Recognising Hypoxia for Student Nurses
Learn how to recognise possible hypoxia, assess the patient's respiratory condition and understand why oxygen saturation should always be interpreted alongside the whole clinical picture.
What is hypoxia?
Hypoxia describes inadequate oxygen availability at tissue level. It can occur for many reasons and may develop alongside respiratory, cardiovascular or other acute illness.
SpO₂
Pulse oximetry provides useful information, but it does not replace assessment of the patient.
Respiratory effort
Increased respiratory rate or work of breathing may provide early evidence that the patient is struggling.
Mental state
Agitation, confusion, drowsiness or reduced responsiveness can be important signs of deterioration.
What might hypoxia look like?
Hypoxia may present differently between patients. Look for a pattern of respiratory, cardiovascular and neurological change.
| Finding | What you might notice | Why it matters |
|---|---|---|
| Respiratory rate | Breathing faster than usual or a changing respiratory pattern. | Increasing respiratory rate can be an early sign of physiological stress. |
| Work of breathing | Accessory muscle use, laboured breathing or visible respiratory distress. | The patient may be working harder to maintain ventilation and oxygenation. |
| Oxygen saturation | A fall below the patient's usual level or prescribed target range. | A falling trend may indicate worsening oxygenation. |
| Speech | Difficulty speaking comfortably because of breathlessness. | This may indicate significant respiratory compromise. |
| Mental state | Restlessness, anxiety, confusion, drowsiness or reduced responsiveness. | Neurological change may accompany worsening oxygen delivery. |
| Skin colour | Pallor or, in severe cases, cyanosis. | Colour changes must be interpreted carefully and alongside other findings. |
Look for change from baseline
A patient whose saturation is usually 97% but is now 92%, with a rising respiratory rate and increasing breathlessness, has a clinically meaningful pattern of change even before the cause is known.
Why SpO₂ is only part of the assessment
Pulse oximetry estimates peripheral oxygen saturation. The reading can be extremely useful, but it has limitations and should always be interpreted in context.
- Check whether the patient is breathing room air or receiving supplemental oxygen.
- Know the patient's prescribed target oxygen saturation where applicable.
- Compare the current value with previous readings.
- Assess the pulse oximeter signal and whether the reading is stable.
- Consider poor peripheral perfusion, cold extremities and movement if the reading seems unreliable.
- Never ignore severe breathlessness or clinical deterioration simply because SpO₂ appears reassuring.
Target saturations differ
Current BTS guidance recommends a target saturation of 94–98% for most acutely ill adults who are not at risk of hypercapnic respiratory failure. Patients with COPD or other recognised risk factors for hypercapnic respiratory failure may have a target of 88–92% pending blood gas results and clinical review.
What should you do when oxygenation is worsening?
Look at the patient
Assess appearance, ability to speak, respiratory effort, consciousness and signs of distress.
Measure observations
Check respiratory rate, oxygen saturation, pulse, blood pressure, temperature and consciousness as appropriate.
Check oxygen therapy
Establish whether supplemental oxygen is being given and what target saturation has been prescribed.
Compare with previous values
Look for falling saturation, rising respiratory rate or increasing oxygen requirement.
Use ABCDE and NEWS2
Assess deterioration systematically and record the patient's observations accurately.
Escalate promptly
Communicate concerning findings to the appropriate registered practitioner and follow local escalation procedures.
Changes that deserve immediate attention
- Oxygen saturation falling below the patient's prescribed target range.
- A rapidly falling oxygen saturation.
- Increasing requirement for supplemental oxygen.
- Markedly increased respiratory effort.
- A significant rise or fall in respiratory rate.
- Difficulty speaking because of breathlessness.
- New confusion, agitation, drowsiness or reduced responsiveness.
- A patient who looks exhausted or unable to maintain breathing effectively.
Putting the observations together
Example
Earlier in the shift, a patient's oxygen saturation was 96% on room air and respiratory rate was 16 breaths per minute.
You now measure an oxygen saturation of 90%. Their respiratory rate is 28, they are struggling to speak in full sentences and appear increasingly anxious.
This is not simply an “SpO₂ of 90%.” It is a pattern of worsening respiratory function and possible hypoxia.
As a student nurse, recognise the deterioration, assess within your competence and promptly escalate the findings to the appropriate registered practitioner.
Hypoxia assessment errors to avoid
- Looking only at SpO₂. Assess breathing, consciousness and the whole patient.
- Assuming every patient needs the same target saturation. Check the prescribed target.
- Ignoring increasing oxygen requirements. Maintaining the same SpO₂ on more oxygen may still represent deterioration.
- Waiting for cyanosis. This can be a late and unreliable sign.
- Ignoring trends. Compare respiratory rate and oxygen saturation with previous observations.
- Repeatedly checking equipment while delaying escalation. If the patient appears unwell, seek help promptly.
Recognise → assess → communicate → escalate
Notice oxygenation change
Identify falling saturation, increasing breathlessness or a change in respiratory effort.
Build the whole picture
Review respiratory rate, oxygen saturation, oxygen therapy, consciousness and other vital signs.
Speak up early
Report the deterioration clearly and follow local escalation procedures when oxygenation is worsening.
Oxygen target information is based on current British Thoracic Society emergency oxygen guidance. BTS currently recommends controlled oxygen therapy, commonly targeting 94–98% in acutely ill adults not at risk of hypercapnic respiratory failure and 88–92% for patients with recognised risk factors for hypercapnic respiratory failure. :contentReference[oaicite:0]{index=0}
British Thoracic Society — Oxygen use in healthcare and emergency settings
Recognising Shock for Student Nurses
Learn how to recognise possible shock, assess circulation and perfusion and identify combinations of observations that may indicate rapidly worsening patient deterioration.
Continue to Recognising Shock →