20 DISEASES: CRITERIA · DIAGNOSTICS · TREATMENT

1. COPD EXACERBATION

  • Definition/Criteria: Acute worsening of dyspnea, cough, and/or sputum beyond day-to-day variation; classified Mild/Moderate/Severe/Life-threatening by speech, SpO2, RR, altered mentation

  • Diagnostics: CXR (exclude pneumonia/pneumothorax); ABG (if SpO2 <92% or severe); CBC, BMP, sputum culture; procalcitonin to guide antibiotics

  • Treatment: SABA + ipratropium q4h; prednisone 40 mg PO x5 days (REDUCE trial); antibiotics (azithromycin or doxycycline) if increased sputum/dyspnea/purulence; NPPV if respiratory failure; supplemental O2 target SpO2 88–92%

2. ASTHMA EXACERBATION

  • Definition/Criteria: Acute worsening of airflow obstruction; severity by PEFR (Mild >70%, Moderate 40–70%, Severe <40%, Life-threatening: silent chest/altered mentation); incomplete bronchodilator reversibility on spirometry distinguishes from COPD

  • Diagnostics: Peak flow, SpO2, CXR if severe or uncertain; ABG if severe (rising CO2 = impending failure); identify trigger

  • Treatment: SABA q20min x3 → continuous nebs if severe; ipratropium add-on in ED/severe; systemic steroids early; Mg sulfate 2g IV in severe; Heliox if refractory; intubation if failing (ketamine RSI); epinephrine 0.3–0.5 mg IM if anaphylaxis component

3. COMMUNITY-ACQUIRED PNEUMONIA (CAP)

  • Definition/Criteria: Pneumonia acquired outside hospital/healthcare; dx requires new infiltrate on imaging + ≥2 of: fever, cough, purulent sputum, leukocytosis; PSI/PORT or CURB-65 guides admission vs. discharge

  • Diagnostics: CXR (PA/lateral); CBC, BMP, procalcitonin; blood cultures x2 before antibiotics in severe; urine Legionella and pneumococcal Ag; sputum Gram stain/culture (before antibiotics); HIV if risk

  • Treatment: Outpatient: amoxicillin or doxycycline; Inpatient non-severe: beta-lactam + macrolide OR respiratory FQ; Severe/ICU: beta-lactam + azithromycin or beta-lactam + respiratory FQ; add MRSA/Pseudomonas coverage if risk factors present

4. HOSPITAL-ACQUIRED PNEUMONIA (HAP) / VENTILATOR-ASSOCIATED PNEUMONIA (VAP)

  • Definition/Criteria: HAP = pneumonia ≥48h after admission, not intubated; VAP = ≥48h after mechanical ventilation; new infiltrate + clinical criteria (fever, leukocytosis, purulent secretions, declining oxygenation)

  • Diagnostics: CXR/CT; BAL or endotracheal aspirate for culture; CBC, BMP; blood cultures; procalcitonin

  • Treatment: Empiric: anti-pseudomonal beta-lactam (pip-tazo or cefepime) ± vancomycin/linezolid (if MRSA risk: prior MRSA, prior IV antibiotics, ICU admission); de-escalate at 48–72h based on cultures; 5–7 day course

5. PNEUMOTHORAX

  • Definition/Criteria: Air in pleural space; Primary spontaneous (young, thin, no lung disease); Secondary spontaneous (underlying lung disease, more dangerous); Tension = mediastinal shift, hemodynamic compromise

  • Diagnostics: CXR (expiratory); ultrasound (absent lung sliding = pneumothorax); CT if uncertain or prior to procedure; point-of-care US fastest at bedside

  • Treatment: Small primary stable (<2 cm apex-to-cupula, asymptomatic): observation; Large/symptomatic: needle aspiration or chest tube; Secondary spontaneous: chest tube always; Tension: immediate needle decompression (2nd ICS MCL) → chest tube; O2 accelerates reabsorption

6. PLEURAL EFFUSION

  • Definition/Criteria: Fluid in pleural space; Light's criteria separates exudate (protein ratio >0.5, LDH ratio >0.6, LDH >2/3 ULN) from transudate; bilateral symmetric transudate → CHF first; unilateral or exudate → thoracentesis

  • Diagnostics: CXR; ultrasound-guided thoracentesis (reduces complications 3-fold); pleural fluid: protein, LDH, glucose, pH, cell diff, Gram stain/culture, cytology, ADA, triglycerides; serum protein/LDH simultaneously

