Respiratory

Acute respiratory distress syndrome: CCS-style ventilator management

Clinical Overview and When to Suspect ARDS

— Onset within 1 week of a known clinical insult or new/worsening respiratory symptoms

— Bilateral opacities on chest imaging not fully explained by effusions, lobar collapse, or nodules

— Respiratory failure not fully explained by cardiac failure or fluid overload (objective assessment — echo if no risk factor)

— Impaired oxygenation graded by PaO₂/FiO₂ on PEEP ≥5 cm H₂O: mild 200–300, moderate 100–200, severe ≤100

— Pulmonary insults: pneumonia (most common), aspiration, inhalation injury, near-drowning, pulmonary contusion

— Extrapulmonary insults: sepsis, pancreatitis, massive transfusion (TRALI), trauma, burns, DKA, drug overdose

— Move location to ICU

— Order echocardiogram to exclude cardiogenic edema (or measure BNP)

— Begin lung-protective ventilation before the case clock advances further

CCS pearl: Do not wait for the formal Berlin label. Once you see "bilateral infiltrates" + worsening hypoxemia + a precipitant on the CCS stem, advance the clock by intubating early and writing for low-tidal-volume ventilation — late escalation is penalized.

Definition (Berlin criteria, 2012; updated 2023): acute hypoxemic respiratory failure with:

2023 update allows diagnosis with high-flow nasal cannula ≥30 L/min and uses SpO₂/FiO₂ ≤315 when ABG unavailable

When to suspect on CCS: any ICU patient with new hypoxemia + bilateral infiltrates within 7 days of:

Step 3 management: in a CCS case, the moment PaO₂/FiO₂ drops <300 with bilateral infiltrates, your orders should pivot to:

Mortality: ~30–45% overall; driven by multiorgan failure, not refractory hypoxemia alone

Pathophysiology pearl: diffuse alveolar damage → surfactant dysfunction, non-cardiogenic pulmonary edema, decreased compliance, V/Q mismatch, and intrapulmonary shunt (hypoxemia poorly responsive to FiO₂ alone)

Presentation Patterns and Key History

— Patient on 6 L NC → escalated to NRB → still SpO₂ 85% = classic shunt physiology

— Sepsis source: fevers, UTI symptoms, recent line, abdominal pain (pancreatitis), cellulitis

— Aspiration risk: witnessed event, altered mental status, dysphagia, recent extubation, GI bleed

— Transfusion history: ARDS within 6 hours of blood product = TRALI

— Trauma: chest wall injury, long-bone fracture (fat embolism), massive resuscitation

— Drugs/toxins: amiodarone, bleomycin, nitrofurantoin, salicylate OD, opioid OD, e-cigarette/vaping (EVALI)

— Travel/exposure: influenza, COVID-19, hantavirus, legionella

— Pancreatitis: epigastric pain radiating to back, alcohol use, gallstones

— Chronic alcohol use doubles ARDS risk after sepsis

— Smoking and obesity increase risk; obesity paradoxically improves survival

— Prior chemotherapy/radiation → consider drug-induced pneumonitis differential

Board pearl: A patient transfused 4 units PRBC for GI bleed who develops bilateral infiltrates and hypoxemia within 6 hours → TRALI (a form of ARDS); stop the transfusion, report to blood bank, and the donor (often multiparous female with anti-HLA antibodies) should be deferred from future donation.

Key distinction: TACO (transfusion-associated circulatory overload) presents with elevated BNP, JVD, HTN, and responds to diuresis; TRALI has normal-to-low CVP and does not respond to diuretics — supportive ventilation is the answer.

Time course: symptoms develop 6–72 hours after the inciting event; nearly always within 1 week (Berlin cutoff)

Cardinal complaint: rapidly progressive dyspnea with refractory hypoxemia despite increasing supplemental O₂

Cough: often nonproductive or pink frothy (mimics cardiogenic edema — history distinguishes)

Mental status: agitation early (hypoxia), then obtundation (hypercapnia, fatigue)

Key historical anchors to ask/order on CCS:

Comorbidity check (modifies risk and management):

Physical Exam Findings and Hemodynamic Assessment

— RR >30, SpO₂ low despite high FiO₂

— Tachycardia from hypoxia and underlying sepsis

— BP variable — hypotension suggests concurrent septic shock

— Fever if infectious driver

— Diffuse bilateral crackles ("velcro" quality), often more prominent in dependent zones

— No focal consolidation typically; dullness if effusion

— Wheezing rare — if present, reconsider asthma/COPD/CHF

— No S3 gallop, no JVD, no peripheral edema typically in pure ARDS

— If present → suspect cardiogenic component or fluid overload

— Bedside echo is the modern standard — assess LV function, RV size, IVC, B-lines

— PCWP historically ≤18 mm Hg (Swan-Ganz no longer routine; pulmonary artery catheters did not improve outcomes — ARDSNet FACTT trial)

— BNP: <100 supports non-cardiogenic; >500 favors cardiac, but overlap exists in critical illness

Step 3 management: When the CCS stem says "bilateral crackles, no JVD, no S3, recent pancreatitis" — do not order furosemide. Order echocardiogram to confirm preserved EF, then proceed with lung-protective ventilation and source control. Diuresis is reserved for the conservative fluid strategy phase after shock has resolved (FACTT trial: conservative fluids → more ventilator-free days, no mortality change).

