Recognising Cyanosis for Student Nurses
Learn how to recognise possible cyanosis, assess colour changes safely across different skin tones and understand why cyanosis may indicate impaired oxygenation or significant patient deterioration.
What is cyanosis?
Cyanosis describes a blue, grey or otherwise abnormal discolouration associated with increased deoxygenated haemoglobin in the blood. Recognition can vary considerably between patients and across different skin tones.
Lips and mucous membranes
Central colour change involving areas such as the lips, tongue or oral mucosa can be associated with reduced arterial oxygenation.
Hands and extremities
Peripheral colour changes may occur where circulation to the extremities is reduced.
Never use colour alone
Respiratory rate, effort, oxygen saturation, circulation and consciousness provide essential additional information.
Assessing colour changes across different skin tones
Clinical signs involving skin colour should be assessed carefully and inclusively. Descriptions based only on patients appearing “blue” can make important changes harder to recognise in some skin tones.
Look for change
Compare with the patient's usual appearance where possible and look for unusual grey, blue or dusky colour.
Inspect mucous membranes
The tongue and oral mucosa can provide useful information when assessing suspected central cyanosis.
Use multiple signs
Combine visual assessment with respiratory rate, work of breathing, oxygen saturation and mental state.
Look for change from the patient's normal appearance
Knowing what is normal for the individual patient can be more useful than expecting one universal colour change. Listen to the patient and family or carers if they report that the patient's appearance is unusual.
What should you assess if cyanosis is suspected?
Assess the airway
Check whether the airway appears patent and recognise signs of obstruction or airway compromise.
Count respiratory rate
Measure the rate accurately and compare it with previous observations.
Assess breathing effort
Look for accessory muscle use, laboured breathing, altered chest movement or difficulty speaking.
Check oxygen saturation
Review SpO₂, the patient's prescribed target range and whether supplemental oxygen requirements have changed.
Assess circulation
Review pulse, blood pressure, peripheral temperature and perfusion.
Assess consciousness
Recognise new agitation, confusion, drowsiness or reduced responsiveness.
What findings increase concern?
| Finding | What you may notice | Why it matters |
|---|---|---|
| Falling SpO₂ | Oxygen saturation is lower than previously or outside the prescribed target. | This may indicate worsening oxygenation and requires clinical assessment. |
| Tachypnoea | The patient is breathing increasingly quickly. | A rising respiratory rate may be an early sign of physiological deterioration. |
| Increased work of breathing | Accessory muscles, laboured breathing or difficulty speaking. | These signs suggest the patient is working harder to ventilate. |
| New agitation | The patient becomes restless, anxious or behaves differently. | Behavioural change can accompany hypoxia or acute illness. |
| Reduced consciousness | Drowsiness or reduced responsiveness develops. | This is a particularly concerning feature alongside respiratory deterioration. |
| Poor perfusion | Cold extremities, delayed capillary refill or circulatory changes. | Peripheral colour changes may occur alongside impaired circulation. |
Treat the patient, not the colour
Suspected cyanosis becomes much more meaningful when interpreted alongside respiratory distress, oxygen saturation, circulation, consciousness and the patient's clinical history.
Do not rely on one measurement
Pulse oximetry is an important part of respiratory assessment, but the reading should always be interpreted alongside the patient's clinical appearance and prescribed oxygen saturation target.
- Check that the pulse oximeter signal is reliable.
- Consider factors that may affect the accuracy of the reading.
- Compare the result with previous observations.
- Know the patient's prescribed oxygen saturation target where relevant.
- Observe respiratory rate and work of breathing at the same time.
- Do not dismiss visible clinical deterioration because one reading appears reassuring.
Putting the findings together
Example
You are caring for a patient who was comfortable earlier in the shift.
They are now visibly breathless and their respiratory rate has risen to 30 breaths per minute.
Their lips and oral mucosa appear unusually dusky compared with earlier, and their oxygen saturation has fallen below their prescribed target.
They can only speak in short phrases and are becoming increasingly agitated.
The concern is the combined pattern of colour change, tachypnoea, worsening oxygenation, increased work of breathing and behavioural change.
As a student nurse, recognise the deterioration, assess using an appropriate ABCDE approach and communicate the findings promptly to the appropriate registered practitioner.
Cyanosis assessment errors to avoid
- Waiting for obviously blue skin. Cyanosis may appear differently across skin tones.
- Looking only at the fingertips. Consider lips, tongue, mucous membranes and the wider patient assessment.
- Using colour as a substitute for oxygen assessment. Check breathing and oxygenation appropriately.
- Looking only at the pulse oximeter. Assess the patient as well as the monitor.
- Ignoring respiratory effort. Visible breathing difficulty may indicate deterioration even before severe desaturation.
- Delaying escalation while trying to decide whether the colour is definitely cyanosis. Escalate the concerning clinical pattern.
Recognise → assess → communicate → escalate
Notice the change
Identify an unusual colour change while recognising that appearance varies between individuals and skin tones.
Check oxygenation and breathing
Assess airway, respiratory rate, effort, SpO₂, circulation and consciousness.
Describe the whole pattern
Report the colour change together with respiratory observations and any associated deterioration.
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Continue to Reduced Urine Output →