Acute (minutes–hours): PE, pneumothorax, MI/CHF, asthma/COPD exacerbation, pneumonia, anaphylaxis. Chronic: COPD, asthma, ILD, CHF, anemia, deconditioning, functional. Most common causes overall: cardiac, pulmonary, anemia, deconditioning, functional.
Acute <3 wk (viral URI, pneumonia), subacute 3–8 wk (post-infectious), chronic >8 wk. Top 3 chronic in non-smokers: upper airway cough syndrome (postnasal drip), asthma, GERD; also ACE inhibitor, chronic bronchitis.
Most common: bronchitis. Don't-miss: malignancy, TB, bronchiectasis, PE. Massive hemoptysis (>200–600 mL/24h) = airway emergency — protect airway, bleeding side down.
| Pattern | FEV1/FVC | FVC | TLC | Examples |
|---|---|---|---|---|
| Obstructive | <0.70 (↓) | normal/↓ | normal/↑ (air trapping) | Asthma, COPD, bronchiectasis |
| Restrictive | normal/↑ | ↓ | ↓ | ILD, neuromuscular, chest wall, obesity |
Hypoxemia = low arterial O₂ (PaO₂ <80 mmHg) vs hypoxia = low tissue O₂ delivery. ABG screens gas exchange/acid–base; A–a gradient distinguishes causes (normal A–a + hypoxemia = hypoventilation or low FiO₂; ↑A–a = V/Q mismatch, shunt, diffusion). Imaging: CXR first; CT for detail; CTA for PE.
Reversible airway inflammation/bronchospasm; episodic wheeze, cough (often nocturnal), dyspnea, triggers (allergens, exercise, cold, URIs, aspirin). Spirometry obstructive with reversibility; methacholine if normal. Stepwise: SABA PRN → low-dose ICS (or ICS-formoterol) → add LABA → ↑ICS → add LAMA/biologics. Reliever = SABA; controllers = ICS. Assess control; avoid LABA monotherapy.
Not fully reversible airflow limitation; smoking. Chronic bronchitis ("blue bloater," productive cough ≥3 mo/yr ×2 yr) vs emphysema ("pink puffer," ↓DLCO, hyperinflation). Dx: post-bronchodilator FEV1/FVC <0.70. Tx: smoking cessation, LAMA/LABA, ICS if frequent exacerbations/eosinophilia; vaccines; pulmonary rehab. Long-term O₂ if PaO₂ ≤55 or SpO₂ ≤88% (improves mortality).
↑Dyspnea, ↑sputum volume/purulence. Tx: SABA/SAMA, systemic steroids, antibiotics (if ↑purulence), controlled O₂ (target 88–92%), consider NIPPV for hypercapnic respiratory failure. CXR to exclude pneumonia.
Bronchiectasis: permanently dilated airways; chronic copious purulent sputum, recurrent infections, hemoptysis; "tram-track"/signet-ring on CT. Causes: CF, recurrent infection, immunodeficiency. α1-antitrypsin deficiency: early panacinar (basilar) emphysema in a young/non-smoker ± liver disease.
Older adults; progressive dyspnea, dry cough, fine "Velcro" inspiratory crackles, clubbing. HRCT: UIP pattern — basilar/subpleural honeycombing. ↓DLCO. Tx: antifibrotics (pirfenidone, nintedanib); transplant; poor prognosis.
Young adults, African American women; non-caseating granulomas. Bilateral hilar lymphadenopathy on CXR; ↑ACE, hypercalcemia, erythema nodosum, uveitis, Bell palsy. Many resolve spontaneously; steroids if symptomatic/organ involvement.
| Disease | Exposure | Clue |
|---|---|---|
| Asbestosis | Shipyards, insulation, demolition | Pleural plaques, lower lobes; ↑mesothelioma & bronchogenic cancer (synergy with smoking) |
| Silicosis | Mining, sandblasting, quarry | Upper lobes, "eggshell" hilar calcification; ↑TB risk |
| Coal worker's | Coal mining | Upper lobes; black lung |
| Berylliosis | Aerospace, electronics | Granulomas (mimics sarcoid) |
Immune reaction to inhaled organic antigens (farmer's lung, bird fancier's). Recurrent flu-like illness + cough/dyspnea after exposure. Tx: avoid antigen; steroids.
Normal lung, can't expand: kyphoscoliosis, obesity, neuromuscular disease (ALS, myasthenia, Guillain-Barré — watch falling vital capacity/NIF). DLCO is normal (unlike ILD).
Usually from a DVT (Virchow triad). Dyspnea (most common), pleuritic pain, tachycardia, hypoxia; clear CXR. Wells score → low: D-dimer (or PERC); high: CTA chest (test of choice), V/Q in pregnancy/renal failure. EKG: sinus tach (S1Q3T3 specific). Tx: anticoagulation; thrombolysis for massive/unstable PE; embolectomy; IVC filter if anticoagulation contraindicated.
mPAP ≥20 mmHg (right heart cath confirms). 5 WHO groups: (1) arterial/idiopathic, (2) left heart disease (most common), (3) lung disease/hypoxia, (4) chronic thromboembolic, (5) misc. Loud P2, RV heave, signs of right heart failure. Group 1 → pulmonary vasodilators; treat the underlying cause for others.
