCTU)同意下並經臨床醫師確認，收集15位發燒病人(體溫大於等於37.9 ℃)與15位未發燒者(體溫小於37.9 ℃)之PPG訊號，分別命名為Fever group與Control group，並依序進行iPRV分析。結果顯示，在頻譜圖的解讀上，不僅僅能從低頻區(0.04Hz~0.15Hz)與高頻區(0.15Hz~0.40Hz)的比值變化看到ANS的活化程度，而正規化條件(原為0.04Hz~0.40Hz)加入特高頻區(0.40Hz~0.90Hz)後，Fever group與Control group的高頻區比值分別為0.19 ±0.07與0.31±0.12，具有統計顯著差異(p<0.05)。然而特高頻區在正規化條件中所隱含意義，以及體溫高低、周邊循環以及特高頻區的關聯性為何，仍需更多實驗來驗證。因此，藉著比對iPRV與心率變異度之間的差異來發掘更多體溫調節與周邊循環的機轉是接續的研究重點。

The body temperature is one of the important indices of human body autoregulation, it is also a discriminate assessment of clinical disease. The body temperature is controlled by the hypothalamus, which also domains the autonomic nervous system (ANS). When somebody has a fever, the body temperature abnormal raises, vasoconstrictions, heart rate increases, the sympathetic (SNS) is activation, the blood pressure increases, etc. Therefore, it is important to indicate what regulation between the body temperature and ANS. The common non-invasive indicator for ANS is based on heart rate variability (HRV). Beside it, pulse rate variability (PRV) also can be a non-invasive indicator for ANS under some conditions (e.g. supine or tilt-up position). However, these two methods have limitation on spectral analysis because of the beat-to-beat timescale property. For higher resolution on spectral analysis, instantaneous PRV (iPRV) was proposed. iPRV adopts empirical mode decomposition and PRV technology to break the restriction of timescale and obtain the higher resolution information on spectral analysis. This study, which was approved by the Research Ethics Committee for Human Subject Protection and confirmed by a pediatrician, was to acquire the photoplethysmography (PPG) signal of 15 fever patients (body temperature ≧ 37.9 ℃) and 15 feverless people (body temperature < 37.9 ℃), assigned to Fever group and Control group, respectively . The signal was used for iPRV analysis. The analysis results show the conventional ranges (Low frequency, LF: 0.04~0.15 Hz; High frequency, HF: 0.15~0.4Hz) of iPRV also observe the activities of ANS. As well, the modified indices including ultra-band (Very high frequency, VHF: 0.4~0.9 Hz) are significant difference (p-value <0.05) between fever and feverless symptoms (i.e. normalized HF in Fever group and Control group are 0.19 ±0.0 and 0.31±0.12, respectively). Based on the statistical evidence, VHF is potential to provide indicator of thermoregulation on peripheral circulation. Nevertheless, it still need more experiments to examine. Therefore, to compare the difference between iPRV and HRV for obtaining more mechanisms of thermoregulation is an important point of following research.