Tuesday, February 11, 2014

2-Handed BVM - Many Hands Make Light Work

A guest post by Anand Swaminathan (@EMSwami) of EM Lyceum and Essentials of EM fame.

I’ve been teaching ACLS and airway workshops for years and I always make a point of focusing on the proper technique for bag-valve-mask (BVM) ventilation. I’ve always taught people both the 1-handed and the 2-handed techniques and said that they’re basically equivalent as long as you feel like you’re getting a good seal. This study brings the efficacy one-hand BVM into question.

The authors performed an interesting study. They took a group of providers (EM residents, attendings, nurses, paramedics and ICU nurses) and had them hold face masks on simulation mannequins with 1-handed and 2 different 2-handed techniques. A ventilator provided a 600 ml tidal volume and then measured the volume returned. Since this is a closed circuit, the volume returned should be equal to the set tidal volume – whatever leaked around the “seal” created by the provider.

What they found was surprising. For the 1-handed only 31% of the set tidal volume was expired while that number was 85% for both of the 2-handed techniques. This difference was found to be statistically significant and I imagine it would also be clinically significant. A study done earlier last year by Hard et al had similar findings.1

So what stands in the way of us completely stopping the teaching and application of 1-handed BVM (unless necessary due to staffing) and embracing 2-handed BVM? Unfortunately, the study is done on simulation mannequins and not on people. What we prefer is to see the application of the study to human patients. But this isn’t always possible. In the same issue of Annals, Wang and Yealy comment in an editorial that not only would it be virtually impossible to do this study in real human patients but also that it’s likely unnecessary.2 BVM is a technique that lends itself well to being studied in a simulation model.

What we have here are two studies showing benefit of a 2-hand BVM technique on mannequins that requires no increased equipment and a minimal increase in necessary resources. Using a 2-hand system is likely a better way to bring the mandible forward and open the nasopharynx allowing for nasal oxygenation. Since we’re unlikely to see a study done on actual patients, this should be enough to change practice.

Article:
"Comparison of Bag-Valve-Mask Hand-Sealing Techniques in a Simulated Model."

References:
1. "Face Mask Ventilation: A Comparison of Three Techniques."
2. "Emergency Airway Research: Using All Tools to Bridge the Knowledge Gaps."

4 comments:

  1. Another interesting bit from Otten et al's study is that the 2-handed technique removed most of the variability related to gender (I'd imagine from hand-size differences, but they did not adjust for this). It also did not matter your experience level when using 1-handed techniques, adding a 2-handed technique improved your ventilations. We've gone to teaching this as the primary technique to EMT's at our service.

    I'm probably preaching to the choir, but if you've never seen Dr. Reuben Strayer's video on emergency ventilation, I highly recommend it!

    http://emupdates.com/2012/01/11/11-minute-screencast-emergency-ventilation/

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  2. I also love the two-handed version for somnolent patients (OD, procedural sedation, etc...) because it allows me to give them a bit of noxious stimuli at the same time by pressing firmly in the "laryngospasm notch." I've never used it in the setting of true laryngospasm so I can't speak to how effective it is in that regard but it allows you to multi-task a bit while being the mask-sealer.

    http://journals.lww.com/anesthesiology/pages/articleviewer.aspx?year=1998&issue=11000&article=00056&type=fulltext#

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  3. "EM residents, attendings, nurses, paramedics and ICU nurses"
    Spot who's missing?

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  4. I think a similar study using humans is, in fact, necessary.

    A crucial step in forming a "good seal" and producing effective ventilation with a BVM is stretching the pliable face skin against the plastic of the mask and sealing the other side with the skin/fat on the other side.

    The plastic mannequin faces are a very poor substitute.

    Although I am a huge believer in the 2-handed technique, I do not think this study supports your conclusions. Rather, it points out that the mannequins may be a poor model for this aspect of airway research.

    I would like to see proper technique (very few EM or medics have even "fair" technique) in humans +/- OPA/NPA...that study with similar results would be something.

    This study just has a self-congratulatory conclusion that we (ME TOO) like to hear.

    HH

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