動靜脈通路為末期腎臟病患者做血液透析治療時提供了重要的通道，使用這些通路一段時間後，可能致使病理變化發生，例如:靜脈產生高壓或血流量的不足。動靜脈通路可以透過觸診感覺顫動與脈動、聽診器、使用血管超音波或血管造影來做阻塞情況評估。雖然超音波檢測是一種有效的非侵入式技術，對於動靜脈通路預測有著高度的準確性，但是此種技術需要依賴醫院儀器與非常專業的操作技巧。因此，我們希望發展一種血管血流監聽檢測法(Phonoangiography)法是可以在家庭裡使用的系統。動靜脈通路的阻塞情形對於血行動力參數與聲音訊號會有重大的影響。因此，在這項實驗研究裡我們建立了一套簡化人體複雜的系統。根據阻塞程度的變化與固定音訊量測點做了一連串的分析，希望能在未來的家居臨床血管血流監聽檢測法系統找到決定性的參數與規則。經過一連串的實驗與臨床資訊驗證後，發現其血行動力參數包含病灶處流量與壓力之斜率改變處為DOS為70-80%區間，這可以解釋為何臨床上都會建議患者在洗腎瘻管達到70%阻塞時進行手術修復瘻管功能。此外在血管血流監聽檢測法的部分，實驗與臨床音訊分析後發現有類似的趨勢。隨著DOS的增加其音訊分析後的SPL值會降低。結果顯示聲音壓力位準(Sound Pressure Level)分析方法的確可以用來做為評估瘻管組塞情形的參考指標。

SUMMARY
This paper proposes a signal processing method for evaluating arteriovenous shunt (AVS) stenosis in hemodialysis patients. AVSs are surgically created pathological or physiological fistulas serving as access routes for end-stage renal disease patients. The distinct and periodic bruit of vascular shunts is clearly audible over the access routes. Thus, a bruit spectral analysis could be considered a valuable noninvasive method for quantifying the severity of vessel stenosis. We intend to determine a more precise relationship of phonography to stenotic lesions; therefore, we must conduct an additional in vitro study to simplify the relationships. To achieve this goal, we must set up a specific mock to simplify the blood flow condition and analyze the stenotic lesions-to-phonoangiography relationship.

Keywords—arteriovenous shunt (AVS) , phonoangiographic signal, AVS stenosis, SPL, mean artery pressure.
 
INTRODUCTION
Chronic kidney disease (CKD) is typically an irreversible and progressive process, and the final stage is kidney failure. Arteriovenous (AV) accesses (surgically created pathological fistula) serve as critical access routes for providing hemodialysis treatment for these ESRD patients. However, after prolonged use of these routes, pathological changes can occur, include: such as venous high pressure (caused by venous outflow obstruction) or insufficient blood flow (arterial inflow or in-graft stenosis). Prompt detection of these pathological conditions is critical for patients, physicians, and nurses. The AV access can be evaluated by feeling thrill and pulsation through palpation, listening for the bruit by using a stethoscope, or by direct examination employing vascular echography or angiography. Therefore, we sought to develop a phonography method for use in a home-based care system.

MATERIALS AND METHODS
A simplified geometric model of AV access was integrated in a closed circuit. The mock loops will offer pulsatile flow and physiological conditions for silicone tubing to simulate cardiovascular cycle. The reduction of the pipe as the stenotic site of AV access will be used as the independent variables in the mock circulatory loop. According to the hemodialysis condition, 600-1000 mℓ/min blood flow and 60-90 beat/min heart rates, different stenotic lesion will be conducted to different the hemodynamic parameters (velocity and pressure) and phonographic signal. However, the degree of stenosis (DOS) is used as an index to classify the AV access condition, and is determined by the narrowing percentage of the normal vessels. The definition of the DOS can be represented as , D is the diameter of the normal vessel and d is the diameter of the stenosis lesion. In this experimental, the DOS was varied from 50%, 70%, 80%, 85%, 90%, 92.5% to 95%. To analysis the bruit signal that includes experiment and clinical signal in SPL method.
 
RESULTS AND DISCUSSION
1. Hemodynamic parameters measured in varied DOS:
In this experiment, the pressure decreased when the fluid passed across the stenosis under the variant DOS conditions (from 50% to 95%). The pressure increased up-stream of the stenotic site according to the severity of the stenosis. In particular, the differential pressures increased substantially, exceeding 40 mmHg in the range of DOS up to 90% to 95%, as Fig. 1 illustrates. However, the effect on the distance parameters (1D, 5D, 10D and 17D) was inconsequential under the same DOS conditions. In the summation of differential pressure, under different DOS conditions (from 50% to 95%), up-stream pressures were higher than the down-stream pressures.

