Acute Medicine: Acute chest pain, breathlessness, collapse and blood gases

• Chest pain: Approach to Acute Chest Pain | Suspected Acute Coronary Syndrome | Suspected Pulmonary Embolism | Aortic Dissection and Other Killers
• Breathlessness: Approach to Acute Breathlessness | Acute Asthma | COPD Exacerbation | Acute Heart Failure | Community-acquired Pneumonia
• Blood gases and respiratory support: Interpreting Arterial Blood Gases | Respiratory Failure | Oxygen, CPAP, High-flow and NIV
• Collapse and palpitations: Transient Loss of Consciousness | Palpitations
• Revision: Chest Pain, Breathlessness and Collapse at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🩺 Acute chest pain, breathlessness, collapse and blood gases -page 4 of the Acute Medicine and Resuscitation chapter. These are among the commonest reasons for acute admission. The task is to rule out the killers quickly -ACS, PE, aortic dissection, tension pneumothorax, life-threatening asthma, cardiac syncope -and then treat or discharge safely. Detailed disease management is in the Cardiology and Respiratory Emergencies chapters; this page covers the front-door approach.
Your four questions for every patient: Could this be immediately life-threatening? What does the ECG (and blood gas) show? Which risk score or test will safely rule a diagnosis in or out? Can this patient go home safely -with what follow-up?

Approach to Acute Chest Pain

• ECG within 10 minutes of arrival for anyone with chest pain -look for STEMI, ischaemia, arrhythmia, right heart strain, pericarditis.
• Life-threatening causes to consider first:

  Cause	Clues	Key test
  Acute coronary syndrome	Central pressure-like pain radiating to arm, jaw or neck; sweating; risk factors; exertional	ECG, high-sensitivity troponin
  Pulmonary embolism	Pleuritic pain, breathlessness, haemoptysis, tachycardia, hypoxia, DVT, risk factors	Wells score, D-dimer, CTPA
  Aortic dissection	Sudden, severe, tearing pain radiating to the back; BP difference between arms; neurological signs	CT aortogram
  Tension pneumothorax	Sudden breathlessness, absent breath sounds, deviated trachea, shock	Clinical -decompress
  Oesophageal rupture	Pain after forceful vomiting, surgical emphysema	CT chest with oral contrast
  Cardiac tamponade	Hypotension, raised JVP, muffled heart sounds	Echo

• Other causes -pericarditis (sharp, pleuritic, eased by sitting forward; saddle-shaped ST elevation, PR depression), myocarditis, pneumonia, pneumothorax, musculoskeletal (reproducible tenderness -but don't rely on it), GORD and oesophageal spasm, biliary colic, peptic ulcer, pancreatitis, shingles (before the rash), anxiety (diagnosis of exclusion).
• Initial management -ABCDE, oxygen if hypoxic (not routinely), analgesia, IV access, bloods (FBC, U&E, troponin, clotting, lipids, glucose), chest X-ray.
• Atypical presentations -women, older people and people with diabetes may have breathlessness, nausea, fatigue or no pain with ACS.

Suspected Acute Coronary Syndrome

• STEMI (ST elevation in 2 contiguous leads, or new LBBB with typical symptoms, or posterior MI -ST depression V1–V3 with dominant R waves):
  • Primary PCI if it can be delivered within 120 minutes of when fibrinolysis could have been given (and symptoms within 12 hours); otherwise fibrinolysis.
  • Aspirin 300 mg, second antiplatelet per PCI centre protocol, analgesia (IV opioid with antiemetic), oxygen only if SpO₂ under 94%.
• NSTEMI and unstable angina -diagnosed by symptoms, ECG changes (ST depression, T wave inversion) and high-sensitivity troponin:
  • High-sensitivity troponin pathways -a single very low troponin on arrival (if symptoms began over 3 hours earlier), or 0 and 1–3 hour samples (per local assay) -rule in or rule out MI quickly.
  • A rise and/or fall in troponin above the 99th centile is needed for MI; raised troponin also occurs in PE, sepsis, myocarditis, heart failure, CKD, tachyarrhythmias, stroke and after cardioversion (type 2 MI and myocardial injury).
  • Treatment -aspirin 300 mg, fondaparinux (unless angiography soon), second antiplatelet per protocol, beta-blocker, GTN; risk-stratify with GRACE -angiography within 72 hours for intermediate or higher risk (see the Cardiology chapters).
• HEART score (History, ECG, Age, Risk factors, Troponin -0–10) -helps identify low-risk chest pain suitable for early discharge (0–3 low risk).
• Discharge after ACS ruled out -consider other causes; outpatient testing for stable angina if symptoms suggest it (CT coronary angiography -NICE CG95).

