Understanding Basic Vital Signs

Is the casualty "Big Sick" or "Little Sick"?

Examining the casualty's Vital Signs allows us to assess the casualty's state of health accurately and objectively.  The Golden Rule on all of our courses is:

"If it's not normal, it's bad!"

The above statement may sound inaccurate or even childish but whether you are a novice First Aider or a Consultant Anaesthetist, the above statement is always true.  This is what we need to remember when assessing the casualty.

In this article we will look at how we can rapidly assess a casualty's state of health, at a basic level, with no reliance on medical terminology, equipment or numbers.


The Common Mistake

Humans are hardwired to react to the sight of blood and generally judge casualties based on their injury rather than their vital signs.

For example, which would you say are Big Sick or Little Sick?

Most people would gauge the injuries on the right as more severe - Big Sick - and the injuries on the left as minor - Little Sick.  Some injuries can be more serious than others but injuries alone do not tell you if the casualty is Big Sick or Little Sick.  Injuries alone cannot tell you if a person is going to live or die or if so, when.  Injuries can only tell you that someone has an injury.

If we look at the two casualties below, which casualty is Big Sick?

Hopefully most people would recognize the casualty displaying chest pain on the left as being Big Sick.  Even though the casualty on the right has a nasty injury and there is plenty of blood, there is nothing in the photo to suggest that the casualty on the right is going to die any time soon.  He is Little Sick.

This is worth remembering - while we judge injuries based on the amount of blood, the bruising or the shape of the limb, we cannot do the same with casualties:

  • Some injuries can look horrific but be relatively minor.  We know that superficial head injuries bleed a lot but the wound may be very small and will easily stop bleeding with direct pressure.
  • Some casualties may have no obvious injuries but the situation can be life threatening.

So how do we judge a casualty who has no visible injury but they tell you the feel 'unwell'?   How do we judge a casualty who is unconscious or uncommunicative?

The answer is to assess their four Basic Vital Signs.


Level of Consciousness

Another common mistake is simply to ask Polar Questions; 'Yes / No' questions or questions which can only be answered with one of two answers.

When we want to know about the casualty's Level of Consciousness (LoC) we tend to ask are they 'conscious' or 'unconscious'.   This is not enough.

If you are reading this you are more than conscious, you are fully ALERT - and that is different to simply being conscious:  Someone who is fully ALERT:

  • Knows where they are
  • Knows who they are
  • Knows roughly what time of day it is
  • Knows the date
  • Can speak clearly
  • Can give appropriate answers

Anyone who is not ALERT is unconscious.

But unconsciousness is not like turning off a switch; there are various shades of unconsciousness.  If they are not ALERT, they are unconscious but can they still respond to VOICE?

  • Don't ask them a question like "Can you hear me?"  They are unconscious and speaking requires one of the highest cognitive functions we have.  Tell them what to do - "Open your eyes!"
  • Don't suggest it in soothing, soporific tones - you want a response so try and initiate one:  Shout "Open your eyes!" in both ears, loud!
  • Remember, you are looking for ANY response.  They might open their eyes fully or they might groan, flinch or move away from the sound.  Any response would indicate they they are unconscious, but responsive to voice.

If they do not respond to VOICE, do they respond to PAIN?

Again, your assessment needs to be effective - pinching the ear is not effect.  Unfortunately, to ascertain if your casualty is able to respond to pain, you must administer genuine pain - BUT - it must be appropriate.

  • Pinch the trapezius - the muscle along the top of the shoulder, at the fleshiest bit, between your finger and thumb, HARD.
  • Look at the casualty's face; their response maybe overt or it may be subtle but any response is a response.
  • There are other tests for pain - some are gentle and therefore ineffective, others are brutal and therefore unethical, this is an effective, appropriate assessment.
  • Obviously, if your casualty is responding to VOICE, do not check to see if they respond to PAIN!

If they do not respond to PAIN, they are Unconscious and UNRESPONSIVE.

Your casualty can now be categorised as follows - A,V, P or U:

Conscious and Alert or

Unconscious but responding to Voice or

Unconscious but responding to Pain or

Unconscious and Unresponsive

REMEMBER:  You do not want to know IF they are unconscious, you want to know HOW unconscious

These are the phrases you will use when contacting help and handing over when help arrives - it may not mean much to you but it means a lot to the person you are telling.

WAIT!  Check this out:

What about the drunk, staggering around the town centre at 2am, hugging lamp posts and singing to the moon:  He is upright, his eyes are open.  Is he conscious?

A better question is 'Is he ALERT?'   Does he know where he is?  Does he know what time it is?  Can he give you an appropriate answer?  Is he speaking clearly?

No.  So he must be....Unconscious?

Yes.  When you shout over to him "Hey!  Are you alright?"  And he swings around, almost loosing balance, all he has done is responded to your voice.

This casualty is Unconscious but responding to VOICE.

In summary, Consciousness has nothing to do with whether their eyes are open or closed or whether they are standing up or lying down.  Their LoC is determined by their ability to respond.



In the same way that people tend to simply ask 'Are they conscious?' people will also ask 'Are they breathing?'  These Yes/No questions are not enough:

REMEMBER:  You do not want  to know IF they are breathing, you want to know HOW they are breathing.

RATE -      Is it too fast or too slow?

RHYTHM - Is it irregular?

