Professional and lay responders use AEDs to resuscitate individuals in cardiac arrest. Cardiac arrest is the sudden, abrupt loss of heart function. Cardiac arrest is a leading cause of death in the US and many countries. Sudden death occurs within minutes. Most cardiac arrest occurrences that lead to sudden death happen when the electrical impulses of the heart become rapid (Ventricular Tachycardia-VT without "perfusion" or flow of blood) or chaotic (Ventricular Fibrillation-VF) or both.
The most common cause of sudden cardiac arrest is VF. The only effective treatment for VF is a shock from a defibrillator.
The AED uses voice prompts to guide the user thru the process. The user places the AED pads on the patient's body as directed by pictures on the pads. The AED then uses a rhythm analysis system to analyze the patient's heart. If a shock-able rhythm is present (VT or VF), the AED will advise a shock.
The following is the correct sequence of events when using an AED:
Imagine a person has just collapsed.
(The person, for the purposes of this demonstration is assumed to be in cardiac arrest-unresponsive, no pulse and not breathing or gasping for a breath intermittently.)
We have called 9-1-1 and grabbed the AED.
1. Place the AED next to the patent's head.
2. Unzip the AED case and turn on the AED. This is done by pressing the green button or pulling the green handle (marked PULL) and lifting the protective cover up and away from the machine.
3. The AED now automatically initiates voice prompts.
VOICE PROMPTS SHOWN IN RED
"Begin by removing all clothing from the patient's chest"
"Cut clothing if needed"
"When patient's chest is bare, remove protective cover and take out white adhesive pads"
"Look Carefully at the pictures on the white adhesive pads"
-----NOTE: The white adhesive pads have pictures on them showing you where to place the pads on the patient.
"Peel one pad from the yellow plastic liner"
-----NOTE: We have placed both pads on the patient.
-----NOTE: The AED is now analyzing the patient's heart rhythm.
"No one should touch the patient"
-----NOTE: While the AED is analyzing the patient's heart, make sure yourself and everyone else is clear of the patient.
-----NOTE: The unit has determined that the patient needs a shock.
"Stay clear of patient"
"Press the flashing orange button now"
-----NOTE: The orange button will continue to flash and the voice prompt will continually prompt you until you press the button.
"Deliver shock now"
-----NOTE: The voice prompts will continue to motivate you to press the button.
-----NOTE: You have pressed the flashing orange button.
"Be sure emergency medical services have been called. It is safe to touch the patient"
-----NOTE: Leave the pads on the patient until EMS personnel arrive.
-----NOTE: If patient is still unconscious, begin CPR. Leave the pads on the patient.
"For help with CPR, press the flashing blue button"
"Place the heel of one hand in the center of the chest between the nipples"
"Place your other hand on top of the first"
"Push the chest down firmly 2 inches"
-----NOTE: When the adult pads cartridge is in the machine, the AED will use adult CPR voice prompts. When the pediatric cartridge is placed in the machine, the AED adjusts CPR voice prompts to pediatric guidelines.
"Keep time with the beat"
-----NOTE: The AED now plays a repeating noise that is the correct timing of CPR compressions. The AED plays 30 compression noises.
"Pinch nose, tilt head and give two full breaths"
"Continue with compressions"
-----NOTE: the same repeating noise for the next 30 compressions is given.
The unit will continue giving CPR guidelines. After the recommended time, the unit will then analyze the heart again and prompt you to give another shock if necessary. The AED used in this sequence is compliant with the current guidelines from the American Heart Association (AHA) at the time of this writing.
The unit used in this demonstration has the capability of adjusting the voice prompts given based on your actions. The unit used in this demonstration has SMART Pads which detect when you pull the green handle. The SMART Pads detect when you place one pad on the patient, then the other pad. If you do not place the other pad on the patient, the unit will prompt you to place the other pad on the patient until you do so. If you do not press the orange button when prompted, the unit will continue to prompt you until the button is pressed.
The unit used in the demonstration also has "artifact detection". When the unit is analyzing the patient's heart, you need to clear the patient. If someone is touching the patient at this point, the unit will detect this. The AED will give you a voice prompt that artifact has been detected and give you a chance to clear the patient then resume analyzing.
The unit used in the demonstration is very safe to use. The unit determines if the patient needs a shock or not. If no shock is needed, the unit is not capable of delivering a shock. If a person has fainted and the rescuer can not detect the pulse or breathing of the patient however the patient has a perfusing rhythm, the unit should be applied, however in this case the AED would determine the patient has a perfusing rhythm and will give the voice prompt "no shock advised". Even if the orange button is pressed, the AED used in the demonstration is not capable of delivering a shock in this instance. The unit used in this demonstration is called a semi-automatic AED. That means that the unit prompts the user to push a button to deliver the shock. "Fully-Automatic" AED units do not have this safety feature of prompting the user to press a button to deliver a shock. Attaching a fully-automatic AED to someone with a perfusing rhythm is not recommended. In areas where the AED might fall into the hands of mischievous individuals, fully-automatic AEDs are not recommended.
The unit used in the demonstration performs daily automatic self-tests of the internal circuitry, waveform delivery system, pads cartridge and battery capacity. When all the systems pass the daily tests, the unit's status indicator blinks green indicating the unit is "Ready for Use". An audible chirp indicates the unit needs maintenance. If the unit needs maintenance, most often the blue button will be flashing. When the blue button is pressed, the unit will indicate a low battery or some other issue.
The battery in the unit used for this discussion is a long-life lithium manganese dioxide battery that is warranted for 4 years. The battery does not need to be charged and the "ready for use" indicator is visible thru the unit's carrying case.
The unit used in the demonstration delivers a shock in less than 10 seconds at the end of a CPR cycle. The manufacturer calls this "Quick Shock".
The unit used in the demonstration delivers 150 Joules of energy in the case of a person weighing 55 lbs. or more. The unit uses 50 Joules for pediatric applications (Under 55 lbs.) (Which is set based on the type of SMART Pads cartridge installed.)
You should not be afraid to use an AED. Most states have "Good Samaritan laws" designed to protect well meaning bystanders during a perceived medical emergency.
Your state's laws should be examined before purchasing an AED.
The preceding explanation of an AED demonstration used the Philips HeartStart OnSite Automatic External Defibrillator (AED) Model M5066A. The Philips OnSite AED is a semi-automatic AED.
NOTE: This is a simplistic overview of how an AED operates. Users are encouraged to obtain the appropriate training in the use of an AED which includes CPR/AED certification from a recognized agency. Defibrillators are just one aspect of a well planned resuscitation program. Some states require medical oversight of an AED Program by a qualified Medical Director.
For more information please visit http://www.TeamEmergencyResponse.com/links.html
Product Specifications of the AED discussed are taken from Philips Healthcare literature. The manufacturer states the OnSite is "Unsurpassed in ease of use in 3 different published studies".
Views expressed are the opinions of Team Surgical, A Division of International Surgical, Inc.
Healthcare facts are from the following sources:
- The American Heart Association
- The American Red Cross
- Andre et al, Prehospital Emergency Care 2004; 8:284-291