Board pearl: Petechiae + hypoxemia + altered mental status 24–72 hours after long-bone fracture = fat embolism syndrome — manage as ARDS with lung-protective ventilation; early fracture fixation is preventive.

General appearance: tachypneic, tripoding, accessory muscle use, paradoxical abdominal breathing (diaphragmatic fatigue), cyanosis when severe

Vital signs pattern:

Pulmonary exam:

Cardiac exam — critical for distinguishing from cardiogenic edema:

Hemodynamic assessment (Berlin requires excluding cardiogenic cause):

Skin/extremities: mottling and prolonged cap refill suggest shock; petechiae over chest/axilla after long-bone fracture → fat embolism syndrome

Diagnostic Workup — Initial Labs, Imaging, and ABG

— Early: respiratory alkalosis with hypoxemia (compensatory hyperventilation)

— Late: respiratory acidosis as fatigue sets in or with permissive hypercapnia on the vent

— Calculate PaO₂/FiO₂ ratio — defines severity and PEEP/prone decisions

— A-a gradient widened (shunt physiology)

— Bilateral patchy alveolar/interstitial opacities sparing costophrenic angles early

— No cardiomegaly, no Kerley B lines, no cephalization (helps distinguish from CHF)

— Progresses to diffuse "whiteout" in severe disease

— Heterogeneous dependent consolidation with anterior sparing ("baby lung")

— Useful to rule out PE, abscess, empyema, lobar pneumonia

— Blood cultures ×2, sputum Gram stain/culture, urinalysis/UA culture

— Respiratory viral PCR (influenza, RSV, SARS-CoV-2)

— Procalcitonin, lactate

— Legionella and pneumococcal urinary antigens for severe CAP

— BNP/NT-proBNP, troponin, ECG

— Bedside echocardiogram — single most useful test to exclude cardiogenic edema

— CBC (leukocytosis, thrombocytopenia in sepsis), CMP, lipase if pancreatitis suspected

— Coags + fibrinogen (DIC common in sepsis-driven ARDS)

— LDH (often elevated; nonspecific)

CCS pearl: On the CCS interface, an efficient opening order set for suspected ARDS reads: ABG, CXR portable, CBC, BMP, lactate, blood cultures ×2, urinalysis, sputum culture, BNP, troponin, ECG, bedside echo. Then advance the clock 30 minutes to receive results and pivot.

Key distinction: Cardiogenic edema = cardiomegaly, vascular cephalization, Kerley B lines, pleural effusions, ↑BNP, ↓EF. ARDS = patchy peripheral opacities, normal heart size, ↔BNP, preserved EF.

Arterial blood gas (essential):

Chest X-ray:

CT chest (if diagnostic uncertainty):

Infection workup (always — sepsis is leading trigger):

Cardiac workup:

Additional labs:

Diagnostic Workup — Advanced and Confirmatory Studies

— Excludes LV systolic/diastolic dysfunction as primary cause

— Assesses RV function — ARDS frequently induces acute cor pulmonale (20–25%), worsening prognosis

— Evaluates IVC for volume status guidance

— Indicated when etiology unclear or immunocompromised host

— Sends for bacterial, fungal, PCP, viral, AFB, cytology

— Distinguishes diffuse alveolar hemorrhage (progressively bloodier returns) from pure ARDS

— Diffuse B-lines with spared areas, subpleural consolidations, irregular pleural line favor ARDS

— Smooth pleural line + symmetric B-lines + bilateral effusions favor cardiogenic edema

— When PE is on differential (sudden hypoxemia, RV strain, no clear infiltrate driver)

— ANA, ANCA, anti-GBM, anti-Jo-1 → diffuse alveolar hemorrhage, vasculitis, antisynthetase syndrome

— IgE, eosinophils → acute eosinophilic pneumonia (steroid-responsive)

— Drug-induced pneumonitis screen (amiodarone, nitrofurantoin, methotrexate, immune checkpoint inhibitors)

Board pearl: Acute eosinophilic pneumonia mimics ARDS in a young smoker with peripheral eosinophilia on BAL — responds dramatically to corticosteroids, unlike most ARDS phenotypes. Don't miss it.

Step 3 management: In refractory ARDS without a clear precipitant, escalate to bronchoscopy with BAL before empiric immunosuppression. The exam rewards making a diagnosis, not blind steroid use.

Key distinction: Diffuse alveolar hemorrhage — hemoptysis (only ⅓ of patients), dropping Hgb, progressively bloody BAL returns; requires immunosuppression, not just ventilatory support.

