Minimizing Interruptions

Approaching Zero Interruption CPR

Building Better Cardiac Arrest Care – Part 4

By now it should be clear that many of the innovations in delivering cardiac arrest care revolve around doing the basics more effectively. The posts in this series have highlighted new tools to help us achieve a more physiology-driven approach to cardiac arrest care, but the strategy remain focused on maximizing coronary perfusion pressure (CPP) by delivering high quality chest compressions of appropriate rate, depth and recoil, and also minimizing interruptions in those chest compressions.

emr05122008_fig1The importance of this last requirement cannot be overstated. After the first few minutes of a VF arrest, myocardial ATP has diminished to a critical level. If coronary perfusion pressure (CPP) is not improved prior to defibrillation, the likelihood of getting return of spontaneous circulation (ROSC) drops precipitously

A core concept related to optimal CPP from chest compressions is that chest compressions are not a simple on/off switch when it comes to CPP. Interrupting them for even a short period of time causes a rapid drop in CPP. Once chest compressions are interrupted, it requires a significant amount of time to achieve pressures that are once again adequate enough for successful defibrillation to occur.

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The reason compression only CPR works is based on this current understanding: that in most cardiac arrest cases coronary perfusion is more important than oxygenation and ventilation. Anything that interrupts compressions will have a large negative effect on CPP that extends well beyond the actual time of the interrupted chest compressions.
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Reducing Rhythm Checks
After research into this critical understanding of CPP was published, by pioneers like Dr Gordon Ewy cardiac arrest algorithms slowly attempted to walk back their previous recommendations, and began recommending reduced interruptions for reasons such as breath delivery. But until recently, most cardiac arrest algorithms still require frequent rhythm and pulse check interruptions at arbitrary intervals that are unrelated to the physiologic condition of the patient. The problem is summarized and highlighted nicely here by R.E.B.E.L EM within the graphics below:
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Two Pauses Before Using Precharging

Smart providers like @srrezaie of REBEL EM have realized that pre-charging the defibrillator prior to the rhythm check can streamline the first and second pauses into one event. Here is the new suggested sequence:

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One Pause After Using Precharging

This ingenious and simple change in the algorithm reduces interruptions, but it still requires several seconds to check the rhythm at each two-minute checkpoint. If an organized rhythm is detected, then chest compressions may be interrupted for and even longer period of time while attempts are made to feel a pulse.

When possible, the physiologic needs of the patient should always be prioritized over the arbitrary steps of any algorithm.

This is arbitrary checkpoint, one created by the historic limitations of technology,  bears no relationship to the physiologic condition of your cardiac arrest patient and what their needs are at the moment of the rhythm or pulse check.

 Algorithmic care often exists when there is a dearth of data about the underlying problem. But “best guess” care is not ideal care. When possible, the physiologic needs of the patient should always take priority over the arbitrary steps of any standardized algorithm.

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Filtering Software

Filtering Software

In cardiac arrest patients, knowing what rhythm the patient is in without  interruptions would improve our attempts to meet both the physiologic demands of the patient, and allow us to identify and treat a reversible cause of cardiac arrest without compromising either goal.

This is now possible: by using an accelerometer with integrated monitor/defibrillator pads, and combining it with filtering software, compression artifact can now be subtracted from an underlying cardiac rhythm. This allows for a shockable rhythm to be detected during active chest compressions without needing to pause for the usual rhythm checks.

The defibrillator may be charged as in the above approach, and then a quick hands-off period of under a second is all that is needed to deliver that shock before resuming compressions. If there is no shockable rhythm then there is no need to stop for rhythm checks at all, further reducing the arbitrary two-minute interruption cycle of the current approach. If the underlying rhythm is again a VF/VT then the process below can be repeated. (We will discuss the possible return of stacked shocks and how to address refractory VF in a later post).

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With Filtering Software


Reducing pulse checks

A similar use of the filtering software combined with ETCO2 can be used for pulse checks. In the current approach, rhythm checks that show an organized rhythm will also involve a potentially extended pulse check, further creating and prolonging detrimental interruptions in chest compressions.

In the new approach, if you encounter what appears to be an organized rhythm, then the next step should not be to check for a pulse, but to check the ETCO2.  A significant rise in ETCO2 should encourage you to check a pulse.  Going forward, a zero interruption vision in chest compressions should be the goal.

The use of other markers beyond ETCO2 and pulse checks for determining a perfusing rhythm will be our next post.  Watch this space.

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