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. The sinoatrial node (also commonly spelled sinuatrial node, abbreviated SA node or SAN, also called the sinus node) is the impulse-generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. These cells are modified cardiac myocytes. Though they possess some contractile filaments, they do not contract. 1

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

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). 3

A typical Pacemakers 4

Pacemakers setting 5

Alternative Names of Pacemaker Artificial pacemaker Permanent pacemaker Internal pacemaker Cardiac resynchronization therapy (CRT) Biventricular pacemaker 6

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). 7

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 8

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. 9

Generator of pacemaker 10

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. 11

Leads of pacemakers 12

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. 13

Block diagram of cardiac pacemakers Power supply oscillator Pulse output circuit Pulse generator electrodes Lead wires 14

Power supply Lithium-ion battery is used as power source for pacemaker. 15

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. 16

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. 17

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. 18

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 19

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? The sinoatrial node (also commonly spelled sinuatrial node, abbreviated SA node or SAN, also called the sinus node) is the impulse-generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. These cells are modified cardiac myocytes. Though they possess some contractile filaments, they do not contract. 20

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 21

Defibrillator Position And Placement Contacts 22

Types of Defibrillator Direct Current Defibrillator Manual internal defibrillator Manual external defibrillator Automated external defibrillator (AED) Semi-automated external defibrillators Implantable Cardioverter-Defibrillator (ICD)

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 24

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 25

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. Units are used in conjunction with (or more often have inbuilt) electrocardiogram readers, which the healthcare provider uses to diagnose a cardiac condition (most often fibrillation or tachycardia although there are some other rhythms which can be treated by different shocks). 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 26

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. 27

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. These units are a compromise between a full manual unit and an automated unit. They are mostly used by pre-hospital care professionals such as paramedics and emergency medical technicians . These units have the automated capabilities of the AED but also feature an ECG display, and a manual override, where the clinician can make their own decision, either before or instead of the computer. Some of these units are also able to act as a pacemaker if the heart rate is too slow (bradycardia) and perform other functions which require a skilled operator. 28

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. 29

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. After Hurricane Katrina, dedicated staff "bagged" patients in New Orleans hospitals for days with simple bag valve masks. 30

Types of Medical Ventilator Negative Pressure Ventilator Positive Pressure Ventilator 31

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. 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. While the exchange of oxygen and carbon dioxide between the bloodstream and the pulmonary airspace works by diffusion and requires no external work, air must be moved into and out of the lungs to make it available to the gas exchange process. In spontaneous breathing, a negative pressure is created in the pleural cavity by the muscles of respiration, and the resulting gradient between the atmospheric pressure and the pressure inside the thorax generates a flow of air. In the iron lung by means of a pump, the air is withdrawn mechanically 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. As the vacuum is released, the pressure inside the tank equalizes to that of the ambient pressure, and the elastic coil of the chest and lungs leads to passive exhalation. However, when the vacuum is created, the abdomen also expands along with the lung, cutting off venous flow back to the heart, leading to pooling of venous blood in the lower extremities. There are large portholes for nurse or home assistant access. The patients can talk and eat normally, and can see the world through a well-placed series of mirrors. Some could remain in these iron lungs for years at a time quite successfully. 32

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. 33

Negative vs Positive pressure machines Negative pressure machines Positive pressure machines 34

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