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WEEK 1 - WHAT YOU'VE JUST MASTERED

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WEEK 2 - COMPLETE. HERE'S WHAT YOU'VE JUST MASTERED:

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WEEK 3 - COMPLETE. HERE'S WHAT YOU'VE JUST MASTERED:

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THE 24-DAY PULMONARY MEDICINE COURSE - COMPLETE

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☠️ THE DANGEROUS MISTAKES COMPENDIUM

Pulmonary Medicine: What Students & Doctors Get Wrong

The Errors That Kill, Harm, Delay, and Mislead

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This compendium is organized by category of danger. Every entry is real. Every error has harmed a patient. Study this as carefully as any pharmacology table - because knowing what NOT to do is as important as knowing what TO do.

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SECTION I - INSTANTLY FATAL ERRORS

Get these wrong and the patient may not survive the next hour

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☠️ MISTAKE 1: Waiting for a Chest X-Ray Before Treating Tension Pneumothorax

"Let me get a CXR to confirm tension pneumothorax before I needle it."

Tension PTX → Mediastinal shift → IVC kinking → Venous return collapses
→ Cardiac output falls to zero → Cardiac arrest
Time to arrest: can be < 5 minutes from first signs
A CXR takes 10+ minutes to obtain, report, and act on

• Absent breath sounds on one side
• Tracheal deviation AWAY from the silent side
• Distended neck veins
• Haemodynamic instability (shock → arrest)

Classic Scenario: Ventilated ICU patient suddenly becomes hypotensive with high airway pressures. Junior doctor orders portable CXR. By the time it arrives, the patient is in PEA arrest. Diagnosis: tension PTX from central line placement. Would have survived with immediate needle decompression.

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☠️ MISTAKE 2: Giving High-Flow Oxygen to a COPD Patient with Type 2 Respiratory Failure

"My patient looks blue and breathless - I'll give them 15L O2 via non-rebreather mask."

Chronic CO2 retainer (Type 2 RF):
    Central chemoreceptors are DESENSITISED to CO2 (chronically elevated)
    Respiratory drive MAINTAINED by hypoxic drive (peripheral chemoreceptors)
    ↓
    Give high-flow O2 → PaO2 rises rapidly → hypoxic drive REMOVED
    ↓
    Patient stops breathing deeply → CO2 rises uncontrolled
    ↓
    CO2 narcosis → decreasing consciousness → respiratory arrest
    ↓
    DEATH or emergency intubation

Note: NOT all COPD patients are CO2 retainers. Check their baseline ABG or clinical notes. If unsure, give controlled O2 and get ABG within 30 minutes.

High O2 also causes CO2 retention by two additional mechanisms:
1. O2 displaces CO2 from haemoglobin (Haldane effect) → CO2 released into blood
2. Abolishes HPV → V/Q worsens → more dead space → CO2 rises

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☠️ MISTAKE 3: Interpreting "Silent Chest" in Acute Asthma as Improvement

"Good - the wheeze has settled, I'll step down the treatment."

Wheeze requires AIRFLOW to generate turbulence
Severe asthma → airways SO narrowed → NO airflow moves
→ NO wheeze = NOT better = NEAR-FATAL
→ Patient appears calmer (exhausted, not improving)
→ If untreated: CO2 rises, pH falls, respiratory arrest within minutes

• Wheeze PRESENT + breathless = bad
• Wheeze ABSENT + breathless = CATASTROPHIC
• ALWAYS correlate with work of breathing, accessory muscle use, SpO2, and especially ABG

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☠️ MISTAKE 4: Missing a Rising PaCO2 in Acute Asthma

"PaCO2 is 40 mmHg, that's normal - patient is stable."

ACUTE SEVERE ASTHMA → patient HYPERVENTILATES → PaCO2 should be LOW (30-35)
A "NORMAL" PaCO2 in a patient working hard to breathe = they are TIRING
They can no longer maintain the hyperventilation needed to blow off CO2
PaCO2 rising toward "normal" = THEY ARE CRASHING

• PaCO2 < 35 = hyperventilating (expected, reassuring if work of breathing acceptable)
• PaCO2 35-40 = ALARM - compensatory hyperventilation FAILING
• PaCO2 > 40 = EMERGENCY - near-respiratory failure - prepare for intubation

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☠️ MISTAKE 5: Delaying Thrombolysis in Massive Pulmonary Embolism "Until Imaging"

"I suspect massive PE but I'll wait for CTPA to confirm before giving alteplase."

