High yeild pulmonary medicine wgich must know
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high yield pulmonary medicine USMLE MBBS exam topics must know 2024
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🫁 High-Yield Pulmonary Medicine - Must Know
Sources: Murray & Nadel's Respiratory Medicine, Harrison's Principles (22E), Goldman-Cecil Medicine, Fishman's Pulmonary Diseases, Grainger & Allison's Diagnostic Radiology
1. ASTHMA
Key Facts
- Most common chronic lung disease worldwide (~340 million people); ~8% of US adults affected
- Boys > girls before puberty; women > men after puberty (ratio 1.8:1)
- ~60% heritability (twin studies); genes related to immune mechanisms
- Definition: Recurrent episodes of largely reversible airway obstruction, airway hyperresponsiveness, and airway inflammation
Pathology (Endotypes)
| Type | Feature |
|---|---|
| Atopic/Allergic | IgE-mediated, most common, eosinophilic |
| Non-atopic | Non-IgE-mediated, often triggered by infections |
| Occupational | Workplace sensitizers (isocyanates, latex) |
| Exercise-induced | Bronchospasm 5-15 min post-exercise |
| Aspirin-exacerbated | Samter's triad: asthma + nasal polyps + aspirin sensitivity |
Spirometry in Asthma
- Obstructive pattern: FEV1/FVC < 0.70
- Reversibility: FEV1 increase ≥12% AND ≥200 mL after bronchodilator
- Bronchial provocation test (methacholine): Used when spirometry is normal but asthma is suspected
Severity Classification (GINA)
- Intermittent → Mild persistent → Moderate persistent → Severe persistent
- Based on daytime symptoms, nocturnal awakenings, SABA use, activity limitation, FEV1
Treatment Stepwise (GINA)
- Step 1: PRN low-dose ICS-formoterol (preferred) or SABA alone
- Step 2: Low-dose ICS + SABA PRN
- Step 3: Low-dose ICS-LABA
- Step 4: Medium-dose ICS-LABA
- Step 5: High-dose ICS-LABA + add-on therapy (tiotropium, biologics)
Biologic Targets (Severe/Refractory Asthma)
| Drug | Target | Indication |
|---|---|---|
| Omalizumab | Anti-IgE | Allergic asthma |
| Mepolizumab, Reslizumab | Anti-IL-5 | Eosinophilic asthma |
| Benralizumab | Anti-IL-5Rα | Eosinophilic asthma |
| Dupilumab | Anti-IL-4Rα | Type 2 inflammation |
| Tezepelumab | Anti-TSLP | Broad severe asthma |
Status Asthmaticus - High-Yield Management
- O2 to keep SpO2 > 92%
- SABA nebulization (salbutamol) every 20 min x3, then continuous
- Ipratropium bromide (add to SABA in severe)
- Systemic corticosteroids (IV methylprednisolone or oral prednisolone)
- IV magnesium sulfate (2g over 20 min) - smooth muscle relaxation
- Heliox (helium-oxygen 70:30) in refractory cases
- Intubation if GCS declining, exhaustion, silent chest
2. COPD
Key Facts
- FEV1/FVC < 0.70 post-bronchodilator (fixed ratio)
- Smoking is the #1 risk factor (15-20% of smokers develop COPD)
- Alpha-1 antitrypsin deficiency: panacinar emphysema, young patients, lower lobes
- GOLD Staging by FEV1 (% predicted): GOLD 1 ≥80%, GOLD 2 50-79%, GOLD 3 30-49%, GOLD 4 <30%
Emphysema Types
| Type | Location | Cause |
|---|---|---|
| Centrilobular (centriacinar) | Upper lobes | Smoking |
| Panlobular (panacinar) | Lower lobes, diffuse | α1-antitrypsin deficiency |
| Paraseptal | Subpleural | Associated with spontaneous pneumothorax |
