Posts Tagged ‘ambu’


First I will give you a little section on the vacuum, for those who are starting from the beginning.

Basic Vacuum.
The word vacuum means a space completely empty of all gases.
This word is not often used in its strictest sense by most people, but is used to describe a degree of pressure that is less than the standard atmospheric pressure of 14.7 psi (at sea level). If a vacuum pump is attached to a closed tank and half of its contents are removed, the pressure in the tank will be reduced to half, and all the gas in the tank will expand to fill the space in the tank.
In this situation, a negative pressure or vacuum has been created within the tank.
If you now open a tap on the tank, the air will rush into the tank because the air outside the tank is at a higher pressure than that inside. This in-rush of air is creating a suction at the tap and will continue to do so until the pressure outside the tank is the same as that inside.
The strength of suction exerted will depend upon the amount of pressure difference between the inside and the outside of the tank, that is the level of negative pressure within the tank. Pressures are measured in terms of gauge pressure, this is the pressure above or below ambient atmospheric pressure (ambient means surrounding).
The usual atmospheric pressure used for calibrations is 760 mm Hg, (14.7 psi), this is the standard at sea level.
Negative pressure is any amount of pressure that is less than atmospheric or zero on the pressure gauge.
So vacuum can be described as a negative pressure and suction is the application of that negative pressure and relates to the movement of gas, fluids or solids caused by the negative pressure.

Measuring Vacuum pressure.
Negative pressure is measured in terms of the amount of vacuum force acting on a given area to lift liquid up a column of a given height. It is generally indicated by the height of either mercury or water in inches, centimetres or millimetres.
So you may find both mercury and water marked on the same gauge.
Comparatively speaking a water column, being 13.6 times longer than a mercury one, is more sensitive.
Gauges calibrated in water generally cover a smaller range of pressures than those calibrated in mercury.
One inch of mercury negative pressure means the amount of vacuum required to lift mercury up a column 1 inch or 25.4 millimetres long. The same amount of vacuum will lift water up a column to a height of 13.6 inches or 34.5 centimetres.
There are four main types of sucker that you will come across.

1. The venturi sucker.
The operation of which I explained in the section on resusitaires.

2. The electric sucker.
This works with a motor which operates a suction pump which evacuates a bottle, and it is from this bottle that your suction tube will lead to the patient.
There will be a system of regulating the vacuum by allowing air to be drawn in from the room, and a pressure gauge so that you can see what you are getting. Some operate with a reciprocating motor moving a diaphragm within and out valves, and some operated from a rotary vane motor.
One of the best is made by Eschmann called a Matburn VP12s (there are other models). These are the Rolls Royce of suction units.


They have a large motor driving the pump. They are large but very quiet. They have an oil reservoir, this is filled with 200 ml of vacuum oil and needs to be checked every 1000 hours of use, which for a sucker that is only on for short spells, is a long time.
If the oil level drops below 10ml the unit will not operate as well as it should.

Below is another good unit made by MG Electric.


3. Wall supplied suction.
This will normally work in the same way as the electric suction, the difference is that the motor generating the suction will often be some way away and be feeding several outlets.
Because of this, it has to be of a much greater capacity as more than one outlet may be in use at one time.
Another difference is that where as the portable electric suction is turned on only when you need it, the wall one will have a large tank that is evacuated and from which you will get your suction, inside this tank will be a pressure switch that detects the pressure in the tank, should this pressure rise or the vacuum reduce (whichever way you want to look at it), beyond a set level as people use the system, the switch will automatically turn on the pump to keep the vacuum available at the correct level.
Most vacuum units will have some form of regulating the level of vacuum, on the simplest it will simply be a bleed off screw, on some it will be a spring operated device that keeps the vacuum at the set level.
On the wall type you will often see a high vacuum unit that is for normal suction giving greater than 55 lpm, a low vacuum unit, the low ones are most often used for children and babies giving in excess of 20 lpm. Sometimes you may find thoracic suckers, these are very low vacuum suckers used for wound drainage, some check drains and other applications that need very gentle suction, they will also give in excess of 20 lpm. The LPM figures given are this quoted by Therapy Equipment Ltd.
The graduations on modern suckers will be in kPa (kilopascals) and a low vacuum will go to around 30 kPa, a high vacuum unit will go to around 100 kPa.
You will probably find other units on the gauges such as mmHg and inches Hg but with the conversion factors given at the end of this in you will be able to relate one with another.

