This is probably the SCARIEST capacitor I've ever removed from a circuit. It's entire purpose in life is to stop people's hearts - but for a good reason.
The days of defibrillators being big scary hospital machines are long in the past. These days they are a very affordable piece of first aid equipment that should be in every public place and workshop.
The science behind modern units is stunning. When the pads are applied to the chest of someone in a suspected state of ventricular fibrillation (heart out of sync), the unit will monitor the heart's electrical signal and decide if it is good or if there is an issue that needs a resync pulse. If the pulse is needed it calculates the best timing and strength of pulse to achieve the highest success in bringing the heart back into sync.
During the whole event the unit talks you through every part of the process, and even applying the pads is made easy by the clear instructions printed on them.
It's important to note that the unit will not "shock" a heart in what it regards as a safe condition. It only applies a resynchronisation pulse if it detects that the heart is out of sync and that death is imminent. Sadly it can't do anything if the heart is flatlining, as that is a tough task even for trained paramedics, that may involve injection of drugs to directly stimulate the heart.
It is MASSIVELY important that a defibrillator is applied as soon as possible in the event of an incident occurring, as the chance of survival reduces dramatically with time.
If in any doubt about whether there is a heart issue then apply the unit, as it can help make a medical diagnosis. Paramedics will often keep the original electrodes in place with an adaptor to suit their own equipment.
The cost of a replacement set of electrode pads is insignificant compared to the loss of a life.
Although originally designed to save the lives of American utility workers (who usually work on live high voltage equipment), it's unfortunate that many do not have these in their utility trucks yet, despite the fact that their cost is insignificant compared to many of the other specialist tools they use.
The Zoll units (not a sponsor) are one of the most affordable available, as they use standard batteries and the pads have much longer storage life (up to five years) than many other brands.
Most modern defibrillator units keep a record of every event they are involved in for future refinement of software and functionality. I do recommend sharing the logged data with the manufacturer to allow them to improve the functionality of their units.
The circuitry in these units is very impressive, since it can use the same pads to monitor very low voltage biological signals and also apply high voltage and high current pulses.
It appears the little square device in the chest compression box is an accelerometer. It must be measuring the force as physical displacement.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators
The days of defibrillators being big scary hospital machines are long in the past. These days they are a very affordable piece of first aid equipment that should be in every public place and workshop.
The science behind modern units is stunning. When the pads are applied to the chest of someone in a suspected state of ventricular fibrillation (heart out of sync), the unit will monitor the heart's electrical signal and decide if it is good or if there is an issue that needs a resync pulse. If the pulse is needed it calculates the best timing and strength of pulse to achieve the highest success in bringing the heart back into sync.
During the whole event the unit talks you through every part of the process, and even applying the pads is made easy by the clear instructions printed on them.
It's important to note that the unit will not "shock" a heart in what it regards as a safe condition. It only applies a resynchronisation pulse if it detects that the heart is out of sync and that death is imminent. Sadly it can't do anything if the heart is flatlining, as that is a tough task even for trained paramedics, that may involve injection of drugs to directly stimulate the heart.
It is MASSIVELY important that a defibrillator is applied as soon as possible in the event of an incident occurring, as the chance of survival reduces dramatically with time.
If in any doubt about whether there is a heart issue then apply the unit, as it can help make a medical diagnosis. Paramedics will often keep the original electrodes in place with an adaptor to suit their own equipment.
The cost of a replacement set of electrode pads is insignificant compared to the loss of a life.
Although originally designed to save the lives of American utility workers (who usually work on live high voltage equipment), it's unfortunate that many do not have these in their utility trucks yet, despite the fact that their cost is insignificant compared to many of the other specialist tools they use.
The Zoll units (not a sponsor) are one of the most affordable available, as they use standard batteries and the pads have much longer storage life (up to five years) than many other brands.
Most modern defibrillator units keep a record of every event they are involved in for future refinement of software and functionality. I do recommend sharing the logged data with the manufacturer to allow them to improve the functionality of their units.
