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Joined: Dec 2002
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Simpo Offline OP
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I'm in an enquiring mood today, so, can anyone shed light on the purpose of the excite(r)leads within an invasive blood pressure test lead. They are shown on the lionheart tester pin out diagrams for making an IBP test lead but i can find no explanation of purpose.

As always any help is massively appreciated.

Simpo

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Hi Simpo,

IBP leads usually consist of 4 connections (plus screen): 2 pressure signal inputs to the monitor (+/-) and two excitation outputs from the monitor (plus screen).

The IBP module supplies a differential excitation voltage to the pressure transducer that connects to the IBP lead. The monitor e.g. Datex S3/S5 provides this ecitation voltage to the transducer that, typically, is a semiconductor wheatstone-bridge circuit.

The pressure transducer ususally gives a differential output voltage from the bridge of 5uV/V/mmHg (typical in most monitors) or 40uV/V/mmhg i.e. 5/40uV per volt excitation per mmHg pressure applied to the transducer. This signal is amplified by the IBP circuitry and gives the pressure waveform.

The signal output is proportional to the excitation voltage supplied by the monitor that's all. The monitor powers the transducer and scales the output with this voltage as well.

In practice, when using a simulator, you connect the excitation from the monitor to the respective excitation inputs of the Lionheart and then connect the signal outputs from the lionheart to the monitor inputs. Select 5uV/V/mmHg on the Lionheart and you should be able to zero then apply a simulated waveform via the Lionheart.

Alternatively if you can obtain a digital manometer, syringe and a disposable pressure transducer you can provide simple IBP function/lead checks using a syringe to apply pressure to the transducer via a 3-way tap connected to the manometer.

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Hero
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If you just want static electronic calibration you can make up a bridge and put it slightly out of ballance with a switch and a resistor.
The calculation of the resistor I will leave to you but the maths is as above from Richard.
I had one for the HP Rifleshots which have an analogue amplifier and a pot on the front you used to cal it. It was all built in to an HP plug with a push button on it. Very useful but not needed in these days of electronically stored cal factors.
If I can find it I will read the resistor colour codes and let you know the values.
Resistor colour codes, now there is a skill that is on the way out, how about that as an interview question? It would really sort out the academics from the hands on people. Or even use it as an entry requirement for VRCT. laugh
Robert


My spelling is not bad. I am typing this on a Medigenic keyboard and I blame that for all my typos.
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Super Hero
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Good stuff, Richard. Up to your usual high standard, we’re pleased to see. Welcome back Mate, you’ve been sorely missed.

I wonder which mnemonic you prefer, Robert? smile


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Simpo Offline OP
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Gentlemen

The clouds parted and all became clear.

I have used the suggestion of a disposable transducer and manometer for a quick check. However for completeness (and standardisation, traceability etc) it suits to use a simulator across the fleet of equipments.

Thank you for your responses, much appreciated and happy new year.

Oh and Robert resistor colour codes Black,Brown,Red,Aubergine,Mauve erhm, Taupe! thank god I've still got a year or two before i have to get a real job.

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Hi all,

There was a mention of a lionheart tester pinout diagram earlier in the post, does anyone have a copy of this they can email/fax to me???
In the absence of any cables for IBP testing am trying to make my own...without any documentation!!! Am very much in the dark...

Please help me see the light!!!

Thanks for your time,
Dani Forster.

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The IBP cables will need to be patient-monitor specific. You could modify some existing IBP cables by removing the transducer connector and fitting a AMPHENOL or DIN plug to connect to the Lionheart instead of the pressure tranducer. I suppose if you asked your local representative, who supplies pressure transducers (disposables?), you could get hold of some for free.

Of course connections are specific to the patient monitoring you intend to use the simulator with so you'll probably need the IBP pin-allocations of the monitor so you can determine which connections are excitation and which are inputs within the IBP cable. You will need to take a look in the patient monitor service manual to determine which pins are excitiation and which are inputs and connect the AMPHENOL or DIN as necessary to the Lionheart via the cable. What types of monitors do you intend to connect to?

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Hiya,

I am trying to connect to the Picco plus, I have done some experimentation already with the Picco cable and the pressure transducer and have determined (i think!!) which are the excitation and input pins...

But I don't have a pinout diagram for the lionheart (all documentation, cables etc seem to have gone walkabout) so I don't know which pins of the DIN connector for the lionheart to connect them to.

All assistance is very muchly appreciated!!!

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Unfortunately we don't use the lionheart here - I'd fax the DIN pin-outs otherwise. Anybody help?

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Well, here's one i should be able to help with!

On the red connector for the transducer the pins are
1.+EX
2.-Signal
3.-EX
4.+Signal

But, with in the transducer on the desposable there is a resistor(6810R) to determine which catheter type you are using, between pins 1+3 (if you dont have this the Picco Plus will never 'see' the catheter type and you will always get invalid catheter.)

We dont use the Lionheart, but i will find the pin outs and post it.
Did you not buy the Netech mini simulator, thats the one we use for the job.

Regards
Scott.

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