The next area that we should look at is how the oxygen, that is supplied by the machines detailed in Chapter 1, is carried around the body.

 

The obvious answer is by the blood; the average human body contains about 10 pints of blood. This however, does not move around the body of its own accord. It needs to be pumped around the veins, arteries and capillaries in order for them to reach the bodies vital organs.

 

The bodies pump is called the heart. This enables the blood to be pumped around the body carrying all the vital nutrients to the vital organs.

 

The heart is made up of four chambers, the left and right atrium and the left and right ventricle. De- Oxygenated blood enters the right atrium and is pumped through into the right ventricle; from there it is pumped via the pulmonary arteries to the lungs where it collects the oxygen that the individual has inhaled. From there the oxygenated blood is carried through the pulmonary veins into the left atrium, from there it is pumped into the left ventricle and so around the body to the vital organs until the oxygen is used up and the de-oxygenated blood returns to the left side of the heart again to start the process all over again.

  

There are 4 main valves within the heart control the flow of blood, these are

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1.            The atrio-ventricular valve. (r)

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This controls the flow of de-oxygenated blood   from the right atrium into the right ventricle.

 

2.            The pulmonary valve.

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This controls the flow of de-oxygenated blood from the right ventricle into the pulmonary artery and so to the lungs.

 

3.            The atrio-ventricular valve. (l)

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This controls the flow of oxygenated blood   from the left atrium into the left ventricle

 

4.            The aortic valve.

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This controls the flow of blood from the left ventricle into the aorta and so round the body.

 

The heart is controlled by a series of electrical impulses, which pass across it. Occasionally these electrical impulses can go slightly out of synchronisation.

 

One-way in, which suitably qualified personnel can treat these problems externally, is defibrillation.

  

This is when the muscles of the heart are stunned with an electrical charge, causing them to lose their electrical polarity with the intention of correcting the problems within the hearts electrical circuit.

 

However before the faults can be corrected, they must of course, first be detected. In order for this to be done the patient needs to be connected up to an electro-cardiogram, or E.C.G. for short.

 

 Most of the earliest E.C.G. Machines were made up of valves, rather than the present day printed circuit boards, however it should be pointed out at this time that the armed forces request a large quantity of their instrumentation be made with valves as these are easier to replace in the theatre of war than printed circuit boards.

 

One example of a valve operated electro cardiogram this was made by a company called `Cambridge` and was called the `elect rite cardiographer` this was a rather impressive looking machine in a dark wood case with a hinged lid, which lifted to reveal a black control panel with a paper trace printer in the top left hand corner. The instructions and control markings were in gold writing. Inside the lid was storage space for the paper and the electrodes which, unlike on present day models are adhesive, these were applied to the patient by means of suction. The leads were then clamped into small collars at the side of these `dutch bulbs` and connected to the port on the side of the machine.

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At the front and the back of the black control panel were two small handles which, when pulled up, lifted the entire machine out of its wooden case to reveal an impressive array of valves and electric circuits, this was the heart of the machine.

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So, we can now detect irregularities in the hearts electrical function. Now we need to try and correct this. This is where cardiac recorders came into their own with: - the red devil. This certainly lived up to its name, the early version being self contained on a trolley, the only problem was that, in order to charge it, you had to manually wind it up, as it did not connect to the mains. Fortunately, later models were mains powered but certainly not any easier to transport.

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A doctor from Ireland who designed a portable defibrillator, which was literally hand held, solved this problem, his name was Professor Frank Pantridge and Cardiac Recorders produced his Pantridge defibrillator for a number of years. This can be seen in the image below.

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Another development along this line came when Cambridge introduced their `Life-Aid Electro-Cardiographer and Defibrillator. This combined an E.C.G. Machine and a defibrillator into one small case, which certainly made it easier to transport. The only major other difference was that the E.C.G. Trace was displayed on an screen rather than on a paper trace, however it was possible to have a `hard copy` taken from the screen by simply plugging in a separate printer.

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This idea has continued to present day and, with the introduction of printed circuits, the portability of them has greatly improved with units such as Artema’s `LS` which has the ability to assess and advise the user what should be done as does Medtronic Physio-Control’s `Life Pac 250` which interacts with their ‘Life Pac 5’ E.C.G. Monitor. It should be pointed out however, that this idea was by no means a new one when the 250 was produced, in fact Cardiac Recorders  E.C.G. Machine and ‘2610’ Defibrillator could be connected together so that the defibrillator could be synchronised to the information it received from the E.C.G. Monitor.

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Finally, let us take a look back at some of the developments that have taken place involving the use of defibrillators since the start of the NHS.

 

1947 saw the worlds first successful internal A.C. Internal defibrillation on a 14 year old boy

 

1956 saw an American by the name of Paul Zoll perform the first successful external A.C. Defibrillation

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1958 saw Simonsen & Weel introduce the first Danish A.C. Defibrillator, called the ‘shock box anno’

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It is important that, before we close this chapter, it must be understood that

UNDER NO CIRCUMSTANCES 

should anyone attempt to use any of these items as they are

DEADLY

in the wrong hands