ABC mnemonic in nursing: airway, breathing, circulation — and the full ABCDE primary survey

When a patient deteriorates, there is no time for hesitation. You need a framework that tells you where to look first, what to assess, and what to do when something is wrong. The ABC mnemonic — Airway, Breathing, Circulation — is that framework. It is the first thing you learn in emergency response training and the last thing you should need to remember, because it should become automatic.

In its expanded form, ABCDE adds Disability (neurological status) and Exposure (full body examination). This five-step primary survey is the standard approach in Advanced Cardiovascular Life Support (ACLS), Advanced Trauma Life Support (ATLS), and most hospital rapid response protocols. Whether you are responding to a code, assessing a patient found unresponsive, or working through a rapid deterioration on the floor, ABCDE is your systematic guide from first contact to stabilization.

What ABC and ABCDE stand for

The order is intentional. A blocked airway kills faster than inadequate breathing; inadequate breathing kills faster than poor circulation. You work through the letters in sequence, addressing each life-threatening problem before moving to the next step. Finding something abnormal at A means you manage it before you move to B.

Detailed breakdown

A — Airway

The airway is the first priority because nothing else matters if air cannot reach the lungs. Airway assessment starts the moment you approach the patient.

What to assess:

• Responsiveness. If the patient speaks to you in clear sentences, the airway is open. An intact voice is strong evidence of a patent airway.
• Visual inspection. Look in the mouth for foreign bodies, blood, vomit, secretions, or tongue prolapse. In unconscious patients, the tongue is the most common cause of airway obstruction.
• Sounds. Listen for abnormal sounds that indicate partial obstruction: snoring suggests pharyngeal obstruction (typically the tongue); stridor (a high-pitched inspiratory sound) indicates narrowing at the larynx or upper trachea; gurgling indicates fluid in the airway.
• Effort. A patient working hard to breathe with minimal air movement may have severe obstruction.

When findings are abnormal:

Partial obstruction in an unconscious patient: perform a head-tilt chin-lift (or jaw thrust if spinal injury is suspected) to open the airway. Suction secretions if present. Place a nasopharyngeal or oropharyngeal airway as a bridge to definitive management.

Complete obstruction is a code-level emergency. Activate the rapid response team or code team immediately. Prepare for bag-valve-mask ventilation, laryngoscopy, or surgical airway if basic maneuvers fail.

Do not move to B until airway patency is confirmed or a corrective maneuver is in progress.

B — Breathing

Once the airway is open, breathing must be assessed. An open airway does not guarantee adequate ventilation — the patient must be moving air effectively.

What to assess:

• Rate. Count respiratory rate for a full minute. Normal in adults: 12–20 breaths per minute. Tachypnea (>20) suggests respiratory distress, sepsis, metabolic acidosis, pain, or anxiety. Bradypnea (<12) suggests CNS depression, opioid toxicity, or impending respiratory failure.
• Depth and effort. Shallow breaths fail to achieve adequate tidal volumes even at normal rates. Look for accessory muscle use (neck, intercostal, subcostal muscles) — this indicates that normal respiratory mechanics are insufficient and the patient is compensating.
• Symmetry. Watch the chest wall rise and fall. Asymmetric expansion can indicate pneumothorax, hemothorax, pleural effusion, or a mainstem bronchus intubation.
• Oxygen saturation. Apply pulse oximetry. Target SpO₂ ≥ 94% in most patients; in COPD patients, the target is typically 88–92% to avoid suppressing hypoxic respiratory drive.
• Auscultation. Listen to all lung fields bilaterally: apices and bases, anterior and posterior. Absent or diminished breath sounds over one lung suggest pneumothorax, effusion, or consolidation. Crackles (rales) suggest fluid — pulmonary edema, pneumonia. Wheezing indicates bronchospasm. Stridor heard here (rather than over the neck) suggests lower airway obstruction.

