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High voltage capacitor defibrillator

  1. Sep 28, 2015 #1
    If defibrillation is not required is there an alternative method to save the enrgy for the next needed defibrillation rather than to discharge the capacitor using a resistor ?
     
  2. jcsd
  3. Sep 28, 2015 #2

    mfb

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    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.
     
  4. Sep 28, 2015 #3

    berkeman

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    And the defibrillator is only charged up if the EKG shows a shockable rhythm. I've never seen an aborted defibrillation -- have you?
     
  5. Sep 28, 2015 #4
    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
     
  6. Sep 28, 2015 #5

    mfb

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    I guess the charge is discarded if the patient gets a pulse before getting shocked.
     
  7. Sep 28, 2015 #6

    berkeman

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    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?
     
  8. Sep 28, 2015 #7
    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
     
  9. Sep 28, 2015 #8
    yes, that's what i meant :)
     
  10. Sep 28, 2015 #9

    berkeman

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    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
    zoll_aed_plus2_lg.jpg
     
  11. Sep 28, 2015 #10

    Baluncore

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    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.
     
  12. Sep 29, 2015 #11
    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.
     
  13. Sep 29, 2015 #12
    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
     
  14. Sep 29, 2015 #13

    berkeman

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    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.
     
  15. Sep 29, 2015 #14

    berkeman

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    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! :smile: ), 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...
     
  16. Sep 29, 2015 #15
    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.
     
  17. Sep 29, 2015 #16
    can we consider not pressing the discharge button as self-tests?
     
  18. Sep 29, 2015 #17

    berkeman

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    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/

    :smile:
     
  19. Oct 6, 2015 #18
    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.
     
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