Slightly OT - BP measuring equipment ... ?

Never repaired one myself but what don't you understand? It measures the systolic pressure the heart produces with each beat and the diastolic pressure in between beats. I suppose it does this with the same mechanism used to blow up the cuff.

A typical blood pressure in mmHg is 120/80 the systolic is always first.

As I understand it, some of them use sound to trigger the measurements, listening for the thump of the bloodflow to stop pumping up the cuff and taking the first measurement, then as the pressure drops and the blood starts to flow again to take the second measurement.

As to the actual mechanics of the system, I dont know.

There`s no doubt some expert on the group who can tell you otherwise.

Ron ;^)

OK, here's the story then. Not a repair as such, hence the "slightly OT" in the subject.

The unit is actually mine. It's a fully automatic job, made by Nissei, who are quite respected in the field, I believe. It has a wrist-sized velcro secured air cuff, connected to the main unit by a single small bore air hose. No electrical connections between the two. When you hit the "start" button, the cuff inflates to a preset (selectable for four values) pressure, which is shown on the LCD as a genuinely 'measured' - i.e. not just a figure put there by the CPU - mmhg value. The machine then starts a controlled deflation of the cuff, picking up pulse soon after this starts. It appears to be assessing blood stopped / blood flowing by measuring the minute changes in air pressure in the connecting tube, caused by the vein pulsing under the cuff.

Now, I've recently been sucked into the 'high blood pressure' thing by my doctor's surgery, and they are determined to treat me for it. Fair enough. However, my 'clinical care expert' - actually a feisty practice nurse with the disposition of a bear with a thorn in its paw - will not accept that a blood pressure monitor that does its measuring from the wrist, has any validity at all. I would like to be able to monitor my own pressure on a compatible basis with her, because I feel that I am a rather good example of elevated pressure due to white coat syndrome. This is a factor that she seems to ignore as being a contributory element to any readings. I don't dispute that my blood pressure is higher than ideal, I just don't think that it is as high (on average) as she insists it is, and I don't want to be over-medicated for the condition.

So, onto the real question. My monitor is just about identical to the one she is using in the surgery. Same measurement sequence, same sound from the compressor, similar sized unit, similar length of time to inflate and deflate etc. The only difference is that mine has a plug-in wrist cuff, and hers has a plug-in arm cuff. She actually changed to a larger sized cuff to fit my arm when I was in there a couple of weeks ago, which is what led me to my next thought. Arm cuffs, on their own, are available from a pharmacy chain store down the road. They're not cheap, but nothing like as expensive as a whole new machine. Given that it seems to work by measuring the pressure pumped into the cuff to reach a primary inflation point to work down from, and then apparently does the 'business' measurements by looking at the pressure variations caused by the vein inside the cuff pulsing, can anyone see why my monitor should not work just the same with an arm cuff plugged in, instead of a wrist cuff ? I don't really want to just shell out on an arm cuff in the fond hope that it *will* work, and then find out that it doesn't, but then neither do I want to spend even more money on a replacement unit, if I don't have to.

Any opinions / insights / genuine knowledge anyone ? :-)

Arfa

Yes, I suppose I could as long as they don't mind taking a cuff out of the box, and allowing me to hook it up to my machine. Perhaps I should go in and have a chat with the pharmacist, or see if they will do a refund if I buy one to try, and it doesn't work.

Arfa

I think your assessment has validity.

I feel quite sure *technique* is the issue.

Arfa Daily Inscribed thus:

Good Morning Arfa,

I've had exactly the same issues with my Doctor and practice nurse which resulted in me buying one on the advice of my Doctor. I bought the one recommended at £10 from Lloyds Pharmacy.

The advice given was that everyone has high blood pressure at some time. However elevated blood pressure for an extended period (more than a few days) should be investigated.

For years I have had a lower blood pressure than normal ! All the fuss came about because the practice nurse decided that my blood pressure was abnormally high and insisted that I see the Doctor.

I rather got the impression that the Doctor didn't want to get into a conflict with the nurse and actually disagree with her !

