'THE BREATH OF LIFE'

If we take one of the most natural and equally essential product that most living things need to survive, i.e. oxygen, then the developments in resuscitation devices are an obvious place to start.

To do this in the first instance we will refer to a Thesis written by Mr Brian Wilson for his HND in Engineering (Text in Italics)

Manual Pulmonary Resuscitator

'Manual Pulmonary Resuscitators (or MPR's) are used to provide support to a patient whose airway is open but whose breathing is inadequate or absent.

It is the object of this project to investigate and analyse the function and design of this piece of equipment.

Introduction

The Human body has evolved over hundreds of years into what is today a remarkable machine consisting of multiple systems all working as one to maintain its very existence.

It is a self maintaining system requiring the correct environment, fuel, rest and psychological support. From these basic requirements, it offers performance and features unparalleled by any of man's creations.

From Conception to maturity, the body grows by a process of cell division. After the age of 30 - 35 deterioration of the cells gradually occur. Finally, through the process of natural ageing, one or more of the bodies systems fail, resulting in natural death.

Although a controversial issue, the process of natural death should not be interfered with, except to make it as pain free and comfortable as possible for the individual.

Unfortunately, due to man's modern social environment and unnatural activities, the human body is sometimes subjected to injury, abuse and disease all of which manifest themselves into acute, chronic or congenital conditions, or a combination of all three. These will result in temporary or permanent disability or possibly premature death.

One of the many systems in the Human Body is the Respiratory System, part of which involves the functioning of breathing. It is an automatic procedure that we do not even think about until something goes wrong. If it stops or becomes ineffective, through Trauma or Disease, it may well be a matter of minutes before serious brain damage or death occurs.

It is only through the intervention of modern skills and procedures that the life of an individual may be saved, This is the time when Basic Life Saving techniques (BLS), such as mouth to mouth resuscitation (figure 1.1) may be the only hope of survival until the arrival of skilled help and equipment.

Amongst the many pieces of equipment, there will be a means of providing respiratory support. One such piece of equipment that is commonly used for this purpose, by the medical and emergency services, is the Manual Pulmonary Resuscitator, or more commonly referred to as the 'Bag and Mask' (figure 1.2)

Figure 1.1 Mouth to Mouth Resuscitation

Figure 1.2 The Manual Pulmonary Resuscitator

THE MANUAL PULMONARY RESUSCITATOR

As Previously stated, the MPR is a Medical piece of equipment that is used to provide respiratory support. This support may be required during emergencies involving pulmonary arrest in and out of hospital, or when a patient on mechanical ventilation must be disconnected for transport to another area.

There are other methods for providing respiratory support, however one of the major benefits of the MPR is the ability it offers in increased oxygen concentrations to the patient.

Ambient air contains 21% Oxygen of which the body normally requires 4%. If the body requires respiratory support, due to Trauma or disease, initial oxygen concentrations of 100% are required. The MPR allows the ambient air to be enriched with up to a 100% oxygen while performing manual respirations.

With the ever increasing risk of Cross Contamination being a modern Social Factor (such as COVID 19), the MPR offers a further advantage by providing a high level of isolation. The unit physically separates the rescuer from the patient.

ORIGIN

The concept for the current design of MPR is based on an idea dating back to 177 AD. It was 'Galen', the personal physician to 'Emperor Marcus Auralius', who performed the first pulmonary resuscitation experiments.

By cutting the medulla in the brain of an individual, he caused respiratory arrest. He then used a pair of bellows to inflate the lungs.

The Bellows (fig 2.1) works on the principle of using a bag that can be inflated and deflated.

When inflating, a negative pressure is created inside the bag causing a one way valve (also referred to as a clack valve) to open at the inlet allowing air to be drawn inside. At the same time, a second one way valve closes at the outlet orifice.

When the bag is compressed, a positive pressure is created inside causing the inlet valve to close. At the same time the outlet valve opens, allowing air to flow through the outlet.

DESCRIPTION

Today's many designs of MPR, are all based on the original bellows concept of using a bag with a series of one-way valves. Currently, there are many manufacturers producing their own versions of this piece of equipment, all of which fit into two categories; disposable or reusable.

Both types are similar in appearance and function in the same manner. Most manufacturers offer two or three sizes which include adult, child and infant (fig. 2.2 and 2.3) The main difference between them is the volume of air that is supplied to the patient during use.

