<?php
// Register RankMath meta fields for REST API write access
// Required for publisher script to set focus keyword via REST API
add_action("init", function () {
foreach (
["rank_math_focus_keyword", "rank_math_title", "rank_math_description"]
as $key
) {
register_meta("post", $key, [
"show_in_rest" => true,
"single" => true,
"type" => "string",
"auth_callback" => function () {
return current_user_can("edit_posts");
},
]);
}
});

Untitled

— SEO TITLE: “AMC MCQ Respiratory Medicine: High-Yield Topics and Pitfalls” META TITLE: “AMC MCQ Respiratory Medicine: High-Yield Topics and Pitfalls | MplusX” META DESCRIPTION: “Comprehensive guide on respiratory medicine AMC MCQ for international medical graduates preparing for the AMC MCQ exam.” URL SLUG: “respiratory-medicine-amc-mcq” TARGET KEYWORD: “respiratory medicine AMC MCQ” CONTENT PILLAR: “P4” SEARCH INTENT: “Info” FUNNEL STAGE: “TOFU” GOAL: “Authority”


AMC MCQ Respiratory Medicine: High-Yield Topics and Pitfalls

Last reviewed: May 2026 | Written by the MplusX Editorial Team


📌 Key Takeaways

    – In COPD exacerbations, target oxygen saturation is 88–92% — uncontrolled high-flow O2 causes hypercapnic respiratory failure and is a classic AMC MCQ distractor.
    LTOT is indicated when PaO2 <= 55 mmHg on air at rest (confirmed on two measurements at least 3 weeks apart), or <= 60 mmHg if polycythaemia or cor pulmonale is present.
    – A silent chest in acute asthma is a pre-arrest sign — escalate immediately to IV MgSO4 2g over 20 minutes and consider intubation threshold.
    – In suspected PE during pregnancy, LMWH (enoxaparin) is the treatment of choice — DOACs are contraindicated.
    Lambert-Eaton syndrome (SCLC paraneoplastic) causes proximal weakness that improves with repetition — the opposite of myasthenia gravis; this distinction is repeatedly tested.
    – A CURB-65 score >= 3 warrants consideration of ICU-level care — not just hospital admission.
    – Ready to drill these topics with exam-format questions? See the Full MplusX Subject Series →

    A 58-year-old man with known COPD is brought in by ambulance after a nurse placed him on 10 L/min O2 at home because his sats dropped to 85%.

    On arrival he is drowsy, RR 8, SpO2 98%, pCO2 78 mmHg.

    The nurse meant well. The AMC MCQ examiner knows it.

    Respiratory medicine is one of the highest-yield content areas in the AMC MCQ exam, appearing across multiple clinical presentations that test your ability to recognise severity, apply guidelines accurately, and avoid the elegant distractors the exam is famous for.

    This guide covers every major respiratory topic — from acute asthma to ILD — with clinical classification tables, management algorithms, and scenario-based distractor analysis, all referenced to eTG Complete 2026, RACGP, and current Australian practice.


    1. The AMC MCQ Respiratory Blueprint

    Before diving into individual topics, understanding how frequently each area appears helps you prioritise your study time. The table below reflects the distribution pattern seen in AMC MCQ practice materials and candidate feedback.

    TopicAMC MCQ FrequencyWhy It’s Tested
    Asthma (acute + chronic)Very HighSeverity classification, step-up therapy, critical signs
    COPDVery HighO2 targets, exacerbation management, LTOT thresholds
    Community-Acquired PneumoniaHighCURB-65, atypical organisms, antibiotic selection
    Pulmonary EmbolismHighWells criteria, PERC, investigation pathway, pregnancy
    Lung CancerModerateHistological types, paraneoplastic syndromes
    Pleural EffusionModerateLight’s criteria, exudate vs. transudate
    ILDLowerIPF vs. sarcoidosis pattern recognition

    The examiner’s strategy in respiratory medicine is consistent: present a clinical scenario where one piece of data (SpO2, PEFR, urea level, travel history) changes the entire management approach. Candidates who rely on broad pattern recognition rather than numerical thresholds consistently choose the elegant distractor.


