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In-vivo Blood Pressure Sensor

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  1. In-vivo Blood Pressure Sensor Anup Pillai Dhanya Premkumar Nair

  2. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  3. Need to measure blood pressure • To diagnose critical medical conditions like hypertension -causes strokes, heart attacks, heart failures • Low blood pressure causes hypotension, which results in dizziness, fainting or shock

  4. Conventional blood pressure monitoring systems (non-invasive sensors) Auscultatory method Mercury Manometer

  5. Current blood pressure sensors in use With the new sensor, no cuff is required Device takes advantage of the method called pulse wave velocity which allows blood pressure to be calculated by measuring the pulse at 2 points along an artery This was developed at MIT's d'Arbeloff Laboratory for Information Systems and Technology

  6. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  7. Background • In vivo-Latin for “within the living” • Experimentations are done using a whole, living organism • In vivo monitoring is critical for developing effective treatments

  8. Background (Contd.) • Long-Term Implantable Blood Pressure Monitoring System • Wireless Battery less In VIVO Blood PressureSensing Micro system

  9. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  10. Long-Term Implantable Blood Pressure Monitoring System • The system employs an instrumented elastic cuff, wound around a blood vessel • Operates in a linear “diameter v.s. pressure” region of the vessel for real time blood pressure monitoring • The elastic cuff is made of soft bio-compatible rubber, filled with bio-compatible insulating fluid with an immersed MEMS pressure sensor • The MEMS sensor detects the vessel blood pressure wave form with a constant scaling factor, independent of the cuff bias pressure exerting on the vessel.

  11. Implantable blood pressure monitoring system MEMS sensor Insulating Liquid Vein Cuff

  12. Advantages • This technique avoids vessel insertion • Also substantially minimizes vessel movement restriction due to the soft cuff elasticity • Attractive for minimizing long-term adverse biological effects

  13. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  14. Wireless Battery less In VIVO Blood PressureSensing Micro system • Wireless powering and data telemetry are also incorporated in the micro system • This eliminates the need of external wire connections and any bulky battery • The micro system can be used to obtain reliable measurements without suffering from stress induced distortion

  15. Wireless Battery less In VIVO Blood PressureSensing Micro system

  16. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  17. Microsystem architecture

  18. The in vivo blood pressure sensor inside an actual lab rat

  19. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  20. Our Objectives • The sensor specified in the background exhibits increased noise levels • The transmitter of the same dissipated a 80% of the system power • Our objectives are: a) To design a similar sensor which exhibits less noise levels b) To design a better and more power efficient transmitter for the sensor

  21. Objective 1 • To find a solution which exhibits less noise levels • We began by investigating the reason for the high noise levels in the current design

  22. Reason for noise • Animal body vapor penetration into the device • Affect the functioning of the electrical connections within the sensor.

  23. The damage caused • The high impedance node can be highly sensitive to vapor penetration • Electrical connections between the sensor diaphragm and IC chip

  24. Solution proposed • Protection for moisture penetration is required for the sensor diaphragm as well as the electrical connections between the sensor diaphragm and IC chip.

  25. Solution proposed (Contd.) • A passivation layer, such as silicon dioxide (SiO2) and silicon nitride (Si3N4), can be deposited on the top of diaphragm. • An encapsulant material with strong moisture resistance can be used to protect the bond wires between the sensor and IC before applying silicone passivation layer.

  26. Objective 2 • To design a better and more power efficient transmitter for the sensor • In the microsystem, an oscillator based FSK transmitter was employed for data telemetry • This transmitter was on throughout and hence resulted in 80% power dissipation

  27. Solution • To use a transmitter operating with a low duty cycle • One can also use a transmitter with an increased bandwidth

  28. Numerical Calculations • If the sampling frequency is 2 kHz, with data rate of 48 kbps, corresponding bit rate is 24 per 0.5 ms • This is the current specification for the system

  29. Numerical Calculations (Contd.) • Instead if we the transmitter is designed to be on for 0.05 ms and off for the remaining 0.45 ms • This results in one order magnitude power reduction at increased data rate of 480 kbps • This corresponds to 72% overall system power reduction

  30. Outline • Current blood pressure sensors in use • Background • Long-Term Implantable Blood Pressure Monitoring System and Advantages • Wireless Battery less In VIVO Blood PressureSensing Micro system and Advantages • System Architecture • Our Objectives • Timeline and Division of work • Conclusions

  31. Timelines

  32. Division of Work • First Objective: To design a similar sensor which exhibits less noise levels-A. Pillai • Second Objective: To design a better and more power efficient transmitter for the sensor-D. Nair

  33. Conclusions • A review of current in-vivo blood pressure sensors was presented in this review study • We identified the potential problems with existing solutions • We have proposed two solutions that will enhance the performance of the current design

