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CH13 THERAPEUTIC AND PROSTHETIC DEVICES

13.1 CARDIAC PACEMAKERS AND OTHER ELECTRIC STIMULATORS 13.2 DEFIBRILLATORS AND CARDIOVERTERS 13.3 MECHANICAL CARDIOVASCULAR ORTHOTIC AND PROSTHETIC DEVICES 13.4 HEMODIALYSIS 13.5 LITHOTRIPSY 13.6 VENTILATORS 13.7 INFANT INCUBATORS 13.8 DRUG DELIVERY DEVICES 13.9 SURGICAL INTRUMENTS

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CH13 THERAPEUTIC AND PROSTHETIC DEVICES

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  1. 13.1 CARDIAC PACEMAKERS AND OTHER ELECTRIC STIMULATORS 13.2 DEFIBRILLATORS AND CARDIOVERTERS 13.3 MECHANICAL CARDIOVASCULAR ORTHOTIC AND PROSTHETIC DEVICES 13.4 HEMODIALYSIS 13.5 LITHOTRIPSY 13.6 VENTILATORS 13.7 INFANT INCUBATORS 13.8 DRUG DELIVERY DEVICES 13.9 SURGICAL INTRUMENTS 13.10 THERAPEUTIC APPLICATIONS OF THE LASER CH13THERAPEUTIC ANDPROSTHETIC DEVICES

  2. Content of this chapter

  3. 13.1 Cardiac Pacemaker Targets of stimulation: Epicardium Myocardium Endocardium What to cure: Pathalogical condition: heart block

  4. asynchronous cardiac pacemaker Provides a train of stimulus pulses at a constant rate. The output circuit: Constant current Constant voltage A free-running oscillator Figure 13.1 Block diagram of an asynchronous cardiac pacemaker Epicardial electrode Intramyocardial electrode Endocardial or intraluminal electrode Good conductor Mechanically strong Good insulation

  5. Package design: (1) Compatible, tolerated by the body (2) To protect the circuit (3)Comfortability Electrode (and lead wire) materials: Platinum, Stainless steel, Carbon, titanium, Alloys (Elgiloy, MP35N)

  6. Figure 13.2

  7. To place a pacemaker, a lead wire is inserted into the cephalic vein of the shoulder and fed into the heart chambers (B). An electrode is implanted in the heart muscle of the lower chamber, and the device is attached (C). www.surgeryencyclopedia.com/La-Pa/Pacemakers.html

  8. Synchronous pacemakers SA node (spontaneous) Artificial pacemaker • Reason of using sync. Instead of async. Pacemakers: • Often the patient requires pacing only intermittently. • Continuous stimulation may result in serious complications. (1) Demand pacemaker (2) Atrial-synchronous pacemaker

  9. ECG Timing (counter) Out Reset Figure 13.3 A demand-type synchronous pacemaker Electrodes serve as a means of both applying the stimulus pulse and detecting the electric signal from spontaneously occurring ventricular contractions that are used to inhibit the pacemaker's timing circuit.

  10. For normal atrium and abnormal ventricle V 1g V 1g V1 V2 V3 V4 OUT ECG Figure 13.4 An atrial-synchronous cardiac pacemaker, which detects electric signals corresponding to the contraction of the atria and uses appropriate delays to activate a stimulus pulse to the ventricles. Figure 13.5 shows the waveforms corresponding to the voltages noted.

  11. Rate-responsive pacemaker Figure 13.5 Block diagram of a rate-responsive pacemaker

  12. Figure 13.5

  13. Figure 13.6

  14. Example 13.1

  15. Bladder 囊、膀胱 Detrusor 壓迫肌之統稱(如:膀胱之肌肉). Mucosal 黏膜的 Orifice 門、口，孔 Prostatic 攝護腺的 Seminal vesicle 精囊;精囊腺 Sphincter 括約肌 Trigone 三角區 Ureter 輸尿管 Urethra 尿道 Urinary incontenence 尿失禁 (ages female) Unable to pass the urine (empty the bladder) (aged male) Source: http://sci.rutgers.edu/forum/showthread.php?t=130246