    2. Asthma

    Severity Classification

    The AMC MCQ will give you a clinical vignette and ask you to classify severity or select the next management step. You must know these thresholds without hesitation.

    ParameterMildModerateSevereLife-Threatening
    SpO2 (air)>= 95%92–94%<92%<92% + fatigue
    Respiratory RateNormal20–25/min>25/minSlowing (exhaustion)
    PEFR (% predicted)>75%50–75%33–50%<33% (or unmeasurable)
    SpeechFull sentencesPhrasesWords onlyUnable to speak
    WheezePresentPresentLoud / bilateralSilent chest
    Heart Rate<100100–120>120Bradycardia (pre-arrest)
    Critical point: A silent chest means airflow is so severely reduced that wheeze cannot be generated. It is a pre-arrest sign, not a sign of improvement. This is one of the most commonly misinterpreted findings on the AMC MCQ.

    Acute Severe Asthma Management

    Management follows a stepwise escalation based on severity. Key AMC MCQ decision points:

    • Controlled oxygen: Target SpO2 93–95% (not high-flow unless life-threatening hypoxia)
    • Salbutamol 5 mg nebulised every 20 minutes for 3 doses in the first hour; continuous nebulisation if life-threatening
    • Ipratropium 0.5 mg nebulised added to salbutamol for moderate-severe presentations (combined neb significantly outperforms salbutamol alone)
    • Oral prednisolone 40–50 mg (or IV hydrocortisone 200 mg if unable to swallow) — start immediately, do not delay
    • IV MgSO4 2g over 20 minutes — indicated for severe or life-threatening asthma not responding to initial bronchodilators; causes smooth muscle relaxation independent of β2 pathways
    • Intubation threshold: Silent chest, exhaustion, falling GCS, or rising pCO2 — call anaesthetics early

    Chronic Asthma Step-Up Therapy

    The exam may ask you to identify the correct next step when a patient’s asthma is inadequately controlled.

    StepTreatment
    Step 1SABA (salbutamol) as needed only
    Step 2Low-dose ICS (e.g., budesonide 200 mcg/day) + SABA prn
    Step 3ICS/LABA combination (e.g., budesonide/formoterol) + SABA prn
    Step 4Medium-high dose ICS/LABA + LAMA (tiotropium)
    Step 5Add-on biologics (e.g., dupilumab, mepolizumab for severe eosinophilic asthma) — specialist referral

    Mermaid Diagram 1: Acute Asthma Severity -> Management Escalation

    graph TD

    A[“Patient presents with acute wheeze”] –> B{“Classify Severity”}

    B –>|”Mild: SpO2 >= 95%, PEFR >75%”| C[“Salbutamol MDI 4–8 puffs via spacer

    Reassess in 20 min”]

    B –>|”Moderate: SpO2 92–94%, PEFR 50–75%”| D[“Salbutamol 5mg neb + Ipratropium 0.5mg neb

    Oral prednisolone 40–50mg

    O2 target 93–95%”]

    B –>|”Severe: SpO2 <92%, PEFR 33–50%"| E["As moderate PLUS

    IV MgSO4 2g over 20 min

    Call senior clinician”]

    B –>|”Life-threatening: Silent chest

    Falling GCS / Bradycardia”| F[“Continuous salbutamol neb

    IV hydrocortisone 200mg

    Call anaesthetics — intubation threshold”]

    C –> G{“Response after 1 hour?”}

    D –> G

    E –> G

    G –>|”Good response”| H[“Step down, discharge plan

    Review preventer therapy”]

    G –>|”Poor response”| I[“Escalate to next severity tier

    Consider HDU/ICU admission”]

