heart lung machine_1
Post on 05-Apr-2018
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Heart LungMachine
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A bike mechanic vs A Surgeon
A mechanic was removing a cylinder head from themotor of a Harley motorcycle when he spotted a well-
known heart surgeon in his shop. The surgeon wasthere, waiting for the service manager to come and takea look at his bike.
The mechanic shouted across the garage, Hey, Doc,
can I ask you a question? The surgeon a bit surprised,walked over to the mechanic working on the motorcycle.
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The mechanic straightened up, wiped his hands on arag and asked, So Doc, look at this engine. I open its
heart, take valves out, fix em, put em back in, and
when I finish, it works just like new. So how come I getsuch a small salary and you get the really big bucks,when you and I are doing basically the same work?
The surgeon paused, smiled and leaned over, andwhispered to the mechanic Try doing it with the
engine running.
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The magicians hat - HLM
During open heart surgery, (say correction ofcongenital mal formation, or valve prosthesis)it is necessary to bypass the heart to enablethe surgeon to work in a bloodless field.
HLM is a machine which provides the extracorporeal blood circulation thus maintaining
the blood supply to body while the heart is bypassed and operated upon.
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During an open-heart surgery (such as valvesurgery), an extracorporeal (i.e. outside thebody) equipment called the heart-lung machine
takes over the functions of the heart and lungs,so that the heart can be carefully stopped whilethe vital organs continue to receive blood and
oxygen.
The surgeon can then operate in a blood-freesurgical field without interference from bleedingor the heart's pumping motion.
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The HLM under working
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Part by part study of HLM
Lung = Oxygenator
Heart = Blood Pump
Valves = Traps and Filters
Heat exchangers
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Heart-Lung Machine
The machine basically consists of a pump (to replacethe heart) and an oxygenator (to replace the lungs).
Acting as a mechanical heart and lungs, it keepsoxygen-rich blood flowing throughout the body afterthe patient's heart has been carefully stopped.
In a process called perfusion , the machine receives
the patient's blood, removes the carbon dioxide andother waste products, adds oxygen, warms (or cools)the blood and pumps it back through the body.
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Heart-Lung Machine
Cooling the blood, in turn, lowers body temperature.This helps protect the body's organs while the heart-
lung machine is in use.
After the surgery is completed, the heart is restarted,the heart-lung machine is stopped and the machine isdisconnected from the patient.
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Oxygenator
Maintains a mixture of oxygen and 2 to 5% of CO2to avoid respiratory alkalosis.
Oxygenate 5litres/min of blood
Have lower priming volume
Cause minimum trauma to blood
Should safe, simple and reliable to use
Should be in sterilized condition Ensure no microembolus formation
Short preparation time
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Types of Oxygenator
Bubble Oxygenator
Film Oxygenator
Foam Oxygenator Screen Oxygenator
Blood film over sponge type Oxygenator
Rotating Disc Film Oxygenator
Membrane Oxygenator
Liquid - Liquid Oxygenator
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Blood Pumps
Pump blood upto 6litres/min
Not cause any damage to cellular and non cellular
components of blood
Easy to clean and sterilize
Ensure smooth clot-less flow of blood
Easy to calibrate
Provide option of manual operation (for emergency) Provide flow with minimum turbulence and should
not have any mechanical stress
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Types of Blood Pumps
Pulsatile pumps
Non pulsatile pumps
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The heart-lung machine, schematically shown below,
uses five pump heads; one for perfusion of the body, two
suckers and two for perfusion of the coronary arteries.
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The design of heart-lung machine should involve the four majorconsiderations:
1) The artificial lung to accomplish the required gas transfer.
2) The mechanical pumps to replace the heart action in movingthe blood from the patient's low-pressure venous systemthrough the machine and back into the patient's higherpressure arterial system.
3) The handling of the blood itself, which raises questions ofchemistry, materials of construction and surgical cleanliness.
4) The system of control to provide for as much automaticperformance as possible during the course of the operation.
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