  16. Bladder stimulator

  17. 13.2 Defibrilators and Cardioverters The disease： Cardiac fibrilation: ◆ Individual myocardial cells contract asynchronously with only very local patterns. ◆ Cardiac output ～ 0 ◆ Risk: Irreversible brain demage; death How to resuscitate? Reestablish a normal cardiac rhythm with electric shock to the heart What to use? Defibrillators

  18. 13.2 Defibrilators and Cardioverters (cont.) http://www.britsattheirbest.com/ingenious/ii_20th_century_1950_1970.htm http://www.sciencemuseum.org.uk/images/I050/10319037.aspx?keywords=pack

  19. Japanese English Simp. Chinese Korean 2010.06.24 攝於日本神奈川県鎌倉市長谷寺 Hase-dera Temple, KamakuraCity, Kanagawa, Japan

  20. 13.2 Defibrilators and Cardioverters (cont.) Capacitive-discharge dc dfibrillator Why is this not desired? Why is this desired? What is the function of L? Ans: What will be the waveform of vp without L? Ans: Figure 13.9 (a) Basic circuit diagram for a capacitive–discharge type of cardiac defibrillator. (b) A typical waveform of the discharge pulse. The actual waveshape is strongly dependent on the values of L, C, and the torso resistance RL.

  21. Secondary 2000 V 0.5 A 1000 W Primary 100 V 10 A 1000 W 10 200 turns turns 13.2 Defibrilators and Cardioverters (cont.) Designing the step-up transformer： The energy level required for defibrillation = 400 J. The power source is 100 V. C = 10 to 200 μF. How high is the voltage across C? • Ans: • E = Cv2/2 • v = √(2E/C) = √[2 × 400/(10 × 10-6)] = 8944.272 V v = √(2E/C) = √[2 × 400/(200 × 10-6)] = 2000 V

  22. 13.2 Defibrillation is a process in which an electronic device, called an automated external defibrillator (AED), helps reestablish normal contraction rhythms in a heart that's not beating properly. It does this by delivering an electric shock to the heart. All emergency personnel should be trained and allowed to use a properly maintained defibrillator if their job requires them to respond to people having cardiac arrest. This includes all first-responding emergency personnel, both hospital and non-hospital. CAPACITIVE-DISCHARGE dc DEFIBRILLATORS RECTANGULAR-WAVE DEFIBRILLATORS DEFIBRILLATORS ELECTRODES CARIOVERTERS IMPLANTABLE AUTOMATIC DEFIBRILLATORS

  23. What is ventricular fibrillation? The heart beats when electrical signals move through it. Ventricular fibrillation (“V fib“)is a condition in which the heart's electrical activity becomes disordered. When this happens, the heart's lower (pumping) chambers contract in a rapid, unsynchronized way. (The ventricles “twitch" rather than beat.) The heart pumps little or no blood. http://www.americanheart.org/presenter.jhtml?identifier=4784 AHA Scientific Position (Abnormal Heart Rhythms) Ventricular fibrillation is very serious. Collapse and sudden cardiac death will follow in minutes unless medical help is provided immediately. If treated in time, V fib and ventricular tachycardia (extremely rapid heartbeat) can be converted into normal rhythm. This requires shocking the heart with a device called a defibrillator. Today one effective way to correct life-threatening rhythms is by using an electronic device called an implantable cardioverter-defibrillator. This device shocks the heart to normalize the heartbeat if the heart's own electrical signals become disordered

  24. Cardioverter = a defibrillator + a cardiac monitor A stimulus possibly leads to fibrillation if it occurs in the interval of T wave This is the reason why the cardioverter is used.

  25. QRS complex 0.1 mV PR segment 0.04 ms Q ST interval S PR interval QT interval R ST segment T P U

  26. Fig. 13-11

  27. Figure 13.12A cardioverter The defibrillation pulse in this case must be synchronized with the R wave of the ECG so that it is applied to a patient shortly after the occurrence of the R wave.