Suspected Pulmonary Embolism

• Features -breathlessness (sudden), pleuritic chest pain, haemoptysis, tachycardia, tachypnoea, hypoxia, syncope, signs of DVT; may be subtle or absent; collapse or shock (massive PE).
• Risk factors -recent surgery or immobility, active cancer, previous VTE, pregnancy and post-partum, oestrogens (COC, HRT), long-haul travel, obesity, thrombophilia.
• Two-level Wells score (NICE NG158):
  • Clinical signs of DVT (3), PE the most likely diagnosis (3), HR over 100 (1.5), immobilisation or surgery in the past 4 weeks (1.5), previous DVT or PE (1.5), haemoptysis (1), active cancer (1).
  • Over 4 -PE likely → CTPA (immediately, or give interim anticoagulation if delayed).
  • 4 or less -PE unlikely → D-dimer -if positive, CTPA; if negative, PE is excluded.
• PERC rule -in low-probability patients, PE can be excluded without a D-dimer if all 8 criteria are met (age under 50, HR under 100, SpO₂ 94% or more, no haemoptysis, no oestrogen, no previous VTE, no unilateral leg swelling, no recent surgery or trauma).
• CTPA contraindicated (contrast allergy, severe CKD, pregnancy in some) -V/Q scan.
• Other tests -ECG (sinus tachycardia commonest; S1Q3T3 and RV strain less common), chest X-ray (often normal; excludes other causes), troponin and BNP (risk), echo (RV dilatation in massive PE), leg Doppler.
• Treatment:
  • Anticoagulation -DOAC (apixaban or rivaroxaban) for most; LMWH in pregnancy and some cancers; at least 3 months (longer if unprovoked or ongoing risk).
  • Massive PE (hypotension, shock) -thrombolysis (alteplase) unless contraindicated; embolectomy otherwise.
  • Outpatient treatment for low-risk patients (PESI or sPESI low, Hestia criteria) -ambulatory pathways.

Aortic Dissection and Other Killers

• Aortic dissection:
  • Sudden severe chest or back pain ("tearing", maximal at onset), may move; syncope, stroke, limb ischaemia, abdominal pain (mesenteric), paraplegia, new aortic regurgitation murmur, BP difference over 20 mmHg between arms, pulse deficits.
  • Risk factors -hypertension, Marfan and other connective tissue disorders, bicuspid aortic valve, cocaine, pregnancy, recent cardiac procedures.
  • Easily missed -may mimic MI (dissection into the right coronary -inferior STEMI) -don't thrombolyse if dissection is possible.
  • CT aortogram (or transoesophageal echo if unstable); chest X-ray may show a widened mediastinum (often normal).
  • Type A (ascending) -emergency surgery; type B -BP control (IV labetalol, target systolic 100–120 mmHg, HR under 60) ± TEVAR (see the Vascular and Cardiothoracic Surgery pages).
• Oesophageal rupture (Boerhaave's) -severe chest pain after vomiting, surgical emphysema (Hamman's crunch), shock; CT; nil by mouth, antibiotics, surgery.
• Spontaneous pneumothorax -sudden pleuritic pain and breathlessness; chest X-ray; aspiration or drain if symptomatic or large; tension needs immediate decompression (see the Respiratory Emergencies chapter).
• Myocarditis -chest pain, breathlessness, arrhythmia after viral illness; raised troponin; cardiac MRI.

