ABC, ABCD and ABCDE rule in emergency medicine: what the rescuer must do

The “ABC rule” or simply “ABC” in medicine indicates a mnemonic technique that reminds rescuers in general (not only doctors) of the three essential and life-saving phases in the assessment and treatment of the patient, especially if unconscious, in the preliminary phases of Basic Life Support

The acronym ABC is in fact an acronym of three English terms:

  • airway: airway;
  • breathing: breath;
  • circulation: circulation.

The patency of the airway (i.e. the fact that the airway is free from obstructions that could prevent airflow), the presence of breath and the presence of blood circulation are in fact three vital components for the survival of the patient.

The ABC rule is especially useful for reminding the rescuer of the priorities in stabilising the patient

Thus, airway patency, presence of breath, and circulation must be checked and, if necessary, re-established in this precise order, otherwise subsequent manoeuvres will be less effective.

In simple terms, the rescuer providing first aid to a patient should:

  • First check that the airway is clear (particularly if the patient is unconscious);
  • Then check if the casualty is breathing;
  • then check for circulation, e.g. radial or carotid pulse.

The ‘classic’ formula of the ABC rule is aimed primarily at rescuers in general, i.e. those who are not medical staff.

The ABC formula, like the AVPU scale and the GAS manoeuvre, should be known by everyone and taught from primary school.

For professionals (doctors, nurses and paramedics), more complex formulas have been devised, called ABCD and ABCDE, which are more commonly used in healthcare by rescuers, nurses and doctors.

In some cases even more comprehensive formulae are used, such as ABCDEF or ABCDEFG or ABCDEFGH or ABCDEFGHI.

ABC is more ‘important’ than the extrication device KED

In the event of a road accident with an accident victim in the vehicle, the first thing to do is to check the airway, breathing and circulation, and only then can the accident victim be fitted with a neck brace and KED (unless the situation calls for rapid extraction, e.g. if there are no intense flames in the vehicle).

Before ABC: safety and state of consciousness

The first thing to do after ascertaining whether the victim is in a safe place in a medical emergency is to check the patient’s state of consciousness: if he/she is conscious, the risk of respiratory and cardiac arrest is averted.

To check whether the victim is conscious or not, simply approach him or her from the side where his or her gaze is directed; never call out to the person because if there is trauma to the cervical spine the sudden movement of the head could even be fatal.

If the victim responds it is advisable to introduce oneself and inquire about his/her state of health; if he/she reacts but is unable to speak, ask to shake hands with the rescuer. If there is no response, a painful stimulus should be applied to the victim, typically a pinch to the upper eyelid.

The victim may react by trying to escape the pain but remain in an almost asleep state, without responding or opening their eyes: in this case the person is unconscious but both breathing and heart activity are present.

To assess the state of consciousness, the AVPU scale can be used.

Before ABC: safety position

In the absence of any reaction, and therefore of unconsciousness, the patient’s body should be placed supine (belly up) on a rigid surface, preferably on the floor; the head and limbs should be aligned with the body.

To do this, it is often necessary to move the casualty and have him or her make various muscle movements, which should be done with caution, and only if vitally necessary, in the case of trauma or suspected trauma.

In some cases it is necessary to place the person in the lateral safety position.

Great care must be taken in handling the body in case of head, neck and spinal cord injuries: in case of injuries in these areas, moving the patient may only worsen the situation and potentially cause irreversible damage to the brain and/or spinal cord (e.g. total body paralysis if the injury is at cervical level).

In such cases, unless you know what you are doing, it is best to leave the casualty in the position in which they are (unless of course they are in a totally unsafe environment, such as a burning room).

The chest must be uncovered and any ties must be removed as they can obstruct the airway.

Clothing is often cut off with a pair of scissors (so-called Robin’s scissors) to save time.

The “A” of ABC: Airway patency in the unconscious patient

The greatest danger for an unconscious person is airway obstruction: the tongue itself, due to loss of tone in the muscles, can fall backwards and prevent breathing.

The first manoeuvre to be performed is a modest extension of the head: one hand is placed on the forehead and two fingers under the chin protuberance, bringing the head backwards by lifting the chin.

The extension manoeuvre takes the neck beyond its normal extension: the action, while not having to be performed violently, must be effective.