  34. References • "Normal Blood Pressure Range Adults". Health and Life. • http://www.nhlbi.nih.gov/health/dci/Diseases/hyp/hyp_whatis.html •  Klabunde, Richard (2005). Cardiovascular Physiology Concepts. Lippincott Williams & Wilkins. pp. 93–4. ISBN 978-0781750301. • Chobanian AV, Bakris GL, Black HR, et al (December 2003). "Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure".Hypertension 42 (6): 1206–52. doi:10.1161/01.HYP.0000107251.49515.c2. PMID 14656957. • "Diseases and conditions index - hypotension". National Heart Lung and Blood Institute. September 2008. Retrieved 2008-09-16. •  "Hypertension: management of hypertension in adults in primary care". NICE clinical guideline 34. London: National Institute for Health and Clinical Excellence (NICE). June 2006. Retrieved 2008-09-15. •  "Understanding blood pressure readings". American Heart Association. 11 January 2011. Retrieved 30 March 2011. •  Pesola GR, Pesola HR, Nelson MJ, Westfal RE (January 2001). "The normal difference in bilateral indirect BP recordings in normotensive individuals". American Journal of Emergency Medicine 19 (1): 43–5. doi:10.1053/ajem.2001.20021. PMID 11146017. •  Reckelhoff, Jane F (1 May 2001). "Gender differences in the regulation of blood pressure". Hypertension 37 (5): 1199–208. PMID 11358929.

  35. References (Contd.) • National Heart, Lung and Blood Institute. Blood pressure tables for children and adolescents. (Note that the median BP is given by the 50th percentile and hypertension is defined by the 95th percentilefor a given age, height, and gender.) • (Pickering et al. 2005, p. 145) See Isolated Systolic Hypertension. • "...more than half of all Americans aged 65 or older have hypertension." (Pickering et al. 2005, p. 144) • Eguchi K, Yacoub M, Jhalani J, Gerin W, Schwartz JE, Pickering TG (February 2007). "Consistency of blood pressure differences between the left and right arms". Arch Intern Med 167 (4): 388–93.doi:10.1001/archinte.167.4.388. PMID 17325301. • Agarwal R, Bunaye Z, Bekele DM (March 2008). "Prognostic significance of between-arm blood pressure differences". Hypertension 51 (3): 657–62. doi:10.1161/HYPERTENSIONAHA.107.104943.PMID 18212263. • Appel LJ, Brands MW, Daniels SR, Karanja N, Elmer PJ, Sacks FM (February 2006). "Dietary approaches to prevent and treat hypertension: a scientific statement from the American Heart Association".Hypertension 47 (2): 296–308. doi:10.1161/01.HYP.0000202568.01167.B6. PMID 16434724. • Mayo Clinic staff (2009-05-23). "Low blood pressure (hypotension) — Causes". MayoClinic.com. Mayo Foundation for Medical Education and Research. Retrieved 2010-10-19. • Rosenson RS, Wolff D, Green D, Boss AH, Kensey KR (February 2004). "Aspirin. Aspirin does not alter native blood viscosity". J. Thromb. Haemost. 2 (2): 340–1. PMID 14996003. • Klabunde, RE (2007). "Cardiovascular Physiology Concepts - Mean Arterial Pressure". Retrieved 2008-09-29. Archived version 2009-10-03

  36. References (Contd.) • Klabunde, RE (2007). "Cardiovascular Physiology Concepts - Pulse Pressure". Retrieved 2008-10-02. Archived version 2009-10-03 • Markham LW, Knecht SK, Daniels SR, Mays WA, Khoury PR, Knilans TK (November 2004). "Development of exercise-induced arm-leg blood pressure gradient and abnormal arterial compliance in patients with repaired coarctation of the aorta". Am. J. Cardiol. 94 (9): 1200–2. doi:10.1016/j.amjcard.2004.07.097. PMID 15518624. • Messerli FH, Williams B, Ritz E (2007). "Essential hypertension". Lancet 370 (9587): 591–603. doi:10.1016/S0140-6736(07)61299-9. PMID 17707755. • O'Rourke M (1 July 1995). "Mechanical principles in arterial disease". Hypertension 26 (1): 2–9. PMID 7607724. • Mitchell GF (2006). "Triangulating the peaks of arterial pressure". Hypertension 48 (4): 543–5. doi:10.1161/01.HYP.0000238325.41764.41. PMID 16940226. • Klabunde, RE (2007). "Cardiovascular Physiology Concepts - Arterial Baroreceptors". Retrieved 2008-09-09. Archived version 2009-10-03 • Booth, J (1977). "A short history of blood pressure measurement". Proceedings of the Royal Society of Medicine 70 (11): 793–9. PMC 1543468. PMID 341169. Retrieved 2009-10-06. • "Vital Signs (Body Temperature, Pulse Rate, Respiration Rate, Blood Pressure)". OHSU Health Information. Oregon Health & Science University. Retrieved 2010-04-16. • Deakin CD, Low JL (September 2000). "Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study". BMJ321 (7262): 673–4. doi:10.1136/bmj.321.7262.673. PMC 27481. PMID 10987771. • Interpretation - Blood Pressure - Vitals, University of Florida. Retrieved on 2008-03-18. • G8 Secondary Survey, "Manitoba". Retrieved on 2008-03-18. • (Pickering et al. 2005, p. 146) See Blood Pressure Measurement Methods.