Approach to Acute Breathlessness

• ABCDE with oxygen to target, SpO₂, ABG, ECG, chest X-ray, bloods (FBC, U&E, CRP, BNP, D-dimer if appropriate, troponin).
• Causes by speed of onset:
  • Seconds to minutes -PE, pneumothorax, anaphylaxis, foreign body, acute pulmonary oedema (flash), arrhythmia.
  • Hours to days -asthma, COPD exacerbation, pneumonia, heart failure, pleural effusion, metabolic acidosis (DKA, sepsis, AKI -"air hunger" with Kussmaul breathing).
  • Weeks to months -anaemia, ILD, lung cancer, effusions, neuromuscular weakness, heart failure, obesity.
• Examination clues:
  • Wheeze -asthma, COPD, anaphylaxis, cardiac asthma.
  • Bilateral crackles -pulmonary oedema, ILD, bilateral pneumonia.
  • Focal crackles and bronchial breathing -pneumonia.
  • Dull, reduced breath sounds -effusion, collapse.
  • Hyper-resonant, absent breath sounds -pneumothorax.
  • Clear chest with hypoxia -PE, early pneumonia, shunt.
  • Clear chest, normal SpO₂, fast deep breathing -metabolic acidosis, anxiety (diagnosis of exclusion).
• Bedside ultrasound (if trained) -B-lines (oedema), effusion, pneumothorax, LV and RV function.
• Neuromuscular causes (Guillain–Barré, myasthenia, MND) -breathlessness with weakness; FVC (not SpO₂) tracks respiratory muscle failure -refer to critical care if FVC falling or under 20 mL/kg.

Acute Asthma

• Treatment:
  • Oxygen to SpO₂ 94–98%.
  • Nebulised salbutamol 5 mg (oxygen-driven), repeat or back-to-back if severe.
  • Nebulised ipratropium 500 micrograms (acute severe or life-threatening).
  • Steroids -prednisolone 40–50 mg orally (or IV hydrocortisone 100 mg) for at least 5 days.
  • IV magnesium sulfate 2 g over 20 minutes (acute severe or life-threatening not responding).
  • IV aminophylline (senior advice), IV salbutamol (rarely).
  • Critical care for life-threatening or near-fatal features, deterioration, exhaustion or rising CO₂.
• Before discharge -PEF over 75% of best, inhaler technique, personal asthma action plan, steroid course, GP review within 2 working days.

COPD Exacerbation

• Features -worsening breathlessness, cough, sputum volume or purulence; triggers -viral or bacterial infection, pollution, non-adherence, heart failure, PE.
• Assess -SpO₂, ABG (hypercapnia, acidosis), chest X-ray (pneumonia, pneumothorax), ECG, bloods, sputum culture.
• Treatment:
  • Controlled oxygen -target 88–92% (Venturi mask 24–28%) in patients at risk of hypercapnia; recheck ABG after 30–60 minutes.
  • Nebulised bronchodilators -salbutamol and ipratropium (air-driven if hypercapnic, with nasal oxygen alongside).
  • Prednisolone 30 mg daily for 5 days.
  • Antibiotics if sputum is purulent or pneumonia (per local guidance -e.g. amoxicillin, doxycycline or clarithromycin).
  • NIV -for acute hypercapnic respiratory failure (pH under 7.35 and PaCO₂ over 6.5 kPa) persisting despite optimal medical treatment (BTS).
• Ceiling of care -discuss early whether intubation would be appropriate if NIV fails.
• Before discharge -inhaler technique, smoking cessation, pulmonary rehabilitation, rescue packs, vaccinations, follow-up.