    F –> J[“HDU / ICU — do not delay”]

    style A fill:#0F2D5C,stroke:#fff,color:#fff

    style B fill:#2A7D7B,stroke:#fff,color:#fff

    style C fill:#166534,stroke:#fff,color:#fff

    style D fill:#D69E2E,stroke:#fff,color:#fff

    style E fill:#D69E2E,stroke:#fff,color:#fff

    style F fill:#991B1B,stroke:#fff,color:#fff

    style G fill:#2A7D7B,stroke:#fff,color:#fff

    style H fill:#166534,stroke:#fff,color:#fff

    style I fill:#D69E2E,stroke:#fff,color:#fff

    style J fill:#991B1B,stroke:#fff,color:#fff


    3. COPD

    Diagnosis

    The AMC MCQ will sometimes present a patient with a history of smoking and breathlessness and ask how to confirm COPD. The answer is always post-bronchodilator spirometry showing FEV1/FVC <0.7. You cannot diagnose COPD on clinical grounds alone — this is a frequent distractor where candidates select “clinical diagnosis” based on examination findings.

    GOLD Staging by FEV1 % Predicted

    GOLD StageFEV1 % PredictedSeverity
    GOLD 1FEV1 >= 80%Mild
    GOLD 250–79%Moderate
    GOLD 330–49%Severe
    GOLD 4<30%Very Severe

    GOLD staging is used after confirming obstruction (FEV1/FVC <0.7). The exam may also ask about symptom burden scoring (mMRC, CAT) but staging by FEV1 remains the most tested numerical classification.

    COPD Exacerbation Management

    An exacerbation is defined as an acute worsening of respiratory symptoms beyond normal day-to-day variation requiring a change in medication. Key management points:

    InterventionDetail
    Controlled oxygenTarget SpO2 88–92% — not higher. High-flow O2 blunts hypoxic drive and causes CO2 retention. Use Venturi mask (28% or 24%) not nasal prongs at >2 L/min.
    BronchodilatorsSalbutamol 2.5–5 mg neb + ipratropium 0.5 mg neb; titrate frequency to response
    CorticosteroidsOral prednisolone 30–40 mg daily for 5 days (eTG Complete 2026) — shorter course has equivalent efficacy
    AntibioticsIndicated if purulent sputum present. First-line per eTG 2026: amoxicillin-clavulanate 875/125 mg BD x 5 days. Doxycycline if penicillin allergy.
    NIV (BiPAP)Consider if pH <7.35 and pCO2 rising despite medical therapy — reduces intubation rates

    Long-Term Oxygen Therapy (LTOT)

    LTOT is one of the most numerically precise topics in the AMC MCQ. Know these thresholds exactly:

    • PaO2 <= 55 mmHg on air at rest -> LTOT indicated
    • PaO2 <= 60 mmHg if polycythaemia (Hct >55%) OR cor pulmonale OR pulmonary hypertension -> LTOT indicated
    • Must be confirmed on two measurements at least 3 weeks apart during a stable period (not during an exacerbation)
    • Minimum 15 hours per day of oxygen use for benefit
    • SpO2 alone is insufficient — arterial blood gas is required for LTOT qualification
    High-yield distractor: A question presents a COPD patient with SpO2 88% and asks whether LTOT is indicated. The correct answer requires an ABG measurement first — SpO2 does not qualify as the criterion. Choosing “commence LTOT now” without ABG confirmation is the trap.

    4. Community-Acquired Pneumonia

    CURB-65 Score

    CURB-65 is the cornerstone clinical decision tool for CAP severity and is directly tested on the AMC MCQ.

    CriterionDefinitionPoints
    C — ConfusionNew confusion (AMT <= 8 or AMTS disorientation)1
    U — UreaBlood urea >7 mmol/L1
    R — Respiratory RateRR >= 30 breaths/min1
    B — Blood PressureSystolic <90 mmHg OR diastolic <= 60 mmHg1
    65 — AgeAge >= 65 years1
    ScoreInterpretationRecommended Setting
    0–1Low severityOutpatient treatment (home)
    2Moderate severityHospital admission
    >= 3High severityConsider ICU-level care or HDU

