Study guide
5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation
ABIM Internal Medicine Exam
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1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy
0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan
2 Chapter 1: Cardiovascular Disease (14% of Exam)
1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection
3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)
2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia
4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)
3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV
5 Chapter 4: Infectious Disease (9% of Exam)
4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections
6 Chapter 5: Pulmonary Disease (9% of Exam)
5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule
7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)
6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease
8 Chapter 7: Hematology (6% of Exam)
7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation
9 Chapter 8: Medical Oncology (6% of Exam)
8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care
10 Chapter 9: Nephrology & Urology (6% of Exam)
9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria
11 Chapter 10: Neurology (4% of Exam)
10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders
12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)
11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health
13 Chapter 12: Dermatology (3% of Exam)
12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease
14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)
13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications
15 Chapter 14: Geriatric Syndromes (3% of Exam)
14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings
16 Chapter 15: Allergy & Immunology (2% of Exam)
15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders
17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology
16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design
18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)
17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity
19 Chapter 18: Perioperative Medicine & Medical Consultation
18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications
20 Chapter 19: Ophthalmology (1% of Exam)
19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease
21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)
20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders
5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation
Key Takeaways Explain This Topic AI
Acute respiratory distress syndrome and management of ventilators are separately enumerated blueprint subsections under Pulmonary Disease.
Lung-protective ventilation using roughly 4 to 8 mL per kilogram of predicted body weight with a plateau pressure at or below 30 cm of water reduces mortality.
Predicted body weight, calculated from height and sex, must be used for tidal volume rather than actual body weight.
Prone positioning improves survival in severe acute respiratory distress syndrome with a markedly reduced oxygenation ratio.
Daily spontaneous awakening and spontaneous breathing trials shorten ventilation duration and are the standard weaning approach.
Last updated: August 2026
Critical care pulmonology and pleural diseases encompass life-threatening conditions where rapid diagnosis and protocolized, evidence-based management directly determine patient survival. The ABIM examination frequently tests mechanical ventilation physiology, ARDS clinical trial parameters, weaning indices, pleural fluid biochemical interpretation using Light's criteria, and the emergent management of complicated effusions and tension pneumothorax.
1. Acute Respiratory Distress Syndrome (ARDS)
ARDS is a catastrophic form of acute, diffuse, inflammatory lung injury resulting in increased alveolar-capillary membrane permeability, loss of aerated lung tissue (non-cardiogenic pulmonary edema), surfactant inactivation, and severe intrapulmonary shunt physiology.
The Berlin Definition of ARDS
To establish a diagnosis of ARDS, a patient must meet all 4 of the following criteria :
Timing: Acute onset within 1 week of a known clinical insult (sepsis, severe pneumonia, aspiration, major trauma, pancreatitis, TRALI) or new/worsening respiratory symptoms.
Chest Imaging: Bilateral opacities on chest radiograph or CT scan not fully explained by pleural effusions, lobar/lung collapse, or pulmonary nodules.
Origin of Edema: Respiratory failure not fully explained by cardiac failure or fluid overload . If no clear ARDS risk factor is present, objective assessment (e.g., transthoracic echocardiogram) is required to exclude hydrostatic/cardiogenic pulmonary edema.
Oxygenation Impairment (measured with PEEP >= 5 cm H2O):
- Mild ARDS: 200 mmHg < PaO2/FiO2 <= 300 mmHg
- Moderate ARDS: 100 mmHg < PaO2/FiO2 <= 200 mmHg
- Severe ARDS: PaO2/FiO2 <= 100 mmHg
- Evidence-Based ARDS Management Protocols
Therapeutic Strategy Trial & Evidence Base Exact Clinical Parameters & Targets
Low Tidal Volume Ventilation ARMA Trial (ARDSNet): Lower tidal volumes reduced 28-day mortality by 22% (31% vs 39.8%) compared to traditional 12 mL/kg ventilation by preventing volutrauma and barotrauma . - Initial tidal volume: 6 mL/kg of Predicted Body Weight (PBW) (range: 4–8 mL/kg PBW).; - PBW Formula (Men): 50 + 0.91 × ( Height in cm − 152.4 ) 50 + 0.91 \times (\text{Height in cm} - 152.4) 50 + 0.91 × ( Height in cm − 152.4 ) ; - PBW Formula (Women): 45.5 + 0.91 × ( Height in cm − 152.4 ) 45.5 + 0.91 \times (\text{Height in cm} - 152.4) 45.5 + 0.91 × ( Height in cm − 152.4 ) ; (Never use actual body weight, which leads to fatal overventilation).
Plateau Pressure Limitation ARDSNet Protocol: Measured during an end-inspiratory occlusion pause (0.5 sec) in a passive patient. - Target Plateau Pressure ( P p l a t P_{plat} P pl a t ) <= 30 cm H2O .; - If P p l a t > 30 P_{plat} > 30 P pl a t > 30 , decrease tidal volume in 1 mL/kg steps down to 4 mL/kg PBW.