As to whether arm or wrist cuffs are better, mine is an arm cuff and is actually the same instrument that the practice nurse uses.

HTH

Can't help with the wrist vs arm question. A spare cuff (3 sizes) is £2.99 from LLoyds pharmacy (Product Code: 8212482) or a complete unit with cuff for £12.99. As far as the working of the beast - AFAIK it is done by fuzzy logic. The sound of the blood flow changes very slightly at the low pressure point and this is what the doctor/nurse is trained to pick up. I personally think that it is a subjective thing and subject to variation - but the Doc who does my annual medical argues forcefully against that view.

I tried a wrist monitor and could not get reliable readings. Are yours consistant? I read some just don't have good readings on the wrist. I use the old fashion type, manual.

There are natural food suppliments for HBP. There are breathing excersises for HPB. And there is exercise and fasting.

greg

ANother thing, have the doctor remeasure the pressure after you have been settled for a while.

greg

Yes, I suppose I could as long as they don't mind taking a cuff out of the

Arfa, before expending the money, at your next visit simply take your unit with the wrist cuff and compare the results with what the nurse gets.

That is what I did.

Caveat: use the same arm and leave some time between machines to allow the arteries to relax back to "normal".

Charlie

Hi Charlie. That's kinda where I was getting to, but I have now discovered that Lloyds Pharmacy chain do a range of 'own brand' fully automatic BP monitors at a very good price. They come ex the cuff, which is then available in three different sizes for next to nothing, so I think my next move is going to be to buy just a cuff and try it on my monitor. If I get 'sensible-looking' ball park figures, then I will take it along to the surgery next time, and check it against theirs. If it doesn't seem to give realistic figures, then I'll just finish the job off, and buy the own-brand monitor unit, to go with the cuff already bought. Bingo ! The job's a good'un, as they say ... d;~}

Arfa

I would have to say they work the same.

I've been taking my blood pressure regularly for about 8 years using an assortment of BP measuring machines. My latest is an Omron HEM-775. (a bit old) None of the motorized variety work for me and always read far too high. When do it at the doctors office of myself with a stethescope and manual cuff, the BP reads correctly and typically 120/75. After many experiments and discussions with doctors, nurses, Omron, and the local witch doctor, the current guess is that my veins are located much deeper in the arm than would normally be expected. The manual BP method probably compensates for this, but the electronic BP meter does not.

I've also tried a cheap wrist cuff meter, which was admittely more convenient, but resulted in much larger variations in BP as with the motorized BP arm cuff. While the arm cuff was not particularly accurate (for me), it was fairly consistent. I can't say the same for the wrist cuff. I suggest you avoid using a wrist cuff and stay with the arm cuff.

Incidentally, at one point, my cardiologist decided to trust the readings from my long history of BP from the motorized BP meter. He increased the dosage of my assorted BP medicines. After a few days, I was phlegmatic and nearly passed out several times. My real BP went too low. We went back to believing the office manual BP measurements or used a mathematically fudged version of my graphs.

At one time, I thought that the BP meter was in some way defective. By comparing it with 4 other motorized meters, I eventually determined that this was not the case. However, that didn't stop me from ripping it apart to see how it works. Basically, a pump, pressure transducer, calibrated leak, and microprocessor for storing and presenting the results. Some had pressure calibration adjustments, but most did not. Other than mechanical damage, there's not much to repair inside.

Some interesting stuff there Jeff. I guess the deeper in the vein is, the more soft tissue (muscle?) there is between the cuff and the vein. I guess that would have to make the cuff inflate to a higher pressure before the 'spring' had been taken out of the intervening tissue, and pure squeeze was being placed on the actual vein. In a case like this, I can see how doing it manually by listening for a pulse, might yield a better result. What you had inside your one sounds pretty much identical to what's inside mine. See my new follow up post "BP measuring equipment - Part 2" and a couple of the interesting replies that have been posted in that thread, one in particular with some links to other material on the measurement principle.

Arfa