有鑑於目前穿戴式裝置的開發面臨諸多實務上的挑戰與困境，普遍無法獲得穩定可靠的PPG訊號，也因此不具備解析血管特性的能力。若是能夠逐步排除影響波形品質的干擾因素，將有助於取得更穩定可靠的PPG訊號。另外，本實驗室裝置目前主要應用於醫院場域中，已經累積多項臨床研究成果，若要應用於社區場域或其他非正式醫療場域中，由於裝置外型上的限制在使用上的便利性較低。因此若能以過去累積的成果為基礎，再更進一步改善裝置以及開發新的PPG腕帶量測，將會對心血管疾病或慢性疾病等的深入研究產生助益。
為了改善與設計出兼具外觀、可靠性與實用度的穿戴式系統，本研究將會對實驗室舊有的系統進行改良，使改良系統更加實用美觀，同時增加穿戴式系統的親和與可靠性。將會達成以下幾點：
(1) 以實驗室舊有的系統為基礎，改善並設計出更便利實用且可靠美觀的穿戴式系統，並能應用於社區及一般非專業醫療場域。
(2) 尋找與確立可能對PPG波形造成的干擾因素。
(3) 驗證設計的PPG腕帶能否部分取代力學式BP腕帶。
(4) 建立雙光學式量測系統，包含PPG腕帶與改良PPG指環，藉此比較上下游動脈的脈波差異，以評估脈波衰減情況。
因此，在系統改良完成後，為了檢測改良後的系統效能是否較舊有系統佳，並且驗證本研究設計的PPG腕帶之實用性等，本研究設計以下三項實驗驗證：
(1) 驗證BP改良電路與PPG改良電路效能實驗
(2) PPG腕帶與BP腕帶相關性比較實驗
(3) PPG指環與PPG腕帶的上下游比對實驗
為了確保改良電路的使用效能比舊有電路更好，設計實驗進行五項比較，包含訊雜比、濾波器效能、擷取訊號頻譜分析、可靠度，與再現性比較。並檢驗PPG腕帶與BP腕帶的相關性，評估兩者的關聯。採用PPG腕帶與指環同時量測的方式，比較兩者間的波形頻譜差異及相關性，藉此得知上下游動脈的衰減效率。
實驗結果表示，本研究改良之電路與舊電路相比其訊雜比更好、更可靠，並且在頻譜分析上更具備優勢。同時PPG腕帶與BP腕帶的頻譜相關性在2至10諧波均有R2高於0.6的高度相關性，表示本研究開發PPG腕帶可以部份取代BP腕帶。在評估上下游動脈的衰減效率中，結果顯示Ratio在所有諧波上均有明顯差異，CV、Angle等參數則在特定諧波上也有明顯變化，若能持續完善相關測試，將能夠應用於更多心血管疾病與其他慢性疾病的早期偵測達成早期預防的目標。
上述結果可得以下結論：
(1) 改良舊有BP電路與PPG電路，經過實驗全面評估確認改良電路效能優於舊電路。整合硬體系統改良外觀，達成裝置能用於於一般及社區場域。
(2) 委託洽富科技一同改良舊有PPG指環外觀，並開發設計PPG腕帶，讓收案工作能有更多選擇，在BP腕帶量測不到時，能夠使用PPG腕帶做為替代。
(3) 確立與找尋可能對PPG波形造成的干擾因素。
(4) 使用PPG腕帶時，若遇到橈動脈血管較深的受測者，可以使用手掌向下量測姿勢，可能可以解決PPG訊號量測不到的問題，並且頻域分析結果顯示Ratio成分不受影響。
(5) 經過實驗驗證PPG腕帶與BP腕帶有高相關性，2至10諧波的相關係數均高於0.6，代表兩者間具有高度相關。
(6) 藉由PPG腕帶與PPG指環的實驗結果得知，手腕橈動脈至手指小動脈與微血管時，其Ratio、CV、Angle的影響與差異以及相關性。可以作為之後研究血液循環特性的指標。

因此，在達成以上結論後，在社區及一般場域中使用本研究所改良的穿戴式裝置將能夠更便利於收案，開發設計的PPG腕帶也能夠使收案多一項選擇，讓收案更有效率。並且找出多項對PPG波型的影響因素，讓後面的使用者或改良者能夠了解變因，從而知道量測時注意的要素，才能夠收取完好的PPG波型進行後續的分析。並藉由PPG腕帶與PPG指環的實驗結果，待後續實驗完善後，能夠作為血液循環特性的指標。

