Manual Versus machine Blood Pressures

How do you want to be known as a Paramedic/EMT?

A. Reliable
B. Frequently wrong

According to a recent article in JEMSDitch the Machine to Improve Accuracy in Blood Pressure Measurement and Diagnostics, “automated blood pressure readings are frequently inaccurate.”

Is this a surprise to anyone?

Yet, many of us continue to relay on automated BP cuffs to direct our clinical actions.

In a March 2016 article in the Journal of Clinical and Diagnostic Research, Which is More Accurate in Measuring the Blood Pressure? A Digital or an Aneroid Sphygmomanometer:, digital devices:

  1. should be used with caution, doubt and suspicion
  2. are not up to standard
  3. (can cause many people to be) wrongly or misdiagnosed
  4. may prove disastrous

Powerful words.

The JEMS article points out that even the manual for the Physio-Control Lifepack 15 contains this warning:  

“shock may result in a blood pressure waveform that has a low amplitude, making it difficult for the monitor to accurately determine the systolic and diastolic pressures.”

Got that.  Your Lifepack 15 is not capable of providing reliable blood pressures if your patient is in shock.

Cardiogenic shock
Hypovolemic shock 
Anaphylactic shock 
Septic shock 
Neurogenic shock

Your machine BP is unreliable when addressing these conditions.  It is frequently wrong.

How are you going to make clinical decisions with bad data?

You need to take manual blood pressures.

As an EMS Coordinator, I see run forms with blood pressures like these:

158/71
210/190
143/84
95/87
170/119

All for the same patient.  With no explanation.

As a paramedic, I have had my patient in afib brought into a level one medical room because the triage BP machine said my patient had a blood pressure of 79/40.   Why are we in here? the doctor asked as he looked at my calm, warm, dry patient.

Because the triage system at this hospital relies on digital blood pressures. 

Don’t relay on machines to take a blood pressure in patients with atrial fibrillation.

Here are my guidelines:

  • Make your first blood pressure manual
  • Treat your machine pressures as an inexperienced partner
  • Before making a critical clinical decision, take another manual pressure.

Make certain you know how to take a proper blood pressure.

Here are some good articles to help us improve our manual blood pressures:

Taking a Manual Blood Pressure: Techniques & Pitfalls

Blood pressure reading tips and tricks for EMS

 

I get it.  It is hard and nearly impossible sometimes in EMS to obtain optimal conditions for taking a blood pressure.

Just know that the blood pressure you obtain under those impossible conditions (using short cuts) may not be accurate.

Don’t let inaccurate and unreliable readings cloud your clinical judgement.

Take a manual, and if you can’t hear, palpate a blood pressure.

 

 

 

3 Comments

  • Electronic NIBP is notoriously innacurate… almost as inaccurate as human ears.

    For every erroneous NIBP reading I’ve seen, I’ve been given a BP of odd numbers taken off an aneroid sphygmomanometer, with even-numbered hashmarks. Or even worse, the guy who consistently gets a BP that ends in zero: 120/80, 150/90, and so on.

    One thing that IS accurate, however, is the MAP obtained by NIBP machines. It correlates very closely to MAP via arterial lines, and when titrating therapies these days, I generally rely on MAP rather than systolic BP.

    NIBP machines directly measure MAP, and mathematically derive systolic and diastolic BP, which is the exact opposite of how we do it.

  • CityMedic says:

    Spot on. And I’m usually faster and/or more accurate than my Zoll monitor.

    BUT:

    For those of us who work in systems where incentives are lined up toward avoiding liability instead of providing good patient care, an automated NIBP — no matter how inaccurate — is the recorded “proof” of that patient’s pressure and when it was taken. In my system, a great way to get called on the carpet is upgrading or downgrading a transport based on your manual pressure if it differs significantly from your automated NIBP.

  • Jacob Miheve says:

    I have one quibble with this article: the cited Journal of Clinical and Diagnostic Research study is being used here to claim that automated BP (NIBP) is less accurate than a manual BP, but that’s not what the study shows. That’s not even the study’s intent. Its intent is to determine whether a specific type of manual BP device (aneroid sphygnomanometer (aBP)) or an NIBP machine are more consistently in line with a long-standing “gold standard” device, the *mercury* sphygnomanometer (HgBP).

    The HgBP used as the control in this study is also a manual device. Therefore, the study *cannot* show whether manual BP is more “accurate” than an NIBP device, because the definition of “accurate” for the study is determined by a manual BP device. To truly make that determination would require comparison with some other method, such as an arterial line.

    Both manual BP and NIBP have their strengths and weaknesses. It is our job as providers to know these, and to take those factors, along with the patient’s history and clinical presentation, into account when trying to decide on treatments and priorities for our patients.

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