Automatic vs. Manual BP

[Dustdevil]

Is anyone really surprised by this?

http://www.jems.com/news_and_articles/arti...+eNews+06-02-09

Automatic vs. Manual BP

Michael Melnyk, Paramedic II

2009 Jun 1

A study conducted in the Greater Toronto Area over a three-month period from June to September 2007 set out to find out how automatic blood pressure (BP) readings compare to those of the traditional manual sphygmomanometer readings taken in the prehospital setting.

Readings were taken by professional paramedics in various types of situations. Patients were stable to varying degrees and types of shock. Medics were asked to perform two BP measurements: one by automatic machine and one manually.

At the appropriate times, paramedics obtained readings and recorded results. The readings were taken within two minutes of each other in order to maintain a mean consistency with minimal variance. If a reading was done in a stationary position, the second reading was also done while stationary, and conversely, when it was taken in a moving vehicle, to maintain consistency with ambient noise interference, movement and physiological changes. A total of 194 readings where obtained.

ALS and BLS paramedics gathered BPs in the prehospital study setting. Results of the readings were recorded, along with the patient’s age, sex, pulse rate and regularity. Proper size cuffs were ensured to accommodate the patient.

Findings

Of the total pressures taken, about 22% were taken while mobile or en route, and 78% were performed while stationary. Some 6% were taken from patients that were in an "established" form of shock and were following some form of standing order or prescribed treatment, other than supplemental oxygen.

The average patient tested was 57.34 years old. During mobile testing, the youngest patient was a 12-year-old male (pulse 71 regular, automatic BP 109/51, manual BP 106/78). The oldest was a 95-year-old female (pulse 81 regular, automatic BP 150/103, manual BP 210/100).

During stationary testing, the youngest patient was a 13-year-old male (pulse 80 regular, automatic BP 153/95, manual BP 170/70). The oldest was a 94-year-old male (pulse 104 regular, automatic BP 159/79, manual BP 160/60).

It was found that about 34% of pressures taken had a greater than 15 mmMg systolic differential. Some 7% had a differential spread of greater than 10 mmMg diastolically. This would account for a total of 55% of BPs that had discrepancies between automatic and manual readings. Out of the 6.19% of patients who were in shock and being treated under standing orders, about 48% had a differential (either positive or negative) of 15 mmMg either systolically and/or diastolically.

There was an 11% differential seen between automatic and manual readings. Thirty-two percent of the automatic pressures were higher, and half of these were mobile. Seventy-eight percent of manual pressures taken were higher than the automatic readings, and 55% of these were taken during transport. Some 54% of the total patients in this scenario had an irregular pulse rate.

Irregular pulses accounted for about 6% of patients, and of these, only about 5% presented with a positive or negative differential 10 mmMg. Nearly 95% of pulses were regular and sinus in nature.

It was interesting that only 14.94% of the total automatic and manual readings taken had a positive or negative differential of 4mmMg systolically and/or diastolically.

Conclusions

* Automatic and manual BP readings complement each other very infrequently.

* There doesn't appear to be any evidence that age plays a factor in the differentials found.

* The movement of a vehicle seems to have an effect of automatic and manual BPs, more so of increased manual readings. Whether this is due to a calibration issue of the automatic device or the sensitivity of ones own ear is unable to be determined by this study.

* There also seemed to be a greater differential in the systolic readings by both methods during movement.

* Almost half of the patients who presented and were being treated for "shock" showed a high variance.

* Age of the patient does not appear to play a factor in irregularities or variances of readings obtained.

* An irregular pulse did not significantly affect the variance spread of BPs taken.

Setting a Standard

Standing orders that require BP must specify one method for obtaining readings. That method needs to be determined by medical committees to ensure consistency of recorded vital signs and standardized delivery of medical care for patients, with a maximum beneficial outcome.

Manufacturers of automatic devices should perform regular preventive maintenance and calibration of equipment to ensure accuracy of BP readings obtained. It would be prudent to reiterate to the users of these devices that although the use of automatic pressure devices do free up a set of hands, all signs and symptoms be scrutinized when deciding the treatment of a patient.

This study shows that there is only a 15% similarity between auto and manual BP readings. Standing orders that rely on BP readings should specify by which method this vital sign must be obtained. The whole idea of a "normal blood pressure" should be reconsidered, leaving the question: What is the definition of a "true blood pressure reading"? A manual or automatic 125/85?

Michael Melnyk, Paramedic II, works for the largest ambulance service in Ontario, Canada, and as volunteer firefighter. Contact him at mmelnyk3@sympatico.ca.As an aside, I'm a little amused that the author tacks being a volunteer fireman onto his tag line, as if it somehow elevates his medical qualifications. I guess he's been watching too much Turd Watch.