DEPTH -   How much air is moving? Is it shallow / light / weak or is it deep / heavy / strong?

NOISE -   Breathing should be silent.  Are they Wheezing?  Gurgling?  Rasping?

None of these are normal.  All of these are bad.  Anyone whose breathing is not normal is Big Sick.

Isn't all of this a bit pedantic? 

Watch the short clip below and ask yourself, is the casualty Big Sick or Little Sick?

Is the casualty Alert?  No, and that's not normal, that's bad.

Is the casualty Breathing? Yes.  But it's not normal, that's bad.

This is what differentiates Big Sick from Little Sick; because the casualty's Vital Signs aren't normal, that's bad, this casualty is Big Sick.   We don't necessarily know what is wrong with him at this stage but we know he is a serious casualty.

The reason we have to look for, notice and record the description of how unconscious the casualty is and how they are breathing is also for when we send for help.

When we contact help - whether it is the emergency services, the office or base camp - people will ask simple questions, and these prompt simple answers.

For the casualty in the clip above it would be reasonable for a lay-person to respond in the following way: 

Call Handler: "Are they conscious?"

You: "Yes."

Call Handler: "Are they breathing?"

You:  "Yes."

So what have you just told the person you are requesting help from?  They are conscious and breathing.  Are they at all concerned?

Better replies would be:

Call Handler:  "Are they conscious?"  

You:  "No, but they are responding to Voice."

Call Handler:  "Are they breathing?"

You:  "Yes, but it is fast, deep and noisy."

These descriptors inform the person you are contacting that the Vital Signs are not normal (and that's bad!) and with this information, professional help will begin to form an opinion of what could be wrong with the casualty.

An experienced emergency services call handler will continue to ask more probing questions but we cannot guarantee that everyone we contact will have that ability.  If we are relaying information to the Emergency Services via a 'runner' we need to ensure the runner can answer these questions appropriately.



Skin colour is another obvious, intuitive Vital Sign; we all judge - consciously or not - an individual's skin colour; we will notice when someone looks pale or flushed.  We can tell which one of the passengers is looking sea sick!

Most changes to skin colour are intuitive:

  • Pale - Blood is moving away from the skin, typically to the core, to protect us when we are cold loosing blood or short of oxygen.
  • Blue - If the cold, blood loss or lack of oxygen is not resolved, we eventually go blue, at the extremities first (peripheral cyanosis) followed by blueness around the mouth and eyelids (central cyanosis).  This is not normal.  This is Bad!
  • Red - blood is moving towards the skin, usually to help us cool.  If the person has a history of exercise and is in a hot climate this would be normal.  This would be little sick.   If the casualty is sat at their desk in an air conditioned office but is hot and red, this is not normal, this is bad.   This is Big Sick.
  • Yellow - Jaundice, for example, can have an effect of skin colour due to a build up of bilirubin which stains the blood an orangey colour, which appears yellow through the skin.
  • Green - Do people go green?  Who knows, but you can quite accurately tell when someone is going to be sick just by the look of them.


Changes in skin colour are most noticeable in Caucasian skin because the skin is contains less pigmentation making it almost translucent, a bit like grease proof paper (if you have ever peeled off the flap of skin left over from a blister).  We are able to see blood through the skin and how it is changing - whether it is moving close to the surface, further away or if there is a stain to it.

In casualties with strong ethnicities, this becomes more difficult as the greater amount of pigmentation in the skin masks the changes we would otherwise see.

Whilst it can be difficult to notice changes in skin colour when dealing with people of different ethnicities, it is not impossible:

We are all pale in the same places; everyone has pink lips and finger nails which will go pale or blue.

Colour is closely associated with temperate - blue is cold, red is hot.  This is a universal.

Jaundice will also reveal itself in staining the sclera, the 'white' of the eye.

While it can be harder to notice abnormal skin colours in strangers because you do not have a normal baseline reference, we are able to notice changes in the skin colour of peopl e we know because, regardless of ethnicity, we know what normal is for them.



So you all remember that the core temperature of the human body is 37°C?  Or something like that?  That's useful but mainly for Pub Quizzes.  To measure someone's temperature you need a thermometer and if you don't have a thermometer knowing this number is useless.

Casting you're mind back to when you were a little boy or little girl, you Mum would usually measure your temperature by feeling your forehead with her hand.  And we know that Mums are always right.

If your casualty feels hot, they are hot.  If your casualty feels cold, they are cold.  All we have to ask is "Is it normal?"

Is it normal for:

  • The environmental temperature
  • Their levels of activity
  • Their clothing


  • It is the Vital Signs that tell us if the casualty is Big Sick or Little Sick and all we have to ask is "Are they normal?" 
  • A casualty may have horrific injuries but if they are Alert, breathing normally, with normal skin colour and at a normal temperature, they are Little Sick.  They are not going to die any time soon.  And that is reassuring because while the injuries may be disturbing we know we have plenty of time.
  • A casualty may have no injuries at all but if they have a reduced level of consciousness, their breathing is not normal, their skin colour has changed or they are not a normal temperature, they are Big Sick.  And this is important because it prompts us to act even though there is no obvious injury.
  • If we monitor the Vital Signs over time we will notice changes.  This may reveal if the casualty is improving, deteriorating or stable.

Advanced Vital Signs

In the next article we will look at additional Vital Signs, introduce values and begin to interpret what certain changes in the Vital Signs mean.

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