  • Treatment: Transudate: treat underlying cause (diuresis for CHF); Exudate: antibiotics ± chest tube for parapneumonic/empyema; chest tube for empyema (pH <7.2, glucose <40, organisms); malignant: serial drainage/pleurodesis/PleurX catheter; chylothorax: TPN/fat restriction or surgery

7. PULMONARY EMBOLISM (PE)

  • Definition/Criteria: Thrombus in pulmonary vasculature; classified by hemodynamic impact: Massive (obstructive shock/arrest), Submassive (RV dysfunction without shock), Low-risk; Wells score guides pre-test probability; PESI score for severity

  • Diagnostics: D-dimer if low/intermediate probability (PERC if very low risk); CT-PA = definitive; Echo if too unstable for CT; bilateral lower extremity US; ABG; troponin + BNP for risk stratification

  • Treatment: Anticoagulation (LMWH/UFH → DOAC); Massive: systemic thrombolysis (tPA 100mg over 2h) or catheter-directed; Submassive with deterioration: consider thrombolysis; IVC filter only if absolute anticoagulation contraindication; DOAC (rivaroxaban or apixaban) for long-term

8. ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS)

  • Definition/Criteria: Berlin criteria: acute onset <1 week of known insult; bilateral opacities not explained by effusion/atelectasis/nodules; PaO2/FiO2 <300 on PEEP ≥5; not fully explained by cardiac failure/fluid overload; Mild: P/F 200–300, Moderate: 100–200, Severe: <100

  • Diagnostics: CXR/CT (bilateral diffuse infiltrates); echo/BNP to exclude cardiogenic cause; ABG; identify and treat underlying cause; BAL if infection uncertain

  • Treatment: Low tidal volume ventilation (6 mL/kg IBW, plateau ≤30 cmH2O); PEEP titration per ARDSNet table; prone positioning ≥16h/day in severe (P/F <150); neuromuscular blockade if dyssynchrony; conservative fluid strategy; treat underlying cause; no steroids routinely (methylprednisolone may help late fibroproliferative phase)

9. ACUTE HYPERCAPNIC RESPIRATORY FAILURE (Type 2)

  • Definition/Criteria: PaCO2 >45 + pH <7.35; results from alveolar hypoventilation; underlying: COPD, asthma, obesity hypoventilation, NMD, sedation; distinguishable from Type 1 by high CO2 (not just hypoxia)

  • Diagnostics: ABG (key: confirms hypercapnia and acuity); CXR; spirometry history; check for mixed disorder; metabolic alkalosis may compensate chronically

  • Treatment: NPPV (BiPAP) first-line for COPD/OHS — reduces intubation rate and mortality; treat underlying cause; titrate supplemental O2 carefully (target SpO2 88–92% in COPD); intubate if failing BiPAP or altered mentation/aspiration risk

10. ACUTE HYPOXEMIC RESPIRATORY FAILURE (Type 1)

  • Definition/Criteria: PaO2 <60 mmHg (or SpO2 <90%) on room air; PaCO2 normal or low; mechanisms: V/Q mismatch (PE, PNA), shunt (ARDS, atelectasis), diffusion limitation; A-a gradient elevated

  • Diagnostics: ABG (confirm type, calculate A-a gradient); CXR; CT-PA if PE suspected; echo; CBC, BMP, procalcitonin; HFNC trial as diagnostic and therapeutic

  • Treatment: Supplemental O2 → HFNC (preferred over simple mask for moderate-severe); HFNC superior to NIV in non-hypercapnic ARF; BiPAP if CHF/COPD component; intubation if HFNC fails (SpO2 <88% despite flow ≥60L, rising RR, altered mentation); treat underlying cause; prone if ARDS

11. OBSTRUCTIVE SLEEP APNEA (OSA) / OBESITY HYPOVENTILATION (OHS) — Inpatient Decompensation

  • Definition/Criteria: OSA = recurrent upper airway collapse during sleep; OHS = BMI ≥30 + PaCO2 >45 without other cause; inpatient decompensation often triggered by opioids, sedatives, positional changes, pneumonia

  • Diagnostics: ABG (daytime hypercapnia = OHS until proven otherwise); serum bicarb elevated chronically; CXR; sleep study (outpatient); TSH to exclude hypothyroidism

  • Treatment: CPAP (OSA) or BiPAP (OHS); avoid opioids/sedatives; supplemental O2 with caution; positional therapy; HFNC bridge; weight loss as definitive long-term strategy; CPAP compliance critical at discharge

