CPR — Basic Life Support
C–A–B — and why the order changed ★★★
The deck opens with three letters: C–A–B. Circulation, Airway, Breathing. If you have seen first-aid teaching before, you may remember A–B–C, and the reversal is deliberate.
Two reasons, and both are about time.
First, at the moment of a sudden cardiac arrest the blood is still oxygenated — the person was breathing normally seconds ago. What has stopped is not oxygen supply but circulation. Pushing that already-oxygenated blood to the brain is more urgent than adding more oxygen to it.
Second, opening an airway and delivering rescue breaths takes time and confidence, and it is the step untrained bystanders hesitate over. Putting compressions first means something useful starts immediately rather than after a delay.
So: press first, then open the airway, then breathe.
- What does C–A–B stand for? → Circulation, Airway, Breathing
- Why do compressions come before breathing? → Blood is still oxygenated at arrest; circulation is what has stopped — and it removes the delay before anything useful happens
The seven steps ★★★
The deck gives an explicit review list. This is the flowchart to reproduce if the exam asks for the CPR sequence — and the rubric permits a flowchart.
- Assess the scene and protect yourself.
- Judge consciousness and observe breathing — about 10 seconds. Tap the patient's shoulder lightly and shout: “Sir, what's wrong with you?”
- Call for help quickly. Shout for help, call emergency services, and ask someone to find an AED.
- Chest compressions.
- Check and clean up oral foreign bodies — turn the head to one side and remove them.
- Open the airway — head tilt, chin lift.
- Artificial breathing.
Note that step 2 has a stated duration and step 3 names three separate calls for help. Those specifics are where marks live.
| Detail | As taught |
|---|---|
| Rescuer position | Kneeling on the right side of the patient — the 'ambulance position' |
| Patient position | Supine on a hard surface. Use the flip-patient method if needed |
| What to shout | “Help! Someone has fainted here.” · “Please call emergency services.” · “Please help me find an AED.” · “Who knows first aid, come and help!” |
The wording of the calls for help is worth noticing. They are four separate, specific instructions — not a general cry. Assigning a named task to a named person is the difference between a crowd watching and a crowd helping.
- List the seven steps. → Assess scene → judge consciousness and breathing → call for help → chest compressions → clear oral foreign bodies → open airway → artificial breathing
- How long is spent judging consciousness and breathing? → About 10 seconds
- Where does the rescuer kneel? → On the patient's right side
- What surface must the patient be on? → Supine on a hard surface
Chest compression in the adult ★★★
This is the heart of exam question 6, so the specifics matter more here than anywhere else in the subject.
| Parameter | Adult |
|---|---|
| Position | The centre of the chest — the midpoint of the line connecting the two nipples, at the lower part of the sternum |
| Hand placement | The heel of the hand — the hand strength area — with the second hand on top |
| Depth | At least 5 cm |
| Rate | 100–120 per minute |
| Compression : ventilation ratio | 30 : 2 |
| Reassessment | After 5 consecutive cycles, check whether breathing and heartbeat have returned |
The deck does not say "press on the heart" — it gives you a way to find the place under stress: the midpoint of the internipple line, which puts your hands over the lower sternum.
That matters because the two commonest positional errors have opposite consequences. Too high and you are compressing the manubrium, achieving nothing. Too low and you are over the xiphoid process, risking liver injury. The landmark exists to keep you between the two.
And using the heel of the hand rather than the palm concentrates force through bone rather than spreading it over soft tissue and ribs.
- Where do you compress in an adult? → Centre of the chest — midpoint of the internipple line, lower sternum
- Which part of the hand? → The heel — the hand strength area
- Depth and rate? → At least 5 cm, at 100–120 per minute
- Compression:ventilation ratio? → 30:2
- When do you reassess? → After 5 consecutive cycles
Children and infants ★★★
| Child | Infant | |
|---|---|---|
| Position | Same position as adults | Middle of the chest, below the internipple line |
| Technique | One or both palms | Two fingers — middle and ring fingers held together |
| Depth | At least ⅓ of the anterior–posterior chest diameter (about 5 cm) | At least ⅓ of the anterior–posterior chest diameter (about 4 cm) |
| Rate | 100–120 per minute | 100–120 per minute |
Notice that the depth is not really three separate facts. For every age the rule is one third of the chest's front-to-back diameter — it only looks different because children and infants have smaller chests. About 5 cm in a child, about 4 cm in an infant, and at least 5 cm in an adult.