Massive PE → cardiac output falls → BP < 90 → coronary and cerebral ischaemia
Right ventricle acutely dilates → RV ischaemia → RV infarction
Downward spiral: ↓ CO → ↓ coronary perfusion → arrhythmia → cardiac arrest

• You cannot get CTPA immediately
• Bedside echo shows acute RV dilation + D-septum
• Clinical picture is convincing

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SECTION II - DRUG ERRORS THAT MAIM

The prescribing mistakes that cause serious harm

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💊 MISTAKE 6: Prescribing Beta-Blockers (Including Eye Drops) in Asthma

Prescribing atenolol for hypertension, bisoprolol for heart rate control, or timolol eye drops for glaucoma in a patient with asthma.

Beta-2 receptors in bronchial smooth muscle maintain bronchodilation
Beta-blockers BLOCK beta-2 receptors → UNOPPOSED bronchospasm
Even topical eye drops (timolol): 50-80% is systemically absorbed
→ Nasolacrimal duct → systemic circulation → reaches lung beta-2 receptors
→ SEVERE bronchospasm

• Oral (atenolol, bisoprolol, propranolol, metoprolol)
• IV (labetalol, propranolol)
• Topical ophthalmic (timolol, betaxolol)

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💊 MISTAKE 7: LABA Monotherapy in Asthma (Without ICS)

Prescribing salmeterol or formoterol alone as maintenance therapy in asthma to "avoid steroid side effects."

LABAs provide bronchodilation but have NO anti-inflammatory effect
Underlying TH2 eosinophilic inflammation CONTINUES silently
Airway remodeling PROGRESSES undetected
LABA masks symptoms → patient seems controlled → no escalation
Sudden severe asthma attack can be fatal because:
    - Disease was more severe than apparent
    - Inflammatory burden was never treated
    - SMART trial (2006): salmeterol monotherapy → 4x increased asthma-related deaths

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💊 MISTAKE 8: Not Adjusting Theophylline Dose When Adding Interacting Drugs

Admitting a COPD patient on theophylline for a chest infection and prescribing ciprofloxacin or azithromycin without checking theophylline levels.

Theophylline: Therapeutic window 10-20 mg/L; Toxic: >20 mg/L
Ciprofloxacin, erythromycin, azithromycin, cimetidine → INHIBIT CYP1A2
→ Theophylline metabolism SLOWED → levels RISE
→ Levels >20 mg/L: Tachycardia, arrhythmias, seizures, DEATH

Phenytoin, rifampicin, carbamazepine, SMOKING → INDUCE CYP1A2
→ Theophylline levels FALL → loss of efficacy
Also: A patient who STOPS SMOKING has their theophylline levels RISE
(Smoking induced the enzyme; stopping removes the induction → levels rise)

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💊 MISTAKE 9: Using ASV (Adaptive Servo-Ventilation) in Heart Failure with EF < 45%

Treating Cheyne-Stokes breathing / central sleep apnea in heart failure patients with ASV.

SERVE-HF trial (NEJM 2015):
    ASV in heart failure with EF < 45% + predominantly central SA
    → INCREASED cardiovascular mortality (hazard ratio 1.28)
    → INCREASED sudden cardiac death
    Mechanism: ASV suppresses Cheyne-Stokes → but may have adverse haemodynamic effects
    on the failing heart; removes adaptive sympathetic stimulation

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💊 MISTAKE 10: Giving Salmeterol Without ICS to a Patient Switching from Salbutamol PRN

A patient uses salbutamol PRN 3x/week (Step 1 asthma). Doctor decides to "step up" and prescribes a LABA without first trialling ICS.

• ICS is Step 2 in asthma management
• LABA is never Step 2 alone
• Correct escalation: PRN SABA → add ICS (low dose) → then add LABA to ICS
• Jumping to LABA without ICS = LABA monotherapy = banned

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SECTION III - DANGEROUS DIAGNOSTIC ERRORS

The misses and misinterpretations that delay treatment

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🔍 MISTAKE 11: Accepting a "Normal" Chest X-Ray to Exclude PE

"CXR is normal, so PE is unlikely."

