# Questions on the AED



## DragonClaw (Sep 1, 2019)

1. Why doesn't it detect a pulse? Why not add a pulse Ox thing or another way to get a pulse. Is it just irrelevant because even with a good pulse, a shockable rhythm will be shocked anyway?

2. Why isn't a "professional" AED with a 12 lead and not 2 pads? Or both?  How are 2 pads good enough to figure out if a shock is advised (and they're not as specifically placed), but a 12 lead is used for cardiac events. A 12 lead is more than just a shockable rhythm, but how are 2 pads enough for that? 

(Also, what's that phrase about a 4 lead placement, smoke over fire, something else?)


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## DesertMedic66 (Sep 1, 2019)

1.) the rhythms that the AED will shock are not a rhythm that can be sustained by the heart. It would also increase the cost of the AEDs and possibly make them more complicated for bystanders to use.

2.) you really only need one lead to interpret a cardiac rhythm. A 12-lead is mainly used when you are looking for a STEMI which is not what an AED does. So a single set of pads with easy placement is quick and good enough for what the AED does.

3.) Smoke over Fire, Clouds above Grass.


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## Martyn (Sep 2, 2019)

I always remember the 4 lead placement as, when I am looking at the front anatomical plane, from top right going clockwise, as Salt, Pepper, Ketchup and Guacamole


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## NomadicMedic (Sep 2, 2019)

The AED uses lead II to determine a shockable rhythm. That's easily detected by the typical pad placement. 

A 12 lead isn't something that is ever needed on an AED, so there is no reason to integrate one. However, I DO wish there was a small, rugged AED with a 12 lead for our bike team. Someday. Maybe zoll will build one. 

The Heartstart FR2 AED has a screen that allows you to use the display to determine a rhythm so you can treat your patinet with pharmacological means.


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## Akulahawk (Sep 2, 2019)

1) An AED only needs to look at a single lead (approximates lead II) as that's all that is necessary to detect a cardiac rhythm. Since the AED only "cares" about 2 rhythms (VF and VT) and you are only supposed to use an AED when someone is pulseless, that meets criteria to shock if the AED "sees" either of those two rhythms as both are lethal in that situation. 

2) A 12-lead is used to look primarily for STEMI. The fact that we can determine a LOT more from it makes it very useful in quite a few other situations. Monitor-Defibrillators that can do 12-leads can have AED and pace functionality built into them but to build a 12-lead function into an AED is pointless and expensive. 

3) I don't do 4 lead, I do 5 lead... but I too remember "Smoke over fire, Cloud over Grass" for that 4 lead placement.


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## Tigger (Sep 2, 2019)

SpO2 does not often work particularly well in patients that are poorly perfusing. Also things like nail polish and being dirty can cause the sensors to read poorly.


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## DragonClaw (Sep 2, 2019)

Tigger said:


> SpO2 does not often work particularly well in patients that are poorly perfusing. Also things like nail polish and being dirty can cause the sensors to read poorly.


I didn't mean for the O2 usefulness, but can it do one without the other?


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## DesertMedic66 (Sep 2, 2019)

DragonClaw said:


> I didn't mean for the O2 usefulness, but can it do one without the other?


The only rhythms that the AED will shock are V-Fib and V-Tach (hopefully without a pulse). Both of those rhythms will not have any pulse so the SpO2 sensor would not be giving any sort of reading or waveform.


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## DragonClaw (Sep 2, 2019)

DesertMedic66 said:


> The only rhythms that the AED will shock are V-Fib and V-Tach (hopefully without a pulse). Both of those rhythms will not have any pulse so the SpO2 sensor would not be giving any sort of reading or waveform.



So then to summarize,  it is completely useless because you won't have a pulse anyway,  and if you need a shock,  you need a shock. As usual,  correct me if I'm wrong.


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## DesertMedic66 (Sep 2, 2019)

DragonClaw said:


> So then to summarize,  it is completely useless because you won't have a pulse anyway,  and if you need a shock,  you need a shock. As usual,  correct me if I'm wrong.


This sums it up pretty well.


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## Tigger (Sep 3, 2019)

DragonClaw said:


> I didn't mean for the O2 usefulness, but can it do one without the other?


An SpO2 sensor may not find a pulse despite one being present.


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## DragonClaw (Sep 3, 2019)

Tigger said:


> An SpO2 sensor may not find a pulse despite one being present.



Then what are we paying it for?! Huh?! >:c


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## luke_31 (Sep 3, 2019)

DragonClaw said:


> Then what are we paying it for?! Huh?! >:c


To measure the saturation of the hemoglobin in the blood to see how much oxygen is present , or in the presence of carbon monoxide it will show it as fully saturated at 100% sometimes even though the carbon monoxide is bound to the hemoglobin instead of oxygen.


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## DragonClaw (Sep 3, 2019)

luke_31 said:


> To measure the saturation of the hemoglobin in the blood to see how much oxygen is present , or in the presence of carbon monoxide it will show it as fully saturated at 100% sometimes even though the carbon monoxide is bound to the hemoglobin instead of oxygen.



I'm sorry,  it was a joke.  As I always say,  y'all know I'm not good at jokes or you'll find it out shortly.


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## NomadicMedic (Sep 3, 2019)

DragonClaw said:


> Then what are we paying it for?! Huh?! >:c



I know you’re joking, but this might help by explaining how a pulse ox works and why it wouldn’t be effective in a poorly perfused person, even if they had a pulse. 









						How pulse oximeters work explained simply
					

We will discuss the following aspects. Please scroll down and start reading.   	Introduction  	Oxygen Saturation  	Physical properties used in pulse oximetry  	Calibration  	Pulse oximeters measure pulsatile arterial blood  	Signal is very small  	Plethysmographic trace (pleth)  	Light source...




					www.howequipmentworks.com


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