Echocardiography (essential confirmatory):

Bronchoscopy with BAL:

Lung ultrasound (point-of-care):

CT pulmonary angiography:

Autoimmune/specialized workup (if no obvious trigger):

Open lung biopsy: rarely indicated; reserved for refractory cases without diagnosis after BAL

Pulmonary artery catheter: not routine — FACTT showed no mortality benefit, more complications

Risk Stratification and Initial Management Logic

— Mild (P/F 200–300): trial HFNC or NIV in select patients (no shock, alert, cooperative)

— Moderate (P/F 100–200): intubate, lung-protective ventilation, higher PEEP, consider prone

— Severe (P/F <100): intubate, prone positioning ≥16 h/day, consider neuromuscular blockade, ECMO referral

— HFNC (FLORALI trial) reasonable in non-hypercapnic hypoxemic respiratory failure

— NIV higher failure rate in moderate–severe ARDS; reserve for immunocompromised, COPD overlap, or cardiogenic component

— Intubate early if: P/F <150, shock, altered mental status, accessory muscle use after 1 hour of HFNC, rising RR

— ROX index (SpO₂/FiO₂ ÷ RR) <4.88 at 12 h on HFNC predicts intubation

— Tidal volume 6 mL/kg ideal body weight (calculated by height/sex, not actual weight)

— Plateau pressure ≤30 cm H₂O

— Driving pressure (Pplat − PEEP) <15 cm H₂O — strongest predictor of mortality

— PEEP titrated per FiO₂ using ARDSNet table; higher PEEP for moderate–severe

— SpO₂ goal 88–95%, PaO₂ 55–80

— pH ≥7.20 (permissive hypercapnia accepted)

CCS pearl: A first-pass CCS vent order should read: "Intubate, mechanical ventilation: AC/VC, TV 6 mL/kg IBW, RR 18, FiO₂ 1.0, PEEP 10, titrate to SpO₂ 88–95% and Pplat ≤30." Then advance the clock 1 hour and recheck ABG and plateau pressure.

Board pearl: Driving pressure (ΔP = Pplat − PEEP) is the single most important modifiable mechanical variable; keep <15.

Severity stratification (Berlin) drives therapy intensity:

Decision: intubate vs. noninvasive support:

Initial ventilator goals (ARDSNet):

Hemodynamic support: norepinephrine first-line for septic shock; conservative fluids after shock resolves

Pharmacotherapy and Adjunctive Medical Management

— Fentanyl infusion for analgesia (first-line per PADIS guidelines)

— Propofol or dexmedetomidine for sedation; avoid benzodiazepines (delirium, longer vent days)

— Target RASS −2 to 0; perform daily spontaneous awakening trials

— Cisatracurium ×48 hours for severe ARDS (P/F <150) with ventilator dyssynchrony despite deep sedation

— ACURASYS showed benefit; ROSE trial neutral — current use is selective, not routine

— Always pair with deep sedation; monitor train-of-four

— Dexamethasone 20 mg IV daily ×5 days, then 10 mg ×5 days (DEXA-ARDS) — moderate–severe ARDS within 30 days of onset

— Dexamethasone 6 mg ×10 days for COVID-19 ARDS requiring O₂ (RECOVERY)

— Avoid in unresolved infection without source control; screen for strongyloides in endemic populations

— Empiric broad-spectrum within 1 hour if sepsis/pneumonia suspected (vanc + pip-tazo or cefepime; add oseltamivir during flu season)

— De-escalate based on cultures

— Conservative strategy (FACTT) once shock resolved: net even-to-negative balance with diuretics → more ventilator-free days

— Inhaled nitric oxide or epoprostenol — rescue for refractory hypoxemia or RV failure; improves oxygenation transiently, no mortality benefit

Step 3 management: Stress ulcer prophylaxis (PPI/H2 blocker) and VTE prophylaxis (LMWH or heparin SC) are required orders on every ventilated patient — these are CCS checkbox items.

Board pearl: Daily SAT + SBT (ABCDEF bundle) reduces vent days and ICU mortality — don't forget the A2F bundle orders.

Sedation and analgesia (first priority post-intubation):

Neuromuscular blockade:

Corticosteroids:

Antibiotics:

Fluid management:

Inhaled pulmonary vasodilators:

Avoid: routine β-agonists (ALTA trial — harmful), statins (HARP-2 — no benefit), surfactant in adults

Procedures and Advanced Ventilator/Rescue Strategies

— Volume-control AC, TV 6 mL/kg IBW (start 8, reduce over 2 h to 6, can go to 4 if Pplat high)

— PEEP/FiO₂ tables — low or high PEEP strategies; higher PEEP for moderate–severe per LOVS/ExPress meta-analysis

— Pplat ≤30, ΔP <15, pH ≥7.20 (RR up to 35 allowed for permissive hypercapnia)

— Severe ARDS, P/F <150 on FiO₂ ≥0.6, PEEP ≥5

— ≥16 hours/day (PROSEVA trial — absolute mortality reduction ~16%)

— Continue until P/F >150 in supine for 4 hours

— Risks: pressure injuries, ETT displacement, line dislodgement, facial edema

— Refractory hypoxemia despite optimized vent, prone, and NMB

— P/F <50 for >3 h, P/F <80 for >6 h, or uncompensated hypercapnia with pH <7.25 (EOLIA criteria)

— Best at high-volume ECMO centers — early transfer improves outcomes

— Contraindications: irreversible underlying disease, severe comorbidity, prolonged high-pressure ventilation >7 days (relative)

— Consider at day 10–14 if prolonged ventilation anticipated; no mortality benefit to early trach but improves comfort/weaning

CCS pearl: Refractory hypoxemia escalation order on CCS: deepen sedation → neuromuscular blockade → prone → inhaled vasodilator → ECMO referral. Each step should be tried before the next; the exam rewards a stepwise, evidence-based ladder.