In ACUTE PE:
    CXR is normal in the MAJORITY of cases
    Even massive PE may show only sinus tachycardia and a normal CXR
    Classic findings (Hampton's hump, Westermark sign, Fleischner sign) are
    present in < 30% of PEs
    → Normal CXR in a breathless patient with risk factors INCREASES the
       probability of PE (it excludes pneumonia, pneumothorax, pulmonary oedema)

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🔍 MISTAKE 12: Confusing Lambert-Eaton Myasthenic Syndrome with Myasthenia Gravis

Diagnosing proximal weakness with fatigue as myasthenia gravis without considering LEMS (and missing an underlying SCLC).

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🔍 MISTAKE 13: Missing the H-Type TEF in a Child with Recurrent Pneumonia

"This child has recurrent aspiration pneumonia from reflux" - treating with antacids and PPI for years while the H-type fistula goes undiagnosed.

H-type (Type E) TEF:
    No esophageal atresia → feeds pass normally
    Fistula is small → intermittent leakage only
    Standard barium swallow often MISSES IT
    Symptoms: cough with feeds, recurrent same-lobe pneumonia, bronchiectasis
    Can present in CHILDHOOD or ADULTHOOD

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🔍 MISTAKE 14: Diagnosing COPD Without Post-Bronchodilator Spirometry

"FEV1/FVC is 0.63 on routine spirometry - this patient has COPD" - without giving a bronchodilator first.

Unconfirmed pre-bronchodilator obstruction:
    May represent ASTHMA (reversible)
    In asthma: FEV1/FVC may normalize after bronchodilator
    Diagnosing COPD instead of asthma = wrong treatment
    (Patient gets LAMA/LABA instead of ICS which they actually need)

GOLD DEFINITION OF COPD:
    Post-bronchodilator FEV1/FVC < 0.70 (or < LLN)
    MUST be confirmed AFTER bronchodilator

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🔍 MISTAKE 15: Treating Pleural Effusion in CHF as an Exudate Due to Diuretic Effect

Patient with known heart failure is on frusemide. Thoracocentesis results: protein ratio 0.55 (>0.5). Doctor concludes "exudate - must be malignancy or infection" and initiates extensive workup.

DIURETICS concentrate pleural fluid:
    Protein concentration rises in fluid as water is removed by diuresis
    LDH also concentrates
    → CHF effusion (TRUE TRANSUDATE) meets Light's criteria for exudate
    → Misclassification rate up to 25-30% in diuretised CHF patients

Serum albumin - Pleural albumin > 1.2 g/dL = TRANSUDATE regardless of Light's criteria (The albumin gradient is not affected by diuretics as both are concentrated proportionally)

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🔍 MISTAKE 16: Not Excluding TB Before Starting Steroids for Sarcoidosis

"Bilateral hilar lymphadenopathy with non-caseating granulomas = sarcoidosis. Start prednisolone."

TB and sarcoidosis can BOTH cause:
    Bilateral hilar lymphadenopathy
    Non-caseating granulomas on biopsy (TB granulomas can be non-caseating)
    Elevated ACE
    Positive ANA
    Systemic symptoms

Starting STEROIDS in undetected TB:
    → Immunosuppression → TB disseminates
    → Miliary TB → TB meningitis → death

1. IGRA (QuantiFERON Gold) + Mantoux
2. Sputum AFB × 3 + culture
3. HIV test (TB + HIV coexists)
4. ZN stain on biopsy tissue
5. Consider: biopsy should show necrosis = TB until proven otherwise

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🔍 MISTAKE 17: Dismissing an Upper Lobe Mass as "Old TB Scarring" Without Biopsy

"Patient has old TB, that upper lobe mass is just scarring" - especially in the context of recent weight loss and cough in a smoker.

Squamous cell carcinoma: UPPER LOBE CENTRAL predilection
Lung cancer in TB background: INCREASED risk (especially squamous, adenocarcinoma)
TB scarring (scar carcinoma): lung cancer can arise IN old TB scars
Missed early lung cancer = late-stage at diagnosis = inoperable = curative window lost

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🔍 MISTAKE 18: Confusing A-a Gradient in Hypoventilation with Intrinsic Lung Disease

"Patient has PaO2 of 58 mmHg, therefore they must have V/Q mismatch or shunt."