Acute Heart Failure

• Features -breathlessness (orthopnoea, paroxysmal nocturnal dyspnoea), pink frothy sputum, bilateral crackles, wheeze ("cardiac asthma"), raised JVP, peripheral oedema, third heart sound, hypoxia.
• Precipitants -ACS, arrhythmias (AF), uncontrolled hypertension, infection, fluid overload, non-adherence, NSAIDs, valve disease, thyroid disease, anaemia.
• Tests -ECG, troponin, BNP or NT-proBNP (normal level makes heart failure unlikely), chest X-ray (cardiomegaly, upper lobe diversion, Kerley B lines, effusions, bat-wing shadowing), echo (within 48 hours of admission -NICE), U&E.
• Treatment (NICE CG187):
  • Sit up; oxygen if hypoxic.
  • IV furosemide (e.g. 40–80 mg; higher if already on diuretics); monitor urine output, weight, U&E.
  • CPAP for severe pulmonary oedema with hypoxia or acidosis.
  • Nitrates (IV GTN) for hypertension, ischaemia or severe mitral or aortic regurgitation -avoid if hypotensive.
  • Don't routinely give opioids.
  • Treat the cause -PCI for ACS, rate control for AF, BP control.
  • Cardiogenic shock -inotropes and critical care (see page 3).
• Continue or start disease-modifying drugs (ACE inhibitor/ARNI, beta-blocker, MRA, SGLT2 inhibitor) for reduced ejection fraction once stable; specialist heart failure team input.

Community-acquired Pneumonia

• Features -cough, fever, purulent sputum, pleuritic pain, breathlessness, focal chest signs; older people may present with confusion only.
• CURB-65 (in hospital -one point each):
  • Confusion (new -AMTS 8 or less).
  • Urea over 7 mmol/L.
  • Respiratory rate 30 or more.
  • Blood pressure -systolic under 90 or diastolic 60 or less.
  • Age 65 or more.
• Interpretation -0–1 low severity (consider home treatment); 2 moderate (hospital); 3–5 high severity (consider critical care if 4–5). Use alongside clinical judgement (CRB-65 in the community).
• Tests -chest X-ray, FBC, U&E, CRP; blood cultures, sputum culture, pneumococcal and Legionella urinary antigens (moderate to high severity); viral PCR (influenza, COVID-19, RSV) in season.
• Antibiotics (NICE NG138, local guidelines) -within 4 hours of diagnosis (1 hour if sepsis):
  • Low severity -amoxicillin (doxycycline or clarithromycin if allergic) for 5 days.
  • Moderate -amoxicillin ± clarithromycin (atypical cover).
  • High severity -co-amoxiclav plus clarithromycin (or local alternatives).
• Review -failure to improve: empyema, abscess, resistant organisms, wrong diagnosis (PE, cancer, heart failure); chest X-ray at 6 weeks for smokers and over-50s with persistent symptoms.

Interpreting Arterial Blood Gases

• Normal values (approximate):

  Measurement	Normal range
  pH	7.35–7.45
  PaO2	Over 10 kPa on room air (expected on oxygen is about FiO2% minus 10 kPa)
  PaCO2	4.7–6.0 kPa
  Bicarbonate (HCO3)	22–26 mmol/L
  Base excess	−2 to +2
  Lactate	Under 2 mmol/L

• A systematic approach:
  1. How is the patient? -and what is the FiO₂?
  2. Oxygenation -is the patient hypoxaemic (PaO₂ under 8 kPa = respiratory failure)?
  3. pH -acidaemia (under 7.35) or alkalaemia (over 7.45)?
  4. PaCO₂ -respiratory component (high CO₂ = respiratory acidosis; low = respiratory alkalosis).
  5. Bicarbonate and base excess -metabolic component (low = metabolic acidosis; high = metabolic alkalosis).
  6. Which is primary? -the one that matches the pH direction.
  7. Compensation -is the other system moving to correct it (partial if pH still abnormal; full compensation rarely returns pH completely to normal)?
  8. Anion gap in metabolic acidosis (see page 6); lactate, glucose, electrolytes.
• Venous blood gas -useful for pH, bicarbonate, lactate, potassium and glucose (not for oxygenation; venous CO₂ slightly higher).
• Mixed disorders are common (e.g. salicylate -respiratory alkalosis plus metabolic acidosis; COPD with diuretics -respiratory acidosis plus metabolic alkalosis).