    Causative Organisms and Clinical Clues

    OrganismClinical PatternAMC MCQ Clue
    Streptococcus pneumoniaeLobar pneumonia, productive cough, pleuritic pain, rust-coloured sputumCommonest CAP organism
    Mycoplasma pneumoniaeYoung adults, insidious onset, dry cough, CXR worse than clinical findingsErythema multiforme, cold agglutinins, doxycycline/azithromycin
    Legionella pneumophilaTravel history, hotel/spa exposure, hyponatraemia, diarrhoea, confusionAzithromycin or fluoroquinolone treatment
    Staphylococcus aureusPost-influenza, cavitation, rapid deteriorationConsider MRSA if healthcare-associated
    Klebsiella pneumoniaeAlcoholic/immunocompromised, right upper lobe, red currant jelly sputum

    eTG 2026 Empirical Treatment

    SeverityPreferred Regimen
    Mild-moderate CAP (outpatient)Amoxicillin 1g TDS + doxycycline 100mg BD (orally) x 5–7 days
    Moderate CAP (inpatient, non-ICU)IV benzylpenicillin 1.2g Q6H + doxycycline 100mg BD
    Severe CAP (ICU)IV benzylpenicillin + azithromycin 500mg IV daily; OR moxifloxacin 400mg IV daily as monotherapy
    Atypical-only coverage neededAzithromycin 500mg daily (first dose) then 250mg daily x 4 days

    Aspiration Pneumonia

    Location depends on patient position at time of aspiration:

    • Upright/semi-recumbent: Right lower lobe (most common)
    • Supine: Right upper lobe (posterior segment) or bilateral lower lobes

    Treatment requires anaerobic cover: amoxicillin-clavulanate (875/125 mg BD) is first-line per eTG 2026. Metronidazole can be added for severe disease or lung abscess.


    5. Pulmonary Embolism

    Wells PE Criteria

    CriterionScore
    Clinical signs/symptoms of DVT (leg swelling, pain on palpation)3
    PE is the most likely diagnosis or equally likely3
    Heart rate >100 bpm1.5
    Immobilisation >3 days OR surgery in prior 4 weeks1.5
    Previous DVT or PE1.5
    Haemoptysis1
    Malignancy (treatment ongoing or within 6 months)1
    Total ScorePre-test Probability
    <2Low
    2–6Moderate
    >6High

    PERC Rule

    The Pulmonary Embolism Rule-out Criteria (PERC) can exclude PE without imaging if the patient has low pre-test probability (Wells <2) AND all 8 criteria are negative:

    1. Age <50 years

    2. Heart rate <100 bpm

    3. SpO2 >= 95% on room air

    4. No unilateral leg swelling

    5. No haemoptysis

    6. No recent surgery or trauma (within 4 weeks)

    7. No prior PE or DVT

    8. No exogenous oestrogen use

    If ALL eight PERC criteria are met in a low-probability patient, PE is effectively excluded — no D-dimer or CTPA required.

    PE Treatment by Clinical Scenario

    ScenarioPreferred Treatment
    Standard PE (confirmed, haemodynamically stable)Rivaroxaban 15mg BD x 21 days, then 20mg daily OR apixaban 10mg BD x 7 days, then 5mg BD (eTG 2026)
    Severe renal impairment (CrCl <15 mL/min)UFH infusion + warfarin (overlap until INR 2–3 for 2 consecutive days)
    PregnancyLMWH (enoxaparin) — DOACs contraindicated
    Massive PE with haemodynamic compromiseThrombolysis (alteplase 100mg IV over 2 hours) — not anticoagulation alone
    Subsegmental PE, low clot burdenAnticoagulation (DOAC preferred); consider surveillance in selected cases

    Mermaid Diagram 2: Suspected PE — Investigation and Treatment Decision Tree

    graph TD

    A[“Suspected Pulmonary Embolism”] –> B[“Calculate Wells PE Score”]

    B –> C{“Wells Score?”}

    C –>|”Low <2"| D["Apply PERC Rule"]

    C –>|”Moderate 2–6″| E[“D-dimer (high-sensitivity)”]

    C –>|”High >6″| F[“CTPA — proceed directly

    (do not delay for D-dimer)”]