12. LUNG ABSCESS

  • Definition/Criteria: Localized necrotic cavitation in lung parenchyma with air-fluid level; primary (aspiration in alcoholics, seizure, dysphagia) vs secondary (obstruction, immunosuppressed); causative organisms: anaerobes, S. aureus, gram-negatives

  • Diagnostics: CXR (air-fluid level, usually posterior segments or right lower lobe); CT chest (better delineates, excludes malignancy, identifies empyema); sputum/blood cultures; bronchoscopy if no improvement or to exclude malignancy/foreign body

  • Treatment: Antibiotics 3–6 weeks minimum: amoxicillin-clavulanate PO or beta-lactam + metronidazole IV; clindamycin no longer preferred; postural drainage; surgical or CT-guided drainage if >6 cm, no response at 2 weeks, or immunocompromised; exclude underlying malignancy

13. MALIGNANT PLEURAL EFFUSION

  • Definition/Criteria: Exudative effusion confirmed caused by malignancy (positive cytology or pleural biopsy); most common: lung, breast, lymphoma, mesothelioma; often large and rapidly reaccumulating; median survival 3–12 months by primary

  • Diagnostics: Thoracentesis: cytology (positive ~60–70%), cell diff, LDH, protein (Light's exudate); PleurX if rapid reaccumulation; CT chest/abdomen/pelvis; PET-CT; consider thoracoscopy if cytology negative and malignancy strongly suspected

  • Treatment: Therapeutic thoracentesis for symptom relief; indwelling pleural catheter (PleurX) preferred for trapped lung or recurrence; pleurodesis (talc) if lung fully expandable; chemotherapy/targeted therapy may control effusion; avoid large-bore tubes unless empyema

14. PULMONARY HYPERTENSION (PH) — Inpatient Decompensation

  • Definition/Criteria: mPAP >20 mmHg at rest on RHC; Group 1 (PAH): idiopathic/heritable/CTD/HIV/drugs; Group 2: left heart disease (most common); Group 3: lung disease/hypoxia; Group 4: CTEPH; decompensation = RV failure with ↑JVP, edema, low CO

  • Diagnostics: Echo (first-line: estimate RVSP, assess RV function); RHC (definitive); 6MWT; BNP/NT-proBNP; CT-PA (exclude CTEPH); PFTs; serologies for connective tissue disease

  • Treatment: Group 1 (PAH): PDE-5 inhibitors (sildenafil), endothelin receptor antagonists (ambrisentan/macitentan), prostacyclins (epoprostenol IV in severe); avoid aggressive diuresis (preload dependent RV); supplemental O2; treat acute decompensation with IV prostacyclin, careful diuresis, vasopressors (norepinephrine/vasopressin); Group 2/3: treat underlying cause; Group 4: anticoagulation + pulmonary endarterectomy

15. MESOTHELIOMA

  • Definition/Criteria: Malignant pleural (or peritoneal) tumor arising from mesothelial cells; strongly associated with asbestos exposure (latency 20–50 years); pleural thickening/nodularity, not typical effusion; does NOT respond to steroids or antibiotics

  • Diagnostics: CXR/CT (irregular pleural thickening, encasing lung, not effusion alone); VATS or thoracoscopic biopsy (key — cytology alone insufficient, need architecture); immunohistochemistry (calretinin+, CEA−); asbestos exposure history essential

  • Treatment: Cisplatin + pemetrexed (first-line systemic); pembrolizumab/nivolumab (immunotherapy increasingly used); pleurodesis or PleurX for effusion palliation; multimodal approach (surgery only in select early-stage patients at expert centers); median survival 12–18 months

16. TUBERCULOSIS (TB) — Pulmonary

  • Definition/Criteria: Mycobacterium tuberculosis infection; Primary vs reactivation (upper lobe cavities); latent TB (TST/IGRA positive, no symptoms) vs active TB (symptoms + positive culture/smear/NAAT); airborne isolation mandatory

  • Diagnostics: CXR (upper lobe infiltrate/cavitation/hilar adenopathy); sputum AFB smear x3 and NAAT (GeneXpert MTB/RIF = rapid); sputum culture (gold standard, 6–8 weeks); IGRA or TST; bronchoscopy if unable to produce sputum; HIV test; drug sensitivity testing

