Defibrillator installation

seconded- both St Johns folk who do our scout leader training and also the chap at the FA at work course

both described it as a more of a stop it fluttering and reset to a steady beat, rather than an actual start.

The defib shock energy  is 150-300  joules so well over the 10 joule absolute max for non lethal electric fences and the 1 joule action limit we have at work for deciding if things need bleed resistors or not.

Hence it is very important not to be holding the patient during the zap- the modern machines actually say  something to the effect of 'stand clear' prior to it.

Mike

mapj1 said:

The defib shock energy  is 150-300  joules so well over the 10 joule absolute max for non lethal electric fences and the 1 joule action limit we have at work for deciding if things need bleed resistors or not.

'Tis a very strange thing that the cure for a shock which puts you into VF is another one.

The First Aid booklet we were given has a chart detailing the COVID-19 CPR adaptations, instead of rescue breaths (kiss of life) it advises some material such as a tea towel should be placed over the mouth and nose of the person who needs resuscitation, also their head should not be tipped back to clear the airway.

I’m no expert, but I would describe their chances of survival as virtually nonexistent.

yes - but it is a long shock, compared to the natural heartbeat period that is likely to cause fibrillation,

Note the curved nature  in the boundary of zone 3 - temporary arrest, no VF correspond to fractions of a second - ths is no accident, a slow adult heartbeat from a fit human maybe 50bpm, is a touch over 1 second period,  while a fast one of perhaps 150bpm - running very hard, would be 1/3 second.

The longer the shock duration the greater the fraction of the population would be at risk from it - so there is a general statement that longer shocks or higher current ones are the more dangerous.

The Defib zap in contrast is a short duration shock,  of high current can be 10-20A peak, but lasting for a few milliseconds at most. Actually most modern machines deliver bursts of shorter 'biphasic' pulses, i.e. pulses that alternate in polarity. With voltage peaks in the hundreds to 1kV range.

Mike

Just as an aside, the inventor of the portable defibrillator was professor Frank Pantridge, a cardiologist at the Royal Victoria Hospital Belfast. He was born and lived much of his life in Hillsborough, very close to my own home. He was an enigmatic character. I often seen him on his own huddled in the corner of the bar in local hotel. Unfortunately, that seemed to be a feature of his twilight days. Who knows why, perhaps because of his horrific experiences at the hands of his captors in a Japanese prisoner of war camp. His book is well worth a read.

I love Reading everyone’s answers, it’s a good mix of sound advice and good humour with a nice splatter of side topic science. Thanks for everyone’s input.
With regards to CPR I’m just glad that they don’t advise rescue breaths anymore, I never fancied getting lip to lip with the old tramp on the pavement, luckily research indicates it’s best to just keep pumping down on that heart as best you can! I was once told during a 999 call that someone who needs CPR is already dead and you can’t kill them twice so don’t worry about doing it wrong, just do it.

I’m just glad that they don’t advise rescue breaths anymore, I never fancied getting lip to lip with the old tramp on the pavement

The last time I did my first aid course (a few years ago now) the "rescue" breaths - i.e.the first two attempts before starting chest compressions had been dropped, but the breaths between each batch of chest compressions remained. I think the idea was that if the patient had collapsed because of heart problems (most likely with adults that suddenly collapse) then were was likely to be some oxygen in the blood still, so pumping it around was the first priority - but where the air supply had failed first (e.g. choking or drowning - more likely with children) then the first priority was to try and get oxygen into their system - so rescue breaths first still. In any event oxygen in the body will be being used up - so breaths still needed after each batch of chest compressions (30 now I think rather than the traditional 'nelly the elephant' 15). I think "no breaths at all" is only advised where the person giving aid hasn't been trained to perform CPR properly and is unlikely to be able to do everything else that's needed - clearing airways and so on or it's impossible to get a seal on the mouth (major trauma to the patient's face etc.)  Even will full CPR with breaths the patient's chances are pretty slim - without breaths it can only be worse.

   - Andy.