Board pearl: PROSEVA proning works because it improves V/Q matching, reduces overdistension of nondependent lung, and reduces ventilator-induced lung injury.

Lung-protective ventilation (ARDSNet protocol — the bedrock):

Prone positioning:

Recruitment maneuvers and high PEEP: selective use; ART trial showed harm with aggressive strategy — individualize

Neuromuscular blockade: as above, cisatracurium 48 h for severe with dyssynchrony

Inhaled vasodilators (iNO, epoprostenol): rescue only

ECMO (venovenous):

Tracheostomy:

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher baseline mortality; frailty score predicts outcomes better than age alone

— Reduced respiratory reserve, sarcopenia → harder weaning, longer ventilator days

— Goals-of-care discussion early — clarify code status, intubation preferences, advance directives before crisis escalation

— Delirium risk high: avoid benzodiazepines, prioritize dexmedetomidine, early mobilization

— Sedation pharmacokinetics altered: lower propofol doses; monitor for hypotension and hypertriglyceridemia

— AKI develops in ~40% of ARDS patients — synergistic mortality

— Conservative fluids especially important; avoid nephrotoxins (aminoglycosides, IV contrast when possible)

— CRRT (continuous renal replacement) preferred over intermittent HD in hemodynamically unstable ARDS — better fluid removal tolerance

— Dose-adjust meds: cefepime (neurotoxicity risk), piperacillin-tazobactam, vancomycin (trough/AUC monitoring)

— Cisatracurium preferred NMB in renal failure (Hofmann elimination, no active metabolites)

— Higher ARDS mortality; hepatopulmonary syndrome can confound oxygenation assessment

— Coagulopathy increases procedural bleeding risk (central lines, bronchoscopy)

— Avoid acetaminophen >2 g/day, benzodiazepines (encephalopathy), nephrotoxic NSAIDs

— Propofol dose reduction; fentanyl preferred over morphine (no active metabolites)

— Watch for hepatorenal syndrome with aggressive diuresis

— Use ideal body weight for TV calculation, not actual

— Higher PEEP often needed (chest wall stiffness, atelectasis)

— Reverse Trendelenburg improves mechanics

— Paradoxical survival advantage ("obesity paradox") in ARDS

Step 3 management: Before escalating to ECMO or prolonged ventilation in an elderly patient with limited functional baseline, document a goals-of-care conversation with surrogate — the exam rewards proactive communication.

Board pearl: Cisatracurium is the NMB of choice in renal/hepatic failure due to organ-independent Hofmann elimination.

Elderly (>65):

Chronic kidney disease / AKI:

Hepatic impairment / cirrhosis:

Obesity:

Special Populations — Pregnancy, Pediatrics, and Immunocompromised

— Physiologic changes: ↑minute ventilation, ↓FRC, baseline respiratory alkalosis (pH ~7.42, PaCO₂ ~30)

— Target PaO₂ ≥70 and SpO₂ ≥95% — fetal oxygenation depends on maternal PaO₂

— Permissive hypercapnia limited — fetal acidosis risk; keep PaCO₂ <60 if possible

— Left lateral tilt to relieve aortocaval compression after 20 weeks

— Common precipitants: influenza, COVID-19, pyelonephritis, amniotic fluid embolism, preeclampsia/pulmonary edema

— Delivery considerations: if maternal status worsening near term, delivery may improve respiratory mechanics

— Multidisciplinary team: OB, MFM, neonatology, ICU

— Uses oxygenation index (OI = FiO₂ × MAP × 100 / PaO₂) instead of P/F ratio

— Mild OI 4–8, moderate 8–16, severe ≥16

— Same lung-protective principles; TV 5–8 mL/kg IBW

— Surfactant not routinely beneficial in pediatric ARDS (unlike neonatal RDS)

— Broader infectious differential: PCP, CMV, invasive aspergillus, mucormycosis, nocardia

— Early bronchoscopy with BAL strongly indicated

— Add empiric TMP-SMX (PCP), voriconazole (aspergillus) until cultures back

— NIV may be reasonable trial in selected immunocompromised patients (avoid VAP risk) — but don't delay intubation if failing

— Adjust immunosuppression in consultation with primary service

Board pearl: ARDS in pregnancy + influenza season → start oseltamivir empirically without waiting for testing; maternal influenza mortality is high and treatment is time-sensitive.

Key distinction: Amniotic fluid embolism — sudden hypoxemia, hypotension, DIC, and altered mental status during labor/delivery; supportive management with lung-protective ventilation, blood products, and uterotonic support; mortality very high.

Pregnancy:

Pediatric ARDS (PARDS — PALICC criteria):

Immunocompromised (HSCT, solid organ transplant, HIV, chemotherapy):

Complications and Adverse Outcomes

— Volutrauma (overdistension), barotrauma (high pressures), atelectrauma (cyclic opening/closing), biotrauma (cytokine release)

— Prevented by lung-protective ventilation — the entire rationale

— Sudden ↓SpO₂, ↑peak pressure, ↓BP, unilateral absent breath sounds → needle decompression then chest tube

— Develops >48 h after intubation

— Prevent with HOB elevation 30–45°, oral chlorhexidine, daily SAT/SBT, subglottic suction ETT, DVT and PUD prophylaxis (the VAP bundle)

— Treat with broad-spectrum coverage including MRSA and pseudomonas; de-escalate per cultures