The one illustrated below is made by the very helpful company of Therapy equipment Ltd in the UK.


4. Battery operated.

These are used where you need portability. It is important that when they are not in use they are left on charge.

You do not want the risk of going to use one only to find that the battery is flat. The one illustrated below is made by Laerdal.


This type is the most simple type of suction unit and is operated by using your foot to press a piston, on its return stroke pushed by a spring, the suction is created, and a series of valves will direct the flow this way and that.
The maintenance on these will be fairly simple and will often only involve making sure that the one way valves are working correctly and that there are no leaks in the system.
The English firm of Cape Engineering make the most often-found foot operated suction unit. Penlon are the firm that sell them.

An early Ambu foot operated sucker.


A later Ambu sucker.

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Be they electrical units, gas operated (venturi) or pipeline suction, the process of repair is much the same and quite simple, assuming that the motor on an electrical unit is working and that there is gas for a gas-powered unit, then it is a process of elimination in leak detection.
Start as close to the power source as possible and work slowly back towards the suction catheter end checking for loose connections and cracked bottles and pipes.
The only other thing with an electrical unit is to check inside the head of the motor that the one way valves are clean and undamaged and that the diaphragm on top of the piston is not split.
To do this you will have to take the head off, take care to note what went where.
Also check that the con rod (connecting the end of the motor to the piston top) is not broken,
These form 95% of all problems classified as no suction.
The others will be something like no electricity, no gas, blown fuse, the unit not turned on or the pressure relief valve wide open.

If there is any doubt about the electrical supply, plug in something you know is working.
Treat the insides of suction units and the collection jars with care, they are filthy things, send them to be sterilised first and always wear gloves when working on them.
Wash your hands afterwards.

6. Reciprocating Piston pumps.

piston pump

Often known as Roberts pumps. I guess that were made by a company called Roberts or invented by Mr Roberts. These pumps generally have two pistons, but some have one that are operated by an induction motor, with each piston sucking in turn.
The suction will be taken from a bottle connected to the unit, this will incorporate a pressure gauge and a pressure relief valve so that you can regulate the unit to the pressure that you need.
These type of units will only be able to draw a small vacuum as a rule, and are thus most often used for wound drainage following operations.
Maintenance is mainly keeping them well oiled, they run very quietly but do need constant oiling, and will stop running or go very slowly if this is not done.

They were also used for adding air bubbles to indoor fish tanks, in this case they blew rather than sucked.

7. Hand operated suction unit.

This one is made by Ambu. It is used for removing mucus.

Ambu mucus sucker

Maintenance of suckers.
The correct colour, in England at least, for Vacuum hose is YELLOW.
One thing that you must be very careful of when repairing these units is cleanliness, do make sure that the machines are sterilised before you start working on them, and do not put any parts to your mouth, indeed this hold good for any item that you may be repairing, and wash your hands afterwards.
Some pretty nasty things can be sucked up into these units and you do not want to catch anything from them.
Maintenance of suckers is for the most part not difficult.
Get to know what level of suction to expect from a unit when it is working well, anything less will indicate a problem somewhere.
Probably the most often found problem is a leak somewhere, it may be in the tubes outside or inside the unit, it may be that the bottle is not screwed in place properly, check the sealing washer, check that the bottle itself is not cracked.