  37. References (Contd.) • (Pickering et al. 2005, p. 147) See The Oscillometric Technique. • Laurent, P (2003-09-28). "Blood Pressure & Hypertension". Retrieved 2009-10-05. • Elliot, Victoria Stagg (2007-06-11). "Blood pressure readings often unreliable". American Medical News (American Medical Association). Retrieved 2008-08-16. • Jhalani, Juhee; Tanya Goyal, Lynn Clemow, et al (2005). "Anxiety and outcome expectations predict the white-coat effect". Blood Pressure Monitoring 10 (6): 317–9. doi:10.1097/00126097-200512000-00006. PMID 16496447. Retrieved 2009-10-03. • (Pickering et al. 2005, p. 145) See White Coat Hypertension or Isolated Office Hypertension. • (Pickering et al. 2005, p. 146) See Masked Hypertension or Isolated Ambulatory Hypertension. • Mancia G, De Backer G, Dominiczak A, et al. (June 2007). "2007 Guidelines for the management of arterial hypertension: The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC)". Eur Heart J 28 (12): 1462–536. doi:10.1093/eurheartj/ehm236. PMID 17562668. • Niiranen, TJ; Kantola IM, Vesalainen R, et al (2006). "A comparison of home measurement and ambulatory monitoring of blood pressure in the adjustment of antihypertensive treatment". Am J Hypertens19 (5): 468–74. doi:10.1016/j.amjhyper.2005.10.017. PMID 16647616. • Shimbo, Daichi; Thomas G. Pickering, Tanya M. Spruill, et al (2007). "Relative utility of home, ambulatory, and office blood pressures in the prediction of end-organ damage". Am J Hypertens 20 (5): 476–82. doi:10.1016/j.amjhyper.2006.12.011. PMC 1931502. PMID 17485006.[dead link] • National Heart, Lung and Blood Institute. Tips for having your blood pressure taken. • Table 30-1 in: Trudie A Goers; Washington University School of Medicine Department of Surgery; Klingensmith, Mary E; Li Ern Chen; Sean C Glasgow (2008). The Washington manual of surgery. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. ISBN 0-7817-7447-0. • Dugdale, David. "Blood Pressure". Retrieved 1 April 2011. • Klabunde, Richard. "Arterial Blood Pressure". Retrieved 31 March 2011. • Fung, Yuan-cheng (1997). Biomechanics:Circulation. New York: Springer. pp. 571. ISBN 038794383.

  38. References (Contd.) • Munson; Young, Okiishi, Huebsch (2009). Fundamentals of Fluid Mechanics (Sixth ed.). New Jersey: John Wiley &Sons, Inc.. pp. 725. ISBN9780470262849. • Womersley, J. R. (1955). "Method for The Calculation of Velocity, Rate of Flow and Viscous Drag in Arteries When The Pressure Gradient is Known". Journal of Physiology127: 553–563. • Sircar, Sabyasach (2008). Principles of Medical Physiology. India: vistasta Publishing. ISBN978158890572. • Fung, Yuan-cheng; Zweifach, B.W. (1971). "Microcirculation: Mechanics of Blood Flow in Capillaries". Annual Review of Fluid Mechanics3: 189–210. • What Is Pulmonary Hypertension? From Diseases and Conditions Index (DCI). National Heart, Lung, and Blood Institute. Last updated September 2008. Retrieved on 6 April 2009. • Chapter 41, page 210 in: Cardiology secrets By Olivia Vynn Adair Edition: 2, illustrated Published by Elsevier Health Sciences, 2001 ISBN 1560534206, 9781560534204 • Struijk PC, Mathews VJ, Loupas T, et al (October 2008). "Blood pressure estimation in the human fetal descending aorta". Ultrasound Obstet Gynecol32 (5): 673–81. doi:10.1002/uog.6137.PMID18816497. • Sharon, S. M. & Emily, S. M.(2006). Foundations of Maternal-Newborn Nursing. (4th ed p.476). Philadelphia:Elsevier. • Textbook of Medical Physiology, 7th Ed., Guyton & Hall, Elsevier-Saunders, ISBN 0-7216-0240-1, page 220. • Gottdiener JS, Panza JA, St John Sutton M, Bannon P, Kushner H, Weissman NJ (July 2002). "Testing the test: The reliability of echocardiography in the sequential assessment of valvular regurgitation".American Heart Journal144 (1): 115–21. doi:10.1067/mhj.2002.123139. PMID12094197. Retrieved 2010-06-30.