topic Re: Heart Rate and Blood Pressure Monitor in Life Science

Heart Rate and Blood Pressure Monitor

Pete.Dunc — Fri, 30 Jan 2009 13:13:44 GMT

Hi there, this is my first post so be nice

Basically this is a university project I've been thrown in the deep of. The specification is to produce a heart rate and blood pressure monitor, the heart rate and blood pressure are to be displayed onscreen. My responsibility is to take our "heart rate" signal and interpret the results to display the value.

I thought LabView would be good for this.

Although I have completed the "LabView 101" course I have very limited knowledge of data acquisition, obviously there is a plethora of information on this site (2871 articles) I was just looking to be steered in the right direction.

If you would like anymore information don't hesitate to ask.

Peter

Re: Heart Rate and Blood Pressure Monitor

Coq_Rouge — Fri, 30 Jan 2009 14:19:40 GMT

For about a year ago I built such a monitor with Labview. I measured the invasive blood pressure and also extract the heart rate from this signal. I used the peak detection function for this task. I can not send you any program. But feel free to ask me questions regarding this matter.

If this system are going to be used on humans, it must comply with the IEC 60601. The hardest part is often to make the system IEC 60601 compatible ;). The measuring part is quite simple

Message Edited by t06afre on 01-30-2009 03:16 PM

Message Edited by t06afre on 01-30-2009 03:17 PM

Message Edited by t06afre on 01-30-2009 03:19 PM

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Fri, 30 Jan 2009 20:03:53 GMT

t06afre wrote:
For about a year ago I built such a monitor with Labview. I measured the invasive blood pressure and also extract the heart rate from this signal. I used the peak detection function for this task. I can not send you any program. But feel free to ask me questions regarding this matter.
If this system are going to be used on humans, it must comply with the IEC 60601. The hardest part is often to make the system IEC 60601 compatible ;). The measuring part is quite simple

Thank you for the quick reply.

This is a group project and gaining the measurement signals will be undertaken by other students. I'm really concerned with what to use to get these signals "into" the PC.

The information on the IEC 60601 is great thanks again.

Re: Heart Rate and Blood Pressure Monitor

Coq_Rouge — Thu, 05 Feb 2009 11:53:56 GMT

Hi PjayD

Is your project on the right track, or do you need a life buoy...

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Thu, 05 Feb 2009 12:10:39 GMT

Good morning

Later this afternoon our group will be presenting our specification and method to a group of lecturers. This is an informal presentation with the purpose of getting feedback from them on whether or not we're heading in the right direction in terms of planning. So after that I'll be able to get going properly.

I'll post on here again in a few hours with an update.

Pete

Re: Heart Rate and Blood Pressure Monitor

ROtake — Tue, 03 Mar 2009 16:55:24 GMT

there are several medical devices in the market that does that. They all already comply with safety regulations. Most of those devices have an analog external signal that you can read using any simple Data Acquisition board or a digital output like serial RS 232 or any other connection. This way, your system is not connected with the patient and you don't have any conerns about safety. You only need to make sure your program makes the right calculations.

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Thu, 05 Mar 2009 15:50:10 GMT

Sorry I took so long replying!

I've been working through "Learning with LabVIEW 7 Express" by Bishop.

This has given me a slightly better understanding of the capabilities of the

program. Now I can start work on the actual project, I'll be updating on

here much more regularly.

The methods by which the heart rate and blood pressure will be obtained

have been finalised so the input signals are now known;

Heart rate -

This will be a square wave which changes voltage level on each heart beat.

Blood pressure -

This will be a continuous voltage trace and the program will require the

ability to pick off two values (for high and low blood pressure); although

these are not the maximum and minimum values of the graph. The

user will select when readings are taken.

The devices used to gain these signals are still being produced so for

now I'll be simulating the waves in LabVIEW. I'm having trouble using

the "Simulate Signal" tool. I add it, set up the parameters for my square

wave and fed it into a Waveform Chart. I then select run continuously

and only one period of the wave is displayed. I was expecting a similar

output to feeding a function generator into an oscilloscope.

All help appreciated!

Peter

Message Edited by PjayD on 03-05-2009 09:50 AM

Re: Heart Rate and Blood Pressure Monitor

ROtake — Thu, 05 Mar 2009 16:14:14 GMT

Blood pressure signals are something like this...

o o o o

o o o o o o

o o oo o o o o

o o o o o oo o

o o o o o

o o o oo

So you will need to read the analog signal (if you're using an analog input with a daq card) and split cycles . On each cycle, you will need to detect the max pressure and the minimal pressure of your signal.

One way to implement this is to create a virtual buffer in memory with the data you read from the card and then process all the calculations you need: separate cycles, then measure max and min press on each cycle, then, you can make an average withing the cycles you detect.

The average values will be this way a little delayed, since you will show the values as an average of the last 3 or 4 cycles.