Right heart failure from a primary pulmonary cause (COPD, PE, PHTN) — RV dilation/failure, peripheral edema, JVD, hepatomegaly. Treat the lung disease and hypoxia.
Cardiogenic (↑hydrostatic pressure — LV failure): bilateral infiltrates, ↑BNP, treat with diuretics/nitrates/O₂. Non-cardiogenic (ARDS): ↑permeability, normal cardiac pressures — see Emergencies.
Typical: S. pneumoniae (most common), H. influenzae — lobar, productive cough, fever, consolidation. Atypical ("walking"): Mycoplasma, Chlamydophila, Legionella (hyponatremia, GI/neuro, water exposure) — interstitial pattern. Severity: CURB-65 (Confusion, Urea, RR ≥30, BP low, age ≥65) guides admission.
HAP/VAP (≥48 h after admission/intubation): cover Pseudomonas and MRSA. Aspiration: dependent segments (RLL, RML, right upper-lobe posterior if supine); anaerobes; risk of lung abscess (air-fluid level, foul sputum).
Cough >2–3 wk, fever, night sweats, weight loss, hemoptysis; upper-lobe disease, cavitation; reactivation. Screen: TST/IGRA; confirm: sputum AFB/culture, NAAT. Active = RIPE (Rifampin, Isoniazid, Pyrazinamide, Ethambutol) ×2 mo then INH+rifampin. Latent: INH (± rifapentine) to prevent progression. Always combination therapy for active TB.
Acute bronchitis: viral — cough ± wheeze, normal CXR; no antibiotics. Fungal: Histoplasma (Ohio/Mississippi, bird/bat), Coccidioides (Southwest), Blastomyces. Influenza (oseltamivir if early), COVID-19. PCP in immunocompromised (TMP-SMX).
Repetitive upper-airway collapse during sleep → snoring, witnessed apneas, daytime sleepiness, morning headaches, HTN, AF, pulmonary HTN. Screen: STOP-BANG. Dx: polysomnography — AHI ≥5 with symptoms (≥15 regardless). Tx: CPAP (first-line), weight loss, oral appliance, avoid alcohol/sedatives; surgery selected.
Obesity (BMI ≥30) + awake daytime hypercapnia (PaCO₂ >45) without another cause; often coexists with OSA. Hypoxemia, polycythemia, cor pulmonale. Tx: PAP (CPAP/BiPAP) + weight loss; supplemental O₂ as needed.
No respiratory effort during apneas (vs obstructive effort in OSA); seen with heart failure (Cheyne-Stokes), opioids, high altitude, CNS lesions. Treat the underlying cause; PAP/adaptive servo-ventilation in selected cases.
Thoracentesis classifies fluid as exudate if ANY: pleural/serum protein >0.5, pleural/serum LDH >0.6, or pleural LDH >2/3 upper normal serum LDH. Transudate (none) = CHF, cirrhosis, nephrotic (↑hydrostatic/↓oncotic). Exudate = pneumonia/parapneumonic, malignancy, PE, TB, empyema. CXR blunts costophrenic angle; lateral decubitus/US for size & tap.
Primary spontaneous: tall thin young men, smokers. Secondary: COPD, etc. Sudden pleuritic pain + dyspnea, decreased breath sounds, hyperresonance. Tension = hypotension, tracheal deviation, distended neck veins → needle decompression then chest tube (clinical diagnosis, don't wait for imaging).
Empyema = pus in pleural space (complicated parapneumonic) → drainage + antibiotics. Hemothorax, chylothorax (milky, ↑triglycerides). Pleurisy = pleuritic pain + friction rub.
Costochondritis (reproducible with palpation, multiple junctions) and Tietze syndrome (single swollen costochondral junction) are musculoskeletal — but always exclude cardiac/PE/dissection first when risk factors are present.
5 A's: Ask, Advise, Assess, Assist, Arrange. Pharmacotherapy: varenicline (most effective), bupropion, nicotine replacement. Cessation is the single most impactful intervention for COPD and cancer risk.
