Zoll M Series not reading rhythm

[cruiseforever]

We use Zoll M series monitors. Twice in the last couple of weeks I have noticed monitors not showing the rate of the rhythm when I am using 4 lead placement. But the monitor will show the heart rate using the pulse ox.

I have tried increasing the size without any changes. Put the pulse ox probe on and we have a rate. Place the 4 lead the rate indicator goes to zero. I believe both pts. had a pacemaker. Any ideas?

 

[Ensihoitaja]

I don't use Zoll's, so this may not apply... with our Lifepaks if there's a low amplitude QRS in the top channel, it sometimes isn't enough for the monitor to capture a rate from. Usually changing the lead on the channel (for example change from Lead I to Lead II) is enough to get the monitor to pick up a rate.