Editing Defibrillation (section)

== Interface ==
{{unreferenced section|date=August 2014}}

The connection between the defibrillator and the patient consists of a pair of electrodes, each provided with [[Electrical conductor|electrically conductive]] gel in order to ensure a good connection and to minimize [[electrical resistance]], also called chest impedance (despite the DC discharge) which would burn the patient.  Gel may be either wet (similar in consistency to [[surgical lubricant]]) or solid (similar to [[gummi candy]]).  Solid-gel is more convenient, because there is no need to clean the used gel off the person's skin after defibrillation. However, the use of solid-gel presents a higher risk of burns during defibrillation, since wet-gel electrodes more evenly conduct electricity into the body.  Paddle electrodes, which were the first type developed, come without gel, and must have the gel applied in a separate step.  Self-adhesive electrodes come prefitted with gel.  There is a general division of opinion over which type of electrode is superior in hospital settings; the American Heart Association favors neither, and all modern manual defibrillators used in hospitals allow for swift switching between self-adhesive pads and traditional paddles.  Each type of electrode has its merits and demerits.

=== Paddle electrodes ===
{{ double image|total_with=400px
| image1   =
| caption1 = An automated external defibrillator: this model is a semi-automatic due to the presence of a shock button
| image2   =
| caption2 = The same AED with electrodes attached
}}

The most well-known type of electrode (widely depicted in films and television) is the traditional metal "hard" paddle with an insulated (usually plastic) handle. This type must be held in place on the patient's skin with approximately 25&nbsp;lbs (11.3&nbsp;kg) of force while a shock or a series of shocks is delivered. Paddles offer a few advantages over self-adhesive pads.  Many hospitals in the United States continue the use of paddles, with disposable gel pads attached in most cases, due to the inherent speed with which these electrodes can be placed and used. This is critical during cardiac arrest, as each second of [[perfusion|nonperfusion]] means tissue loss.  Modern paddles allow for monitoring ([[electrocardiography]]), though in hospital situations, separate monitoring leads are often already in place.

Paddles are reusable, being cleaned after use and stored for the next patient.  Gel is therefore not preapplied, and must be added before these paddles are used on the patient.  Paddles are generally only found on manual external units.

=== Self-adhesive electrodes ===
[[File:Philips self-adhesive electrodes of adefibrillator-9859.jpg|thumb|Self-adhesive electrodes of a defibrillator]]

Newer types of resuscitation electrodes are designed as an adhesive pad, which includes either solid or wet gel.  These are peeled off their backing and applied to the patient's chest when deemed necessary, much the same as any other sticker. The electrodes are then connected to a defibrillator, much as the paddles would be. If defibrillation is required, the machine is charged, and the shock is delivered, without any need to apply any additional gel or to retrieve and place any paddles.  Most adhesive electrodes are designed to be used not only for defibrillation, but also for [[transcutaneous pacing]] and synchronized electrical [[cardioversion]].  These adhesive pads are found on most automated and semi-automated units and are replacing paddles entirely in non-hospital settings.  In hospital, for cases where cardiac arrest is likely to occur (but has not yet), self-adhesive pads may be placed prophylactically.

Pads also offer an advantage to the untrained user, and to medics working in the sub-optimal conditions of the field.  Pads do not require extra leads to be attached for monitoring, and they do not require any force to be applied as the shock is delivered.  Thus, adhesive electrodes minimize the risk of the operator coming into physical (and thus electrical) contact with the patient as the shock is delivered by allowing the operator to be up to several feet away.  (The risk of electrical shock to others remains unchanged, as does that of shock due to operator misuse.)  Self-adhesive electrodes are single-use only.  They may be used for multiple shocks in a single course of treatment, but are replaced if (or in case) the patient recovers then reenters cardiac arrest.

Special pads are used for children under the age of 8 or those under 55&nbsp;lbs. (22&nbsp;kg).<ref>{{cite web|date=2018-05-16|title=What is the Difference Between Adult and Pediatric Pads|url=https://www.aedbrands.com/blog/what-is-the-difference-between-adult-and-pediatric-pads/|access-date=2021-08-06|website=AED Brands|language=en-US}}</ref>

=== Placement ===
[[File:Defib electrode placement.png|thumb|upright|Anterior-apex placement of electrodes for defibrillation]]

Resuscitation electrodes are placed according to one of two schemes. The anterior-posterior scheme is the preferred scheme for long-term electrode placement. One electrode is placed over the left precordium (the lower part of the chest, in front of the heart). The other electrode is placed on the back, behind the heart in the region between the scapula. This placement is preferred because it is best for non-invasive pacing.

The anterior-apex scheme (anterior-lateral position) can be used when the anterior-posterior scheme is inconvenient or unnecessary. In this scheme, the anterior electrode is placed on the right, below the clavicle. The apex electrode is applied to the left side of the patient, just below and to the left of the pectoral muscle. This scheme works well for defibrillation and cardioversion, as well as for monitoring an ECG.

Researchers have created a software modeling system capable of mapping an individual's [[human thorax|chest]] and determining the best position for an external or internal cardiac defibrillator.<ref name="HR2008" />