A defibrillator stores electrical energy and, when directed by its control system and user workflow, delivers a controlled pulse through compatible electrodes. Many clinical units also provide ECG monitoring, synchronized cardioversion, external pacing, recording, data transfer, and automated self-tests. AEDs automate rhythm analysis and user prompting for a narrower emergency workflow.

Key takeaways

  • The charging supply, energy-storage capacitor, switching, output network, and electrodes form the therapeutic energy path.
  • ECG acquisition and rhythm analysis are measurement functions distinct from energy delivery.
  • Batteries, pads, cables, internal self-tests, calibration, and accessories are critical to readiness.

01

Charging and energy delivery

A high-voltage charging circuit raises battery or line-derived power and stores energy in a capacitor. Control electronics verify requested energy and readiness. A switching network shapes and directs the waveform to paddles or adhesive electrodes. Internal discharge and protection circuits manage unused energy and fault conditions.

02

ECG, synchronization, and pacing

The ECG front end acquires low-level cardiac signals through leads or therapy electrodes with isolation and protection from the defibrillation pulse. Synchronized cardioversion depends on reliable R-wave detection and timing. External pacing delivers controlled current pulses while sensing and display functions provide workflow feedback.

03

AED analysis and user interface

An AED acquires the rhythm, checks signal quality, applies its validated shock-advisory algorithm, charges when appropriate, and guides the rescuer through prompts and indicators. Pads, connector, battery condition, environmental limits, software, and self-test status are all part of device readiness.

04

Maintenance and identification

Monitor-defibrillators may include printers, record storage, wireless communication, SpO₂, NIBP, capnography, or other modules. Record the exact family, software, therapy cable, pad or paddle type, battery, installed options, and accessories. Return-to-service work may require analyzers that verify delivered energy, waveform, pacing, synchronization, ECG, alarms, battery, and electrical safety.

Safety boundary

Defibrillators generate hazardous high voltage and therapeutic energy. Internal capacitors can retain charge. Only qualified personnel using approved analyzers and discharge procedures should open, test, calibrate, or return these devices to service.

Related terminology

Terms with a published definition link directly to the glossary.

defibrillatorAEDcardioversionexternal pacingECGenergy storage

Authoritative starting points

These external sources support additional study; always use the version applicable to your equipment and jurisdiction.

FDA: Automated External Defibrillators ↗