COPD vs. Asthma - Key Distinguishing Features
| Feature | COPD | Asthma |
|---|---|---|
| Age | >40 yrs, smoker | Often young |
| Obstruction | Fixed | Reversible |
| Eosinophilia | Sometimes | Common |
| DLCO | Reduced | Normal |
| Response to steroids | Partial | Good |
Pulmonary Hypertension in COPD
- COPD is the most common lung disease associated with PH (>80% of all CLD-PH)
- Most common PH definition: mPAP > 25 mmHg; newer threshold >20 mmHg
- Severe PH (mPAP ≥40 mmHg) is rare in COPD - look for alternate cause
- Low DLCO and arterial PO2/PCO2 predict severe PH - Murray & Nadel's, p. 85
COPD Exacerbation Management
- Controlled O2 (target SpO2 88-92%)
- SABA + SAMA (salbutamol + ipratropium)
- Oral prednisolone 40mg x5 days
- Antibiotics if: increased sputum purulence, increased dyspnea, increased sputum volume (Anthonisen criteria)
- Non-invasive positive pressure ventilation (NIV/BiPAP): PaCO2 >45 with pH <7.35
- Intubate if NIV fails or contraindicated
3. PULMONARY EMBOLISM (PE)
Wells Score (Pretest Probability)
| Clinical Feature | Points |
|---|---|
| Clinical signs of DVT | 3 |
| PE more likely than alternative diagnosis | 3 |
| Heart rate >100 bpm | 1.5 |
| Immobilization or surgery in past 4 weeks | 1.5 |
| Prior DVT/PE | 1.5 |
| Hemoptysis | 1 |
| Malignancy | 1 |
- Score ≤4: PE "unlikely" → D-dimer; if D-dimer <500 ng/mL: PE excluded
- Score >4: PE "likely" → proceed directly to CTPA
Massive PE
- Hemodynamic instability (shock, systolic BP <90 for ≥15 min)
- Treatment: Systemic thrombolysis (tPA alteplase 100mg over 2h) - first line
- Surgical embolectomy or catheter-directed therapy if thrombolysis contraindicated
Submassive PE
- RV strain on echo/CT but hemodynamically stable
- Anticoagulate; consider thrombolysis if deteriorating
PE in Pregnancy
- LMWH is first-line anticoagulation (warfarin and DOACs are contraindicated)
- D-dimer is less reliable in pregnancy (elevated at baseline)
- V/Q scan preferred over CTPA when possible (less radiation to breast tissue)
4. INTERSTITIAL LUNG DISEASES (ILD)
ILD Pattern Recognition on HRCT
| Pattern | HRCT Findings | Key Diagnosis |
|---|---|---|
| UIP | Basal, subpleural reticular opacities + honeycombing + traction bronchiectasis | IPF |
| NSIP | Bilateral symmetric ground-glass opacities, spares subpleural; no/sparse honeycombing | CTD-associated ILD |
| COP | Patchy subpleural consolidation, may migrate; reversed halo (atoll) sign | Cryptogenic Organizing Pneumonia |
| DIP | Diffuse ground-glass; smokers | Desquamative Interstitial Pneumonia |
| HP | Upper lobe centrilobular nodules, air-trapping mosaic; fibrosis in chronic | Hypersensitivity Pneumonitis |
| Sarcoidosis | Bilateral hilar lymphadenopathy + perilymphatic nodules | Sarcoidosis |
IPF (Idiopathic Pulmonary Fibrosis)
- UIP pattern on HRCT is diagnostic (in right clinical context; may avoid surgical biopsy)
- Treatment: Pirfenidone or Nintedanib (antifibrotic, slow progression - proven 2014)
- Immunosuppression (steroids) was previously used - now shown to increase morbidity/mortality
- Median survival 3-5 years from diagnosis; lung transplant is definitive therapy
- Harrison's 22E, p. 2306: antifibrotic therapy may also benefit other forms of progressive pulmonary fibrosis