Standard Models are supplied with a mask that fits and seals over the patients mouth and nose. A means of enriching the inspired air with medical oxygen is also provided.

Child and infant sizes usually come with a pressure relief valve.

Disposable MPR

Shown in fig 2.2 is one range of disposable resuscitators from AMBU. Compared to the reusable models their cost is relatively low. According to AMBU their online catalogue gives an approximate price of £18.00. Being a sealed unit, they cannot be disassembled for cleaning. They are designed to be used only once and then disposed of in a correct manner.

Ideally suited for low risk situations when this type of equipment may be used infrequently, such as First Aid Rooms

Reusable MPR

Shown in fig. 2.3 is one range of reusable resuscitators from Asmund S Laerdal. As with most reusable MPR's they are expensive. According to Laerdal's website it gives the approximate price of £160.00 Exc. VAT for the Adult size.

All reusable MPR's are able to be disassembled and cleaned. Ideally suited for situations when this type of equipment is used extensively, such as paramedic equipped vehicles and emergency departments.

The materials used in their construction are of a high quality, providing an almost indestructible unit. The materials also allow the unit to be decontaminated by current methods.

These units are claimed to provide extensive trouble free use, however, should repair be required or parts replacing, manufacturers offer such a service, but at a high cost.

Figure 2.1 The Bellows

Figure 2.2 AMBU SPUR DISPOSABLE MPR

Figure 2.3 LAERDAL MPR

TWO CASUALTIES RATHER THAN ONE!

Over the years various versions of MPR's have come and gone as with many medical developments

One of the more 'unusual' designs that uses the original bellows design was the

PORTON RESUSCITATOR

The Porton resuscitator was devised in 1951 at the British Chemical Defence Experimental Establishment in Porton, Salisbury, as a bellows-valve-mask resuscitator. Extensive testing was undertaken over eight years, with the device being successfully used for air transport of polio patients, for emergency resuscitation in hospital wards, and by hospital orderlies.

Once the person’s airway and mouth were cleared of any obstruction– including vomit, their tongue or even dentures – the facemask could be placed over the mouth and nose. The presence of such equipment in the workplace shows a dramatic change from previous centuries when the health of workers was of little interest to factory owners.

The instructions on the side of the box recommended pumping 12-16 times a minute and to continue until normal breathing resumed.

The instructions warned that this could take up to two to two and a half hours.

At that time anyone would have been able to use the resuscitator.

Today, only those who are specially trained are allowed to give first aid.

PORTON (1)

PORTON (2)

PORTON (6)

PORTON (1)

1/6

AUTOMATED OXYGEN THERAPY UNITS

In comparison to today's equipment those that were available at the start of the 1900 were tank like in comparison to say the least.

An example of this can be found in Siebbe Gorman’s “Novox” (1) and “Novita”. (2)

These were `portable` resuscitation units designed for use in `irrespirable atmospheres. `(1) unlike most present day units these worked on a mixture of oxygen and carbon dioxide, this is because of the bodies need for co2. These units had either one or two cylinders within a rigid case, the oxygen was fed to the mask via a corrugated tube via a bladder housed in a steel cylinder.

On the mask there was an atmospheric valve, which allowed the operator to adjust the % of atmospheric air that the patient inhaled with the O2/CO2 mix. The only problem that this produced was when the units were used in such places as mines, if the valve was left open then whatever poison was in the air would mix in with the O2/CO2 from the unit and so place the casualty in considerable danger.

One of the next advances came from a rather unusual source; Dr Robert James Minnit was a consultant Anaesthetist at the David Lewis Memorial Hospital in Liverpool. He is possibly best known for the `Minnit Apparatus`, this was a gas and air anaesthetic machine, which he designed for use in gynaecology and obstetrics. What is possibly not so well known is that he also designed an item that became the mainstay of the ambulance service and a large number of early crash trolleys within hospitals. The name of this piece of equipment was the `Stephenson's Minuteman`

This device was purely oxygen powered worked on Pressure Cycle rather than a Timed Cycle as with present units. The only problem that he had to overcome was that he was not able to manufacture it in this country. The next best option was for him to take his design over to America. This he did, the `minuteman` was produced under licence and then retailed back to this country. The last `Minuteman' was sold by Datex Ohmeda in the late 80's.