In case of suspected cervical trauma, the manoeuvre should be avoided like any other movement of the patient: in this case, in fact, it should only be performed if absolutely necessary (in the case of a patient in respiratory arrest, for example), and should only be partial, to avoid even very serious and irreversible damage to the spinal column and therefore to the spinal cord.

The rescuers and the emergency services use devices such as oro-pharyngeal cannulae or delicate manoeuvres such as subluxation of the jaw or intubation to keep the airways open.

The oral cavity should then be inspected using the ‘purse manoeuvre’ which is carried out by twisting the index finger and thumb together.

If objects are present that obstruct the airway (e.g. dentures), they should be removed by hand or with forceps, taking care not to push the foreign body further in.

If water or other liquid is present, as in the case of drowning, emesis or bleeding, the victim’s head should be tilted to the side to allow the liquid to escape.

If trauma is suspected, the whole body should be rotated with the help of several people to keep the column in axis.

Useful tools for wiping up fluids may be tissues or wipes, or better still, a portable suction unit.

“A” Airway patency in the conscious patient

If the patient is conscious, signs of airway obstruction may be asymmetrical chest movements, breathing difficulties, throat injury, breathing noises and cyanosis.

The “B” of ABC: Breathing in the unconscious patient

After the airway patency phase it is necessary to check if the casualty is breathing.

To check for breathing in the unconscious, you can use the “GAS manoeuvre”, which stands for “look, listen, feel”.

This involves ‘glancing’ at the chest, i.e. checking for 2-3 seconds whether the chest is expanding.

Care must be taken not to confuse the gasps and gurgles emitted in the event of cardiac arrest (agonal breathing) with normal breathing: it is therefore advisable to consider absent breathing if the victim is not breathing normally.

If there are no respiratory signs it will be necessary to administer artificial respiration by mouth or with the aid of protective equipment (pocket mask, face shield, etc.) or, for rescuers, a self-expanding balloon (AMBU).

If breathing is present, it should also be noted whether the respiratory rate is normal, increased or decreased.

“B” Breathing in the conscious patient

If the patient is conscious, it is not necessary to check for breathing, but the OPACS (Observe, Palpate, Listen, Count, Saturation) should be performed.

The OPACS is mainly used to check the ‘quality’ of breathing (which is certainly present if the subject is conscious), while the GAS is mainly used to check whether the unconscious subject is breathing or not.

The rescuer will then have to assess whether the chest is expanding correctly, feel whether there are any deformities by palpating the chest lightly, listen for any breathing noises (rales, whistles…), count the respiratory rate and measure the saturation with a device called a saturation meter.

You should also note whether the respiratory rate is normal, increased or decreased.

“C” in ABC: Circulation in the unconscious patient

Check for carotid (neck) or radial pulse.

If neither breathing nor heartbeat is present, immediately contact the emergency number and advise that you are dealing with a patient in cardiopulmonary arrest and start CPR as soon as possible.

In some formulations, C has taken on the meaning of Compression, referring to the vital need to immediately perform cardiac massage (part of cardiopulmonary resuscitation) in the event of breathlessness.

In the case of a traumatised patient, before assessing the presence and quality of the circulation, it is necessary to pay attention to any major haemorrhages: abundant blood loss is dangerous for the patient and would render any attempt at resuscitation useless.

“C” Circulation in the conscious patient

If the patient is conscious, the pulse to be assessed will preferably be the radial one, since the search for the carotid may cause the victim further concern.

In this case, the assessment of the pulse will not be to ascertain the presence of the pulse (which can be taken for granted as the patient is conscious) but mainly to assess its frequency (bradycardia or tachycardia), regularity and quality (“full” or “weak/flexible”).

Advanced cardiovascular resuscitation support

Advanced cardiovascular life support (ACLS) is a set of medical procedures, guidelines and protocols, which are adopted by medical, nursing and paramedical staff in order to prevent or treat cardiac arrest or improve outcome in situations of return to spontaneous circulation (ROSC).

The variable ‘D’ in ABCD: Disability

The letter D indicates the need to establish the patient’s neurological condition: rescuers use the simple and straightforward AVPU scale, whereas doctors and nurses use the Glasgow Coma Scale (also called GCS).