  28. Implantable automatic defibrillators

  29. 13.3 Mechanical Cardiovascular Orthotic and Prosthetic Devices cardiovascular 心臟血管的 orthotics 矯正學 prosthetic 義肢的，假體的，人體代用品的.

  30. Cardiac-assist devices To aid the failing heart after acute traumatic insults such as myocardial infarction or cardiac surgery CO2 is used instead of O2. Why? CO2: more soluble in blood O2: fatal gas embolism The balloon does much of the work normally done by the left ventricle in causing the blood to circulate to the periphery. USPatent 3,769,960 (1973) Intra-aortic system embolism 栓塞 trauma 外傷，傷口 traumatic 創傷的，外傷的 myocardial infarction 心肌梗塞

  31. Example 13.3 An intra-aortic balloon pump device is being applied to a patient in cardiovascular shock. The patient's blood pressure is 80/60, and his heart rate is 85 beats per min. The patient's cardiac output has been determined to be 2.5 liters/min. Once the balloon cardiac-assist device has been started, the patient's systolic blood pressure at the heart drops to 65 mm Hg; the heart rate and cardiac output remain the same. After several hours on the balloon, the systolic pressure is back to 80 mm Hg, the heart rate has dropped to 78 beats/min, and the cardiac output has risen to 3.4 liters/min. Estimate the work done by the heart per beat and per minute before and after the balloon pump was started, as well as several hours later. If the balloon pumps against an average diastolic pressure of 60 mm Hg, how much work is it doing? -1-(Before a balloon is used) BP = 80/60 mmHg, HR = 85 bpm, CO = 2.5 L/min -2- (Once the balloon cardiac-assist device has been started) BP = 65/-- mmHg, HR = 85 bpm, CO = 2.5 L/min -3- (After several hours on the balloon) BP = 80/-- mmHg, HR = 78 bpm, CO = 3.4 L/min Q: The work done by the heart = ? in -1-, -2-, and -3-. Q: The work done by the balloon to pump against 60 mmHg = ?

  32. Pump Oxygenator Blood and oxygen are in direct contact. This can denature some of the protein components of the blood, which can lead to formation of clots and emboli. • Used during certain procedures of a cardiac surgery • Used to allow the diseased lung of an infant to rest for several days pump-oxygenator: 唧筒換氧機,(心臟外科,體外循環用). Figure 13.13Connection of a pump oxygenator to bypass the heart A disk-type oxygenator is used with a roller pump. Venous blood is taken from a cannula in the right atrium, and oxygenated blood is returned through a cannula in the femoral artery. cannula 套管 venous 靜脈的 femoral 股骨的，大腿骨的

  33. Total Artificial Heart AbioCor Jaarvic 7

  34. 13.4 Hemodialysis (血液透析) • Renal replacement therapies: • renal transplant • Hemodialysis • peritoneal dialysis renal 腎的 peritoneal 腹膜的 dialysis 透析，洗腎

  35. 13.4 Hemodialysis (血液透析) Dialysate = water + various solutions Types of exchangers: (1) The coil-dialyzer (2) The parallel-plate dialyzer (3) The hollow-fiber kidney – 10,000-15,000 parallel hollow fibers with 0.2-mm in diameter and 150 mm in length dialysate 透析液

  36. Figure 13.14 An artificial kidney The dialysate delivery system in this unit mixes dialysate from a concentrate before pumping it through the exchange chamber. Measuring the gross concentration of electrolytes of the dialysate: (1) By impedimetric method Detection of blood leakage: (1) By colorimetric or optical density change (2) By pressure change The semipermeable allows the waste components in the blood to diffuse through to the dialysate. Detection of bubbles in the blood: (to prevent emboli)