關鍵字：穿戴式裝置、脈波訊號、光容積變化、橈動脈、心血管疾病

Given that the development of the wearable measurement device is now facing many challenges and difficulties in practice, it is incapable to acquire stable and reliable PPG signal, as well as to analyze vascular features through the existent device. Therefore, if the confounding factors influencing the quality of waveform can be eliminated, the PPG signal will become more stable and reliable. In addition, the device of this laboratory has already applied in various medical practices and accumulated bountiful clinical practice results, whereas due to the limitation of the appearance, it is not very convenient to be utilized in communities or other non-medical fields. For this reason, if the study could further revise and improve the original device and invent a new PPG wrist-based measurement on the basis of the previous achievement of the laboratory, it will contribute to more in-depth research for cardiovascular disease and other chronic disease in the future.
In order to improve and invent a more user-friendly and artistic wearable measurement system, this study will focus on improving the original system in the laboratory to enhance its reliability, user-friendliness and aesthetics. The new wearable system will accomplish several points mentioned below.
(1) Improving the original system in the laboratory and designing a more user-friendly and reliable wearable system, which can be applied to communities and other non-medical fields.
(2) Finding out and ensuring the confounding factors, which might influence the quality of waveform, for instance, the measurement posture and conditions, to ensure the reliability of the pulse wave and provide a well foundation for the following spectrum and AI analysis.
(3) Ensuring that the new PPG wristband is able to partly replace the mechanical BP one.
(4) Establishing optical measurement system, including PPG wristband and revised PPG finger-ring, to compare the pulse wave difference between upstream and downstream arteries and evaluate the attenuation effect.

After the improvement of the system, in order to verify whether the revised device performs better than the original one, and prove the reliability of the newly designed PPG wristband, the study adopts three validation tests mentioned below.
(1) The performance experiment of the verification of BP improved circuit and PPG improved circuit
(2) The comparison experiment of the correlation between PPG wristband and BP wristband
(3) The comparison experiment of the upstream and downstream between the PPG finger-ring and PPG wristband
In order to ensure the efficacy of the improved circuit being better than the original one, the study conducts five comparison experiments, including signal-to-noise ratio, the efficacy of wave filter, spectral density, reliability and reproducibility. Then the study tests the correlation between PPG wristband and BP wristband to evaluate the association between the two. Besides, the study measures the PPG wristband and finger-ring simultaneously to compare the difference and correlation of the waveform spectrum to know the attenuation effect between the upstream and downstream arteries.
Experimental results show that the revised circuit in this study actually performs better and has advantage in signal-to-noise ratio, reliability and spectrum analysis, compared to the original one. Moreover, in harmonic number 2nd to 10th, the spectrum correlation index (R2) of PPG wristband and BP wristband is higher than 0.6, which indicates the high correlation between these two devices. The figure implies that the newly-designed PPG wristband in the study can partly replace the BP wristband. In the evaluation of attenuation effect between the upstream and downstream arteries, the result points out that Ratio performs differently among all the harmonic numbers, while CV, Angle and other parameters show obvious variation in specific harmonic numbers. If the measurement system can be continuously enhanced and improved based on this study results, it will be able to be applied to the early detection of more cardiovascular cases and achieve the goal of primary prevention.

Based on previous results, the study comes to several conclusions as below.
(1) The study improves the original BP circuit and PPG circuit, and verify that the improved circuit performs better than the original one through comprehensive experimental evaluation. Then the study also integrates the hardware system and revises the appearance of the device to make it applicable to non-medical fields.
(2) The study cooperates with CHEER FOUR TECHNOLOGY COMPANY to improve the appearance of the original PPG finger-ring, and design a new PPG wristband, which provides alternatives for the cases acceptance process.
(3) The study finds out and ensures the confounding factors, which might influence the quality of PPG waveform.
(4) While using the PPG wristband, if the radial artery of the respondent is in a deeper place, which leads to the difficulty of receiving the PPG signal, the pronation position could be adopted to solve the measurement problem. In addition, it is proved by the spectral density results that the Ratio would not be affected by this way of measurement.
(5) Through the experiment the study finds out that the spectrum correlation index, R2, of PPG wristband and BP wristband is higher than 0.6 in harmonic number 2nd to 10th, which indicates the high correlation between these two devices.
(6) Through the experimental results of the PPG wristband and finger-ring, the study finds the influence, difference and correlation of Ratio, CV and Angle between the radial artery, and the acral finger arterioles and capillary.
Therefore, after reaching the conclusions above, applying this wearable device improved by the study to the communities or other non-medical fields would make the cases acceptance more convenient. In addition, the newly-designed PPG wristband would also provide the cases acceptance an alternative tool, which makes the working process more efficient. The study also figures out several confounding factor, which might influence the quality of PPG waveform. That findings inform the following users or reformers the variable, as well as the noteworthy points during the measurement, which is beneficial to acquire high-quality PPG waveform for the subsequent analysis. As a result, if the experiment of PPG wristband and PPG finger-ring could be continuously refined by the followers, it would become an index for the feature of circulating blood.

Keywords: wearable device, pulse signal, photoplethysmography, radial artery, cardiovascular disease

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