# and how do these things work?



## firetender (Jul 28, 2012)

Here's a thread we have going about a synchronized cardioversion that was synchronized to the vulnerable stage of the EKG complex BY the machine:

http://www.emtlife.com/showthread.php?t=31070

I'm really curious as to the way monitor/defibrillators are set up for this and how it would have been possible for the machine to offer three potential "target" areas on each complex.

Is this a design flaw or operator error?

Thanks!


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## Physio Control (Jul 30, 2012)

Thanks for the question. Will follow-up with the appropriate Physio-Control subject matter experts and get back to you soon.


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## Physio Control (Jul 31, 2012)

firetender said:


> Here's a thread we have going about a synchronized cardioversion that was synchronized to the vulnerable stage of the EKG complex BY the machine:
> 
> http://www.emtlife.com/showthread.php?t=31070
> 
> ...



This is neither a design flaw or operator error. They are trying to synch off lead II, which happens to have a rounded R wave peak and greatly truncated S waves. This combination is making it difficult for the R-synch algorithm to locate the proper peak to time-off of, thus causing intermittent double counting and improper synch markers. If they could have switched lead III (or probably even lead I as well) to the top position, the device would have used it for synchronization. It’s very likely that the R peak would have been correctly identified. Lead III has much more defined R and S waves and acute slope changes.


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## Christopher (Jul 31, 2012)

Physio Control said:


> This is neither a design flaw or operator error. They are trying to synch off lead II, which happens to have a rounded R wave peak and greatly truncated S waves. This combination is making it difficult for the R-synch algorithm to locate the proper peak to time-off of, thus causing intermittent double counting and improper synch markers. If they could have switched lead III (or probably even lead I as well) to the top position, the device would have used it for synchronization. It’s very likely that the R peak would have been correctly identified. Lead III has much more defined R and S waves and acute slope changes.



Thanks for the feedback, this was my guess as to the cause as well!

I added the advice to ensure the markers not only correspond to the R- or S-waves nadir, but to ensure the marker *rate* was appropriate as well.


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## firetender (Aug 2, 2012)

*Devil's Advocate*



Physio Control said:


> This is neither a design flaw or operator error. They are trying to synch off lead II, which happens to have a rounded R wave peak and greatly truncated S waves. This combination is making it difficult for the R-synch algorithm to locate the proper peak to time-off of, thus causing intermittent double counting and improper synch markers. If they could have switched lead III (or probably even lead I as well) to the top position, the device would have used it for synchronization. It’s very likely that the R peak would have been correctly identified. Lead III has much more defined R and S waves and acute slope changes.


 
Okay, then. If a Lead II complex is going to show multiple times for cardioversion then Lead II (certainly in that case) should not be used.

But how does the medic know when to switch the synch to another lead?

That brings us to the readout. Chris, you showed a "strip" that indicated three "arrows" on the complex. From your narrative I gathered that the medic was able to see those markers. If that was the case, then the medic would have had to have known something was amiss. 

Perhaps my point is -- especially in the case of synchronized cardioversion -- we are taught to (blindly!) trust the machine and in this case, the medic did and it put the patient's life in jeopardy.

I have to play Devil's Advocate here and challenge the notion that neither operator error or mechanical failure occured. I see both. But the onus is on the monitor/defibrillator.

First, the idea of synchronized cardioversion is that there is ONE place on a complex to hit that will minimize the possibility of stomping on the vulnerable phase. That's what the monitor/defib is suppposed to do - a "synchronized" cardioversion. This was synchronized as a one-in-three chance of fatal result!

The machine failed because it identified THREE possible targets on each complex and it didn't "catch" it as being a problem. 

This leaves the "checks and balances" part completely up to the medic, and in this case, the medic had nothing to warn him and nothing in his education to prepare him to "spot" that three marks on a complex as a potential problem.

If the machine is designed to safely execute a synchronized cardioversion then it should have checks and balances built in to reduce the possibility of misinterpretation, which was the case here. At the very least, it should alert the operator to any logical discrepancies.

Hopefully, this was a very rare situation, but couldn't an algorhythm be programmed into the machine that more than one target-moment on a complex -- ESPECIALLY if, as was seen there's a much more clear view of complete complexes in Leads I and III -- warrants a warning to the Operator to change Leads?

The medic was amiss in that he didn't catch the absurdity of three potential target-moments on a complex. But how could he even know unless he was pre-warned of that possibility? After all, we're just instructed to turn the dial, place the paddles and push the buttons!

(Was the medic even taught to review the printout with appropriate markers on it?)

This case shows if it can happen once, it can happen again (and it probably has!). This tells me there is a need to either re-program the units to catch the problem or, re-program the medics to watch for the potential of the monitor/defibrillator to synchronize its discharge to the wrong Lead.

The printout shows a huge discrepancy between Leads II and III -- III clearly showing a more easily identified moment to discharge. If the medic doesn't know that the machine has the potential to target the wrong Lead, then how can he/she act to prevent it?

Let's put it this way. If the patient had been thrown into V-fib and NOT re-converted and died (from a synchronized cardioversion gone wrong) who'd catch the weight from the Ambulance Chaser?

Likely the medic would first, but the real money would be in the deep pockets of the manufacturer of the equipment.


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## Christopher (Aug 2, 2012)

firetender said:


> That brings us to the readout. Chris, you showed a "strip" that indicated three "arrows" on the complex. From your narrative I gathered that the medic was able to see those markers. If that was the case, then the medic would have had to have known something was amiss.



That was a summary printed after-the-fact. I believe during the call they used the visuals on the screen itself and did not rely on any printed copy. They immediately recognized the problem on the printed copy.


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## firetender (Aug 2, 2012)

Christopher said:


> That was a summary printed after-the-fact. I believe during the call they used the visuals on the screen itself and did not rely on any printed copy. They immediately recognized the problem on the printed copy.


 
That significantly clarifies the problem: the medics had nothing but their blind faith in the monitor/defibrillator to go on.


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## Christopher (Aug 6, 2012)

firetender said:


> That significantly clarifies the problem: the medics had nothing but their blind faith in the monitor/defibrillator to go on.



I'd classify it as a Human Factors failure. If nobody tells you that it may not be readily apparent that the monitor oversensing, you probably wouldn't think to scrutinize the markers.

Likely there are improvements which could be made to the visuals on the cardiac monitor w.r.t. synchronization. Likely there could be algorithmic improvements for synchronization. I can't remember who, but somebody suggested that the HR be put alongside the Sync Rate to see if they "match" up, but those are only as accurate as the monitor's calculation of the HR (which can double and triple count in certain situations, re: Littmann's Sign).

In the nuclear industry we identify Items Relied on for Safety, some of which are classified as Sole IROFS, i.e. there are no checks and balances in place beyond the operator appropriately handling the task. Human verification of the synchronization is a Sole IROFS.

About the only improvement I could see would be to automatically print a 10 second strip whenever Synchronization is enabled. At this point the operator is presented with all of the information available to make the decision:

Visual indicators of synchronization on the screen
Physical copy of the indicators to compare


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## Akulahawk (Aug 6, 2012)

I probably would have caught the problem, but my training did not address how to deal with this particular error. Given that the monitor would have put markers on waveforms other than the R wave, I probably would have switched over to an unsynchronized cardioversion. I appreciate the response by Physio-Control, as now, I know that if I see that particular problem again, I can switch to a different lead. That is a darn good thing to know!


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