In PURE HYPOVENTILATION (opioid overdose, NMJ failure, central hypoventilation):
    PaCO2 RISES → pushes O2 out of the alveolus (per alveolar gas equation)
    PAO2 = 150 - (PaCO2 / 0.8) → falls as PaCO2 rises
    PaO2 falls → HYPOXAEMIA
    BUT the alveoli THEMSELVES are working perfectly fine
    → A-a GRADIENT IS NORMAL
    → 100% O2 corrects hypoxaemia immediately

If doctor misinterprets as V/Q mismatch → misses narcotic overdose → patient doesn't get naloxone

• Normal A-a gradient + hypoxia = hypoventilation or low FiO2 - look for the cause of hypoventilation
• Wide A-a gradient + hypoxia = intrinsic lung disease (V/Q mismatch, shunt, diffusion defect)

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SECTION IV - CLINICAL REASONING ERRORS

The conceptual mistakes that lead to wrong management

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🧠 MISTAKE 19: Ventilating an ARDS Patient with Normal Tidal Volumes

"My 80 kg patient normally breathes 600 mL tidal volumes - I'll set the vent at 600 mL."

ARDS = "Baby Lung"
Only 20-30% of alveoli are aerated (the rest are flooded)
Delivering 600 mL to 20-30% of the lung = effective volume of 2000 mL to those alveoli
= MASSIVE OVERDISTENSION = volutrauma = biotrauma = worsening ARDS

Tidal volumes of 6 mL/kg IBW (not actual weight) vs 12 mL/kg IBW: → Absolute mortality reduction of 9% (40% vs 31%) → Most impactful ventilation trial in history

• Males: IBW = 50 + 2.3 × (height in inches - 60)
• Females: IBW = 45.5 + 2.3 × (height in inches - 60)
• A 130 kg obese patient who is 170 cm tall has IBW of approximately 65 kg → VT = 390 mL

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🧠 MISTAKE 20: Auto-PEEP: Treating Ventilator Hypotension with Fluids Instead of Disconnection

Ventilated asthma patient suddenly becomes hypotensive. Junior doctor gives 500 mL bolus of normal saline. Patient gets worse.

AUTO-PEEP (intrinsic PEEP / air trapping):
    Asthma/COPD on ventilator:
    Bronchospasm + high RR + insufficient expiratory time
    → Air traps → lung hyperinflates → intrinsic PEEP builds up
    → ↑ Intrathoracic pressure → compressed IVC → ↓ venous return
    → HYPOTENSION (mimics haemorrhage or tension PTX)

Giving FLUIDS does NOTHING because problem is MECHANICAL not VOLUME
CORRECT TREATMENT: Disconnect from ventilator for 15-30 seconds
    → Air rushes out → lung deflates → pressure normalizes → BP recovers
    Then: reduce RR, lengthen expiratory time (I:E 1:4), reduce tidal volume

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🧠 MISTAKE 21: Proning a Patient at the Wrong Threshold (or Not Proning at All)

"Proning seems extreme - I'll try some more PEEP first" with a P/F ratio of 110 mmHg.

PROSEVA trial (NEJM 2013) - LANDMARK:
    Severe ARDS (P/F < 150 mmHg) → prone 16+ hours/day
    vs. supine
    28-day mortality: 16% vs 32.8% (HALVED mortality)

If P/F < 150 and patient is not proned within the first 12-24 hours:
    → Window for maximum benefit is being wasted
    → Late proning (after 24-48h) shows diminished benefit

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🧠 MISTAKE 22: Using Spirometry Values Instead of Post-Bronchodilator Values for COPD Severity

Using pre-bronchodilator FEV1 to stage COPD severity (GOLD stage) and guide treatment decisions.

Pre-bronchodilator FEV1 underestimates functional capacity
GOLD staging uses POST-BRONCHODILATOR FEV1 % predicted:
    GOLD 1: ≥ 80%
    GOLD 2: 50-79%
    GOLD 3: 30-49%
    GOLD 4: < 30%

Using pre-BD values → patient appears worse → over-treatment
Comparing serial spirometry: MUST use same conditions (pre vs post)

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🧠 MISTAKE 23: Misinterpreting a Unilateral White-Out on CXR

A unilateral white-out on CXR → doctor diagnoses pleural effusion without checking tracheal position.

