High voltage capacitor defibrillator

[ernd59]

If defibrillation is not required is there an alternative method to save the energy for the next needed defibrillation rather than to discharge the capacitor using a resistor ?

 

[mfb]

If you add something to convert the high voltage back to low voltage to charge a battery, sure. Adding that costs much more than one capacitor charge for the rare cases where the defibrillator is used.

 

[berkeman]

And the defibrillator is only charged up if the EKG shows a shockable rhythm. I've never seen an aborted defibrillation -- have you?

 

[ernd59]

And the defibrillator is only charged up if the EKG shows a shockable rhythm. I've never seen an aborted defibrillation -- have you?

it takes some time to charge the high voltage capacitor, and in a defibrillation every second counts. Normally while the EKG is working the capacitor is charging, I've never seen an aborted defibrillation too but theoretically it is possible

 

[mfb]

I guess the charge is discarded if the patient gets a pulse before getting shocked.

 

[berkeman]

it takes some time to charge the high voltage capacitor, and in a defibrillation every second counts. Normally while the EKG is working the capacitor is charging, I've never seen an aborted defibrillation too but theoretically it is possible

Not where I work. You always read the EKG to see if it is shockable rhythm, then it if is, you push the charging button. Where do you work where the defibrillator is charged before reading the EKG?

 

[ernd59]

Not where I work. You always read the EKG to see if it is shockable rhythm, then it if is, you push the charging button. Where do you work where the defibrillator is charged before reading the EKG?

i'm a student working on bachelor thesis, the Professor told me or what i think he told me, that in some AED "Automated external defibrillator" the charging of the capacitor and the EKG reading are done in the same time to minimise waiting period and assure the effectiveness of the defibrillation

 

[ernd59]

I guess the charge is discarded if the patient gets a pulse before getting shocked.

yes, that's what i meant :)

 

[berkeman]

i'm a student working on bachelor thesis, the Professor told me or what i think he told me, that in some AED "Automated external defibrillator" the charging of the capacitor and the EKG reading are done in the same time to minimise waiting period and assure the effectiveness of the defibrillation

I am not aware of any AEDs that do that. Can you find out a specific brand and model?

I suppose you could propose that it could be a new feature, if you could return the energy to the battery if no defibrillation was needed. On the other hand, it is pretty dangerous to be charging the defibrillation capacitor if you aren't going to use it. All it takes is one slip near the controls to discharge the capacitor into the patient and whoever else is in contact with them. I'm not sure you could get safety approvals for such a "feature". My AED charges in just 2-3 seconds, and that amount of time is not going to make a big difference in mortality or morbidity...

ZOLL AEDPlus:
http://www.dremed.com/catalog/images/zoll_aed_plus2_lg.jpg

 

[Baluncore]

How energy recovery might be done will depend on the capacitor voltage and how the charger works. If it is an oscillator–transformer–rectifier charger then only the rectifier diode needs to be HV rated. It would be difficult to find a semiconductor to switch the energy back through the transformer to the rechargeable batteries.

If the HV pulse was generated by a Marx Generator, the energy recovery could be done more easily since the parallel capacitor connection has a much lower voltage.

But either way it is probably not worth the extra complexity. The equipment will still need it's battery recharged when idle.

 

[256bits]

I am not aware of any AEDs that do that. Can you find out a specific brand and model?

I suppose you could propose that it could be a new feature, if you could return the energy to the battery if no defibrillation was needed. On the other hand, it is pretty dangerous to be charging the defibrillation capacitor if you aren't going to use it. All it takes is one slip near the controls to discharge the capacitor into the patient and whoever else is in contact with them. I'm not sure you could get safety approvals for such a "feature". My AED charges in just 2-3 seconds, and that amount of time is not going to make a big difference in mortality or morbidity...

So how does this work.
You check the patient - possible cardiac arrest or similar and irregular rhythm determined.
Defibrillation is chosen
Patient zapped
EKG tested - turns out OK
Defribulator turned to zero position
Paddles returned to their holding location on machine

Would it be a safety issue to have another KNOB or POSITION of the knob for Discharge to Battery.
I would think most operators in the spirit of the moment would find this distracting and perhaps confusing.
One would have to wait to return the paddles to their holding location for Discharge to Battery setting so that one can be sure arcing would not occur.
At least that is the way I see the safety issue.

Your thoughts.

 

[ernd59]

I am not aware of any AEDs that do that. Can you find out a specific brand and model?

I suppose you could propose that it could be a new feature, if you could return the energy to the battery if no defibrillation was needed. On the other hand, it is pretty dangerous to be charging the defibrillation capacitor if you aren't going to use it. All it takes is one slip near the controls to discharge the capacitor into the patient and whoever else is in contact with them. I'm not sure you could get safety approvals for such a "feature". My AED charges in just 2-3 seconds, and that amount of time is not going to make a big difference in mortality or morbidity...

ZOLL AEDPlus:
http://www.dremed.com/catalog/images/zoll_aed_plus2_lg.jpg

look at this Patent of a Portable defibrillators, they had a different goal but the idea is the same https://www.google.com.ar/patents/US7236823

 

[berkeman]

look at this Patent of a Portable defibrillators, they had a different goal but the idea is the same https://www.google.com.ar/patents/US7236823

Yeah, if you're going to be doing self-tests that charge up the output circuit, it makes sense to try to recover the energy. Keep in mind that AEDs generally use non-rechargeable batteries. Professional monitors with defibrillation capability use rechargeable batteries.

 

[berkeman]

So how does this work.
You check the patient - possible cardiac arrest or similar and irregular rhythm determined.
Defibrillation is chosen
Patient zapped
EKG tested - turns out OK
Defribulator turned to zero position
Paddles returned to their holding location on machine

Each shock is separately charged. When you see the shockable rhythm, you push the charge button and wait a couple seconds for the light to come on. Then you call "everybody clear" (very important step! ), and press the discharge button. I don't know what happens if you don't press the discharge button. But I wouldn't want to be working on a patient while the HV was still charged up...

 

[256bits]

Each shock is separately charged. When you see the shockable rhythm, you push the charge button and wait a couple seconds for the light to come on. Then you call "everybody clear" (very important step! ), and press the discharge button. I don't know what happens if you don't press the discharge button. But I wouldn't want to be working on a patient while the HV was still charged up...

OK thanks. Seen them in action but only in the movies, where they always do say "Clear", so I was wondering about the actual protocol.

 

[ernd59]

Each shock is separately charged. When you see the shockable rhythm, you push the charge button and wait a couple seconds for the light to come on. Then you call "everybody clear" (very important step! ), and press the discharge button. I don't know what happens if you don't press the discharge button. But I wouldn't want to be working on a patient while the HV was still charged up...

can we consider not pressing the discharge button as self-tests?

 

[berkeman]

can we consider not pressing the discharge button as self-tests?

Not on most AEDs that I'm familiar with.

However, on manual Monitor/Defibrillators like the ZOLL X-Series, there are some self-tests that involve charging the HV power supply (both for Pacing and Defibrillating). AEDs can be used effectively by trained laypeople, but Monitors are for trained and licensed EMS and Hospital folks. See the section of the manual on Self-Testing:

http://www.zoll.com/medical-products/product-manuals/

 

[ernd59]

i found this in a master thesis dating back to 2003, it is called Automatic discharge :
The automatic discharge is needed to avoid the main capacitor being left at
high voltages when not operated. For instance, if the capacitor is charged and
the medical personnel finds it unnecessary to complete the defibrillation, the
capacitor should be discharged without connecting the load (the patient).
This
protection is most easily achieved by letting the Microcontroller monitor the time
passed since the charging stopped.