Pacemakers

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Pacemakers

• Q-1. What do you mean by pacemaker?
• Q-2. What are the types of pacemaker?
• Q-3. What are the alternate names of pacemaker?
• Q-4. What are the applications of pacemaker?
• Q-5. Describe different parts of pacemaker?
• Q-6. Draw block diagram of cardiac pacemaker and
  explain each block in brief.

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Pacemakers

• A pacemaker is a life supporting therapeutic
  medical device used at cardiac center for cardiac
  patient
• It works as pulse generator in SA (sinoatrial or
  sinus) node of heart.
• Pacemakers are two types
• (i) Temporary pacemaker
• (ii) Permanent pacemaker

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Pacemakers (Contd.)

• A pacemaker is a small, battery-operated device
  that helps the heart beat regularly and at an
  appropriate rate.
• The cardiac pacemaker is a electric stimulator
  that produces periodic electric pulses that are
  conducted to two electrodes located on the
  surface of the heart (epicardium) within the
  heart (myocardium) or within the cavity of heart
  (endocardium).

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A typical Pacemakers
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Pacemakers setting
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Alternative Names of Pacemaker

• Artificial pacemaker
• Permanent pacemaker
• Internal pacemaker
• Cardiac resynchronization therapy (CRT)
• Biventricular pacemaker

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Pacemakers (Contd.)

• Traditional pacemakers help to control the right
  side of the heart to control the heart beat.
• This is called AV (atrioventricular)
  synchronization.
• A special type of pacemaker, called a
  biventricular pacemaker, works on both sides of
  the heart.
• It synchronizes the right and left chambers
  (ventricles) of the heart and keeps them pumping
  together.
• This is called cardiac resynchronization therapy.
• All of today's biventricular pacemakers can also
  work as an implantable cardio-defibrillator
  (ICD).

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Pacemaker Parts

• Two parts
• Generator - contains the battery and the
  information to control the heartbeat.
• Leads - wires used to connect the heart to the
  generator and send the electrical impulses to the
  heart to tell it to beat

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Generator

• The generator is a small, flat box that stores
  data and provides battery power.
• It's about the size of two saltine crackers
  stacked together.
• Today's generators weigh a little less than an
  ounce (30 grams).
• The pacemaker's battery life time about 7 to 8
  years.
• It will be routine checked by doctor, and
• Replacement is required as need based.

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Generator of pacemaker
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Leads

• The leads are thin wires that connect the
  generator to the heart.
• Send the electrical impulses to the heart to tell
  it to beat
• Intelligent, deliver shocks to the heart when
  needed.
• Consists of inter wound helical coils of spring
  wires alloy molded in a silicone rubber
  polyurethane cylinder.

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Leads of pacemakers
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Importance and uses of pacemakers

• A pacemaker is often the treatment of choice for
  people who have a heart condition that causes
  their heart to beat too slowly (bradycardia).
• Less commonly, pacemakers may also be used to
  stop an abnormally rapid heart rate
  (tachycardia).
• Biventricular pacemakers have been used to treat
  severe heart failure.

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Block diagram of cardiac pacemakers
Pulse output circuit
Power supply
oscillator
Pulse generator
electrodes
Lead wires
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Power supply
Lithium-ion battery is used as power source for
pacemaker.
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Timing circuit

• A free running oscillator is required for timing
  pulse to determine when a stimulus should apply
  to heart.
• In modern technology, free running oscillator
  replaced by micro processor or complex logic
  based circuit.

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Pulse output circuit

• It produces actual electrical stimulus that is
  applied to heart.
• At each trigger from the timing circuit, pulse
  output circuit generates an electrical stimulus
  pulse for stimulating the myocardium through
  electrode.
• Asynchronous pacemaker range from 70 to 90 beats
  per minutes.

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Types of Artificial Cardiac Pacemakers

• Single chamber - only one chamber is regulated,
  usually the ventricles.
• Dual chamber - two leads are used. Information
  from the atria regulates the contractions of the
  ventricles.

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Problem with leads and electrodes
Technical problem
Non-technical problem

• Displacement
• Exit block(increase in the threshold for
  satisfactory pacing above pacemaker output)
• Surgical
• Extrusion
• Infection
• Penetration

• Broken conductors
• Broken insulation
• Poor interface with pulse generator

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Defibrillator Medical Ventilator

• Q-1. Define defibrillation defibrillator?
• Q-2. What are the different types of
  defibrillator?
• Q-3. Define medical ventilator.
• Q-4. What are the different types of medical
  ventilator?

