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
13.10 THERAPEUTIC APPLICATIONS OF THE LASER
Content of this chapter
Previous chapters
diagnostic instruments
This chapter
therapeutical instrument, stimulator, prosthesis
(義肢, 假牙, 義體), incubator, ventilator, heartlung machine, artificial kidney, diathermy
device, electrosurgical instrument
13.1 Cardiac Pacemaker
Targets of stimulation:
Epicardium
Myocardium
Endocardium
What to cure:
Pathalogical condition: heart block
asynchronous cardiac pacemaker
Provides a train of stimulus pulses at a constant rate.
The output circuit:
A free-running
oscillator
Constant current
Constant voltage
Figure 13.1 Block diagram of an asynchronous
cardiac pacemaker
Epicardial electrode
Good conductor
Mechanically strong
Good insulation
Intramyocardial electrode
Endocardial or intraluminal electrode
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)
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 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
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.
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.
Rate-responsive pacemaker
Physioogical variable
Sensor
Blood temperature (in right ventricle)
Stimulus-to-T-wave interval (in ECG)
R-wave area (in ECG)
Blood pH
Rate of pressure change (of right ventricle)
Blood oxygen saturation (in vein)
Intracardiac volume changes
Respiratory rate and/or volume
Body vibration
Thermister
ECG electrodes
ECG electrodes
Electrochemical pH electrode
Semiconductor strain-gage pressure sensor
Optical oximeter
Electric-impedance plethysmography (intracardiac)
Electric-impedance plethysmography (thoracic)
Accelerometer
Figure 13.5 Block diagram of a rate-responsive pacemaker
Figure 13.5
Figure 13.6
Example 13.1
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
Unable to pass the urine (empty the bladder)
Source: http://sci.rutgers.edu/forum/showthread.php?t=130246
(ages female)
(aged male)
Bladder stimulator
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
13.2 Defibrilators and Cardioverters
http://www.britsattheirbest.com/ingenious/ii
_20th_century_1950_1970.htm
(cont.)
http://www.sciencemuseum.org.uk/images/I050/10319037.aspx?key
words=pack
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, Kamakura City, Kanagawa, Japan
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.
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
Primary
100 V
10 A
1000 W
10
turns
200
turns
Secondary
2000 V
0.5 A
1000 W
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
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 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.
QRS complex
R
0.1 mV
PR segment
ST segment
0.04 ms
T
P
U
Q
ST interval
S
PR interval
QT interval
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
defibrillator
Artificial
pacemaker
Tachyarrhythmia (fibrillation)
Bradyarrhythmia
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.
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
US Patent 3,769,960 (1973) Intra-aortic system
The balloon does much of the
work normally done by the left
ventricle in causing the blood to
circulate to the periphery.
embolism 栓塞
trauma 外傷，傷口
traumatic 創傷的，外傷的
myocardial infarction 心肌梗塞
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 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.
1.
2.
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 13.13 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.
cannula 套管
venous 靜脈的
femoral 股骨的，大腿骨的
Total Artificial Heart
AbioCor
Jaarvic 7
13.4 Hemodialysis (血液透析)
Renal replacement therapies:
(1)renal transplant
(2)Hemodialysis
(3)peritoneal dialysis
renal 腎的
peritoneal 腹膜的
dialysis 透析，洗腎
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
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)
Example 13.4
The electric conductivity  (S/cm) of an electrolytic solution such as a dialysate can be
approximated by
   Ni qi i
(E13.19)
i
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
   N i qi i
(E13.19)
i
 0.9  6.0231023 / L 103 L / cm3  1.6  1019 C  0.623 0.986cm2 / V  s 
 139.6 S / cm
(B) The conductivity of the dialysate solution will become
  0.95 6.0231023 / L 103 L / cm3 1.6 1019 C  0.623 0.986cm2 / V  s 
 0.95 / 0.9 139.6 S / cm  1147.4 S / cm
13.7 Infant Incubator (保溫箱)
amazing medical co.,Ltd
Product ID: YP-910
infant incubator
Brief 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 selfchecking 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.
http://www.allproducts.com/manufacture97/sunglowltd/product5.html
amazing medical co.,Ltd
Product ID: YP-910
infant incubator
Technical specification:
Power supply : AC220V，50HZ
Power input: 600VA
Air 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: ≤30min
Noise 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：66Kg
Net Weight： 55Kg
Measurement：1085mm×640mm×915mm
Notice：
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
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
Figure 13.16 Block diagram of a proportional temperature controller used to maintain the
temperature of air inside an infant incubator.
Thermistor
Bridge
Power
line
Amplifier
1
Comparator
Set-point
resistor
1-Hz
sawtooth
generator
2
3
Gate
4
pulse
generator
Siliconcontrolled
switch
5
Heater
13.9 Surgical Instruments
Electrosurgical unit
http://www.ihe-online.com/products/surgicalor/electrosurgery-accessories/hospitalequipment/electrosurgical-units1/index.html?tx_ttproducts_pi1%5BbackPID%5D=
1334&cHash=2e28600aef
http://yesng.english.eyp.com.tw/eyp/front/bin/
ptdetail.phtml?Category=4206&Part=Access
ories-3
Figure 13.20 (a) Block diagram for an
electrosurgical unit. High-power, highfrequency 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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