— From high PEEP, hypoxic vasoconstriction, hypercapnia

— Manage: minimize Pplat, ΔP; optimize oxygenation; consider iNO; prone

— Risk factors: prolonged NMB, corticosteroids, hyperglycemia, immobility

— Causes prolonged ventilator weaning; early mobilization helps

— Persistent dyspnea, reduced DLCO (often normalizes by 1 year)

— Cognitive impairment (40–50% at 1 year)

— PTSD, depression, anxiety

— Functional disability — many do not return to baseline employment

Step 3 management: When peak pressure rises suddenly on a stable vent — first disconnect from vent and bag manually, then assess for DOPE: Displacement (ETT), Obstruction (mucus, kink), Pneumothorax, Equipment failure. CCS rewards systematic troubleshooting.

Board pearl: Survivors of ARDS need pulmonary rehab, mental health screening, and cognitive assessment — refer at discharge.

Ventilator-induced lung injury (VILI):

Barotrauma: pneumothorax (5–15%), pneumomediastinum, subcutaneous emphysema

Ventilator-associated pneumonia (VAP):

Right heart failure / acute cor pulmonale:

Critical illness myopathy/polyneuropathy:

Delirium: ~80% of ventilated patients; reduce with ABCDEF bundle

DVT/PE: all ventilated patients need pharmacologic prophylaxis unless contraindicated

GI bleeding: stress ulcers — PPI or H2 blocker for high-risk (coagulopathy, >48 h vent)

Long-term sequelae (post-ICU syndrome):

When to Escalate Care — ICU, Consults, and Transfer

— P/F <150 despite optimized PEEP/FiO₂ → consider prone positioning and NMB

— P/F <80 despite proning → consult ECMO center early

— Worsening RV failure on echo → reduce Pplat, add iNO, consider VV-ECMO

— Severe hypoxemia (P/F <50 ×3 h, or <80 ×6 h)

— Uncompensated hypercapnia (pH <7.25 with PaCO₂ ≥60 ×6 h despite RR 35)

— Refractory to standard rescue therapies

— Earlier is better — transfer before catastrophic deterioration; >7 days of high-pressure ventilation is a relative contraindication

— Pulmonary/critical care: primary management

— Infectious disease: for unusual organisms, immunocompromised hosts, persistent fever

— Cardiology: if cardiogenic component suspected or RV failure

— Nephrology: for CRRT in concurrent AKI

— Palliative care: early integration for symptom management and goals-of-care

— Nutrition: enteral feeding within 24–48 h (trophic feeds adequate first week)

— Stabilize first: secure airway, adequate sedation, vasopressors as needed

— Communicate vent settings, ABG, hemodynamics, medications in handoff

— Use specialized transport teams for ECMO candidates

CCS pearl: On CCS, when the case escalates beyond your current facility's capability, the correct order is "Transfer to tertiary care center with ECMO capability" — and continue stabilizing in transit (don't drop sedation or vasopressors).

Step 3 management: Early palliative care consultation (within 72 h of ICU admission for ARDS) is associated with better goals-concordant care without increasing mortality — a high-yield Step 3 systems-based answer.

ICU admission is automatic once ARDS is diagnosed — no role for floor management

Escalate ventilator support when:

ECMO referral criteria (EOLIA):

Specialty consults:

Inter-hospital transfer considerations:

Key Differentials — Same-Category (Hypoxemic Respiratory Failure)

— JVD, S3, peripheral edema, ↑BNP, cardiomegaly, cephalization, Kerley B lines on CXR

— Echo shows ↓EF or diastolic dysfunction

— Responds to diuresis, afterload reduction, NIV (BiPAP)

— Can cause ARDS but typically starts focal before bilateral

— Productive cough, focal consolidation, positive cultures/antigens

— Note: severe pneumonia is an ARDS trigger when bilateral involvement develops

— Witnessed aspiration → chemical injury → bilateral infiltrates within hours

— Often involves right lower lobe and posterior segments

— Supportive care; antibiotics only if pneumonia develops (>48–72 h fever, leukocytosis)

— Sudden hypoxemia, clear CXR or oligemia, RV strain on echo/ECG

— CTPA confirms; treat with anticoagulation ± thrombolysis

— Hemoptysis (variable), dropping Hgb, progressively bloody BAL

— Causes: ANCA vasculitis, anti-GBM, SLE, drugs

— Treat with high-dose steroids + immunosuppression ± plasmapheresis

— Idiopathic, rapidly progressive; histologically identical to ARDS

— Diagnosis of exclusion after BAL/biopsy; high mortality

— Young smokers, peripheral eosinophilia, steroid-responsive within hours

— Exposure history (birds, molds, hot tubs); resolves with avoidance + steroids

Key distinction: ARDS vs. cardiogenic edema is the single most tested distinction — anchor on history (precipitant), echo (EF), BNP, and exam (JVD/S3). When in doubt, get an echocardiogram.

Board pearl: Severe CAP that progresses to bilateral infiltrates and refractory hypoxemia is ARDS — both diagnoses coexist; treat the pneumonia AND apply lung-protective ventilation.