    D –>|”All 8 PERC negative”| G[“PE excluded

    No further investigation”]

    D –>|”Any PERC positive”| E

    E –>|”D-dimer negative”| G

    E –>|”D-dimer positive”| H[“CTPA

    (or V/Q if CrCl <30 or contrast allergy)"]

    F –> I{“CTPA Result?”}

    H –> I

    I –>|”PE confirmed”| J{“Haemodynamically stable?”}

    I –>|”PE excluded”| K[“Investigate alternative diagnosis”]

    J –>|”Yes — stable”| L{“Pregnant?”}

    J –>|”No — shock/arrest”| M[“Thrombolysis: alteplase 100mg IV

    + call critical care”]

    L –>|”Yes”| N[“LMWH (enoxaparin)

    DOAC contraindicated”]

    L –>|”No — CrCl >= 15″| O[“DOAC preferred:

    Rivaroxaban or Apixaban

    (eTG 2026)”]

    L –>|”No — CrCl <15"| P["UFH + Warfarin

    (overlap until INR 2–3 x 2 days)”]

    style A fill:#0F2D5C,stroke:#fff,color:#fff

    style B fill:#2A7D7B,stroke:#fff,color:#fff

    style C fill:#2A7D7B,stroke:#fff,color:#fff

    style D fill:#2A7D7B,stroke:#fff,color:#fff

    style E fill:#2A7D7B,stroke:#fff,color:#fff

    style F fill:#D69E2E,stroke:#fff,color:#fff

    style G fill:#166534,stroke:#fff,color:#fff

    style H fill:#2A7D7B,stroke:#fff,color:#fff

    style I fill:#2A7D7B,stroke:#fff,color:#fff

    style J fill:#2A7D7B,stroke:#fff,color:#fff

    style K fill:#166534,stroke:#fff,color:#fff

    style L fill:#D69E2E,stroke:#fff,color:#fff

    style M fill:#991B1B,stroke:#fff,color:#fff

    style N fill:#D69E2E,stroke:#fff,color:#fff

    style O fill:#166534,stroke:#fff,color:#fff

    style P fill:#D69E2E,stroke:#fff,color:#fff




    6. Lung Cancer

    Histological Types — High-Yield Features

    TypeLocationKey FeaturesParaneoplastic Syndrome
    Squamous Cell CarcinomaCentralCavitating lesion, associated with smoking, direct bronchial involvementPTHrP -> hypercalcaemia (commonest cause of malignant hypercalcaemia)
    AdenocarcinomaPeripheralMost common type overall; pleural effusion; may arise in non-smokers; bronchoalveolar subtypeRare paraneoplastic
    Small Cell Lung Cancer (SCLC)CentralRapidly progressive; early metastasis; strongly linked to heavy smokingSIADH (hyponatraemia), Cushing’s (ectopic ACTH), Lambert-Eaton myasthenic syndrome
    Large Cell CarcinomaPeripheralAggressive, rapid growth; diagnosis of exclusionGynaecomastia (hCG)

    Most Tested AMC MCQ Pattern: SCLC Paraneoplastic Syndromes

    SCLC generates paraneoplastic syndromes more than any other lung cancer type. These are disproportionately tested:

    SIADH: SCLC secretes ADH -> dilutional hyponatraemia -> serum Na <130 mmol/L, urine inappropriately concentrated (U-osmolality >100 mOsmol/kg). Treatment is fluid restriction; demeclocycline for refractory cases.

    Lambert-Eaton Myasthenic Syndrome (LEMS):

    • Proximal muscle weakness (lower limb predominant)
    • Weakness IMPROVES with repeated muscle contraction (post-tetanic facilitation) — this is the key distinguishing feature
    • Myasthenia gravis: weakness WORSENS with repeated contraction (fatiguability)
    • LEMS: absent deep tendon reflexes, autonomic features (dry mouth, impotence)
    • 60% of LEMS cases are paraneoplastic — SCLC is by far the commonest association
    • AMC MCQ will describe proximal weakness in a smoker and ask you to distinguish LEMS from MG using the repetition finding

    Cushing’s Syndrome (ectopic ACTH):

    Rapid onset, severe hypokalaemia, metabolic alkalosis, hypertension. CRH suppression test often not suppressible with high-dose dexamethasone. SCLC is the commonest cause of ectopic ACTH.