NSIP
- Most common ILD pattern in connective tissue diseases (especially SSc, PM/DM)
- Better prognosis than IPF
- Responds to corticosteroids
Sarcoidosis
Scadding Radiographic Stages
| Stage | Findings |
|---|---|
| 0 | Normal CXR |
| I | Bilateral hilar lymphadenopathy (BHL) only |
| II | BHL + pulmonary infiltrates |
| III | Pulmonary infiltrates without BHL |
| IV | Pulmonary fibrosis |
Lofgren Syndrome (Acute Sarcoidosis)
- Triad: BHL + erythema nodosum + arthritis/arthralgia (usually periarthritis of ankles)
- Excellent prognosis; often resolves spontaneously
- Uveitis in sarcoidosis → look for hypercalcemia (activated macrophages produce 1,25-OH vitamin D)
Sarcoidosis-associated PH
- Occurs in advanced (Stage IV) sarcoidosis
- Mechanism: fibrotic compression of vessels, granulomatous vasculitis
- Poor prognosis; consider lung transplant
5. PLEURAL DISEASE
Transudates vs. Exudates - Light's Criteria
Exudate if ANY of:
- Pleural/serum protein ratio > 0.5
- Pleural/serum LDH ratio > 0.6
- Pleural LDH > 2/3 upper limit of normal serum LDH
| Transudate | Exudate |
|---|---|
| CHF (most common) | Pneumonia/parapneumonic |
| Hepatic cirrhosis | TB pleuritis |
| Nephrotic syndrome | Malignancy |
| Hypoalbuminemia | PE |
| Autoimmune (RA, SLE) |
TB Pleuritis
- Exudative effusion, lymphocytic predominance
- Low glucose, high LDH
- High adenosine deaminase (ADA) - most useful test (>40 U/L is suggestive)
- Pleural biopsy: granulomas (higher yield than fluid culture for AFB)
Empyema
- pH < 7.2, glucose <60, positive culture or Gram stain → chest tube drainage mandatory
- If multiple loculations → fibrinolytic agents (tPA + DNase) intrapleural
6. PNEUMOTHORAX
Classification
| Type | Features |
|---|---|
| Primary spontaneous | Young tall thin males; subpleural blebs rupture; no underlying lung disease |
| Secondary spontaneous | COPD (most common), CF, Marfan's, Langerhans cell histiocytosis |
| Traumatic | Penetrating/blunt chest trauma |
| Tension | Life-threatening - shifted mediastinum, tracheal deviation away, JVD, hypotension |
| Catamenial | Recurrent right-sided PTX in women coinciding with menstruation; due to pleural endometriosis |
Management
- Small primary (<2 cm on CXR): observation + O2 (accelerates absorption)
- Moderate-large (>2 cm) or symptomatic: aspiration or chest tube
- Tension PTX: immediate needle decompression (2nd ICS, midclavicular line) → then chest tube
- Recurrent: chemical pleurodesis or VATS with bullectomy
7. TUBERCULOSIS
Key Diagnostic Tests
| Test | Sensitivity | Notes |
|---|---|---|
| TST/Mantoux | 77-80% | False negative in immunosuppressed; cross-reacts with BCG |
| IGRA (QuantiFERON) | 80-90% | Not affected by BCG; preferred in BCG-vaccinated populations |
| Sputum AFB smear | 45-80% | 3 early morning samples (x3) |
| Sputum culture (LJ/MGIT) | Gold standard | Takes 2-8 weeks |
| Xpert MTB/RIF (GeneXpert) | 85-90% smear+ve; 67% smear-ve | Rapid (2h), detects rifampicin resistance |
Active TB Treatment
| Phase | Duration | Drugs |
|---|---|---|
| Intensive (RHZE) | 2 months | Rifampicin + Isoniazid + Pyrazinamide + Ethambutol |
| Continuation (RH) | 4 months | Rifampicin + Isoniazid |
Drug Side Effects (Critical!)