Cardiogenic pulmonary edema (CHF):

Pneumonia (severe CAP/HCAP):

Aspiration pneumonitis:

Pulmonary embolism:

Diffuse alveolar hemorrhage:

Acute interstitial pneumonia (Hamman-Rich):

Acute eosinophilic pneumonia:

Hypersensitivity pneumonitis (acute):

Key Differentials — Other-Category Causes of Diffuse Infiltrates

— Within 6 hours of transfusion; donor anti-HLA/anti-neutrophil antibodies

— Stop transfusion, report to blood bank; supportive ventilation

— Volume overload from transfusion; ↑BNP, ↑BP, JVD; responds to diuretics

— Amiodarone, bleomycin, methotrexate, nitrofurantoin, immune checkpoint inhibitors, gemcitabine

— Insidious in chronic exposure; acute with high-dose chemo

— Stop drug; corticosteroids; permanent pulmonary fibrosis risk with amiodarone/bleomycin

— Chronic dyspnea, "crazy paving" on CT, milky BAL — whole-lung lavage treatment

— Rapid ascent >2500 m, exertion; descent + supplemental O₂ + nifedipine

— Post-seizure, severe TBI, SAH; massive sympathetic surge

— Supportive; resolves with treatment of underlying neuro insult

— After rapid drainage of large pneumothorax or pleural effusion (>1.5 L)

— Prevented by limiting initial drainage

— Tinnitus, mixed acid-base disturbance, non-cardiogenic edema; treat with alkalinization, dialysis

— Young adult, vaping (especially THC + vitamin E acetate), bilateral infiltrates, GI symptoms

— Stop vaping; corticosteroids; diagnosis of exclusion (rule out infection)

— Specific therapies: dexamethasone, remdesivir, tocilizumab/baricitinib for severe; same lung-protective principles

Step 3 management: New ARDS in a patient on amiodarone for >2 months → suspect amiodarone pulmonary toxicity; check DLCO if stable, get CT (often basilar/peripheral fibrosis), stop amiodarone, start steroids, and switch antiarrhythmic.

Board pearl: Vaping + bilateral infiltrates + GI symptoms in young adult = EVALI until proven otherwise.

TRALI (transfusion-related acute lung injury):

TACO (transfusion-associated circulatory overload):

Drug-induced pneumonitis:

Pulmonary alveolar proteinosis:

High-altitude pulmonary edema (HAPE):

Neurogenic pulmonary edema:

Re-expansion pulmonary edema:

Salicylate toxicity:

EVALI (e-cigarette/vaping-associated lung injury):

COVID-19 pneumonia / ARDS:

Secondary Prevention, Discharge Planning, and Long-Term Therapy

— Once P/F >300, hemodynamically stable, RSBI <105, passing SBTs on minimal support → extubate

— Step-down to floor when off vasopressors, stable on ≤4 L NC, mentation clear

— Stable oxygenation on room air or low-flow O₂ with home setup arranged

— Tolerating diet, ambulating with PT clearance

— Wound/line care addressed; central lines removed

— Medication reconciliation — particularly important after ICU stays (chronic meds often held)

— Follow-up appointments scheduled before discharge

— Resting SpO₂ ≤88% or PaO₂ ≤55 on room air → qualifies for continuous O₂

— SpO₂ 89% with cor pulmonale, polycythemia, or HF → also qualifies

— Reassess in 60–90 days; many ARDS survivors no longer need O₂

— Influenza (annual), pneumococcal (PCV20 or PCV15+PPSV23), COVID-19, RSV (≥60), Tdap update

— Sepsis → complete antibiotic course, source control verified

— Pancreatitis → address etiology (cholecystectomy for gallstones, alcohol cessation)

— Aspiration → swallow evaluation, dysphagia management, GERD treatment

— Resume chronic outpatient meds (statin, ACE inhibitor, beta-blocker, inhalers) — frequently held during ICU stay

— Avoid amiodarone, nitrofurantoin in ARDS survivors when alternatives exist

Step 3 management: Discharge ARDS survivors with scheduled pulmonologist follow-up within 4–6 weeks, PCP within 1–2 weeks, and a post-ICU recovery clinic referral if available — this reduces readmission and addresses post-ICU syndrome.

Board pearl: Medication reconciliation errors are the #1 source of post-ICU adverse drug events — explicitly review pre-admission med list against discharge list.

Hospital course transition:

Discharge readiness checklist:

Home oxygen criteria (if persistent hypoxemia):

Vaccinations before discharge:

Smoking cessation counseling and pharmacotherapy (varenicline, nicotine replacement) for all smokers

Treat the underlying precipitant:

Medication considerations:

Follow-Up, Monitoring, and Rehabilitation

— Pulmonary function tests (spirometry, lung volumes, DLCO) — DLCO often reduced but improves over 6–12 months

— Repeat chest imaging to assess for residual fibrosis (CT if persistent abnormalities)

— 6-minute walk test for functional assessment

— Oxygen reassessment — wean home O₂ if SpO₂ adequate

— Med reconciliation, BP, glucose, weight

— Screen for post-ICU syndrome: cognitive, psychiatric, functional

— Referral for any survivor with persistent dyspnea, exercise limitation, or deconditioning

— Evidence-based: improves dyspnea, exercise capacity, QoL

— PHQ-9 (depression), GAD-7 (anxiety), screen for PTSD symptoms (nightmares, flashbacks of ICU)