The Stephenson's Minuteman Mk 1 came in a solid case with a hinged lid. Inside this was a metal base plate which held one `d` size cylinder of oxygen. Alongside this was the three point connector unit from which the operator could connect any or all of the three oxygen therapy attachments that came as standard. These were: -

1. The minute head 2. The aspirator 3. The oxygen flow meter

1. The minute head was the most advanced development of its time. It was able to determine when the patients lungs were fully inflated with oxygen and so automatically switch of the supply from the unit, so allowing the lungs to deflate normally, however once the lungs were empty of oxygen the minute head recognised this and reversed its previous action, allowing fresh oxygen to flow into the lungs once again and so the cycle began again.

This cycle could be separately controlled depending on the age of the patient. This control can be seen next to The Minute Head. Later versions did not have this option.

There was a slide control on the minute head which allowed the operator to control how much oxygen the patient received up to 100%.

A further independent control was situated in the centre of the head. This allowed the operator to purge the cycle with oxygen should the situation require it.

2. The aspirator could be used to clear the airway so that the operator could administer oxygen safely. The aspirator was used to clear only the start of the airway of obstructions

3. The oxygen flow meter allowed the operator to Administer oxygen to the patient at anything up to 10 litres per minute.

Another advantage to the minuteman was that it had the option of a second `D` size cylinder which could be fitted to the unit. This was made possible by lifting the unit from its case. To the right hand side there was a duplicate cylinder valve connector which was hinged for easy storage/usage, there was also a cylinder rest at the bottom of the base plate to stabilise the unit.

Whenever the minuteman was used there was one vital check that had to be made whether one or two cylinders were being used. Within the cylinder attachment assembly there was a small washer encased in a metal ring. So long as this `bodex seal` was intact and in place correctly then the oxygen would flow through the system safely, if however, the seal was missing or damaged then the oxygen would escape from the cylinder without going through the system.

A similar version to this was manufactured in the United States of America. It was called the `Ohio`

This was pretty much the same as the `minuteman` except for a few modifications. Firstly the second cylinder of oxygen was not optional, it was mandatory. This was because of the way in which the oxygen was fed from the cylinders through the system to the three therapy devices on the unit. Rather than being independent of each other both of the oxygen cylinders had to be in place otherwise the gas coming out of one cylinder would escape rather than going through the system. The second cylinder did not need to be open, just located in place. The only draw back to this was that the operator was presented with a piece of kit that could be twice as heavy as the `minuteman`.

However, there was another advantage to the `Ohio` in that it came with a wall - mounting bracket for fixing inside vehicles and in accident & emergency departments, this meant that it freed up work surfaces that the `minuteman` previously occupied.

The therapy attachments were pretty much the same as those on the `minuteman`, they were all stored on the base plate either side of the cylinders. The only difference being with the oxygen flow meter which, rather than being a separate unit, was built into the front panel of the unit, as was the cylinder contents gauge.

The same checks had to be made with regards to the `bodex seals` to ensure the system operated properly without any leakage.

SIEBBE GORMAN

NOVOX

SIEBBE GORMAN NOVITA

'THE BREATH OF LIFE'

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If we take one of the most natural and equally essential product that most living things need to survive, i.e. oxygen, then the developments in resuscitation devices are an obvious place to start.

​

To do this in the first instance we will refer to a Thesis written by Mr Brian Wilson for his HND in Engineering (Text in Italics)

​

Manual Pulmonary Resuscitator

​

'Manual Pulmonary Resuscitators (or MPR's) are used to provide support to a patient whose airway is open but whose breathing is inadequate or absent.

​

It is the object of this project to investigate and analyse the function and design of this piece of equipment.

​

Introduction

​

The Human body has evolved over hundreds of years into what is today a remarkable machine consisting of multiple systems all working as one to maintain its very existence.

​

It is a self maintaining system requiring the correct environment, fuel, rest and psychological support. From these basic requirements, it offers performance and features unparalleled by any of man's creations.

​

From Conception to maturity, the body grows by a process of cell division. After the age of 30 - 35 deterioration of the cells gradually occur. Finally, through the process of natural ageing, one or more of the bodies systems fail, resulting in natural death.

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Although a controversial issue, the process of natural death should not be interfered with, except to make it as pain free and comfortable as possible for the individual.

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Figure 1.1

Mouth to Mouth Resuscitation

Figure 1.2

The Manual Pulmonary Resuscitator

THE MANUAL PULMONARY RESUSCITATOR

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