| Drug | Key Side Effect |
|---|---|
| Isoniazid (INH) | Peripheral neuropathy (pyridoxine/B6 prevents), hepatotoxicity, lupus-like |
| Rifampicin | Hepatotoxicity, orange discoloration of secretions, enzyme inducer |
| Pyrazinamide | Hyperuricemia (gout), hepatotoxicity |
| Ethambutol | Optic neuritis (red-green color blindness; check visual acuity monthly) |
LTBI (Latent TB) Treatment
- INH x9 months (standard) or INH + rifapentine x3 months (3HP regimen)
- Screen before starting anti-TNF therapy (biologics)
8. PNEUMONIA
Classification and Organisms
| Type | Common Organisms |
|---|---|
| CAP (typical) | Streptococcus pneumoniae (#1), H. influenzae, Moraxella |
| CAP (atypical) | Mycoplasma, Chlamydophila, Legionella |
| HAP/VAP | Pseudomonas, Klebsiella, MRSA |
| Aspiration | Anaerobes, mixed flora |
| Immunocompromised | PCP (Pneumocystis), CMV, Aspergillus |
Atypical Pneumonia Clues
- Mycoplasma: Young adults, "walking pneumonia," cold agglutinins, bullous myringitis
- Legionella: Water towers, hotel/hospital outbreaks; hyponatremia, diarrhea, mental confusion; urine antigen test (best rapid test); treat with fluoroquinolone or azithromycin
- Chlamydophila psittaci: Bird exposure (parrots, psittacines)
CURB-65 Score (Severity/Admission)
| Variable | Points |
|---|---|
| Confusion | 1 |
| Urea >7 mmol/L (BUN >19 mg/dL) | 1 |
| RR ≥30/min | 1 |
| BP: SBP <90 or DBP ≤60 | 1 |
| Age ≥65 | 1 |
- Score 0-1: Outpatient; Score 2: Short admission; Score 3-5: ICU consideration
PCP (Pneumocystis jirovecii Pneumonia)
- HIV patients with CD4 <200
- Dry cough, dyspnea on exertion, fever; CXR: bilateral ground-glass perihilar infiltrates
- Elevated LDH; diagnosis by BAL (silver stain, immunofluorescence)
- Treatment: TMP-SMX (high dose); add prednisone if PaO2 <70 mmHg
- Prophylaxis: TMP-SMX when CD4 <200
9. LUNG CANCER
Types and Key Features
| Type | Location | Features |
|---|---|---|
| Adenocarcinoma | Peripheral | Most common overall; EGFR, ALK, ROS1 mutations; bronchoalveolar variant |
| Squamous cell | Central/hilar | Cavitates; hypercalcemia (PTHrP); Pancoast tumor |
| Small cell (SCLC) | Central | Neuroendocrine; paraneoplastic syndromes; most aggressive |
| Large cell | Peripheral | Diagnosis of exclusion; gynecomastia (HCG) |
Paraneoplastic Syndromes
| Syndrome | Cancer Type |
|---|---|
| SIADH | SCLC |
| Ectopic ACTH → Cushing's | SCLC |
| Lambert-Eaton myasthenic syndrome | SCLC |
| Hypercalcemia (PTHrP) | Squamous cell |
| Hypertrophic pulmonary osteoarthropathy (HOA) | Adenocarcinoma |
| Dermatomyositis/acanthosis nigricans | Adenocarcinoma |
Pancoast Tumor (Superior Sulcus Tumor)
- Apex of lung invading T1 nerve root, brachial plexus, subclavian vessels, sympathetic chain
- Horner's syndrome: Ptosis + miosis + anhidrosis
- Shoulder/arm pain radiating to ulnar distribution (C8-T2)
- Treatment: Concurrent chemoradiation → surgery
SCLC Treatment
- Extremely chemosensitive; Etoposide + Cisplatin (EP regimen) standard first line
- Prophylactic cranial irradiation (PCI) for limited and extensive stage responders (reduces brain mets)
- Limited stage: chemoradiation
- Extensive stage: chemotherapy ± immunotherapy (atezolizumab/durvalumab)
10. PULMONARY FUNCTION TESTS (PFTs) - The Foundation
Obstructive vs. Restrictive
| Parameter | Obstructive | Restrictive |
|---|---|---|
| FEV1/FVC | <0.70 | Normal or increased |
| TLC | Normal/increased | Decreased |
| FVC | Normal/mild decrease | Decreased |
| DLCO | Decreased (emphysema) | Decreased (ILD, pulmonary fibrosis) |
Flow-Volume Loop Patterns
- Obstructive: Scooped-out expiratory curve, hyperinflation
- Fixed upper airway obstruction: Plateau on both inspiration AND expiration
- Variable extrathoracic obstruction: Plateau on inspiration only (eg vocal cord paralysis)
- Variable intrathoracic obstruction: Plateau on expiration only
DLCO Patterns
| Low DLCO | Normal DLCO |
|---|---|
| Emphysema, IPF, PH, anemia | Asthma, obesity, early sarcoidosis |
| Pulmonary edema, PE | Polycythemia (increased DLCO) |
11. ARTERIAL BLOOD GAS (ABG) INTERPRETATION
Step-by-Step Approach
- pH: acidosis (<7.35) or alkalosis (>7.45)
- Primary disorder: pCO2 (respiratory) vs. HCO3 (metabolic)
- Compensation (is it appropriate?)
