Avionics and Defibrillators

[pilotwolf]

Having read the security thread about electrifying the cockpit door and the risk of damage to the avionics can anyone answer this?

Most airlines now carry medical defibrillators of some description for use onboard. Bearing in mind these will be delivering upto 360 Joules of energy,(assuming current resuscitation guidelines), which if I remeber rightly equates to around 4600V dc, what effect does this have on the avionics?

I seem to remember certain HEMS pilots being very unkeen to have a patient shocked whilst airborne but never really found out why. Although I have never had to shock anyone in the air I have defibrilated patients on aircraft on the stand.

[ 29 January 2002: Message edited by: pilotwolf ]</p>

[SkyMed]

Hello Pilotwolf

I work offshore as a Medic - travel and use of helicopters is routine for crew changes and essential on Medivac's. We are all aware of the safety aspects of helicopters and professionalism of the Pilots which we never take for granted.

If Defib has to be used in a helicopter - the pilot must be advised before a shock delivered. I have asked many other medics (and only a few Pilots)from their experiences but, like yourself, never get a conclusive answer.

In our scope offshore, the reality is not many workers thankfully have the need defib'd whilst in the chopper - it will either be utilised in the Sick Bay or on arrival onshore.

As a PPL myself, it would be interesting to know more on this subject - God forbid one day I may well find myself in this situation. Until then I will take my que from the Pilot in this respect.

I wonder if our American colleagues, namely Flight Paramedics or Flight Physician Assistants and their Pilots may enlighten us - PLEASE respond!

Kind regards

SkyMed

[Hand Solo]

I believe the defib has been used in flight numerous times on BA with no ill-effects on the aircraft. Not sure I'd let it near the flight deck though just in case!

[jbc2001]

Much larger voltages, currents and power is directed at the aircraft wiring whenever the HF is used. The shielding and grounding techniques used on aircraft effectively stop any problems - indeed the worry might be more that the HF induces unwanted waveforms into the defibrillator electrodes!

[Deaf]

Don't know much about defillibrators but would imagine that they work on DC/few Hz at most and the current essentially loops through the chest.

The key problem with EMC (ElectroMagnetic Compatibility) is usually coupling and this gets worse as the frequency increases. HF as previously mentioned can be a problem due to the power ivolved but generally problems occur when the wavelength is similar to the cavity/wire length.

The power pack to the defillibrator (presumably a switchmode at ~ few tens of KHz) could be a problem eg to an ADF but they would be well shielded, just think of the requirements for the hospital environment.

[pilotwolf]

A few further thoughts on this and some updated info.... .. .Assuming most defibrillators operating standards are similar and these figures could be applied to other models..... .. .360 Joules of energy delivered to a patient via chest paddles or self adhesive chest pads completes the electrical circuit of the defibrillator.. .. .But what if the patient is in contact with a part of the aircraft which isn't insulated? Dire warnings not to touch the patient during defibrillation are given during training. Surely some current could leak to earth?. .. .Assuming that the aircraft electrical systems are also connected -ve to earth would that not cause problems?. .. .As an idea of voltages and currents involved I have taken these figures from our operating manual for the machine we use.. .. .Ohms Law states Voltage = Current x Resistance or V=IxR. .. .With a patient skin resistance of 25Ohms the machine delivers 53.1A for approx 10 mSec which equals 1327.5Vdc.. .. .or,. .. .With a skin resistance of 100 Ohms the machine delivers 13.7A for 36.4 mSec which equals 1370Vdc.. .. .I appreciate that HF currents can be much higher than this,(I have several RF burns to confirm!), but the antenna is not connected to the -ve electrical system.. .. .Any further comments would be appreciated.. . . . <small>[ 07 March 2002, 14:06: Message edited by: pilotwolf ]</small>