The rate never changes: 100–120 per minute at every age. What changes is how much of your hand you use — two hands, one or two palms, two fingers — because the goal is the same fraction of a smaller chest.
- Compression technique in an infant? → Two fingers — middle and ring together
- Where on an infant's chest? → Middle of the chest, below the internipple line
- Depth in child and infant? → At least ⅓ of AP chest diameter — about 5 cm and 4 cm
- Does the rate change with age? → No — 100–120 per minute throughout
Airway and rescue breathing ★★
Before breathing, check and clean up oral foreign bodies: turn the head to one side and remove them. Then open the airway by tilting the head back and lifting the chin — and the angle depends on age.
| Head-tilt angle | Blowing method | |
|---|---|---|
| Adult | About 90° | Mouth-to-mouth or mouth-to-nose |
| Child | About 60° | Mouth-to-mouth or mouth-to-nose |
| Infant | About 30° | Mouth-to-nose — cover both nose and mouth |
- Open the airway by head tilt and chin lift, at the angle for the patient's age.
- Pinch the nostrils (adult and child).
- Open your mouth wide and cover the patient's mouth and lips — for an infant, cover both nose and mouth.
- Blow slowly and evenly for 1 second.
- Give two breaths.
- Confirm success: thoracic eminence can be seen — the chest visibly rises.
The chest rising is the only reliable sign the breath went into the lungs rather than the stomach.
It seems backwards — the smaller patient gets the smaller angle. But an infant's airway is soft and short, and over-extending the neck kinks it closed rather than opening it. The 90°/60°/30° sequence tracks how much support the airway's own cartilage provides: an adult's trachea can take the extension, an infant's cannot.
Finally, once circulation and breathing return, place the patient in the recovery position — which keeps the airway open and lets any vomit drain rather than being aspirated.
- How do you open the airway? → Head tilt back, chin lift
- Head-tilt angles by age? → Adult ~90°, child ~60°, infant ~30°
- How long is each rescue breath, and how many? → 1 second each, two breaths
- How do you know the breath worked? → The chest visibly rises (thoracic eminence)
- Which method for an infant? → Mouth-to-nose, covering both nose and mouth
⭐ Answering exam question 6
Position — centre of the chest, at the midpoint of the internipple line, over the lower sternum. Too high is ineffective; too low risks the xiphoid and liver.
Hands — use the heel of the hand (the hand strength area), second hand on top.
Patient position — supine on a hard surface; a soft surface absorbs the compression.
Rescuer position — kneeling at the patient's right side.
Depth — at least 5 cm in an adult; at least ⅓ of the AP chest diameter in a child (~5 cm) or infant (~4 cm).
Rate — 100–120 per minute at every age.
Ratio — 30 compressions : 2 breaths.
Technique by age — two hands in adults, one or both palms in children, two fingers (middle and ring) in infants.
Reassessment — after 5 consecutive cycles, check whether breathing and heartbeat have returned.
Count the numbers in that answer: 5 cm, ⅓, 4 cm, 100–120, 30:2, 5 cycles. Six specific values, plus the landmark, the hard surface, the hand position and the age variations — which is about fifteen scorable items for a fifteen-mark question.
That is almost certainly not a coincidence, and it tells you how to write: a numbered list of specifics, not a paragraph about the importance of good technique. Ten minutes is enough time to write all of it if you are not composing prose.
- Depth, rate, ratio in an adult? → At least 5 cm · 100–120/min · 30:2
- Depth in child and infant? → ⅓ of AP chest diameter — about 5 cm and 4 cm
- Infant compression technique? → Two fingers, middle and ring together
- When to reassess? → After 5 consecutive cycles
- Why must the surface be hard? → A soft surface absorbs the compression instead of transmitting it to the chest
- Two positional errors to avoid? → Too high (manubrium, ineffective); too low (xiphoid, risks liver injury)