The acronym AVPU stands for Alert, Verbal, Pain, Unresponsive. Alert means a conscious and lucid patient; verbal means a semi-conscious patient who reacts to vocal stimuli with whispers or strokes; pain means a patient who reacts only to painful stimuli; unresponsive means an unconscious patient who does not respond to any kind of stimulus.

As you move from A (alert) toward U (unresponsive), the severity status increases.


“D” Defibrillator

According to other formulas, the letter D is a reminder that defibrillation is necessary in the event of cardiac arrest: the signs of pulseless fibrillation (VF) or ventricular tachycardia (VT) will be the same as those of a cardiac arrest.

Experienced rescuers will use a semi-automatic defibrillator, while trained healthcare professionals will use a manual one.

Although fibrillation and ventricular tachycardia account for 80-90% of all cases of cardiac arrest[1] and VF is the leading cause of death (75-80%[2]), it is important to correctly assess when defibrillation is really needed; semi-automatic defibrillators do not allow discharge if the patient does not have a VF or pulseless VT (due to other arrhythmias or asystole), while manual defibrillation, which is the prerogative of trained health professionals only, can be forced after reading the ECG.

“D” Other meanings

The letter D can also be used as a reminder:

Cardiac rhythm definition: if the patient is not in ventricular fibrillation or tachycardia (and therefore not being defibrillated), the rhythm that caused the cardiac arrest must be identified by reading the ECG (possible asystole or pulseless electrical activity).

Drugs: pharmacological treatment of the patient, typically through venous access (medical/nursing procedure).


“E” Exhibition

Once vital functions have been stabilised, a more in-depth analysis of the situation is carried out, asking the patient (or relatives, if they are not reliable or able to answer) if they have allergies or other diseases, if they are on medication and if they have ever had similar events.

In order to mnemonically remember all the anamnestic questions to be asked in the often frantic moments of rescue, rescuers often use the acronym AMPIA or the acronym SAMPLE.

Especially in the case of traumatic events, it is therefore necessary to check whether the patient has suffered more or less serious injuries, even in areas of the body that are not immediately visible.

The patient should be undressed (cutting off clothes if necessary) and an assessment should be made from head to toe, checking for any fractures, wounds or minor or hidden bleeding (haematomas).

Following the head-to-toe assessment the patient is covered with an isothermal blanket to avoid possible hypothermia.


“E” Other meanings

The letter E at the end of the preceding letters (ABCDE) can also be a reminder:

  • Electrocardiogram (ECG): monitoring of the patient.
  • Environment: Only at this time can the rescuer be concerned about minor environmental phenomena, such as cold or precipitation.
  • Escaping Air: Check for chest wounds that have punctured the lungs and could lead to pulmonary collapse.

“F” Various meanings

The letter F at the end of the preceding letters (ABCDEF) can mean:

Fetus (in English-speaking countries fundus): if the patient is female, it is necessary to ascertain whether or not she is pregnant, and if so at what month of pregnancy.

Family (in France): rescuers should remember to assist family members as much as possible, as they can give important health information for subsequent care, such as reporting allergies or ongoing therapies.

Fluids: check for fluid loss (blood, cerebrospinal fluid, etc.).

Final steps: contact the facility that is to receive the critical patient.

“G” Various meanings

The letter G at the end of the preceding letters (ABCDEFG) can mean:

Blood sugar: reminds doctors and nurses to check blood sugar levels.

Go quickly! (Go quickly!): at this point the patient should be transported as quickly as possible to a care facility (emergency room or DEA).

H and I Various meanings

H and I at the end of the above (ABCDEFGHI) can mean

Hypothermia: preventing patient frostbite by using an isothermal blanket.

Intensive care post resuscitation: providing intensive care after resuscitation to assist the critical patient.


AcBC…: a small c immediately after the airways phase is a reminder to pay special attention to the spine.

DR ABC… or SR ABC…: D, S and R at the beginning remind of

Danger or Safety: the rescuer must never put himself or others in danger, and may have to alert specialised rescue services (fire brigade, mountain rescue).

Response: first check the patient’s state of consciousness by calling out loud.

DRs ABC…: in case of unconsciousness shout for help.

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