Respiratory Failure

• Acute vs chronic type 2:
  • Acute -high PaCO₂ with low pH (no time to compensate).
  • Chronic (compensated) -high PaCO₂, normal pH, high bicarbonate (kidneys retain bicarbonate over days).
  • Acute-on-chronic -high PaCO₂, high bicarbonate, but low pH -needs NIV.
• Oxygen-induced hypercapnia -in at-risk patients, excess oxygen worsens CO₂ retention (V/Q mismatch, Haldane effect) -target 88–92%; don't stop oxygen abruptly (rebound hypoxaemia).
• Signs of hypercapnia -drowsiness, confusion, headache, bounding pulse, warm peripheries, flapping tremor (asterixis).

Oxygen, CPAP, High-flow and NIV

• NIV contraindications (relative) -untreated pneumothorax, facial trauma or burns, vomiting, inability to protect the airway, copious secretions, recent upper GI surgery, severe hypoxaemia, haemodynamic instability.
• NIV needs a plan -escalation decision (is the patient for intubation if NIV fails?), ABG at 1–2 hours (improvement in pH and PaCO₂), monitoring in an appropriate area.
• Signs NIV is failing -worsening pH or PaCO₂, falling consciousness, exhaustion.

Transient Loss of Consciousness

• Transient loss of consciousness (TLoC) -usually syncope (reflex, orthostatic or cardiac), epileptic seizure, or psychogenic non-epileptic seizure (see the Older Person chapter on Falls and the Neurology and Cardiology chapters).
• Initial assessment (NICE CG109) -detailed history (before, during, after; witness account), examination (including lying and standing BP, heart murmurs, neurology), 12-lead ECG for everyone.
• Features suggesting syncope -triggers (standing, pain, heat, micturition), prodrome (light-headed, sweating, nausea, visual greying), brief loss, rapid recovery (some brief jerks are common -convulsive syncope).
• Features suggesting a seizure -tongue bitten (especially the side), head turning to one side, unusual posturing, prolonged jerking, prolonged confusion afterwards, déjà vu or aura, cyanosis.
• Red flags -urgent cardiac assessment (within 24 hours):
  • ECG abnormality -conduction disease (heart block, bifascicular block), long QT, Brugada pattern, WPW, ventricular arrhythmia, LVH (HCM), ischaemia.
  • Heart failure or structural heart disease (murmur).
  • TLoC during exertion or while lying down.
  • Family history of sudden cardiac death under 40.
  • New or unexplained breathlessness; palpitations before collapse.
  • Age over 65 with TLoC without prodrome.
• Uncomplicated reflex syncope -explain, reassure, avoid triggers, counter-pressure manoeuvres; no driving restriction for simple faints while standing (DVLA).
• Orthostatic hypotension -drug review, fluids (see the Older Person chapter).
• Driving -give DVLA advice for all TLoC presentations.

Palpitations

• Assess -ABCDE; are there adverse features (shock, syncope, ischaemia, heart failure)? -see page 2.
• ECG during symptoms is key -sinus tachycardia, AF, flutter, SVT, ectopics, VT.
• History -onset and offset (sudden -re-entry SVT; gradual -sinus), rate, regularity (tap it out), triggers (caffeine, alcohol, stimulants, exercise), associated symptoms (syncope, chest pain), drugs, thyroid symptoms, family history.
• Bloods -FBC (anaemia), U&E, magnesium, calcium, TFTs, glucose, troponin if ischaemic symptoms.
• Common causes -ectopic beats (benign), sinus tachycardia (anxiety, anaemia, thyrotoxicosis, fever, dehydration, PE, pregnancy), AF, SVT.
• New AF -rate control, anticoagulation (CHA₂DS₂-VASc), look for triggers (sepsis, thyroid, alcohol, PE); cardioversion if onset under 48 hours or unstable.
• Red flags -syncope, exertional symptoms, family history of sudden death, structural heart disease, broad complex tachycardia, pre-excitation (WPW) -cardiology referral.
• Outpatient monitoring -ambulatory ECG (24-hour to 7-day), event recorders, implantable loop recorder (infrequent symptoms).

Chest Pain, Breathlessness and Collapse at a Glance

Spot the Diagnosis