Article posted on December 6, 2023

Obstacles that can interfere with AED use

While AEDs are designed to be user-friendly, they do have some limitations. Much like any technology, certain conditions can limit an AEDs ability to function properly and assist the patient as intended. Make sure you’re familiar with the circumstances below, and how to avoid them interfering with your use of an AED.

Chest Hair

The AEDs adhesive gel pads need to stick to the patient’s chest to transmit the shock. If there is too much hair in the way, the pads may stick to the hair rather than the patient’s skin. If this happens, the AED may not be able to read the patient’s heart rhythm due to limited contact with the skin, or the shock can be delivered improperly.


If you notice a patient’s chest is hairy prior to applying the pads, immediately shave the chest. AEDs should come with a small kit, about the size of a pencil case, which includes a razor. It is not advisable to use the pads as a method of hair removal, by placing them on the chest and ripping them off. You would require a back-up set of pads to be plugged into the device at this point, but in many instances, and AED will only contain one set of pads that may have just been wasted. It’s better to shave the chest prior to pad placement and remember that only the area where the pads are going to stick to needs to be shaved.



While it is common knowledge that water and electricity are not compatible, have you considered the ways it can impact AED use? If a patient’s chest is wet, due to sweat, swimming, rain, or bodily fluids such a vomit, it will have to be dried off. The moisture can limit the pads’ ability to stick to the patient’s chest. AEDs should come with a small kit, about the size of a pencil case, which includes a disposable towel for drying off a patient’s chest. Remember to wear protective gloves, and make sure the chest is fully dry prior to placing AED pads.



Any clothing needs to be removed from the patient’s chest and abdominal area. This includes undergarments as well; the patient’s chest needs to be fully bare. The removal process needs to be quick and efficient, in order to begin using the AED and performing CPR as soon as possible. Remove the clothing by any means necessary, ideally cutting it away. AEDs should have a pair of scissors stored with the device, either in a small supply kit that is attached, or in a pocket within the AED case.


Cold weather

Some AEDs can be stored in cold temperatures for a limited period of time, but they are generally not designed to work in temperatures below 0. If you are outside when a cardiac arrest happens, you can still use the AED. Have extra vigilance, as this environment can be a dangerous one to be in. As the AED can encounter issues such as battery drainage due to the cold, ensure that it is stored in a warm environment.


Improper maintenance

AEDs need to be inspected on a semi-regular basis to ensure they are ready for use. This includes verifying that the status indicator (which is usually a flashing light) is green, ensuring the pads are plugged in and remain sealed in their package. This also requires verifying the expiration dates of the pads and batteries and replacing them as needed. If rescuers attempt to use an AED, only to find the pads are unplugged, or the pad package opened resulting in the pads being dried out, or the battery is expired and drained, this may cause delays or even the inability to use the AED. It’s imperative that the AED stays in standby, ready-to-use status at all times.


Improper pad placement

To best deliver a shock, the pads need as much surface contact as possible. When placing the pads on a patient’s chest, ensure you press hard and there are no edges lifting away from the patient’s skin. The pads have pictures on them which show where on the body they need to be placed. If these instructions are not followed exactly, the pads may be too far or too close together to deliver a shock properly. Make sure to follow the AED instructions exactly.


Presence of flammable gases

While most people will not encounter these on a regular basis, AEDs may be considered dangerous to use in the presence of flammable gasses such as specially oxygenated environments, such as high oxygen rooms. These devices are safe to use on a patient wearing an oxygen mask, that should not be considered a deterrent in AED use.


Using child pads

For a patient under the age of 8, or less than 55 lbs, child pads should be used if available. In some types of AEDs, there is no need for child pads, and a ‘child mode’ button can be pressed, or a child key inserted into the device. The child pads or child mode will reconfigure the device to follow pediatric algorithms, and regulate the shock delivered to accommodate a child. The pad placement will differ from the standard adult pad placement, so be sure to look closely at the pictures on the pads and follow instructions from the device. As adult pads should always be plugged into the device, these should be unplugged, and the child pads plugged in as needed. If no child pads or child mode is available on the AED, treatment should not be delayed, and the rescuers should consider using the adult pads for the child.


Medicine patches

If the patient has a medicine patch, which is a small sticky square designed to slowly release medication into the system through skin contact, this may need to be removed if it’s in the way of the pads. Remember to wear protective gloves when removing medicine patches.


Patient has an internal defibrillator

For a patient with an ICD (Implantable Cardioverter-Defibrillator), and AED can still be utilized. The implanted device will be identifiable by an elevated square or rectangular implant in the patient’s chest. Ensure the AED pads are not placed directly over top of the visible implant, and otherwise continue to use the AED as indicated.


Not following AED instructions

A rescuer needs to stop touching the patient when a shock is delivered. Listen to the AED instructions, and briefly pause CPR when the AED indicates. In some instances, CPR will need to be paused for the AED to analyze the patient’s heart rhythm, while other AEDs can analyze while CPR is in progress. The AED will always deliver instructions for when it is or is not safe to touch the patient. Make sure you listen to the device and follow instructions.


There are two types of AEDs, either automatic or semi-automatic. Automatic AEDs have no button to push and will automatically deliver a shock after warning rescuers that it’s about to do so. In semi-automatic models, the device will have a flashing button that directs bystanders to press the button and deliver a shock to the patient. This method relies on the rescuer, so take a moment to be sure everyone is clear and not touching the patient, then press the button to deliver the shock. Immediately resume CPR after the shock has been delivered.


For best practice, always follow manufacturer recommendations for storage and maintenance of your device. The AED will have loud voice prompts that instruct rescuers through the appropriate steps in the event of a cardiac arrest. Make sure to listen carefully and follow the instructions from the device. Consult your manufacturers website, and the AED user manual to find out more.

Last Updated: Wednesday, December 06, 2023

Calgary, Alberta, Canada