    Pancoast Tumour (Superior Sulcus Tumour)

    A Pancoast tumour arises at the apex of the lung (superior sulcus) and invades adjacent structures. The AMC MCQ will describe:

    • Horner’s syndrome: ptosis (drooping eyelid), miosis (small pupil), anhidrosis (absent sweating) — ipsilateral; caused by invasion of the sympathetic chain
    • Brachial plexus involvement: C8–T2 nerve roots -> wrist and hand pain, ulnar distribution paraesthesia
    • Rib/vertebral erosion on imaging

    The classic AMC scenario: a smoker with shoulder pain radiating to the arm + Horner’s syndrome = Pancoast tumour -> CT chest + biopsy.


    7. Pleural Effusion and ILD

    Light’s Criteria for Exudate vs. Transudate

    Light’s criteria are applied to pleural fluid obtained at thoracocentesis. An exudate meets AT LEAST ONE of the following:

    CriterionThreshold
    Pleural fluid LDH / Serum LDH ratio>0.6
    Pleural fluid protein / Serum protein ratio>0.5
    Pleural fluid LDH>2/3 of the upper limit of normal serum LDH
    Transudate CausesExudate Causes
    Congestive cardiac failure (most common)Malignancy
    Liver cirrhosisParapneumonic effusion / empyema
    Nephrotic syndromePulmonary embolism
    HypothyroidismTuberculosis
    HypoalbuminaemiaRheumatoid arthritis / SLE
    AMC MCQ tip: If Light’s criteria suggest exudate but the clinical picture strongly suggests CCF (e.g., bilateral effusions, cardiomegaly, BNP markedly elevated), consider the serum-to-fluid albumin gradient. A gradient >12 g/L supports transudate despite meeting Light’s exudate criteria — this is the albumin gradient correction.

    ILD: IPF vs. Sarcoidosis

    These two conditions are regularly tested as pattern-recognition vignettes. Focus on distinguishing features:

    FeatureIPF (UIP Pattern)Sarcoidosis
    DemographicsElderly male (>60 years), smokerYoung-middle adult (20–40), any sex
    Symptom onsetInsidious dry cough, progressive dyspnoeaDyspnoea, sometimes asymptomatic
    AuscultationBibasal fine velcro cracklesOften clear
    CXR / HRCTBasal honeycombing, traction bronchiectasis, UIP patternBilateral hilar lymphadenopathy (BHL), perihilar infiltrates
    Serum markersNone specificElevated serum ACE (not diagnostic but supportive)
    HistologyUsual Interstitial Pneumonia (UIP) — temporal heterogeneityNon-caseating granulomas (unlike TB which caseates)
    ExtrapulmonaryFinger clubbing, cor pulmonaleSkin (erythema nodosum, lupus pernio), eyes (uveitis), hypercalcaemia
    TreatmentNintedanib or pirfenidone (anti-fibrotic) — not curativeOral corticosteroids (if symptomatic / organ-threatening)
    PrognosisPoor — median survival 3–5 yearsOften self-resolving (Löfgren syndrome in particular)

    8. High-Yield Distractor Deconstruction

    The AMC MCQ uses distractors that are almost right. These four scenarios represent the most commonly reported traps from IMGs who have sat the exam.

    Scenario 1: COPD + Confusion + High-Flow O2

    Stem: A 72-year-old ex-smoker with GOLD Stage 3 COPD is admitted with worsening dyspnoea. A paramedic administered 10 L/min O2 via face mask. On arrival: GCS 13, SpO2 99%, RR 8, pCO2 82 mmHg.

    The Trap: Thinking high SpO2 = good management.

    Correct Answer: Reduce oxygen immediately to target SpO2 88–92% using a 28% Venturi mask. Obtain ABG. If pH <7.35 with rising pCO2 despite therapy, initiate NIV (BiPAP).