The check, turn to maximum vacuum

Kink the suction tubing to block it and watch the gauge raise to maximum, with it still kinked turn off the sucker. The pressure should stay at maximum. If it slowly falls you have a leak. The leak could either be in the tubing, the waste bottle or the unit itself.
With the unit to its maximum vacuum, remove the tubing where it comes out from the sucker and put your finger over the end with the unit turned on.
The pressure gauge should go to its maximum point. Turn it off.
If the gauge still drops then there is a problem inside the unit its self, if it does not drop then the problem is with the bottle and the outside tubes. Check these for leaks, missing bottle seals or cracks in the bottle.
If you think that it is a problem with the unit and it is an electrical one, take off the covers and inspect the internal tubing and tightness of the connections. Wall and venturi suckers are difficult to get into and even if you do there is little you can do.
Once inside an electrical unit if the tubing is not at fault and is tightly on the connectors, if the pressure gauge is working properly, then it must lie with the motor itself.
Now it is down to taking apart the motor till you find something that is not as it should be, perhaps a rubber diaphragm has a hole in it or a valve not working.
You might, on the other hand be getting a high vacuum pressure showing on the gauge and nothing at the suction tube when it is open to the atmosphere, this would be more than likely caused by a blockage in the system or that the safety float has stuck up.
It is all a matter of eliminating the obvious problems first.
I repeat again, DO NOT suck or blow into any parts of a sucker, and handle them with care, if you have a cut on your finger, cover it up or put on a pair of gloves, but best of all get it properly cleaned first.
Your health is very important to you, much more important than getting the job done a few moments quicker.

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Resuscitation valves.
There is little to say about these, there are a number of different types, but in general they have internal silicone rubber flap valves of one design or another.
If you think that it is not working correctly, attach a 0.5 litre bag or similar and operate it with the self inflating resuscitation bag, watch the flaps open and close to see if you can spot the problem, otherwise strip it down and check that the flap valves are clean and not damaged.
Check the body for cracks. Clean the parts in warm soapy water and rinse and dry well.
One of the common reasons for valves not working well is that they have been washed and not dried properly and the flaps have stuck down.
Most can be sterilised if they are known to be contaminated.

Advantages are;

1. No possibility of rebreathing provided the dead space of the valve is small.

2. Can be used for spontaneous or controlled respiration.

3. Can be used to measure minute volume if the flow-meters are accurate.

Disadvantages are;
1. Wasteful.

2. Variations of minute volume during spontaneous breathing require frequent adjustment of
the flow-meters to prevent collapse or distension of the reservoir bag.

3. Valves may stick.
Some valves are noisy.

Some examples of non-rebreathing valves;

a. Rubens valve.
A bobbin moves against a spring to act as a uni-directional valve and an outlet valve prevents the taking in of atmospheric air. The dead space is 9 ml, resistance. The resuscitation version has no outlet valve so that the patient who is breathing spontaneously will take in atmospheric air.

Photo of  Rubens valve.


b. The Ambu Valves.
The bobbin of the Rubens valve is replaced by one or two silicone rubber flap valves.
The valve can be dismantled quite easily for cleaning and sterilisation.
Take great care when re-assembling the valve it is possible to do it incorrectly. It can be used with a self inflating bag. The valve with one flap is only suitable for I.P.P.V. (Intermittent positive pressure ventilation.)
The valve with two rubber flaps is suitable for both I.P.P.V and spontaneous respiration.
It has a very low dead space.
There are a few versions of this valve, both for adult and paediatric use.
The ideal valve should have no forward leak, no back leak, low resistance, minimal dead space, minimal opening pressure without sticking, lightweight, transparent, easy cleaning and sterilising, reliability and durability, a single exit port so that the expired air can be collected and measured, and be cheap. When cleaning these valves that have silicone flaps do take care to wash them well, if you leave any soap behind it will dry and stick the flaps down.
Afterwards, connect them to a 1-litre bag and test that they do work properly.

The Ambu valve, I forget which model this is but there are a couple.


This photo shows the Ambu valve taken apart. the yellow thing is a silicone rubber one-way valve, it sits on top of the blue bit and they screw into the body.


Another Ambu valve.


and showing it taken apart.


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