UNILATERAL WHITE-OUT + TRACHEA DEVIATES AWAY:
    → LARGE PLEURAL EFFUSION
    → Volume is PUSHING mediastinum to opposite side
    → Management: drain the effusion

UNILATERAL WHITE-OUT + TRACHEA DEVIATES TOWARD:
    → MASSIVE ATELECTASIS / LOBAR COLLAPSE
    → Volume is PULLED toward the collapsed side (reduced volume)
    → Management: find the cause of collapse (mucus plug, tumour, foreign body)
    → Bronchoscopy to clear obstruction

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🧠 MISTAKE 24: Diagnosing "Pulmonary Fibrosis" Without Excluding Connective Tissue Disease

HRCT shows bilateral basal interstitial fibrosis. Doctor diagnoses IPF and starts pirfenidone.

IPF is a DIAGNOSIS OF EXCLUSION:
    Must rule out CTD-associated ILD first:
    - Rheumatoid arthritis → RA-ILD (UIP or NSIP pattern)
    - Systemic sclerosis → SSc-ILD (NSIP pattern usually)
    - Polymyositis/Dermatomyositis → Anti-synthetase syndrome (NSIP + OP)
    - Sjogren's → LIP pattern

CTD-ILD management is DIFFERENT from IPF:
    → Immunosuppression (mycophenolate, azathioprine, rituximab) NOT antifibrotics alone
    → Missing CTD = treating with wrong drugs
    → CTD may be treatable and REVERSIBLE in early stages

• ANA, RF, anti-CCP, anti-Scl70, anti-Jo1, anti-synthetase panel, ANCA, myositis panel
• Clinical examination for rashes, joint disease, dry eyes/mouth, Raynaud's
• If CTD antibodies present → rheumatology co-management

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SECTION V - EXAMINATION & CONCEPTUAL TRAPS

The tricks that consistently fail students in exams and mislead doctors

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📚 MISTAKE 25: Thinking Compliance = Elastance (and Vice Versa)

"Emphysema has low compliance because the lung is destroyed."

COMPLIANCE = ΔV / ΔP = how easily the lung stretches
ELASTANCE = 1 / Compliance = how much it resists stretch

Emphysema: DESTROYS elastic fibers → lung is FLOPPY
→ Compliance INCREASES (high) → lung inflates very easily
→ Elastance DECREASES

Fibrosis: ADDS stiff collagen → lung is STIFF
→ Compliance DECREASES (low) → hard to inflate
→ Elastance INCREASES

Students almost universally get this BACKWARDS for emphysema.

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📚 MISTAKE 26: Thinking FVC is Only Reduced in Restrictive Disease

"FVC is normal, so there's no restriction."

FVC is reduced in BOTH:
    RESTRICTIVE: ALL volumes shrink (TLC ↓, FVC ↓, FEV1 ↓) → FEV1/FVC PRESERVED
    OBSTRUCTIVE (severe): Air trapping → TLC ↑ but FVC is also REDUCED
        because the patient cannot exhale fully (air trapped as RV)
        FEV1 falls MORE than FVC → FEV1/FVC falls

Key: FVC alone CANNOT distinguish obstruction from restriction
You NEED FEV1/FVC ratio AND ideally TLC measurement

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📚 MISTAKE 27: Assuming Normal PaO2 = No Significant PE

"PaO2 is 88 mmHg, so PE is unlikely."

PE causes V/Q mismatch (dead space predominant) + triggers hyperventilation
Hyperventilation LOWERS PaCO2 → RAISES PAO2 (alveolar gas equation)
→ PaO2 can be MAINTAINED in mild-moderate PE by hyperventilation

CORRECT approach: Calculate A-a gradient
Even with "normal" PaO2, the A-a gradient will be WIDENED in PE
(because the patient is hyperventilating to maintain it)

The ABG pattern in classic PE: PaO2 normal/mildly reduced + PaCO2 LOW + respiratory alkalosis + WIDE A-a gradient

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📚 MISTAKE 28: Confusing Panacinar and Centriacinar Emphysema

Students flip A1AT deficiency emphysema (panacinar) with smoking emphysema (centriacinar).

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📚 MISTAKE 29: Calculating Anion Gap Without Correcting for Albumin

"Anion gap is 13 - normal. No HAGMA."