  • Treatment: Active TB: RIPE x2 months (Rifampin, Isoniazid, Pyrazinamide, Ethambutol) → RI x4 months; DOT strongly recommended; B6 with INH; airborne precautions until smear-negative x3 or 2 weeks on effective therapy; latent: INH 9 months or 3HP (rifapentine + INH weekly x12)

17. ATYPICAL PNEUMONIA (Legionella, Mycoplasma, Chlamydophila)

  • Definition/Criteria: "Walking pneumonia" — subacute onset, non-productive cough, extrapulmonary features (headache, GI, myalgia), multilobar infiltrates disproportionate to clinical appearance; DOES NOT respond to beta-lactam monotherapy; Legionella more severe (smokers, immunocompromised, waterborne)

  • Diagnostics: Urine Legionella Ag (serogroup 1, most common, rapid); urine pneumococcal Ag; Mycoplasma/Chlamydophila IgM/IgG (acute and convalescent); sputum culture unreliable; CXR (patchy, lobar, multilobar); cold agglutinins elevated in Mycoplasma

  • Treatment: Macrolide (azithromycin) or respiratory FQ (levofloxacin) — both cover all three organisms; Legionella: FQ preferred; Mycoplasma/Chlamydophila: macrolide or doxycycline; 5–10 days depending on severity; no beta-lactams alone

18. VIRAL PNEUMONIA (Influenza, COVID-19, RSV)

  • Definition/Criteria: Viral cause of pneumonia; Influenza: abrupt onset fever, myalgias, cough, ± GI; COVID-19: hypoxia often disproportionate to dyspnea ("silent hypoxia"), bilateral ground-glass opacities; RSV: mainly elderly/immunocompromised; distinguish from bacterial by clinical context and rapid testing

  • Diagnostics: Nasopharyngeal PCR multiplex panel (Flu A/B, COVID, RSV); CXR (bilateral GGOs for COVID/Flu); CBC (leukopenia in viral), procalcitonin (low = viral); D-dimer, ferritin, IL-6 in COVID for severity

  • Treatment: Influenza: oseltamivir 75 mg BID x5 days (within 48h; give regardless in hospitalized); COVID-19: remdesivir (hospitalized requiring O2); dexamethasone 6 mg x10 days (if on O2 or ventilated); baricitinib or tocilizumab if worsening; anticoagulation per institutional protocol; RSV: supportive; palivizumab prevention in high-risk; nirsevimab in elderly; no routine steroids for uncomplicated viral PNA

19. INTERSTITIAL LUNG DISEASE (ILD) — Acute Exacerbation

  • Definition/Criteria: Acute worsening (within 30 days) of known or new ILD without identifiable alternative cause; most often in IPF (AE-IPF); characterized by new bilateral GGOs superimposed on fibrotic background; high mortality (40–50%)

  • Diagnostics: HRCT chest (new bilateral GGOs + fibrotic background); BAL (exclude infection/DAH before steroids); PFTs (baseline restriction, decreased DLCO); serologies (ANA, RF, anti-CCP, myositis panel if connective tissue ILD suspected); bronchoscopy to exclude infection

  • Treatment: High-dose methylprednisolone (1g IV x3 days, taper); antibiotics empirically (exclude infection); avoid hyperoxia; supportive respiratory care; pirfenidone/nintedanib continue for IPF (may reduce frequency of exacerbations); NIV/HFNC for respiratory support; ICU for severe; transplant referral in progressive disease

20. DIFFUSE ALVEOLAR HEMORRHAGE (DAH)

  • Definition/Criteria: Bleeding into alveolar spaces from microvasculature; triad: hemoptysis + bilateral infiltrates + anemia; causes: vasculitis (ANCA, anti-GBM/Goodpasture), lupus, coagulopathy, medications; BAL shows progressively bloody return (hallmark)

  • Diagnostics: HRCT (bilateral GGOs/consolidation); BAL (progressively bloody aliquots = diagnostic; hemosiderin-laden macrophages); CBC (anemia), coagulation panel; ANCA (p-ANCA/c-ANCA), anti-GBM antibody, ANA/ANCA-associated panel; renal function (pulmonary-renal syndrome); creatinine + urinalysis for crescentic GN

  • Treatment: High-dose IV methylprednisolone (1g x3 days); cyclophosphamide or rituximab for ANCA vasculitis; plasmapheresis for anti-GBM disease (Goodpasture) — do NOT wait for biopsy; correct coagulopathy; intubation if severe; early nephrology/rheumatology involvement