- Anion gap if metabolic acidosis
Compensation Formulas
| Disorder | Expected Compensation |
|---|---|
| Metabolic acidosis | pCO2 = 1.5 × HCO3 + 8 ± 2 (Winter's formula) |
| Metabolic alkalosis | pCO2 increases 0.7 per 1 mEq/L rise in HCO3 |
| Acute respiratory acidosis | HCO3 increases 1 per 10 mmHg rise in pCO2 |
| Chronic respiratory acidosis | HCO3 increases 3.5 per 10 mmHg rise in pCO2 |
| Acute respiratory alkalosis | HCO3 decreases 2 per 10 mmHg fall in pCO2 |
A-a Gradient
- Formula: PAO2 - PaO2 = [(FiO2 × 713) - (PaCO2/0.8)] - PaO2
- Normal: age/4 + 4 (increases with age)
- Elevated A-a with low PaO2: V/Q mismatch, diffusion limitation, intracardiac/intrapulmonary shunt
- Normal A-a with low PaO2: Hypoventilation, high altitude
12. SLEEP APNEA
OSA vs. Central Sleep Apnea
| Feature | OSA | CSA |
|---|---|---|
| Mechanism | Upper airway collapse | Absent respiratory drive |
| Effort | Present | Absent |
| Associated | Obesity, craniofacial | CHF, opioids, brainstem lesion |
| Treatment | CPAP | CPAP, BiPAP, adaptive servo-ventilation (ASV) |
OSA
- Apnea-Hypopnea Index (AHI): Mild 5-14, Moderate 15-29, Severe ≥30
- STOP-BANG screening tool (≥3 is high-risk)
- CPAP: first-line treatment
- Complications: hypertension, AFib, pulmonary hypertension, metabolic syndrome
13. CYSTIC FIBROSIS
- CFTR gene mutation (chromosome 7q); most common: ΔF508 (Phe508del)
- Thick, tenacious secretions; obstructive pattern on PFTs
- Classic bugs: Pseudomonas aeruginosa (most common after childhood), Staphylococcus aureus, Burkholderia cepacia (worst prognosis)
- Diagnosis: Sweat chloride >60 mEq/L (two tests)
- CFTR modulators: Elexacaftor/tezacaftor/ivacaftor (Trikafta) - game-changing for ΔF508
- Complications: bronchiectasis, pneumothorax, cor pulmonale, male infertility (absent vas deferens), fat-soluble vitamin deficiency, diabetes
14. QUICK HIGH-YIELD MNEMONICS
SPACES - Causes of bloody pleural effusion:
Surgery, Pulmonary embolism, AVM, Cancer, Endometriosis (catamenial), Spontaneous PTX
AEIOU - Indications for intubation in asthma:
Apnea, Exhaustion, Increasing CO2, Obtunded, Unable to speak full sentences
RIPE - TB first-line drugs: Rifampicin, Isoniazid, Pyrazinamide, Ethambutol
CAMELS - Sarcoidosis manifestations:
Calcium elevation, Angiotensin converting enzyme, Machinery-like murmur (no), Erythema nodosum, Lymphocytosis (BAL), Staghorn granulomas
EXAM TRAPS TO AVOID
- Fixed ratio FEV1/FVC <0.70 = COPD (not Z-score; post-bronchodilator)
- IPF: steroids worsen outcomes - give antifibrotics (pirfenidone/nintedanib)
- Massive PE = hemodynamic instability → systemic thrombolysis (not just anticoagulation)
- Legionella: Urine antigen (best rapid test); treat with fluoroquinolone, NOT beta-lactam
- D-dimer is a rule-OUT, not rule-IN test (high sensitivity, low specificity)
- Tension PTX: don't wait for CXR → immediate needle decompression
- TB + HIV: Start ART 2-8 weeks after starting TB treatment (not simultaneously - IRIS risk); EXCEPT if CD4 <50 → start ART within 2 weeks
- SCLC is treated with chemo/radiation, NOT surgery (almost never resectable)
- Methotrexate, amiodarone, bleomycin, nitrofurantoin - drug-induced ILD (exam favorites)
- Spontaneous pneumothorax in a young man + Marfan features → suspect Marfan's
Sources: Murray & Nadel's Textbook of Respiratory Medicine | Harrison's Principles of Internal Medicine 22E | Goldman-Cecil Medicine | Fishman's Pulmonary Diseases and Disorders | Grainger & Allison's Diagnostic Radiology
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