NORMAL ANION GAP assumes normal serum albumin (~40 g/L)
Each 10 g/L decrease in albumin DECREASES the anion gap by 2.5 mEq/L
(Albumin is negatively charged → provides "unmeasured anion" to gap)

In a critically ill patient with albumin of 20 g/L (hypoalbuminaemia):
    Corrected AG = Measured AG + 2.5 × (4 - albumin in g/dL)
    E.g., Measured AG 13, albumin 2.0 g/dL:
    Corrected AG = 13 + 2.5 × (4 - 2.0) = 13 + 5 = 18 → HAGMA PRESENT

Without correction: the underlying HAGMA (e.g., lactic acidosis) is MISSED

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📚 MISTAKE 30: Diagnosing Pulmonary Hypertension by Echo Alone (Without RHC)

"Echo shows RVSP 55 mmHg, I'll start sildenafil for pulmonary arterial hypertension."

1. RVSP on echo is an ESTIMATE, not a measurement
   Poor acoustic windows = grossly inaccurate in 30-40% of patients

2. MOST COMMON PH is GROUP 2 (left heart disease)
   Starting sildenafil/bosentan in Group 2 PH:
   → Pulmonary vasodilation without fixing the left heart
   → MORE blood floods into a failing left heart
   → ACUTE PULMONARY OEDEMA
   → Can be fatal

3. GOLD STANDARD: RIGHT HEART CATHETERIZATION
   mPAP ≥ 20 mmHg + PAWP ≤ 15 mmHg + PVR ≥ 3 WU = Group 1 PAH
   mPAP ≥ 20 mmHg + PAWP > 15 mmHg = Group 2 (left heart origin)

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SECTION VI - THE "LOOKS LIKE / ISN'T" TRAP TABLE

Classic diagnostic imposters

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SECTION VII - THE "NEVER DO" RULES IN PULMONARY MEDICINE

☠️ NEVER wait for a CXR before treating tension pneumothorax
☠️ NEVER give high-flow O2 to a known CO2-retaining COPD patient
☠️ NEVER interpret a silent chest in acute asthma as improvement
☠️ NEVER prescribe a beta-blocker (including eye drops) in asthma
☠️ NEVER prescribe LABA without ICS in asthma
☠️ NEVER start steroids for "sarcoidosis" without excluding TB
☠️ NEVER drain a pneumothorax you haven't confirmed isn't a bulla
☠️ NEVER use normal (12 mL/kg) tidal volumes in ARDS
☠️ NEVER give ASV to a patient with heart failure EF < 45%
☠️ NEVER trust a normal CXR to exclude PE in a breathless tachycardic patient
☠️ NEVER start targeted PAH therapy without confirming Group 1 with RHC
☠️ NEVER diagnose IPF without excluding connective tissue disease
☠️ NEVER give thrombolytics in PE without considering haemostasis (recent surgery, stroke)
☠️ NEVER treat auto-PEEP-induced hypotension with fluids without first trying disconnection
☠️ NEVER calculate anion gap without correcting for hypoalbuminaemia in sick patients

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SECTION VIII - RAPID CLINICAL SAFETY RULES

The 10 clinical safety rules you should recite before every respiratory emergency:

1. BREATHLESS + TACHYCARDIA + NORMAL CXR = PE until proven otherwise
2. ASTHMA + SILENT CHEST = near-fatal, not improving
3. COPD + HIGH O2 = CO2 narcosis risk → 88-92% target
4. TENSION PTX = clinical diagnosis = needle first, image never
5. ARDS = 6 mL/kg IBW + PEEP ≥5 + P/F <150 → PRONE
6. PE + HAEMODYNAMIC INSTABILITY = thrombolyse (after confirming or if rapidly dying)
7. GRANULOMA + "SARCOIDOSIS" = exclude TB before steroids
8. SCLC + PROXIMAL WEAKNESS = LEMS not MG (check VGCC antibodies)
9. PLEURAL WHITE-OUT = check trachea first (away = effusion; toward = collapse)
10. RAISED ANION GAP = correct for albumin; check delta-delta ratio

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This compendium captures the errors that appear most frequently in clinical practice, malpractice cases, USMLE exams, and viva traps. The student who knows what NOT to do is already safer than most - because most harm comes not from ignorance of the exotic, but from the misapplication of the common.

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SUMMARY BY CATEGORY