Annual low-dose CT for adults 50–80, ≥20 pack-year history, currently smoking or quit within 15 years. Solitary pulmonary nodule: stratify by size, growth, and risk; compare to old films.
| Type | Location | Pearls |
|---|---|---|
| Small cell (SCLC) | Central | Smokers; aggressive, early mets; paraneoplastic: SIADH, ectopic ACTH, Lambert-Eaton; chemo/radiation (not primarily surgical) |
| Adenocarcinoma | Peripheral | Most common overall; non-smokers/women; hypertrophic osteoarthropathy |
| Squamous cell | Central | Smokers; cavitation; hyperCalcemia (PTHrP) |
| Large cell | Peripheral | Poorly differentiated |
Pancoast tumor (apex) → Horner syndrome, arm/shoulder pain, brachial plexus. SVC syndrome (facial/neck swelling, distended veins). Mesothelioma = asbestos, pleural-based.
| Condition | Cause / age | Hallmarks & management |
|---|---|---|
| Croup (laryngotracheobronchitis) | Parainfluenza; 6 mo–3 yr | Barking "seal" cough, inspiratory stridor, hoarse voice; steeple sign; stridor improves with crying. Tx: dexamethasone; nebulized (racemic) epinephrine for stridor at rest. Westley score grades severity. |
| Epiglottitis | H. influenzae type b (unvaccinated) | 3 D's: Drooling, Dysphagia, Distress; tripod, toxic, muffled voice; thumbprint sign. Do NOT examine the throat — secure the airway (OR), then antibiotics. Airway emergency. |
| Bronchiolitis | RSV; <2 yr (peak ~6 mo) | Wheeze, tachypnea, retractions after URI. Supportive (suction, hydration, O₂); palivizumab prophylaxis for high-risk infants. |
| Pertussis | Bordetella pertussis | Catarrhal → paroxysmal "whooping" cough + post-tussive emesis → convalescent. Tx: macrolide (azithromycin); prevent with DTaP/Tdap. |
| Foreign body aspiration | Toddlers | Sudden choking/cough/unilateral wheeze; lodges in right bronchus; bronchoscopy. |
Autosomal recessive CFTR chloride-channel defect → thick secretions. Recurrent sinopulmonary infections (Pseudomonas, Staph), bronchiectasis, pancreatic insufficiency (steatorrhea, failure to thrive, fat-soluble vitamin deficiency), meconium ileus, infertility. Dx: elevated sweat chloride, genetics, newborn screen. Tx: airway clearance, inhaled antibiotics/dornase, CFTR modulators, pancreatic enzymes.
Severe asthma not responding to therapy. Silent chest, fatigue, a "normalizing" PaCO₂ (rising from low) signals impending respiratory failure. Tx: continuous/back-to-back SABA + ipratropium, systemic steroids, magnesium, O₂; escalate to NIPPV/intubation. Watching the CO₂ climb is ominous.
Hypotension, distended neck veins, tracheal deviation away, absent breath sounds/hyperresonance. Clinical diagnosis — immediate needle decompression (2nd ICS MCL or 4th/5th ICS AAL) then chest tube. Don't wait for a CXR.
Acute non-cardiogenic pulmonary edema (sepsis, aspiration, pancreatitis, trauma). Berlin: within 1 wk, bilateral infiltrates, not cardiac, PaO₂/FiO₂ ≤300. Tx: treat cause; low-tidal-volume lung-protective ventilation (6 mL/kg), PEEP, prone positioning for severe.
Type 1 (hypoxemic): PaO₂ <60 (pneumonia, edema, PE, ARDS). Type 2 (hypercapnic): PaCO₂ >45 + acidosis (COPD, OHS, neuromuscular, sedation). NIPPV helps type 2 (COPD/OHS); intubate if failing.
Massive PE (hypotension/RV strain): systemic thrombolysis (or embolectomy) if no contraindication. Massive hemoptysis: protect the airway, position bleeding side down, resuscitate, urgent bronchoscopy/IR bronchial artery embolization.
| Setting | Regimen |
|---|---|
| Outpatient, healthy | Amoxicillin (high dose) OR doxycycline OR a macrolide (where resistance low) |
| Outpatient, comorbidities | Beta-lactam + macrolide OR a respiratory fluoroquinolone (levofloxacin/moxifloxacin) |
| Inpatient (non-ICU) | Beta-lactam + macrolide OR respiratory FQ |
| HAP / VAP | Antipseudomonal beta-lactam (pip-tazo, cefepime) ± MRSA coverage (vancomycin/linezolid) |
Macrolides (azithromycin): atypicals, penicillin-allergy alternative; QT prolongation. Respiratory FQs (levo/moxi): CAP monotherapy, HAP, Pseudomonas; tendon/QT/dysglycemia. Beta-lactams (amox, amox-clav, ceftriaxone): typical CAP/aspiration. Doxycycline: mild CAP, atypicals.
QT risk → avoid macrolides & fluoroquinolones. Pregnancy → avoid fluoroquinolones & tetracyclines. Atypicals → macrolide or doxycycline. Severe CAP → beta-lactam + macrolide OR a respiratory FQ.
Active TB = RIPE (Rifampin, Isoniazid + B6, Pyrazinamide, Ethambutol) — always combination therapy. Latent TB: isoniazid (± rifapentine) to prevent progression. Influenza: oseltamivir within 48 h. COVID-19 (high-risk outpatient): nirmatrelvir-ritonavir within 5 days (check interactions).