    Why: COPD patients with chronic hypercapnia rely on hypoxic drive. Abolishing hypoxia with high-flow O2 removes the stimulus to breathe, worsens CO2 retention, and causes type 2 (hypercapnic) respiratory failure.


    Scenario 2: Pregnant Woman with PE

    Stem: A 31-year-old woman at 8 weeks gestation presents with acute dyspnoea and right calf swelling. CTPA confirms PE. She has no renal impairment.

    The Trap: Prescribing rivaroxaban (the standard first-line agent in non-pregnant patients).

    Correct Answer: LMWH — enoxaparin 1 mg/kg subcutaneously twice daily, adjusted to anti-Xa levels.

    Why: DOACs (rivaroxaban, apixaban) cross the placenta and are teratogenic — they are absolutely contraindicated in pregnancy. Warfarin is teratogenic in the first trimester. LMWH does not cross the placenta and is safe throughout pregnancy. This rule applies even if the patient asks for tablets.


    Scenario 3: Atypical Pneumonia with Hyponatraemia

    Stem: A 48-year-old man returns from a conference in Singapore. He presents with a 5-day history of dry cough, confusion, diarrhoea, and fever. CXR shows patchy bilateral infiltrates. Na 127 mmol/L.

    The Trap: Treating as community-acquired pneumonia with amoxicillin alone.

    Correct Answer: Legionella pneumonia — treat with azithromycin 500 mg daily (or levofloxacin). Urinary Legionella antigen confirms Legionella pneumophila serogroup 1 (covers ~80% of cases).

    Why: The clinical triad of travel history + hyponatraemia + GI symptoms (diarrhoea, confusion) = Legionella until proven otherwise. Beta-lactam antibiotics have no activity against intracellular organisms. Legionella urine antigen is the fastest confirmatory test.


    Scenario 4: Massive PE with Haemodynamic Compromise

    Stem: A 55-year-old man collapses 3 days post-hip replacement. He is hypotensive (BP 75/40 mmHg), HR 130, SpO2 82%. Bedside echo shows a dilated right ventricle with septal D-sign. CTPA confirms massive bilateral PE.

    The Trap: Starting anticoagulation alone (therapeutic LMWH or DOAC).

    Correct Answer: Systemic thrombolysis with alteplase 100 mg IV over 2 hours + consider catheter-directed thrombolysis or surgical embolectomy if thrombolysis fails or is contraindicated.

    Why: Massive PE is defined by haemodynamic compromise (sustained hypotension, shock). Anticoagulation alone does not dissolve existing clot quickly enough to relieve right ventricular outflow obstruction. Thrombolysis is the definitive intervention. Contraindications include active internal bleeding, recent (<3 months) intracranial surgery, or haemorrhagic stroke.



    Frequently Asked Questions

    How much of the AMC MCQ is respiratory medicine?

    Respiratory medicine accounts for approximately 10–15% of AMC MCQ questions based on candidate feedback and the AMC’s published blueprint. This places it among the top four highest-yield specialty areas, alongside cardiovascular medicine, mental health, and musculoskeletal medicine. Within respiratory, asthma and COPD together represent the majority of questions, with PE and CAP as close runners-up. Candidates who master numerical thresholds (SpO2 targets, LTOT criteria, CURB-65 cut-offs, Wells scores) in these four topics will have covered the majority of respiratory marks available.

    What is the most important thing to know about oxygen in COPD?

    The single most tested COPD concept on the AMC MCQ is the controlled oxygen target of 88–92% during acute exacerbations. High-flow oxygen suppresses the hypoxic respiratory drive in patients with chronic hypercapnia, leading to progressive CO2 retention, respiratory acidosis, and hypercapnic coma. The 2026 eTG Complete and British Thoracic Society guidance both reinforce Venturi masks (28% or 24%) as the delivery device of choice. Equally important is the LTOT threshold — PaO2 <= 55 mmHg on ABG (not SpO2 alone) confirmed on two occasions at least 3 weeks apart.