The circuitry in these units is very impressive, since it can use the same pads to monitor very low voltage biological signals and also apply high voltage and high current pulses.
It appears the little square device in the chest compression box is an accelerometer. It must be measuring the force as physical displacement.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators
Doctor Mike has entered the chat!
I built the older generation units back in the day. Also Physio Control units. They were the EMS versions. The testing area was a tad scary at times, considering we had a grounded and conductive floor.
Getting stuff like batteries and solvents to the Isle of Man is often a bit fraught – you'd think we were some third world country!
Good video – as always.
Greetings from Sunny Bride.
🙂
That is a fascinating look at the inside of a device I've used quite a few times ( thankfully on the giving end of it).
I may be able to give a few details on the design of the board and electrode pads (I'm a doctor with an interest in tinkering with stuff, not an engineer, so please excuse my lack of electronics technical knowledge).
The divider section is there to control the power output to the pads, as the device will recognize different shockable rhythms, which can be resynchronized at different outputs, not just ventricular fibrillation. The necessary energy to convert said rhythm can vary from 25 joules for some atrial originated rhythms to 200 joules for ventricular fibrillation ( or 360 joules for the older monophasic devices).
That pressure sensor does not only measure the strength of the chest compressions, it will most likely prevent the device from analyzing the rhythm during CPR, as the chest compressions can sometimes mimic a true heart rate, and will prevent the device from discharging if the patient is not clear to prevent shocking the rescuer with potentially disastrous consequences.
The analysis circuitry has to be isolated to allow the heart activity to be read since the average voltage of the heart activity is usually 1 to 2 millivolts at the surface of the chest, and I'll guess there is some sophisticated filtering going on to remove interference from muscle activity, other devices and such.
The pad design is such that the right shoulder pad is the negative electrode and the left lower pad is the positive one and goes over the typical position of the apex of the heart. This is because the direction of current flow in the heart muscle goes from right to left and from the base to the apex, and shocking the heart in reverse polarity will invariably worsen the situation. Also, for rhythm analysis the device would need to know where it is looking at, and this electrode position is the one known as ECG lead II which is usually used for monitoring as it will sense the largest waveform and make recognition easier.
BTW, babies do explode rather frequently, that's why nappies exist😂.
I don't know if I would say that it's entire purpose in life is to stop people's hearts. Depending on how you look at it, one could say that it's entire purpose in life is to START people's hearts. (Ventricular Fibrillation versus Normal Sinus Rhythm)
The orange relay that you pointed to is too light duty to handle the currents of defibrillation which can be 8 to 10 A or more. The switching mechanism from capacitor to chest pads is usually done by a group of very high voltage IGBT and it is done in such a way to deliver a biphasic shock
I have the 123 battery in the smoke detector in my office.
William Kouwenhoven was American, but his surname appears to be Netherlandish or Flemish in origin. How you pronounce the surname thus depends on where the majority of your Dutch-speaking friends are from.
I worked for Heartstream in the 90s in Seattle Washington. We were the first to pioneer the AED and bring the first unit to market. I have a ton of the Icar caps that we used. We also used an H-bridge to deliver a dual-wave pattern which extensive research showed was way more effective. The calculations for the trans-thoracic impedance to calculate energy delivery was impressive.
I used to work at zoll in shipping. Packed those plus units into boxes daily!
As a biomed I will take your advice and start putting a "Not for use on lawyers" sticker on the housing.
CPR these days generally only needs chest compressions – the medical industry has found that the whole mouth to mouth thing is not only unnecessary, but is often the major holdback from the general public from learning and performing CPR. So modern CPR classes only teach the chest compressions making it be known that you don't need to do mouth to mouth to save someone's life. And CR123 batteries are extremely common – they're used in cameras and often have a shelf life of decades making them good for standby operation like these devices. Often they will time expire with the unit (the units are generally only good for 10 years or so before you need to replace them, which is ideal as that's generally how long the battery lasts)