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Archive for the ‘Laryngoscope blade and handle maintenance in pictures’ Category

If you do not have a multi meter below is the basic checker you can make to do the tests in this article.

 

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A cut away showing what is inside the top of the handle.

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This is the spring at the bottom of the handle.

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Repairs in words.

LARYNGOSCOPES.

This is an instrument that aids an anaesthetist to pass an endotracheal tube in to the trachea of a patient so that they can help them to breath if they are on a ventilator, and so that they can safely look after them during operations.
It consists of a handle which contains the batteries, and a blade that goes in to the mouth, this has a bulb on it so that the anaesthetist can see what he is doing.
The bulb will light up when the blade is opened up and locked in to position.
The blades can be purchased in different shapes to suit different circumstances, adults, children, and a variety of other reasons.
The most often found problem is that the bulb won’t light or flickers, this may be caused by a number of things.

a. Check that the bulb is screwed in tightly, and that it is a good one.

b. Check that the batteries are good ones, and that the contacts are clean, if not clean them with some sandpaper, the spring at the bottom of the handle often has corrosion on it and can cause the bulb to not light.
When you have checked that all the contacts are clean, that the bulb is good and screwed in tight, and that you have good batteries and it still does not work, look at the contact between the blade and the handle.
This is a lead contact, or a stainless steel pin on the blade, and a sprung brass contact pin in the handle.
With the lead ones, long use can wear the away, if this is the case than take a soldering iron and very carefully reform the lump back in to a nice round shape.
If this has not made any difference, look at the brass pin.
Check that it is moving in and out correctly, that it is clean both inside and outside the handle.
If all seems well, put some good batteries in to the handle, screw on the bottom, and then with your meter check that there is voltage at the pin contact.
It may become apparent that there is something wrong with this pin; in that case with a long flat bladed screw driver down inside the handle, unscrew the contact and its insulating sleeve.
This sleeve may be made of nylon or a material called tufnol, (tufnol looks a bit like wood, but in fact is normally made up of cloth and resin).
Should this be damaged, repair it as required.
It is possible to make new ones, but it’s not something that you can do in a few moments.
If all this is now as it should be, there is voltage at the contact pin in the handle and the bulb is a good one, it will work, if it doesn’t then there is one more thing to try, and that can be tricky.

With a multi meter, check the continuity between the contact pin at the end of the blade and the body of the blade; this checks the bulb, the contact pin and the wire between the two.
If there is no reading and you have tested the bulb and it was OK then the problem must lie with the wire between the two, the bulb contact or the joining of the wire to the contact at the base of the blade.
Check the wire by clipping your multi-meter probe to a fine piece of wire or a needle and the other probe to the contact at the end of the blade, carefully put the needle into the hole the bulb screws into so you only touch the bulb contact and not the blade and see if you have continuity, if you don’t then there is a problem with the wire.
It is possible that this wire is broken or has become un-soldered. It may be that the contact that touches the bulb has moved to far back into the holder and is not touching the bulb.
In both cases you will have to remove the contact and wire, adjust it or replace it. Proceed as follows:

a. Unsolder the wire at the lead lump end, or pull out the steel pin.

b. Then grasp the contact that the bulb touches and pull the wire through and out of the blade, that is the easy part.
When you pull the wire out take care not to lose the spring and insulating tube behind the bulb contact.

Below is a photo of the replacement one you can buy. Note the brass contact, the spring that keeps the contact pushed out, and the plastic insulating sleeve. Not shown but which you can also buy is a length of plastic insulating tube that keeps the copper wire from touching the body of the blade.

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c. Unscrew the lead contact which is sitting in an insulating threaded insert. This will be made of nylon or tufnol.
Now you can buy replacement wires for some makes of laryngoscopes like the PENLON, but the chances are that you won’t have them as spares so you will have to use something else.
I have found that the best wire that you can use is telephone wire, again you can buy wire of the right size, but if you can get telephone wire it will do just as well and can most often be got for nothing.

d. Having got your telephone wire unsolder the bulb contact from the faulty piece of wire and solder it on to the new wire making sure that you leave the wire long enough to go back through the blade.

e. Now you have to feed this wire through the blade from the bulb end, it has to pass around a rather sharp bend which is where you will have trouble, once in a while it will go straight through with no trouble, but more often it won’t, and getting it to go through is simply a matter of trying again and again until you get it right.

f. You can now cut back the insulation to just below where the threaded bush will end when screwed in place.

g. Screw in the threaded bush, with the bare end of wire passing through the hole. (You may have to re-drill this hole to clear it of lead). If you have the pin type the wire is not soldered to it but just wrapped around the pin.
h. Re-solder the wire in place, and smooth off the end.

If all the other parts are working correctly then it should now work.
Another problem that you may get is that the batteries have been allowed corrode in the handle so much that there is no chance of getting them out in the normal way, this is one way of getting them out.
First of all get a pan of water and put it on a cooker to boil, when the water is boiling put the handle in and leave it in for a few minutes, you may find that it will take some hours, this will sometimes soften them up enough so that you can tap them out.
You may have to drill out the core as much as you can and then chip the rest out.
Lastly clean up the inside with sandpaper, again making sure that the contacts are all clean.
Check the blade, if they are cheap ones or have been badly handled you may get chrome peel, this is where the chrome is peeling from the base metal of the blade, peeling chrome is very sharp, scrape it till you get back to the chrome that is OK then sand down the rough edges till it is very smooth, lastly polish it.
Remember that the blade goes into the mouth and peeling chrome is very unpleasant.
There is new type if laryngoscope available that uses optical fibres in the blade. These will save you a lot of bother, the bulb is in the handle and the blade has a bundle of optical fibres to transmit the light to the tip.
The blades suffer a minor problem in that over a period of time some of the fibres break and the illumination will slowly decrease, the handle may give you much the same problems as with the old type.

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