Edited June 3, 2009 by Dustdevil

[fiznat]

This study is missing a few important factors that really take away from it's scientific relevance. The biggest problem is that there is no control to which we can compare. I would be interested to see what the test-retest reliability is for paramedic-obtained manual blood pressures in the field. I don't think it is all that unreasonable to see a 10 point difference in pressure between two measurements taken a few minutes apart. Noninvasive blood pressures are estimates, not precise measurements.

The way this study should be done is to compare invasive BP monitoring to a simultaneous NIBP (either auto or manual as the independent variable) reading. That way we could see what really matters, which is which method gives us the best estimation of actual blood pressure.

I also think it is a little sad that we seem to have a need for JEMS, who's sole purpose it seems is to process the literature into something simpler that EMS folks are capable of digesting.

Edited June 3, 2009 by fiznat

[WolfmanHarris]

I wouldn't knock him too much Dust, he not only works for TEMS which is not only a solid service, but renowned for it's animosity with Toronto Fire. My guess is he was playing to his audience south of the border by making a connection to the bucket brigade.

That being said, as a result of this and other studies done in Ontario our medical direction (Central East Prehospital Care Program) requires us to take our first baseline pressure manually and to use our judgment on whether subsequent NIBP results are reliable. Generally I stick to manual BP, but that's largely because of the bumpy roads causing time-outs. Two large services though have pulled NIBP as an option. I prefer having it as a tool to use when/if appropriate then having it taken from the truck; but if medics keep relying on it I may lose that option. (Hopefully not though, the medics at my new job all seem very on the ball so far)

Something to consider (though after some quick searching, I can't find corroboration) is that apparently the NIBP adds significant weight to the LP12. I know I'm tempted to ditch NIBP if it means less weight to carry.

Other then that, good article summing up some of what I've read before.

+5 Dust for a Canadian source.

[Dustdevil]

My guess is he was playing to his audience south of the border by making a connection to the bucket brigade.

That's what I was thinking too. I just find it sad that he feels a need to do so.

,,,our medical direction (Central East Prehospital Care Program) requires us to take our first baseline pressure manually...

Well, that answers one of the primary questions I had, which was which BP was taken first, and was that consistently adhered to. If not, that invalidates the results.

[chbare]

This study is missing a few important factors that really take away from it's scientific relevance. The biggest problem is that there is no control to which we can compare. I would be interested to see what the test-retest reliability is for paramedic-obtained manual blood pressures in the field. I don't think it is all that unreasonable to see a 10 point difference in pressure between two measurements taken a few minutes apart. Noninvasive blood pressures are estimates, not precise measurements.

The way this study should be done is to compare invasive BP monitoring to a simultaneous NIBP (either auto or manual as the independent variable) reading. That way we could see what really matters, which is which method gives us the best estimation of actual blood pressure.

I also think it is a little sad that we seem to have a need for JEMS, who's sole purpose it seems is to process the literature into something simpler that EMS folks are capable of digesting.

There is a study in the works comparing NIBP to IBP. http://clinicaltrials.gov/ct2/show/NCT00739700

There are other studies through Springerlink that compare NIBP to Manual B/P in the ICU and PACU.

Take care,

chbare.

[MontvilleFire39]

Dust,

I have exhaustively searched but was unable to find an article discussing a study of NIBP vs. Manual BP vs. IBP in the hospital setting. I don't remember specifcs, but the article claimed that NIBP in the hospital setting to be more acurate than manual BP. Something to think about...

[mobey]

Dust,

I have exhaustively searched but was unable to find an article discussing a study of NIBP vs. Manual BP vs. IBP in the hospital setting. I don't remember specifcs, but the article claimed that NIBP in the hospital setting to be more acurate than manual BP. Something to think about...

Really all this study shows is that there is a varience between machine assist BP, and manual BP. It does not show which is more accurate. Perhaps the machine is the most accurate?

but the article claimed that NIBP in the hospital setting to be more acurate than manual BP

Remember a manual BP is a form of NIBP. This study was comparing 2 ways of obtaining NIBP, Manual, and automatic (machine assist).

Edited June 3, 2009 by mobey

[Happiness]

Personally I like the manual BP.

[mobey]

Personally I like the manual BP.

I always ASSumed that a manual was the more accurate as well, then I saw this post

but the article claimed that NIBP in the hospital setting to be more acurate than manual BP

I will be keeping my eyes open for a study or 2 to back this up, and if the evidence is there, I will have to change my view.

[FireMedic65]

I have always preferred taking a manual BP first. Then I will put the automatic dealie to monitor the patient. If the pressure if grossly different from my manual, I will recheck manually. From what I have noticed though, if you keep your equipment taken care of and calibrated it should work just fine. A lot of the time, when using the automatic on say an LP12, if there is a lot of movement, the machine will restart/re inflate the cuff for a more accurate reading. Unlike the ones at walmart or something, these are more high tech and will work better.