— ~40% of ARDS survivors meet criteria for at least one psychiatric condition at 1 year

— Refer to therapy, consider SSRIs

— MoCA at follow-up; if impaired, refer to neuropsychology and consider occupational therapy

— Cognitive deficits in 40–50% at 1 year, equivalent to mild dementia in some

— Physical therapy, occupational therapy

— Return-to-work counseling — half of working-age survivors do not return to prior employment at 1 year

— Up to ⅓ of family members develop PTSD or depression after a loved one's ICU stay

— Provide resources, support groups (e.g., THRIVE peer support)

Step 3 management: A patient 2 months post-ARDS discharge with persistent fatigue, difficulty returning to work, and intrusive memories → screen for post-ICU syndrome, refer to post-ICU recovery clinic, and address mental health with therapy ± pharmacotherapy.

Board pearl: DLCO is the most sensitive PFT abnormality in ARDS survivors — typically improves but may never fully normalize.

Pulmonology follow-up at 4–6 weeks post-discharge:

Primary care follow-up at 1–2 weeks:

Pulmonary rehabilitation:

Mental health screening:

Cognitive screening:

Functional rehabilitation:

Family/caregiver support:

Vaccinations: ensure complete at follow-up; annual flu and updated COVID boosters

Ethical, Legal, and Patient Safety Considerations

— When patient is hypoxic and altered → emergency exception applies; intubate to save life

— If patient is alert and refusing → assess decision-making capacity, document, respect autonomy if capacity intact

— Obtain surrogate consent when patient lacks capacity per state hierarchy (spouse → adult children → parents → siblings)

— Review POLST/MOLST on arrival; verify with family

— A "DNR" does NOT mean "do not intubate" — clarify each component separately

— Re-address goals of care if trajectory worsens (P/F dropping, multiorgan failure)

— Use REMAP framework: Reframe, Expect emotion, Map values, Align, Plan

— Time-limited trials (e.g., "3 days of aggressive support, then reassess") are ethically appropriate and exam-favored

— Document conversations clearly

— Ethically and legally equivalent to withholding

— Continue comfort care: opioids, benzodiazepines for dyspnea/anxiety; the doctrine of double effect permits this even if it hastens death

— Extubation to comfort care is appropriate when consistent with patient values

— Suspected abuse, occupational lung injury (some states), reportable infections (TB, novel respiratory pathogens, COVID-19)

— Handoff from ICU to floor is a high-risk transition: use structured tools (I-PASS, SBAR)

— Medication reconciliation at every transition

— Verify follow-up appointments scheduled BEFORE discharge — unfilled follow-ups predict readmission

— Mandatory report to blood bank so donor can be deferred — patient safety obligation

— During pandemic-level surge, triage protocols based on SOFA scores, prognosis; institutional/state guidance applies; never base solely on age or disability

Step 3 management: A family member of an intubated ARDS patient asks "Should we keep going?" — propose a time-limited trial with explicit endpoints and a follow-up family meeting in 48–72 hours. This balances hope, realism, and ethics.

Board pearl: Comfort-directed opioids at the end of life are ethically permitted under the doctrine of double effect — relieving suffering is the intent, even if respiratory depression occurs.

Informed consent for intubation:

Advance directives and code status:

Goals-of-care conversations:

Withdrawal of life-sustaining therapy:

Mandatory reporting:

Transition-of-care safety (Step 3 favorite):

TRALI reporting:

Resource allocation (crisis standards of care):

High-Yield Associations and Rapid-Fire Facts

Board pearl: If forced to pick one intervention that saves lives in ARDS — 6 mL/kg IBW tidal volume. Everything else builds on that foundation.

Berlin criteria: acute (<1 week), bilateral opacities, not cardiogenic, P/F ≤300 on PEEP ≥5

Most common precipitant: pneumonia (pulmonary) and sepsis (extrapulmonary)

ARDSNet vent settings: TV 6 mL/kg IBW, Pplat ≤30, ΔP <15, pH ≥7.20, SpO₂ 88–95%

Mortality reducer #1: low tidal volume ventilation (ARMA trial, NEJM 2000)

Mortality reducer #2: prone positioning for severe ARDS (PROSEVA, ~16% absolute reduction)

Mortality reducer #3: dexamethasone in moderate–severe ARDS (DEXA-ARDS) and COVID-ARDS (RECOVERY)

NMB: cisatracurium 48 h for severe ARDS with dyssynchrony (ACURASYS/ROSE — selective use)

PEEP: higher PEEP for moderate–severe; titrate via ARDSNet table or driving pressure

Conservative fluids after shock resolves → more ventilator-free days (FACTT)

ECMO criteria (EOLIA): P/F <50×3h, P/F <80×6h, or pH <7.25 with hypercapnia refractory to optimization

TRALI: within 6 h of transfusion, donor antibodies, supportive care, mandatory blood bank reporting

TACO: volume overload, ↑BNP, JVD, responds to diuresis

Fat embolism: 24–72 h post-long-bone fracture, petechiae, hypoxemia, altered mental status

EVALI: vaping (vitamin E acetate), bilateral infiltrates, GI symptoms, steroid-responsive

Amiodarone toxicity: chronic dyspnea, ↓DLCO, basilar/peripheral infiltrates

Pulmonary artery catheter: NOT routine (FACTT)

β-agonists, statins, surfactant: NOT beneficial in adult ARDS

VAP bundle: HOB 30–45°, oral chlorhexidine, daily SAT/SBT, subglottic suction, DVT/PUD prophylaxis

A2F bundle: Assess pain, Both SAT/SBT, Choice of sedation, Delirium monitoring, Early mobility, Family engagement

Post-ICU syndrome: cognitive, psychiatric, physical impairment in survivors

Acute cor pulmonale: 20–25% in moderate–severe ARDS; assess with echo

DOPE: ventilator troubleshooting — Displacement, Obstruction, Pneumothorax, Equipment

Board Question Stem Patterns

— Distractor: TACO would show ↑BNP, ↑BP, JVD.

