Shockingly Different

Heather Darata

Heather Darata


The emergency line rings, and you answer the phone. When you ask, “Tell me exactly what happened,” the caller says the patient is unconscious and not breathing. This call starts to sound like emergencies you’ve handled before.

But then the caller tells you her father is wearing an external defibrillator while waiting for a heart operation. You freeze while trying to figure out how to handle the situation. What is an external defibrillator? Where do you go from here? Are there special instructions in the protocol for this type of situation?

Grandfather and grandchild walking on a nature path. The grandfather is wearing an external defibrillator (WCD).
(Zoll Cardiac Diagnostics)

The short answer is no, there aren’t specifically scripted instructions in the protocol for a patient with a wearable defibrillator because the situation is too dynamic, said Brett Patterson, IAED™ Medical Council of Standards Chair and Academics & Standards Associate. It is simply not feasible to script out the steps for a situation where someone is unconscious and not breathing while wearing an external defibrillator. In this situation, the defibrillation device guides the steps taken. Before we get into how to handle a call like this, let’s look at wearable defibrillators to understand their design and function.

Wearable cardioverter defibrillator (WCD)

While an implantable cardioverter defibrillator (ICD) is under your skin and quiet,1 an external defibrillator is worn against the skin and can send out alarms. It might also tell you what it’s doing as it’s doing it. Reasons for patients using an external defibrillator include waiting for a diagnosis or treatment plan from a doctor, waiting for a heart operation, choosing not to have an ICD surgically implanted, or a patient being unable to have surgery because of age or other factors.

One common model of these devices, the LifeVest WCD, is worn by tens of thousands of patients throughout the world to protect against sudden cardiac arrest without bystander/outside assistance.2 The external defibrillator system has a garment, monitor, electrode belt, holster, two battery packs, battery charger, and a modem.3 The external defibrillator is designed to be worn around the waist or from a shoulder strap.


There are three levels of alarms—green, yellow, and red—to indicate what the machine is doing. A gong alarm (single tone) for the green level means that the device might be alerting the patient to follow instructions on the screen display. The machine may audibly say “Contact physician” or “Treatment has been given, call your doctor.”4

A siren alarm (two tone) for the yellow level means that the LifeVest cannot detect ECG or the device has delivered the maximum number of treatments. The machine will audibly say “If the patient is not responsive, call for help, perform CPR” or “Device disabled, call ambulance.”

The highest level of alarm (red level) uses a siren alarm (two tone) like the yellow alarm. However, this level has a loud alarm that progressively reaches 100 decibels and indicates that the device has detected a ventricular arrythmia and is preparing to treat the patient. A shock will likely be delivered at this point. If the alarm is triggered but the patient is conscious, only the patient should use the response buttons on the LifeVest. The device will say “Press response buttons to delay treatment,” “Electrical shock possible, do not touch patient,” or “Bystanders do not interfere.”


When the wearable defibrillator detects a heart arrythmia and the machine decides a shock is needed, it sends out conductive gel through therapy pads before delivering the treatment shock. The device does all this without bystander intervention and within one minute from the time of detection to defibrillation.5

When a shock successfully takes care of the heart arrythmia, it resets so a new treatment sequence can take place if another arrythmia is detected. The wearable defibrillator offers up to five shocks per event. The event recorder stores 75 minutes of ECG data at a minimum, which can be reviewed by health care providers to look at treatments, patient compliance, ECG records, and Life Vest system performance.

It is important to note that the data is not reviewed in real time, and the LifeVest doesn’t take care of notifying emergency responders if treatment has been delivered.6


As mentioned previously, bystander CPR can be performed on someone wearing this external defibrillator except when the device says any of these three things: “Press the response buttons,” “Electrical shock possible, do not touch patient,” or “Bystanders do not interfere.”7

The current method for administering CPR in conjunction with a defibrillator is for the bystander to remove his or her hands from the patient (“clear”) when the patient is about to be shocked as a safety measure for the bystander. But Patterson questions whether a defibrillator shock has enough voltage to harm bystanders or emergency personnel performing CPR on the patient. He is not alone in this line of thinking, and other health professionals are questioning whether this practice may be eliminated in the future.

Consider the following articles with some preliminary research on the potential risks/benefits of hands-on defibrillation:

The potential benefit of keeping hands on chest while a defibrillator is administering a shock to the patient is to prevent interruptions in CPR each time hands are removed from the patient’s chest. Another reason for examining this method is to alleviate the bystander’s fear of being shocked while performing CPR, which may lead them to withhold care. Patterson stresses that providing compressions is essential for someone experiencing ventricular tachycardia (VT)—dangerously fast heartbeat—or ventricular fibrillation (VF)—chaotic heartbeat that prevents the heart from getting enough blood to the body.8 This is where you as an EMD come in.

Now what?

A call to 911 is a request for help, and callers reporting these defibrillator-related emergencies are looking to you to guide them through the uncertainty of a life-threatening situation. Let’s talk about how you can navigate the Medical Priority Dispatch System™ (MPDS®) to provide callers with the reassurance and instructions they need.

In most cases, the caller will likely volunteer key information that the patient is wearing an external defibrillator after being asked Case Entry Question 3 “Okay, tell me exactly what happened.” However, if the caller doesn’t know what device the patient is wearing or what it is doing, your knowledge will help decipher what needs to happen as you follow the device’s prompts and navigate the protocol to guide the call. External defibrillators are mentioned in Protocol 9: Cardiac or Respiratory Arrest/Death.

If you discover that the patient is unconscious and not breathing, you will first initiate a 9-E-1 response. After dispatch, you will provide PDI-a “(ECHO) I’m sending the paramedics (ambulance) to help you now. Stay on the line.”

In the case of a Suspected MEDICAL Arrest, Dispatch Life Support will link you to the appropriate PAI pathway—Protocol A, B, or C (Airway/Arrest/Choking (Unconscious)), depending on the patient’s age. Though this situation may feel different because of the wearable defibrillator, according to Axiom 5 on Protocol 9, “CPR is appropriate when advised by the machine or when no warning is audible.”

There are only two reasons an EMD’s instructions may differ from the protocol’s designated pathway: if there is a caregiver directive advising against CPR (Do Not Resuscitate order) or if the wearable defibrillator tells the caller not to do CPR. Remember, “You don’t get any deader than dead.”

As an EMD, your knowledge of external defibrillators combined with the guidance of the protocol can help confidently guide callers and give patients the best possible shot at recovery. You’ve got this.


  1. Mayo Clinic Staff. “Implantable cardioverter-defibrillators (ICDs).” Mayo Clinic. 2019; Nov. 13. https://www.mayoclinic.org/tests-procedures/implantable-cardioverter-defibrillators/about/pac-20384692 (accessed Jan. 26, 2021).
  2. “LifeVest Patient FAQs.” ZOLL. https://lifevest.zoll.com/patients/patient-faqs (accessed Jan. 26, 2021).
  3. “System Technical Specifications.” ZOLL.
  4. “LifeVest Wearable Defibrillator Emergency Patient Management.” ZOLL. 2011.
  5. See note 3.
  6. See note 2.
  7. See note 4.
  8. See note 1.