  37. Example 13.4 The electric conductivity  (S/cm) of an electrolytic solution such as a dialysate can be approximated by Where Ni = number of ions of i per cm3, qi = charge on ions of i, i = mobility of ions of i in solution, cm2/V•s. The equation is summed for all ionic species present in the solution. Assume that the dialysate is made up of 0.9 g equivalents of cations having a single electronic charge per ion and a mean mobility of 0.623 cm2/(V•s) and that the same amount of oppositely charged anions having a mobility of 0.986 cm2/(V•s). (A) Determine the conductivity of the dialysate solution. (B) How much will it change if 0.05 g equivalents of an anions are added to the solution? (A) The conductivity of the dialysate solution is (B) The conductivity of the dialysate solution will become

  38. 13.7 Infant Incubator (保溫箱) http://www.allproducts.com/manufacture97/sunglowltd/product5.html

  39. amazing medical co.,LtdProduct ID: YP-910 infant incubator Technical specification:Power supply : AC220V，50HZPower input: 600VAAir Temperature control range：25℃~37℃Skin Temperature control range：34℃~37℃Sensor precision: ≤0.3℃Changing of temperature: ≤0.5℃Uniformity of temperature: ≤0.8℃Temperature rising time: ≤30minNoise level: ≤55dB（A）Inclination of bassinet: 0°~5°Alarming:audible and visible alarm indication, and it can indicate the real temperature and cut off the power supply of heater (except for the low deviation alarm), meanwhile, the skin temperature indication window can indicate the alarm code. For the alarm 1-6, the relevant light is on, and for the alarm 7, all alarming lights are on; all alarm sound can be cancelled except for the power failure alarm and the system alarm.Over-temp alarm: when the air temperature control ≤38℃, skin temperature control≤40℃；Upper Deviation alarm: air temperature control +3.0℃, skin temperature control +1.0℃；Lower Deviation alarm: air temperature control -3.0℃, skin temperature control -1.0℃；Sensor alarm: when the sensor is disconnected, open circuit, short circuit or put on the wrong place;Fan alarm: when the fan is blocked, speed ≤1000rpm or stop working;Power failure alarm: when there is no power or the power cord is disconnected.System alarm: when there is E2ROM malfunction inside of temperature controller.Package：Gross Weight：66KgNet Weight： 55KgMeasurement：1085mm×640mm×915mmNotice：Some technical data of this model can be changed properly in standard permission range according to the standard and userÂ’s requirement like infant scale, tray. If the technical specification of above product changes, please refer to the standard at selling time. http://www.allproducts.com/manufacture97/sunglowltd/product5.html

  40. United States Patent 6679830 Infant incubator with non-contact sensing and monitoring An infant care unit of the type comprising means for controlling the environment in which the infant resides includes one or more sensors spaced apart from the infant to sense a physiological parameter and provide a sensor output, the controlling means being responsive to the sensor output to change the environment or provide an alarm or other indication of the parameter. The sensors include one or more of an infrared sensor for sensing the infant's temperature, cameras coupled to video processing software for sensing respiration rate, heart rate or skin perfusion, microphones coupled to audio processing software for sensing respiration rate, breathing difficulty, or infant distress. Speakers are provided for cancelling noise or providing audio signals to the infant. The camera, microphone and speakers are capable of being coupled to a computer network for remote monitoring of the infant. http://www.freepatentsonline.com/6679830.html

  41. Figure 13.16 Block diagram of a proportional temperature controller used to maintain the temperature of air inside an infant incubator. Thermistor Power line 1 Bridge Amplifier Gate pulse generator Silicon- controlled switch 3 4 Comparator Set-point resistor 1-Hz sawtooth generator 2 5 Heater

  42. 13.9 Surgical Instruments Electrosurgical unit http://www.ihe-online.com/products/surgical-or/electrosurgery-accessories/hospital-equipment/electrosurgical-units-1/index.html?tx_ttproducts_pi1%5BbackPID%5D=1334&cHash=2e28600aef http://yesng.english.eyp.com.tw/eyp/front/bin/ptdetail.phtml?Category=4206&Part=Accessories-3

  43. Figure 13.20 (a) Block diagram for an electrosurgical unit. High-power, high-frequency oscillating currents are generated and coupled to electrodes to incise and coagulate tissue. (b) Three different electric voltage waveforms available at the output of electrosurgical units for carrying out different functions. coagulate 凝固

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