— Distractor: 8–10 mL/kg (incorrect — VILI).

Step 3 management: When the question gives you a hemodynamically stable ARDS patient with worsening oxygenation, the answer ladder is almost always: optimize PEEP/FiO₂ per ARDSNet → NMB → prone → iNO → ECMO. Memorize this order.

Stem 1 — TRALI vs. TACO: Elderly woman receives 4 units PRBC for GI bleed; 4 hours later develops hypoxemia, bilateral infiltrates, BP 80/50, no JVD. Answer: TRALI — supportive ventilation, stop transfusion, report to blood bank.

Stem 2 — Initial vent settings: 70 kg male (IBW 65 kg) intubated for ARDS from sepsis. Best initial tidal volume? Answer: ~390 mL (6 mL/kg IBW).

Stem 3 — Refractory hypoxemia: P/F 90 on FiO₂ 1.0, PEEP 15, prone 16 h, NMB. Next step? Answer: refer for venovenous ECMO.

Stem 4 — Driving pressure: Pplat 32, PEEP 10, ΔP 22 — next adjustment? Answer: reduce tidal volume to lower driving pressure.

Stem 5 — Cardiogenic vs. ARDS: Bilateral infiltrates, S3, JVD, BNP 1800, EF 25%. Answer: cardiogenic — diurese, afterload reduction, BiPAP, NOT ARDS protocol.

Stem 6 — Fat embolism: 22-year-old with femur fracture, 48 h later hypoxemic with petechiae over axilla and chest, confused. Answer: fat embolism syndrome — supportive lung-protective ventilation.

Stem 7 — COVID ARDS: Hospitalized COVID-19 patient requiring O₂. Mortality-reducing medication? Answer: dexamethasone 6 mg ×10 days.

Stem 8 — Conservative fluids: Day 3 of ARDS, off pressors, P/F 200, net +6 L since admission. Next step? Answer: diuresis (conservative fluid strategy).

Stem 9 — Amiodarone pneumonitis: Patient on amiodarone 18 months develops bilateral basilar infiltrates, ↓DLCO. Answer: stop amiodarone, start corticosteroids, switch antiarrhythmic.

Stem 10 — Goals of care: Elderly DNR patient with severe ARDS, family wants "everything done." Answer: clarify DNR scope, propose time-limited trial, palliative care consult.

Stem 11 — Vent alarm: Sudden ↓SpO₂, ↑peak pressure, unilateral absent breath sounds. Answer: tension pneumothorax — needle decompression then chest tube.

Stem 12 — EVALI: 19-year-old vape user, bilateral infiltrates, GI symptoms, negative infectious workup. Answer: stop vaping, corticosteroids.

One-Line Recap

ARDS is acute hypoxemic respiratory failure with bilateral non-cardiogenic infiltrates and P/F ≤300 on PEEP ≥5, and the cornerstone of management is lung-protective ventilation (6 mL/kg IBW, Pplat ≤30, ΔP <15) layered with prone positioning, NMB, conservative fluids, and ECMO escalation for refractory cases.

CCS pearl: On the CCS interface, the winning ARDS sequence is ICU transfer → ABG/CXR/echo/cultures → intubate with 6 mL/kg IBW + PEEP per ARDSNet → broad-spectrum antibiotics + source control → sedation/analgesia + DVT/PPI prophylaxis + HOB 30° → reassess at 6h and 24h with proning/NMB/ECMO escalation as needed → daily SAT/SBT → extubate when ready → schedule pulm and PCP follow-up before discharge. Get the order and the timing right, and you score.

Board pearl: Of every intervention you can offer, low tidal volume ventilation saves the most lives — never let an ARDS patient leave your CCS case on 10 mL/kg.

Diagnose with Berlin criteria + echocardiogram to exclude cardiogenic edema; treat the underlying precipitant (sepsis, pneumonia, aspiration, pancreatitis, transfusion, trauma).

Ventilate with TV 6 mL/kg IBW, PEEP per ARDSNet table, plateau ≤30, driving pressure <15, permissive hypercapnia with pH ≥7.20, SpO₂ 88–95%.

Escalate stepwise for refractory hypoxemia: deepen sedation → cisatracurium 48 h → prone ≥16 h/day → inhaled vasodilators → VV-ECMO at experienced center (EOLIA criteria).

Survive and recover: dexamethasone for moderate–severe and COVID-ARDS, conservative fluids once shock resolves, A2F bundle daily, address post-ICU syndrome at follow-up, screen for cognitive/psychiatric sequelae, pulmonary rehab, and complete vaccination at discharge.