The heart rate, if i understood correctly, you can just read with analog signals. You will probably have a converting factor to tranform voltage reading to heart rate (bpm).

Ricardo

Re: Heart Rate and Blood Pressure Monitor

Coq_Rouge — Thu, 05 Mar 2009 17:09:38 GMT

Here is an example of arterial blood pressure from a human. As I told you before you shall use peak an valley detection. For determining the diastolic pressure, and systolic blood pressure. The heart rate is related to the time between to systolic or diastolic events. Your plan looks somewhat strange if you ask me.

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Fri, 06 Mar 2009 14:51:59 GMT

Thank you both for replying.

I've not made this very clear; the way the project has been split up I have no say in the way which the input signals are obtained, I agree that it seems strange, but it's out of my hands.

I just have to get the software to work around the inputs so the descriptions in my previous post still stand.

@ROtake -

In order to measure the blood pressure we will be using auscultatory methods (http://en.wikipedia.org/wiki/Blood_pressure#Auscultatory_methods); the guage will be replaced by a pressure transducer to get a voltage. This is why I was saying the software will need to be able to take two samples when a user selects (when the sounds are heard); I can't just do peak and min, as the cuff is blown up to a higher pressure and released until the sounds occur. Reading the sound will be done manually, so there's no need to use LabVIEW for that.

@t06afre -

Thank you for the sample, it would be much easier for me if I had a continuous trace of blood pressure being input. But because of the way 'the group' have decided to tackle the problem, I'm stuck with the situation above.

I think the way we're doing it is not the best by any means, but I've got to work with what's given to me.

Re: Heart Rate and Blood Pressure Monitor

Coq_Rouge — Fri, 06 Mar 2009 15:25:56 GMT

Well if you are going to use the auscultatory method my signal is not very useful. But the auscultatory method is the best (and only) way for students to measure blood pressure. Invasive measurements requires a medical doctor to insert the needle in the arm, and set up the system. Most people find the needle procedure painful. Invasive blood pressure is mostly used in intensive care units. And very seldom in technical schools ;).

Re: Heart Rate and Blood Pressure Monitor

ROtake — Fri, 06 Mar 2009 17:58:55 GMT

So according to you are saying, the user will be hearing the blood vessel then will input the moment to measure the max pressure, then input again the moment to measure the minimun pressure. Is that it ?

At each of those two inputs your program will read the pressure transducer signal. Is that it ?

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Sat, 07 Mar 2009 12:14:00 GMT

@t06afre -

I don't really understand why the guy didn't just but a digital one and take the signals from that. But yeah it was a in the specification that the method had to be non-invasive.

@ROtake -

That's exactly right. Don't know how to achieve this though.

Re: Heart Rate and Blood Pressure Monitor

ROtake — Mon, 09 Mar 2009 13:25:35 GMT

In this case you can read the analog input using a buffered contiuous acquisition and at the same time (in the loop) keep reading a keyboard input (or any other input) as you detect the input, then you will get the data form analog input and place in a digital indicator.

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Thu, 12 Mar 2009 00:18:42 GMT

Thanks ROtake, think that's the solution for blood pressure sorted, just need to find the time to actually do it!

As for blood pressure I have a TTL square signal being input (the one I similuted with a square wave). Can I use a counter to calculate the amount of times it switches level over a predefined time period? What tools/structure would I be using for that?

Thanks again,

Peter

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Thu, 12 Mar 2009 13:01:29 GMT

Hey guys, this is the problem I'm having at the moment (apologies for the big pic)..

My simulation of the square wave is working correctly, but when I try to analyse the frequency I'm getting this message. Where am I going wrong?

Peter

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Thu, 12 Mar 2009 13:38:00 GMT

Just a quick update on how I'm getting on with simulating a sine wave for the blood pressure (again sorry for big pic )

This is the signal I'll have to select two amplitudes from (when the user clicks a button) although the 'Tone Measurement' tool doesn't seem to be working correctly.. I've kinda hit a brick wall here.

Any and all help appreciated!!

Peter

Re: Heart Rate and Blood Pressure Monitor

Ray.R — Mon, 23 Mar 2009 12:35:48 GMT

Are you still stuck?

How was the progress?

Re: Heart Rate and Blood Pressure Monitor

Pete.Dunc — Mon, 23 Mar 2009 17:06:29 GMT

Hi Ray

I believe this is more of a LabVIEW issue rather than Life Science, so I moved the thread to

this location;

http://forums.ni.com/ni/board/message?board.id=170&thread.id=394491&view=by_date_ascending&page=1

Apologies for the poor forum etiquette although I couldn't find an option to delete this thread or

to move it. As for the project I'm currently learning about queues and ways of modularising the

tasks. Also trying to get to grips with using counting functions of my DAQ card.

I have a meeting with a technician in my university this week who deals with all the LabVIEW

here; hopefully be able to make some good progress then.

Peter

Message Edited by PjayD on 03-23-2009 12:06 PM