heart lung machine_1

8/2/2019 Heart Lung Machine_1

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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
http://116570-050-91058fae.jpg/


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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.

heart lung machine_1

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