Tension pneumothorax
Immediately life-threatening
Key features
- Severe respiratory distress
- Absent / reduced breath sounds unilaterally
- Tracheal deviation (late — often absent)
- Hypotension + tachycardia
- JVD if not hypovolaemic
- Hyperresonance on percussion
- SpO2 falling despite O2
- Rapid deterioration
Immediate actions
- Needle thoracostomy if trained — do not wait for definitive confirmation
- High-flow O2
- Pre-alert — immediate transfer
- Avoid positive pressure ventilation until decompressed if possible
Diagnostic uncertainty
Tracheal deviation is a late and unreliable sign. Breath sound asymmetry is hard to detect in COPD or emphysema where both sides are already quiet. In a noisy environment, absent breath sounds may be missed entirely. Hyperresonance is the more useful sign but is underused and operator-dependent. Treat on clinical suspicion — do not wait for the full triad.
Massive pulmonary embolism
Immediately life-threatening
Key features
- Sudden onset breathlessness
- Pleuritic chest pain (may be absent)
- Haemoptysis (minority of cases)
- Tachycardia out of proportion to hypoxia
- Hypotension / shock
- Near-syncope or syncope
- Chest clear on auscultation
- Unilateral leg swelling (suggestive)
Immediate actions
- High-flow O2, IV access, monitoring
- Position of comfort — avoid supine if tolerated
- Pre-alert for thrombolysis consideration
- If cardiac arrest: consider thrombolysis per resus guidance
Diagnostic uncertainty
Massive PE can look identical to severe asthma, COPD exacerbation, or acute cardiac failure prehospital. A clear chest on auscultation in a breathless patient should raise PE on the differential — but many patients have coexisting pathology masking this. The absence of wheeze in a breathless patient is a useful negative sign. Prehospital diagnosis is clinical impression only.
Acute severe / life-threatening asthma
Immediately life-threatening
Key features
- Unable to complete sentences
- SpO2 <92% (life-threatening <90%)
- Silent chest — ominous sign
- Tachycardia, tachypnoea
- Use of accessory muscles
- Peak flow <33% best (if available)
- Altered consciousness — near-fatal
- Cyanosis — near-fatal
Immediate actions
- Salbutamol nebulised (continuous if near-fatal)
- Ipratropium nebulised
- O2 to maintain SpO2 94–98%
- Hydrocortisone IV or prednisolone PO
- Pre-alert — prepare for possible intubation
- Magnesium sulphate IV if available and near-fatal features
Diagnostic uncertainty
Silent chest means air movement is so poor wheeze has disappeared — this is a deterioration sign, not improvement. A patient who was wheezing and has gone quiet requires immediate reassessment of severity. COPD and asthma frequently coexist and are often impossible to distinguish acutely. Treat the physiology, not the label.
Acute pulmonary oedema
Immediately life-threatening
Key features
- Severe breathlessness — often sudden onset
- Orthopnoea — cannot lie flat
- Bilateral basal crackles
- Pink frothy sputum (severe)
- Hypertension (often) or hypotension (cardiogenic shock)
- Tachycardia, diaphoresis
- History of cardiac disease or hypertension
- Wheeze possible — cardiac asthma
Immediate actions
- Sit upright
- GTN sublingual if systolic >90 — titrate carefully
- CPAP if available and no contraindications
- O2 to maintain SpO2 94–98%
- IV access — furosemide per protocol
- Pre-alert
Diagnostic uncertainty
Cardiac asthma (wheeze in APO) is frequently misdiagnosed as bronchospasm. Bilateral crackles can be absent early or masked by wheeze. In COPD patients the picture is further confused by chronic changes. Failure to respond to bronchodilators should prompt reconsideration. GTN responsiveness supports the diagnosis but absence of response doesn't exclude it.
Severe COPD exacerbation / type 2 respiratory failure
Immediately life-threatening
Key features
- Known COPD (often)
- Days of worsening — not always sudden
- Pursed-lip breathing, tripod positioning
- Wheeze and reduced air entry bilaterally
- Reduced conscious level — CO2 narcosis
- SpO2 low — may be chronic baseline
- Cyanosis, peripheral oedema if cor pulmonale
- Shallow, inadequate respiratory effort
Immediate actions
- Controlled O2 — target SpO2 88–92% unless critical hypoxia overrides
- Salbutamol + ipratropium nebulised
- Hydrocortisone IV
- Consider assisted ventilation if respiratory effort failing
- Pre-alert — NIV likely needed in hospital
- At SpO2 <70%: correct hypoxia first — CO2 narcosis concern is secondary to preventing death
Diagnostic uncertainty
This is the diagnosis that obscures everything else. Once COPD is in the frame, every sign has an alternative explanation. Active question: if this patient's own exacerbation treatment isn't working, what else fits? Pneumothorax, PE, and pneumonia all sit behind this label in COPD patients. Exam findings are unreliable in emphysema — globally quiet chest, bilateral hyperresonance, transmitted sounds. Not improving with treatment means consider what you are not seeing.
Upper airway obstruction
Immediately life-threatening
Key features
- Stridor — inspiratory noise
- Drooling, inability to swallow
- Tripod positioning, distress
- Voice change — muffled or absent
- History of allergy, foreign body, infection
- Visible swelling of face / neck / tongue
- Urticarial rash (anaphylaxis)
- Rapid deterioration possible
Immediate actions
- Anaphylaxis: IM adrenaline immediately
- Sit upright — do not force supine
- O2, IV access
- Do not examine oropharynx in suspected epiglottitis — risk of complete obstruction
- Nebulised adrenaline if available and appropriate
- Pre-alert — surgical airway may be needed
Diagnostic uncertainty
Stridor is usually obvious but can be confused with wheeze. Key distinction: stridor is inspiratory and originates above the cords; wheeze is expiratory and from the lower airways. In partial obstruction the patient may maintain SpO2 until suddenly they cannot. Deterioration can be extremely rapid — treat urgency proportionally.
Critically unwell — diagnosis unknown
Diagnostic void
When to apply this category
- Severely unwell with no history available
- Not responding to any assessment attempts
- Scene provides no information
- Presentation doesn't fit any pattern
- Multiple possible explanations, none dominant
- Treatment not working as expected
Immediate actions
- Stabilise physiology before diagnosis — airway, breathing, circulation
- O2 titrated to SpO2 response
- IV access, monitoring, glucose check
- Consider and exclude the reversible: hypoglycaemia, opiate toxicity (naloxone), tension pneumothorax
- Pre-alert with honest uncertainty — "I don't know what's wrong" is valid clinical information
- Move — hospital has what you don't
Diagnostic uncertainty
This is the category where comfort with not knowing is the skill. Your job is not to diagnose — it is to keep the patient alive long enough for someone with a CT scanner and a blood gas to find the answer. Accurate self-awareness about the limits of the prehospital environment is not a failure. Premature diagnostic closure — locking onto any single explanation without evidence — is the error to avoid.