    How does Legionella pneumonia present differently on the AMC MCQ?

    The AMC MCQ will almost always signal Legionella through a combination of three features: a travel history (hotel, cruise ship, spa, air conditioning exposure), hyponatraemia (Na+ often <130 mmol/L due to SIADH), and gastrointestinal symptoms (diarrhoea, nausea, abdominal pain) in addition to respiratory features. The CXR typically shows bilateral patchy infiltrates disproportionately severe compared to the initial clinical impression. Confirm with urinary Legionella antigen (covers serogroup 1, the most common). Treatment per eTG 2026 is azithromycin 500 mg daily or a fluoroquinolone (levofloxacin or moxifloxacin) — beta-lactam antibiotics are ineffective against this intracellular organism.

    What is the AMC MCQ approach to pulmonary embolism in pregnancy?

    The approach differs critically from non-pregnant patients. In pregnancy, the investigation pathway favours compression ultrasound of the legs first (if DVT confirmed, treat without further imaging). If DVT is not confirmed, a V/Q scan is preferred over CTPA to minimise foetal radiation dose, though CTPA is acceptable if V/Q is unavailable or indeterminate. For confirmed PE or proximal DVT, treatment is LMWH (enoxaparin) throughout pregnancy — adjusted to weight and anti-Xa levels. Rivaroxaban, apixaban, and other DOACs are absolutely contraindicated due to placental transfer and teratogenicity. Warfarin is safe in the second trimester but teratogenic in the first and increases bleeding risk near delivery. Post-partum anticoagulation can include DOACs or warfarin once breastfeeding status is confirmed.

    How do I distinguish IPF from sarcoidosis in a clinical vignette?

    The AMC MCQ uses pattern recognition for ILD. Focus on three discriminating axes. First, demographics: IPF presents in elderly men (>60) with a smoking history; sarcoidosis presents in younger adults (20–40) of any background, more common in Black individuals. Second, imaging: IPF shows bilateral basal honeycombing with traction bronchiectasis on HRCT (UIP pattern); sarcoidosis shows bilateral hilar lymphadenopathy (BHL) on CXR — the classic “angel wings” appearance. Third, extrapulmonary features: sarcoidosis causes skin (erythema nodosum, lupus pernio), eye (uveitis), and calcium (hypercalcaemia from granuloma-derived 1,25-dihydroxyvitamin D) involvement. Serum ACE is elevated in sarcoidosis (though non-specific). IPF has no extrapulmonary features but causes finger clubbing and bibasal velcro crackles.

    Drill Respiratory Medicine Today

    Knowing the thresholds is one skill. Applying them under exam pressure — in 90 seconds, against four plausible distractors — is another.

    The MplusX question bank includes over 300 respiratory medicine MCQs mapped to eTG 2026, RACGP guidelines, and the AMC exam blueprint. Each question comes with a detailed explanation that deconstructs the correct answer and explains exactly why each distractor is wrong.

    Our subject series covers all major AMC MCQ content pillars — cardiovascular, respiratory, gastroenterology, psychiatry, obstetrics, and more — so you can drill systematically rather than randomly.

    See the Full MplusX Subject Series →


    Written by the MplusX Editorial Team — dedicated to providing clinically accurate, structured, and practical resources for international medical graduates pursuing licensing with the Australian Medical Council.

    References

    • John Murtagh’s General Practice (8th Edition): Chapter 25: Cough; Chapter 32: Dyspnoea; Chapter 119: Asthma; Chapter 120: COPD.
    • RACGP Red Book (10th edition): Chapter 11: Respiratory disease.
    • Therapeutic Guidelines (eTG): Part 2 Respiratory: Asthma, COPD, Respiratory tract infections.

    Disclaimer: This article is written for AMC MCQ examination preparation and general informational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. Clinical decisions should always be based on individual patient assessment, current Australian Therapeutic Guidelines (eTG), and consultation with qualified healthcare professionals. MplusX is an exam preparation platform and is not a substitute for supervised clinical training.

    Leave a Comment