What to check on a AED (Defibrillator).
An automated external defibrillator is built for one specific emergency: sudden cardiac arrest caused by a shockable rhythm such as ventricular fibrillation. It analyses the casualty's heart rhythm through adhesive pads and only permits a shock if the rhythm is one a shock can actually correct - it will not shock a normal rhythm, asystole, or most other conditions crew might mistake for cardiac arrest. That built-in decision-making is what makes it usable by crew with basic first-aid training rather than a doctor, and it is why an AED is…
What an AED is for and what it is not
An automated external defibrillator is built for one specific emergency: sudden cardiac arrest caused by a shockable rhythm such as ventricular fibrillation. It analyses the casualty's heart rhythm through adhesive pads and only permits a shock if the rhythm is one a shock can actually correct - it will not shock a normal rhythm, asystole, or most other conditions crew might mistake for cardiac arrest. That built-in decision-making is what makes it usable by crew with basic first-aid training rather than a doctor, and it is why an AED is a companion to, not a replacement for, CPR - the device gives voice-prompted instructions to guide compressions between rhythm checks.
Main components
Analysis and shock delivery unit
Contains the rhythm analysis algorithm, the battery, and the capacitor that delivers the defibrillation shock through the pads once the algorithm confirms a shockable rhythm.
Adhesive electrode pads
Single-use, pre-gelled pads that both sense cardiac rhythm and deliver the shock; they have a shelf life and must be replaced before expiry even if never used.
Voice prompt and visual guidance
Step-by-step audible instructions guide a crew member with no medical background through pad placement, rhythm analysis, clearing the casualty before a shock, and CPR compression timing.
Battery
A long-life, non-rechargeable battery on most models, rated for a shelf life measured in years but requiring a status check as part of routine inspection since a flat battery is discovered only when the unit fails to power on.
Selection and sizing
There is no capacity sizing in the usual equipment sense - the relevant factors are:
- Number of units and location on board, driven by response time to any accommodation or work area rather than vessel size alone
- Pad and battery shelf life against the vessel's typical time between port calls, so replacements can be planned rather than discovered expired
- Ruggedness rating for storage in a workshop or deck locker versus a bridge or accommodation cabinet
- Compatibility of the training the crew already holds with the specific model's voice prompts and pad system
Regulations and class
Carriage requirements for an AED depend on flag state medical equipment scales and, for passenger ships, on passenger-carrying regulations that increasingly expect one; SOLAS itself does not universally mandate an AED on cargo ships, so the applicable flag state medical scale and the ship's trading certificate are the references to check, not a single global rule. Where fitted, it typically falls under the same periodic medical locker inspection regime as the rest of the medicine chest.
Typical faults
| Fault | Cause | Consequence |
|---|---|---|
| Expired pads | Shelf-life date missed during routine checks | Reduced pad adhesive performance or unit refusing to operate until pads are replaced |
| Flat battery | Battery reaching end of shelf life unnoticed between drills | Unit fails to power on in an actual emergency |
| Damaged pad packaging | Moisture ingress into a punctured or poorly sealed pad pouch | Dried-out gel, poor skin contact, unreliable rhythm reading |
| Crew unfamiliarity | No refresher drill since initial familiarisation | Delay in application during the response, defeating the time-critical purpose of the device |
What to look for in a supplier
- Clear expiry dates on pads and batteries visible without opening sealed packaging
- Availability of replacement pad and battery kits without needing a whole new unit
- A model with voice prompts in a language the crew actually understands
- Documentation suitable for the flag state's medical equipment inspection record
Check pad and battery expiry dates at every medical locker inspection, not just when the AED is used - it is the one piece of medical equipment where a five-minute check now prevents total failure in the one moment it matters.