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Defibrillator

• Defibrillation is the definitive treatment for
  the life-threatening cardiac arrhythmias,
  ventricular fibrillation and pulseless
  ventricular tachycardia. Defibrillation is the
  process of delivering a therapeutic dose of
  electrical energy to the affected heart with a
  device called a defibrillator.

Defibrillator
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Defibrillator Position And Placement
Defibrillator Contacts
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Types of Defibrillator

1. Direct Current Defibrillator
2. Manual internal defibrillator
3. Manual external defibrillator
4. Automated external defibrillator (AED)
5. Semi-automated external defibrillators
6. Implantable Cardioverter-Defibrillator (ICD)

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Direct Current Defibrillator
Approximately 1000 volts with an energy content
of 100-200 joules then delivering the charge
through an inductance such as to produce a
heavily damped sinusoidal wave of finite duration
(5 milliseconds) to the heart by way of 'paddle'
electrodes
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Manual internal defibrillator

• They are virtually identical to the external
  version.
• Except that the charge is delivered through
  internal paddles in direct contact with the
  heart.
• These are almost exclusively found in operating
  theatres, where the chest is likely to be open,
  or can be opened quickly by a surgeon

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Manual external defibrillator

• This unit is used in conjunction with (or more
  often have inbuilt) electrocardiogram readers,
  which the healthcare provider uses to diagnose a
  cardiac condition
• The healthcare provider will then decide what
  charge (in joules) to use, based on proven
  guidelines and experience, and will deliver the
  shock through paddles or pads on the patient's
  chest.

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Automated external defibrillator (AED)

• Simple-to-use
• Units are based on computer technology which is
  designed to analyze the heart rhythm itself, and
  then advise the user whether a shock is required.
  
• They are designed to be used by lay persons, who
  require little training to operate them
  correctly.

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Semi-automated external defibrillators

• Compromise between manual unit and automated
  unit.
• Mostly used by pre-hospital care professionals
  such as paramedics and emergency medical
  technicians.
• Have the automated capabilities as well as ECG
  display, and a manual override.

• Clinician can make their own decision, instead of
  the computer.
• Some of these units are also able to act as a
  pacemaker.

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Implantable Cardioverter-Defibrillator (ICD)

• Also known as automatic internal cardiac
  defibrillator (AICD). These devices are implants,
  similar to pacemakers (and many can also perform
  the pacemaking function).
• They constantly monitor the patient's heart
  rhythm.
• And automatically administer shocks for various
  life threatening arrhythmias, according to the
  device's programming.

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Medical Ventilator

• A medical ventilator may be defined as any
  machine designed to mechanically move breatheable
  air into and out of the lungs, to provide the
  mechanism of breathing for a patient who is
  physically unable to breathe, or breathing
  insufficiently.
• Modern ventilators are generally computerized
  machines, patients can be ventilated indefinitely
  with a bag valve mask.
• A simple hand-operated machine.

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Types of Medical Ventilator

• Negative Pressure Ventilator
• Positive Pressure Ventilator

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Negative Pressure Ventilator

• Negative-pressure ventilator used for long-term
  ventilation was made by iron lungs and shaw tank
  in 1929.
• The machine is effectively a large elongated
  tank, which encases the patient up to the neck.
  The neck is sealed with a rubber gasket so that
  the patient's face (and airway) are exposed to
  the room air.
• By means of a pump, the air is withdrawn
  mechanically from iron lungs to produce a vacuum
  inside the tank, thus creating negative pressure.
  This negative pressure leads to expansion of the
  chest, which causes a decrease in intrapulmonary
  pressure, and increases flow of ambient air into
  the lungs.

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Positive Pressure Ventilator

• Positive-pressure ventilators were made during
  World War II to supply oxygen to fighter pilots
  in high altitude. Such ventilators replaced the
  iron lungs as safe endotracheal tubes with high
  volume/low pressure cuffs.
• The positive pressure allows air to flow into the
  airway until the ventilator breath is terminated.
  Subsequently, the airway pressure drops to zero,
  and the elastic recoil of the chest wall and
  lungs push the tidal volume--the breath--out
  through passive exhalation.

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Negative vs Positive pressure machines
Negative pressure machines
Positive pressure machines
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