2. Phonography signal analyzed in various DOS status:
Based on our previous clinical study [20][21], the intensity and power spectral density of bruits are associated with the severity of AV access stenosis. The frequency spectra of phonography varied according to the increase in DOS. Based on this experimental study, we proposed that the auditory spectrogram could be represented by the bruits in the time-frequency domain. The experimental results showed that the high frequency occurred. Phonography is a noninvasive and scientific method for investigating the local fluid motion in arterial narrowing and distinguishes arterial dysfunction. The SPL value of the bruits was decreased when the DOS gradually increased. (figure 2)

CONCLUSION
The experimental result shows strongly correlation between phonoangiography and the severity of AV access, the trend of the experimental pressure and flow data correlated to the clinical phenomenon. The analytic method may be helpful for clinician for reference.

[1] 台灣洗腎史50年,民視新聞,中華民國102年6月9日, http://mypaper.pchome.com.tw/teresalover/post/1324623715
[2] Trerotola S.O., Scheel P.J. Jr, Powe N.R., Prescott C., Feeley N., He J., Watson A., “Screening for dialysis access graft malfunction: Comparison of physical examination with US.” Journal of Vascular and interventional Radiology , vol.7,pp.15-20,1996.
[3] National Kidney Foundation, K/DOQI clinical practice guidelines for chronic kidney disease" , 2002.
[4] 什麼是血液透析治療?,台北市:衛生福利部中央健保署, http://www.nhi.gov.tw/mqinfo/Content.aspx?Type=Dialysis&List=7
[5]血液透析. 台北榮總血液透析室. 2012.
[6]徐治煒,腎友一定要知道的～洗腎動靜脈氣球擴張術,臺安醫訊第158期,中華民國100年4月1日, http://www.tahsda.org.tw/newsletters/?p=2257#.UzLpWaiSzTo
[7] Pisoni R.L., Young E.W., Dykstra D.M., Greenwood R.N., Hecking E., Gillespie B., Wolfe R.A., Goodkin D.A., Held P.J., “Vascular access use in Europe and the United States: Results from the DOPPS.” Kidney International, Vol61, pp.305-316,2002.
[8] Mehta S., ”Statistical summary of clinical results of vascular access procedures for hemodialysis”, in Sommer BG, Henry ML (eds): Vascular Access for Hemodialysis-II(ed 2). Chicago, IL, Gore , pp.145-157,1991.

