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#77906 03/07/24 10:57 AM
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Mark.E Offline OP
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Hello EBME people.

I am in dire need of a venturi test tool, which would assist me to create a venturi effect across a patient inspiratory valve. So I can measure the lift off pressure?
I have tried a few home made creations, but they are not consistent, so over to the Guru's who inhabit these forums.
I have asked the miriad of companies who normally plague our workshop, but only one positive response so far. I would expect this to be a common problem with those who service ventillators etc?

Ideally able to create a negative pressure of no more than 10 mBar; as the lift off is usually less than 3 Mbar

any idea's ?

best regards

Mark Edmondson
Acute ICU

Mark.E #77921 18/07/24 11:43 AM
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If I remember correctly, the old Sechrist IV respirator had a jet with a venturi tube in the exhalation block, used to compensate the tubing flow resistance; with standard connection at the inlet and a performance of a few millibar, so by adjusting the jet flow you can have a stable and adjustable vacuum flow as needed.

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Have you got something able to read such a low pressure with precision?

Have your home grown efforts used a syringe?

I'm imagining a (largish) syringe teed off to a gauge (or perhaps an electronic pressure meter) from suitable adaptor(s) to suit the patient valve. You should be able to simulate patient inhalation in such a fashion.

I seem to recall using a bellows to simulate a patient "pulling" (taking a breath) somewhere in the dim and distant past.

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A differential manometer, made from a U-shaped tube or hose filled with water, is a primitive but faithful instrument, as much as a millibar is one centimeter of water.
I understand the need to use a venturi to maintain a continuous and stable flow to detect the threshold of change of state of the valve.

Mark.E #77932 24/07/24 11:44 AM
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Hi Mark,
I recommend you consider the Injector supplied by Draeger. Part No 7900930.
We use this device to achieve a -4 mBar pressure for testing the Emergency Respiratory Valve.
In combination with a Pipeline Reducing Regulator (speak to Oxylitre for this), you are able to adjust to demand to suit your needs.
Danny

Mark.E #77935 25/07/24 12:13 PM
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Mark.E Offline OP
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Yes Geoff I have one of these old Ohemda test lungs, I use to use it testing the Anaesthetic machines, but I cant hold the negative draw long enough to get a viable reading. on the inspiratory valve.

Daniel, because like everyone else in the NHS funds are not available I was looking for a cheaper option than using the £800 drager service tool.

VitaPablo you seemed to have grasped the problem exactly how I see it ..

The solution we found by using a wall mounted vacuum low suction set at a negative draw of 12mmHg. this is the same figure as generated off a dedicated borrowed venturri. ( when a flow between 60-65 litres used.)Solved by my trusty apprentice!

The trainer did state at the time I was trained, that a vacuum controller, could be used but they do not have that facility themselves; and one forgets.

thanks to all for your inputs

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Super Hero
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Promote that apprentice!

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Please i am in Manchester and in dire need of a place I can volunteer to learn on the job, I am a biomedical Engineer with a master degree in Biomedical Engineering. Please help


Kingsdave

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