When findings are abnormal:

Apply supplemental oxygen. Position the patient upright if hemodynamically stable — this optimizes diaphragmatic excursion. If work of breathing is severe and SpO₂ is not responding to supplemental oxygen, escalate to high-flow nasal cannula, non-rebreather mask, or non-invasive positive pressure ventilation (BiPAP/CPAP). Tension pneumothorax requires immediate needle decompression — do not wait for imaging.

C — Circulation

With the airway patent and breathing assessed, turn to circulation. The goal here is to evaluate perfusion — whether blood is reaching the tissues effectively.

What to assess:

• Pulse. Check rate, rhythm, and quality. A rapid, weak (thready) pulse suggests shock. An absent peripheral pulse with a present central pulse indicates vasoconstriction or early decompensated shock. No carotid pulse in an unresponsive patient means CPR starts now.
• Blood pressure. Hypotension (systolic <90 mmHg in adults) is a late finding in shock — by the time blood pressure drops, significant compensation has already failed. Trend matters: a pressure dropping from 130 to 90 is more alarming than a stable 90.
• Skin signs. The skin is a window to perfusion. Assess color (pallor, mottling, cyanosis), temperature (cool and clammy suggests sympathetic activation and poor perfusion), and capillary refill (normal ≤ 2 seconds; delayed refill is a sign of reduced peripheral perfusion).
• Urine output. In a patient with a catheter, oliguria (< 0.5 mL/kg/hr) is an early sign of renal hypoperfusion and inadequate cardiac output.
• Hemorrhage. Look for external bleeding. In trauma, control of major hemorrhage takes priority — direct pressure, tourniquets, and wound packing belong here.

When findings are abnormal:

Establish IV access (two large-bore peripheral IVs in emergency situations). Draw blood for labs. Initiate fluid resuscitation per protocol. Activate the code team or rapid response if hemodynamic instability is present. For suspected cardiac arrest, begin CPR and connect the defibrillator. In acute coronary syndrome, the MONA protocol (Morphine, Oxygen, Nitrates, Aspirin) guides initial management while awaiting physician direction.

D — Disability

D assesses the patient’s neurological status — their level of consciousness and brain function. Two structured tools are used here: AVPU and the Glasgow Coma Scale (GCS).

AVPU scale (quick bedside screen):

• A — Alert: the patient is awake, oriented, and responds normally
• V — Voice: the patient only responds to verbal stimulation
• P — Pain: the patient only responds to painful stimuli (sternal rub, nail bed pressure)
• U — Unresponsive: no response to any stimulation

Any response below A (Alert) demands immediate escalation and rapid reassessment through A, B, and C — altered consciousness often reflects a problem upstream (hypoxia, hypotension, hypoglycemia).

GCS (Glasgow Coma Scale) provides a more granular numerical score (3–15) across three domains: eye opening (1–4), verbal response (1–5), and motor response (1–6). A score of ≤ 8 conventionally indicates a severe level of impairment and is associated with inability to protect the airway — these patients typically require intubation.

Blood glucose. Check a fingerstick glucose at D. Hypoglycemia (< 70 mg/dL) is a reversible cause of altered consciousness that is easy to miss and fast to treat. Never attribute an altered mental status to a known diagnosis without first ruling out hypoglycemia.

Pupils. Check pupil size, equality, and reactivity. Unequal pupils (anisocoria) or a unilaterally fixed and dilated pupil raises concern for herniation or CN III compression. See the cranial nerves assessment guide for the full neurological examination framework.

E — Exposure

The final step requires fully exposing the patient to ensure no significant finding is missed. Trauma, rashes, wounds, swelling, and bleeding can all be concealed by clothing.

What to do:

• Remove clothing to allow full inspection of the trunk, extremities, and back.
• Look for wounds, bruising, deformity (fractures), swelling, rashes, and signs of envenomation or burns.
• Check for medical alert jewelry that may reveal allergies, diabetes, cardiac devices, or anticoagulation.
• Assess the environment: pill bottles, mechanism of injury, temperature of the room.

Prevent hypothermia. Exposure is necessarily brief. Once assessment is complete, cover the patient with warm blankets. Hypothermia worsens coagulopathy, cardiac arrhythmias, and metabolic acidosis — it is a genuine clinical hazard in critically ill and trauma patients, not an afterthought.

