CH13THERAPEUTIC ANDPROSTHETIC DEVICES13.1 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

Content of this chapter

Previous chaptersdiagnostic instruments This chaptertherapeutical instrument, stimulator, prosthesis (, , ), incubator, ventilator, heart-lung machine, artificial kidney, diathermy device, electrosurgical instrument

13.1 Cardiac PacemakerTargets of stimulation:EpicardiumMyocardiumEndocardiumWhat to cure:Pathalogical condition: heart block

asynchronous cardiac pacemakerFigure 13.1 Block diagram of an asynchronous cardiac pacemaker Provides a train of stimulus pulses at a constant rate.The output circuit:Constant currentConstant voltageA free-running oscillatorGood conductorMechanically strongGood insulationEpicardial electrodeIntramyocardial electrodeEndocardial or intraluminal electrode

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

Figure 13.2

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

Synchronous pacemakersReason 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 pacemakerSA node (spontaneous)Artificial pacemaker

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.ECGTiming(counter)OutReset

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.

V1V2V3V4OUTECG

For normal atrium and abnormal ventricleV 1gV 1g

Rate-responsive pacemakerFigure 13.5 Block diagram of a rate-responsive pacemaker

Physioogical variableSensorBlood temperature (in right ventricle)Stimulus-to-T-wave interval (in ECG) R-wave area (in ECG)Blood pHRate of pressure change (of right ventricle)Blood oxygen saturation (in vein)Intracardiac volume changesRespiratory rate and/or volumeBody vibration ThermisterECG electrodesECG electrodesElectrochemical pH electrodeSemiconductor strain-gage pressure sensorOptical oximeterElectric-impedance plethysmography (intracardiac)Electric-impedance plethysmography (thoracic)Accelerometer

Figure 13.5

Figure 13.6

Example 13.1

Source: http://sci.rutgers.edu/forum/showthread.php?t=130246Urinary incontenence (ages female) Unable to pass the urine (empty the bladder) (aged male)Bladder Detrusor (:).Mucosal Orifice Prostatic Seminal vesicle ;Sphincter Trigone Ureter Urethra

Bladder stimulator

13.2 Defibrilators and CardiovertersCardiac fibrilation: Individual myocardial cells contract asynchronously with only very local patterns. Cardiac output 0 Risk: Irreversible brain demage; deathThe diseaseReestablish a normal cardiac rhythm with electric shock to the heartHow to resuscitate?What to use?Defibrillators

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

2010.06.24 Hase-dera Temple, Kamakura City, Kanagawa, JapanJapaneseEnglishSimp. ChineseKorean

13.2 Defibrilators and Cardioverters (cont.)Figure 13.9 (a) Basic circuit diagram for a capacitivedischarge 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.What will be the waveform of vp without L?Ans:What is the function of L?Ans:Capacitive-discharge dc dfibrillatorWhy is this not desired?Why is this desired?

13.2 Defibrilators and Cardioverters (cont.)The energy level required for defibrillation = 400 J. The power source is 100 V. C = 10 to 200 F. How high is the voltage across C?Designing the step-up transformerAns:E = Cv2/2v = (2E/C) = [2 400/(10 10-6)] = 8944.272 V v = (2E/C) = [2 400/(200 10-6)] = 2000 V

13.2Defibrillation is a process in which an electronic device, called an automatedexternal 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

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

Cardioverter = a defibrillator + a cardiac monitorA stimulus possibly leads to fibrillation if it occurs in the interval of T waveThis is the reason why the cardioverter is used.

Fig. 13-11

Figure 13.12 A 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.

Implantable automatic defibrillators

Implantable defibrillatorTachyarrhythmia (fibrillation)Artificial pacemakerBradyarrhythmia

13.3 Mechanical Cardiovascular Orthotic and Prosthetic Devices cardiovascular orthotics prosthetic .

Cardiac-assist devicesTo aid the failing heart after acute traumatic insults such as myocardial infarction or cardiac surgery embolism trauma traumatic myocardial infarction US Patent 3,769,960 (1973) Intra-aortic systemCO2 is used instead of O2. Why?

CO2: more soluble in bloodO2: fatal gas embolismThe balloon does much of the work normally done by the left ventricle in causing the blood to circulate to the periphery.

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 = ?

Pump Oxygenatorpump-oxygenator: ,(,). cannula venous femoral Figure 13.13 Connection 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.Used during certain procedures of a cardiac surgeryUsed to allow the diseased lung of an infant to rest for several daysBlood 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.

Total Artificial HeartAbioCorJaarvic 7

13.4 Hemodialysis ()Renal replacement therapies:renal transplantHemodialysisperitoneal dialysis renal peritoneal dialysis

13.4 Hemodialysis ()Dialysate = water + various solutionsTypes 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

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.Detection of blood leakage:(1) By colorimetric or optical density change(2) By pressure changeThe semipermeable allows the waste components in the blood to diffuse through to the dialysate.Detection of bubbles in the blood:(to prevent emboli)Measuring the gross concentration of electrolytes of the dialysate:(1) By impedimetric method

(A) The conductivity of the dialysate solution is

(B) The conductivity of the dialysate solution will become

Example 13.4The 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/Vs.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/(Vs) and that the same amount of oppositely charged anions having a mobility of 0.986 cm2/(Vs). (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?

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

amazing medical co.,LtdProduct ID: YP-910 infant incubatorBrief introduction: servo-controlled by micro-computer; quite operation windows can reduce the disturbance to the baby during nursing; inclination of the bassinet can be adjusted, touch switch panel with LED digital display, set-temp, real-temp and auxiliary temperature are displayed separately; multiply self-checking alarms with audible and visible; heating power rate indicates 0-100%; whole aluminum water tank, and it can be filled with water or discharge; RS 232 connector, data output. Standard configure: Hood, infant bed, temperature controller, skin temperature sensor, water tank, air filter, Guardrail, I.V. Pole, cabinet.

amazing medical co.,Ltd Product ID: YP-910 infant incubator

Technical specification: Power supply : AC220V50HZ Power input: 600VA Air Temperature control range25~37 Skin Temperature control range34~37 Sensor precision: 0.3 Changing of temperature: 0.5 Uniformity of temperature: 0.8 Temperature rising time: 30min Noise level: 55dBA 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 control40 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 Weight66Kg Net Weight 55Kg Measurement1085mm640mm915mm Notice Some technical data of this model can be changed properly in standard permission range according to the standard and users 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

United States Patent 6679830Infant 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

Figure 13.16 Block diagram of a proportional temperature controller used to maintain the temperature of air inside an infant incubator.15234PowerlineThermistorBridgeSet-pointresistorAmplifierComparatorGatepulsegeneratorSilicon-controlledswitchHeater1-Hzsawtoothgenerator

13.9 Surgical Instrumentshttp://yesng.english.eyp.com.tw/eyp/front/bin/ptdetail.phtml?Category=4206&Part=Accessories-3http://www.ihe-online.com/products/surgical-or/electrosurgery-accessories/hospital-equipment/electrosurgical-units-1/index.html?tx_ttproducts_pi1%5BbackPID%5D=1334&cHash=2e28600aefElectrosurgical unit

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

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