Accuracy of Automatic BP machines?


Hey all, just wondering if you ever question the accuracy of the automatic blood pressure machines, especially when compared to manual bp readings.

I understand that cuff fit is important, and that with manual, there may also be user error.

The reason I ask is that I consistently get 130/90 when taken manually at my doctors office, and consistently get 120/80 via automatic machine - I can take this at school (nursing school), and work (hospital).

People say white coat syndrome but I don't know how much I believe that, considering I do not feel anxious at my doctors office.

Assuming there is a discrepancy between the readings of the automatic / manual not caused by white coat syndrome, could this affect our patients readings as well? (assuming your patients are in hospital, having bp taken automatically.


BrandonLPN, LPN

3,358 Posts

Has 5 years experience.

Manual is more accurate.

Has 13 years experience.

Manual is only as accurate as the person taking it, but if done correctly it is usually more accurate than automatic.


905 Posts

Manual all the way. Automatic sucks, I always get ridiculous numbers,

BrandonLPN, LPN

3,358 Posts

Has 5 years experience.

Manual can be faster too. Some of those automatic cuffs take a ridiculously long time.

And there's plenty of rom for user error with the automatic cuffs. CNAs bring me absurd low BPs and it's often because the pt was laying on their side or they used a bariatric cuff on a 100 lb old lady.


650 Posts

Has 8+ years experience.

Generally I think the automatic machines are accurate enough for routine vital signs. If I'm very concerned about a number or a patient I take a manual BP to compare. If there is a large discrepancy I will continue to monitor manually. If they are close I will continue with the machine with occasional manual comparisons.

ThePrincessBride, MSN, RN, NP

1 Article; 2,592 Posts

Specializes in Med-Surg, NICU. Has 8 years experience.

I really despise the automatic machines, but sometimes I will check manually. Usually, they aren't much off from my readings, but sometimes I'll get a ridiculous number and end up having to take it two, three or even four times. I trust what I hear more than what a rinky dink machine is telling me.

Do-over, ASN, RN

1,085 Posts

Specializes in CICU.

I've found the machines to be fairly accurate.

Tools are only as good as the people using them - manual cuffs or machines.

healthstar, BSN, RN

1 Article; 944 Posts

Machines can be accurate, but one day they may break / not function properly! Your ears will never fail you :)


3,413 Posts

Has 38 years experience.

I never trusted my ears, maybe a mild hearing loss in one ear, plus old age, is to blame.

I trust the automatic machines, the numbers you gave were not that big a variation. You can take a manual or automatic BP every 10 to 15 minutes and I would not trust either if you did not get that type of variation.

No one bases anti-hypertensive therapy on one reading. A critically ill patient would have an A-line. A patient being checking by their PCP would ideally have their blood pressure taken several times a week over a month or two prior to starting anti-hypertensive medication.


437 Posts

Specializes in Med/Surg/Tele/Onc.

If the readings are out of whack, I'll check manually. I trust my ears more than the cuffs, however I think the machines are good for showing trends.

Specializes in Emergency Department. Has 8 years experience.

If I have time, I'll do a manual BP. Why? It's more accurate for me to do it. While I can do a manual BP faster than an auto cuff can do it, in the overall scheme of things, I find it faster to "delegate" the BP taking to the machine. With a manual BP, once the cuff is on, the rest only takes me maybe 20-30 seconds tops. Where I pick up time is that if I'm doing a manual BP, I'm focusing mostly on that, where if I delegate that task out, my attention is focused on that task for as long as it takes me to apply the cuff and press the NIBP button.

Something that I try to do is take a manual BP and then take an auto BP, then compare the two. If they're close, then I'll trust the machine. As to auto BP machines, I have found that if the machine has EKG leads, they get quite accurate and fast because they'll ignore pressure swings outside a certain timeframe after each QRS.

I've done (quite literally) about 25,000 manual BP readings over my career so far, so it's not all that surprising that I got good at it. It's only been relatively recently (start of nursing school) that I have been doing more auto cuff than manual.