Clinical context: when ABCDE is used

ABCDE is the standard approach in any situation involving potential or actual physiological deterioration. You will use it in:

Rapid response activations. When a ward nurse activates the rapid response team, the first clinician to arrive leads an ABCDE assessment to establish what is failing and in what order. The structure ensures no system is missed under pressure.

Cardiac and respiratory arrest. The ACLS algorithm begins with confirming unresponsiveness and calling for help, then immediately moving through A-B-C: airway, ventilation, and circulation (CPR and defibrillation). ABCDE is the framework behind every arrest protocol.

Post-operative deterioration. Patients who were stable in recovery can deteriorate on arrival to the floor. ABCDE gives the receiving nurse a structured approach to any change in condition — airway compromise from residual anesthesia, atelectasis, bleeding, and neurological changes are all captured by the framework.

Trauma assessment. ATLS (Advanced Trauma Life Support) uses ABCDE as the primary survey, with C extended to include hemorrhage control. Every trauma team member operates in this shared framework.

SBAR handover. When escalating any deteriorating patient to a physician or handing off to a colleague, organize your SBAR communication around the ABCDE findings. Situation: what you found. Background: what led here. Assessment: which letters are abnormal and how. Recommendation: what you need.

Common mistakes nursing students make

Skipping the sequence. ABCDE works because the order reflects the speed at which each problem kills. Students who jump to circulation before confirming airway and breathing may miss the primary cause of deterioration — and spend time on downstream effects instead of the root problem.

Moving on before acting. Finding a problem at A does not mean noting it and continuing to B. Each abnormal finding requires a corrective action before you proceed. The assessment and the intervention happen together at each step.

Underusing D. Students often check responsiveness at the start and then skip a structured neurological assessment. The AVPU scale takes 10 seconds. A fingerstick glucose takes 30. Both can identify immediately reversible causes of collapse that would otherwise be missed.

Forgetting hypothermia at E. Exposure without re-warming is incomplete. If you expose a critically ill patient and do not cover them promptly, you are adding a problem rather than solving one.

Documenting once. ABCDE is not a one-time intake. In a deteriorating patient, each reassessment after an intervention is another ABCDE. Document findings with a timestamp before and after each intervention so trends are visible.

Related mnemonics

ABCDE sits at the top of the clinical assessment hierarchy — it comes before detailed symptom evaluation. Once the primary survey is complete and the patient is stabilized, these tools deepen the picture:

• OLDCARTS — a structured framework for taking a full history of any symptom (Onset, Location, Duration, Character, Aggravating factors, Relieving factors, Timing, Severity). Use this for the secondary survey once ABCDE is complete.
• PQRST — a focused pain assessment tool (Provocation/Palliation, Quality, Region/Radiation, Severity, Timing). If the patient’s chief complaint is pain, PQRST structures the assessment within the ABCDE framework.
• MONA — the initial management mnemonic for suspected acute coronary syndrome (Morphine, Oxygen, Nitrates, Aspirin). MONA is the C-level response when ABCDE reveals signs of cardiac ischemia.
• SBAR — the structured handover tool (Situation, Background, Assessment, Recommendation). After any ABCDE assessment, SBAR organizes your findings into a communicable format for the physician or incoming team.
• Cranial nerves — detailed neurological assessment tools that extend the D (Disability) step when a focused neuro exam is warranted.

Summary

The ABC mnemonic — extended to ABCDE — is the universal primary assessment framework for any deteriorating or emergency patient. Work through it in sequence: confirm airway patency before assessing breathing, breathing before circulation, and circulation before neurological status and exposure. Address each abnormal finding before moving to the next step. Check blood glucose at D. Prevent hypothermia at E. Reassess after every intervention. When you need to escalate, organize your findings into an SBAR handover so the receiving clinician can act on clear, structured information.

The value of ABCDE is its reliability under pressure. When the environment is chaotic and the patient is crashing, you do not have to decide what to assess next — the framework decides for you.