Driving Pressure Optimization Amato et al. (NEJM 2015): Δ P = P p l a t − P E E P \Delta P = P_{plat} - PEEP Δ P = P pl a t − PEEP . Driving pressure is the single strongest ventilator variable correlating with survival in ARDS. - Target Driving Pressure ( Δ P \Delta P Δ P ) <= 15 cm H2O .
Permissive Hypercapnia Prevents lung injury by tolerating moderate respiratory acidosis rather than escalating tidal volume or rate. - Target arterial pH >= 7.20 (PaCO2 50–70 mmHg tolerated).; (Contraindicated in severe metabolic acidosis, increased ICP, or severe right heart failure).
Prone Positioning PROSEVA Trial: In moderate-to-severe ARDS ( PaO2/FiO2 < 150 mmHg with PEEP >=10 and FiO2 >=0.6), early prone positioning reduced 28-day mortality from 32.8% to 16.0% ( p < 0.001 p < 0.001 p < 0.001 ). - Must be maintained for >= 16 consecutive hours per day .; - Mechanisms: Homogenizes transpulmonary pressure gradients, recruits dorsal atelectatic alveoli, improves V/Q matching, decreases ventral overdistension.
Neuromuscular Blockade ACURASYS Trial: Early continuous IV infusion of Cisatracurium besylate for 48 hours . - Indicated for severe ARDS (PaO2/FiO2 < 150) with significant patient-ventilator dyssynchrony , breath-stacking, or persistently elevated plateau pressures.
Conservative Fluid Strategy FACTT Trial: Protocolized fluid restriction and diuresis to achieve a neutral-to-negative fluid balance once shock has resolved. - Increases ventilator-free days and ICU-free days without worsening non-pulmonary organ failure or renal replacement therapy rates.
Veno-Venous (VV) ECMO EOLIA Trial & CESAR Trial: Extracorporeal membrane oxygenation for refractory severe hypoxemic ARDS. - Indicated when PaO2/FiO2 < 80 mmHg for >6 hours or PaO2/FiO2 < 100 for >12 hours, or pH < 7.15 despite lung-protective ventilation and prone positioning.
2. Mechanical Ventilation Weaning Protocols
Daily assessment of readiness for liberation from mechanical ventilation accelerates extubation and prevents ventilator-associated pneumonia and vocal cord injury.
Protocolized Weaning Assessment
Spontaneous Awakening Trial (SAT): Daily interruption of all sedatives and opioids in stable patients.
Spontaneous Breathing Trial (SBT): Performed when the patient passes SAT, meets oxygenation stability criteria (PaO2/FiO2 >= 150–200 on PEEP <= 5–8 cm H2O and FiO2 <= 0.4–0.5), has stable hemodynamics without high-dose vasopressors, and demonstrates spontaneous respiratory effort.
SBT Technique: Low-level pressure support (PSV 5 cm H2O / PEEP 5 cm H2O) or T-piece trial for 30 to 120 minutes .
Rapid Shallow Breathing Index (RSBI / Tobin Index):
Calculated during 1 minute of unassisted room air / T-piece breathing: RSBI = Respiratory Frequency (breaths/min) Tidal Volume (Liters) = f V T \text{RSBI} = \frac{\text{Respiratory Frequency (breaths/min)}}{\text{Tidal Volume (Liters)}} = \frac{f}{V_T} RSBI = Tidal Volume (Liters) Respiratory Frequency (breaths/min) = V T f
RSBI < 105 breaths/min/L strongly predicts successful extubation .
RSBI > 105 breaths/min/L indicates respiratory muscle fatigue and high likelihood of extubation failure.
Cuff Leak Test: Deflating the endotracheal tube cuff to verify air movement around the tube. Indicated in patients with risk factors for post-extubation stridor/laryngeal edema (prolonged intubation >6 days, traumatic intubation, female sex). If cuff leak volume is low (<110 mL or <24% of inspired volume), administer IV Methylprednisolone 20–40 mg every 4–6 hours for 12–24 hours prior to re-evaluating extubation.
3. Pleural Effusions: Diagnostic Evaluation & Light's Criteria
A pleural effusion represents an abnormal accumulation of fluid in the pleural space resulting from altered hydrostatic/oncotic forces (transudate) or increased capillary permeability/lymphatic obstruction (exudate).
Diagnostic Thoracentesis Indications
Indicated for any new, unexplained pleural effusion >= 10 mm in thickness on lateral decubitus radiograph or bedside ultrasound.
Exception: Bilateral effusions with classic clinical signs of decompensated Congestive Heart Failure (CHF) do not require immediate thoracentesis unless atypical features are present (fever, pleuritic chest pain, asymmetric effusion size, or lack of response to diuresis).