[9] Perera G.B., Mueller M.P., Kubaska S.M., Wilson S.E., Lawrence P.F., Fujitani R.M., “Superiority of autogenous arteriovenous hemodialysis access: Maintenance of function with fewer secondary interventions.” Annals of Vascular Surgery, vol.18, pp.66-73, 2004.
[10] Huber T.S., Carter J.W., Carter R.L., Seeger J.M., “Patency of autogenous and polytetrafluoroethylene upper extremity arteriovenous hemodialysis accesses: A systematic review.” Journal of Vascular Surgery, vol.38, pp.1005-1011, 2003.
[11] Angioplasty- Causes, Symptoms, Treatment, Diagnosis- Seniors’ Health- Body &Health., 2010. http://bodyandhealth.canada.com/channel_condition_info_details.asp?disease_id=8&channel_id=10&relation_id=10865
[12] Angioplasty Recovery.,2010. http://www.angioplastysurgery.net/recovery.php
[13] William Harvey, An Anatomical Exercise on the Motion of the Heart and Blood in Living Beings., Dover Publications, ISBN 978-0486688275, 1628.
[14] Womersley, J. R., “Oscillatory flow in arteries: The constrained elastic tube as a model of arterial flow and pulse transmission” Physics in medicine and Biology, vol.2, pp.178-187, 1957.
[15] Womersley, J. R., “Oscillatory flow in arteries: The reflection of the pulse wave at junctions and rigid inserts in the arterial system.” Physics in Medicine and Biology, vol.2, pp.313-323, 1958
[16] Milnor, W. R., Bergel, D. H., and Bargainer, J. D., “Hydraulic power associsted with pulmonary blood flow and its relation to heart rate” Circulation Research, vol.19, pp.467-480, 1966.
[17] Milnor, W. R., Conti, C. R., Lewis, K. B., and O’Rourke, M. F., “Pulmonary arterial pulse wave velocity and impedance in man” Circulation Research, vol.19, 1969.
[18] 蔡昇育，”血管橈度與脈搏波速間關係之實驗模擬研究”，國立成功大學航太所碩士論文, 2007.
[19] Jianxing Wu, Chianming Li, Weiling Chen, Chiahung Lin, Tainsong Chen. “Application of Van der Pol oscillator screening for peripheral arterialdisease in patients with diabetes mellitus” Journal of Biomedical Science and Engineering , vol. 6,pp.1143-1154,2013.
[20] Wei-Ling Chen, Chung-Dann Kan, Chia-Hung Lin, Chen, T. ”A Rule-based Decision-making Diagnosis System to Evaluate Arteriovenous Shunt Stenosis for Hemodialysis Treatment of Patients Using Fuzzy Petri Nets”, Institute of Electrical and Electronics Engineers, Journal of Biomedical and Health Informatics, vol. 00, No. 00, 2013
[21] Wei-Ling Chen , Tainsong Chen ,Chia-Hung Lin ,Pei-Jarn Chen , Chung-Dann Kan , “Phonographic signal with a fractional-order chaotic system:a novel and simple algorithm for analyzing residual arteriovenous access stenosis” Medical & Biological Engineering & Computing, Vol. 51 Issue 9, pp.1011,2013.
[22] Wei-Ling Chen, Chia-Hung Lin, Tainsong Chen, Pei-Jarn Chen, Chung-Dann Kan ,“Stenosis Detection Algorithm using the Burg Method of Autoregressive Model for Hemodialysis Patients”, Journal of Medical and Biological Engineering, vol.33,No.4,pp.356-362,2012.
[23] Wei-Ling Chen, Chia-Hung Lin, Tainsong Chen, Chung-Dann Kan, “The feasibility of Application Phonoangiography with Fractional Order Chaotic System in Arteriovenous Shunt Stenosis Detection”, Institute of Electrical and Electronics Engineers International Conference on Orange Technologies ,pp 123-126, 2013.
[24] Joyner, C.R. and Reid, J.M. “Applications of ultrasound in cardiology and cardiovascular physiology.” Progress in Cardiovascular Diseases,vol.5, pp.482,1963.
[25] Strandness D. E., Jr., Schultz R. D., Sumner D. S. & Rushmer R. F., “Ultrasonic flow detection: a useful technic in the evaluation of peripheral vascular disease” The American Journal of Surgery, vol.113, pp.311,1967.
[26] Hinze, J. O., Turbulence , McGraw-Hill, New York, 1959.
[27] Weyers, R. F. R., “Vibration and Near-Field Sound of Thin-Walled Cylinders Caused by Internal Turbulent Flow.” NASA, TN D430 ,1959.
[28] Bakewell, H. P., Carey, G. F., Libuha, J. J., Schloemer,H. H., and Von Winkle, W. A., “Wall Pressure Correlations in Turbulent Pipe Flow” U.S. Navy Underwater Sound Laboratory, Report 559-1-052-00-00 ,1962.
[29] Lees R.S., Dewey C.F. Jr.,”Phonoangiography: A New Noninvasive Diagnostic Method for Studying Arterial Disease” Proceedings of the National Academy of Sciences of the United States of America. Vol.67,No.2, pp.935-942, 1970.
[30] Ross Roeser, Michael Valente, Audiology: Diagnosis , Thieme, 2nd edition , pp. 240,2007.
[31] Morfey, Christopher L., Dictionary of Acoustics, Academic Press, San Diego, ISBN 978-0125069403, 2001.
[32] Koen Van Canneyt, Robrecht Nils Planken, Sunny Eloot, Patrick Segers, and Pascal Verdonck, “Experimental Study of a New Method for Early Detection of Vascular Access Stenoses: Pulse Pressure Analysis at Hemodialysis Needle”, Artificial Organs vol.34,No.2, pp.113–117, 2010.
[33] S. S Stevens Sound and Hearing , Life Science Library , Time-Life Books, Alexandria, VA , pp. 173,1965.
[34] Wei-Ling Chen, Rui-Hung Kao, You-xuan Lin , Chung-Dann Kan, “Comparison phonography signal with hemodynamic parameters in different degree of stenosis in experimental study,” Global Conference on Biomedical Engineering, 2014,
[35] 台灣靜脈學會,靜脈疾病與血管通路,合記圖書出版社. chapter.5,pp. 37-69,2011.