Study guide
29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement
ABIM Critical Care Medicine Study Guide Exam
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1 Chapter 1: Exam Orientation: Format, Blueprint & Study Strategy
1.1 ABIM Critical Care Medicine Exam: Format, Blueprint & Study Strategy
2 Chapter 2: Acute Respiratory Failure & ARDS
2.1 ARDS Definition, Pathophysiology & Phenotypes 2.2 Lung-Protective Mechanical Ventilation 2.3 Refractory ARDS: Prone Positioning, Neuromuscular Blockade & VV-ECMO
3 Chapter 3: Obstructive Airways, Pulmonary Vascular & Pleural Emergencies
3.1 Severe Asthma & COPD Exacerbations in the ICU 3.2 Massive & Submassive Pulmonary Embolism 3.3 Pulmonary Hypertension & Right Ventricular Failure in the ICU 3.4 Massive Hemoptysis, Complex Pleural Effusions & Thoracic Drainage
4 Chapter 4: Airway, Parenchymal & Nonthrombotic Pulmonary Emergencies
4.1 Airway Management, Upper-Airway Obstruction & Artificial-Airway Complications 4.2 Diffuse Alveolar Hemorrhage, Interstitial Lung Disease, Pulmonary Vasculitis & Noncardiogenic Edema 4.3 Severe Community-Acquired & Viral Pneumonia 4.4 Nonthrombotic Embolism (Air, Fat, Amniotic Fluid, Tumor, Septic) & Acute Chest Syndrome
5 Chapter 5: Mechanical Ventilation Modes, Dyssynchrony & Liberation
5.1 Mechanical Ventilator Modes & Advanced Breath Delivery 5.2 Patient-Ventilator Dyssynchrony & Waveform Analysis 5.3 Ventilator Liberation, Spontaneous Breathing Trials & Post-Extubation Support
6 Chapter 6: Shock Syndromes & Hemodynamic Principles
6.1 Shock Classification, Cellular Pathophysiology & Biomarkers 6.2 Hemodynamic Monitoring: Arterial Lines, CVP & Pulmonary Artery Catheter 6.3 Dynamic Assessment of Fluid Responsiveness & Resuscitation Targets
7 Chapter 7: Vasoactive Therapies & Mechanical Circulatory Support
7.1 Vasopressors & Inotropes: Pharmacology & Clinical Titration 7.2 Temporary Mechanical Circulatory Support: IABP, Impella & TandemHeart 7.3 Venoarterial ECMO (VA-ECMO) & Differential Hypoxemia 7.4 Post-Cardiac Arrest Care, Targeted Temperature Management & Neuroprognostication
8 Chapter 8: Acute Kidney Injury & Renal Replacement Therapy
8.1 KDIGO AKI Classification, Etiologies & Diagnostic Evaluation 8.2 Continuous Renal Replacement Therapy (CRRT) vs Intermittent Hemodialysis 8.3 Indications & Timing for RRT in Critical Illness: AKIKI & STARRT-AKI
9 Chapter 9: Electrolyte, Acid-Base & Endocrine Emergencies
9.1 Severe Dysnatremias: Hyponatremia, Hypernatremia & Osmotic Demyelination 9.2 Potassium, Calcium, Magnesium & Phosphate Disorders 9.3 Complex & Mixed Acid-Base Disorders: Boston vs Copenhagen vs Stewart 9.4 Endocrine Crises: DKA, HHS, Thyroid Storm, Myxedema Coma & Adrenal Crisis
10 Chapter 10: Glycemic Control, Hyperammonemia, Pituitary & Adrenal Disorders
10.1 ICU Glycemic Control & Severe Hypoglycemia 10.2 Non-Hepatic Hyperammonemia & Metabolic Encephalopathy 10.3 Pituitary Emergencies, Adrenal Excess & Critical Illness-Related Corticosteroid Insufficiency
11 Chapter 11: Acute Coronary Syndromes & Cardiac Arrhythmias
11.1 Acute Coronary Syndromes & Mechanical Complications of Myocardial Infarction 11.2 Critical Tachyarrhythmias: Atrial Fibrillation with RVR, VT & VF 11.3 Critical Bradyarrhythmias, Conduction Blocks & Temporary Cardiac Pacing
12 Chapter 12: Acute Heart Failure, Valvular & Pericardial Emergencies
12.1 Acute Decompensated Heart Failure & Cardiogenic Pulmonary Edema 12.2 Acute Valvular Regurgitation & Prosthetic Valve Emergencies 12.3 Pericardial Tamponade & Acute Aortic Syndromes
13 Chapter 13: Myocardial Disease, Hypertensive & Cardiac Device Emergencies
13.1 Fulminant Myocarditis, Stress & Peripartum Cardiomyopathy, and Hypertrophic Cardiomyopathy 13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm 13.3 Implanted Cardiac Devices, LVAD Emergencies & Electrical Storm
14 Chapter 14: Sepsis & Systemic Infectious Diseases
14.1 Sepsis-3 Definitions & Surviving Sepsis Campaign 2026 Guidelines 14.2 Refractory Septic Shock & Adjunctive Therapies 14.3 Multidrug-Resistant Pathogens & Antimicrobial Stewardship in the ICU
15 Chapter 15: ICU-Acquired & Severe Focal Infections
15.1 Hospital-Acquired & Ventilator-Associated Pneumonia 15.2 Central Line-Associated Bloodstream Infections & Catheter-Associated UTIs 15.3 Intra-Abdominal Sepsis, Necrotizing Soft Tissue Infections & CNS Infections
16 Chapter 16: Focal, Special-Host & Systemic Infections
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess 16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections 16.3 Infective Endocarditis, Device Infections & Other Focal Cardiovascular Infections 16.4 Antimicrobial Pharmacokinetics, Allergy, Toxicity & Infection Prevention 16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses
17 Chapter 17: Neurocritical Care & Coma
17.1 Coma, Altered Mental Status & Acute Delirium in the ICU 17.2 Status Epilepticus & Non-Convulsive Status Epilepticus 17.3 Acute Ischemic Stroke & Intracranial Hemorrhage
18 Chapter 18: Cerebrovascular Syndromes, Encephalopathy & Withdrawal States
18.1 Cerebral Venous Sinus Thrombosis, PRES & Reversible Cerebral Vasoconstriction Syndrome 18.2 Alcohol & Sedative Withdrawal, Wernicke Encephalopathy & Drug-Induced Encephalopathy
19 Chapter 19: Intracranial Hypertension & Neuromuscular Weakness
19.1 Intracranial Pressure Monitoring, Cerebral Perfusion & Tiered ICP Management 19.2 Acute Neuromuscular Respiratory Failure, ICU-Acquired Weakness & Brain Death Determination
20 Chapter 20: Traumatic Brain Injury, Spinal Cord Injury & Toxin-Mediated Paralysis
20.1 Traumatic Brain Injury Management & Paroxysmal Sympathetic Hyperactivity 20.2 Acute Spinal Cord Injury, Neurogenic Shock & Autonomic Dysreflexia 20.3 Toxin-Mediated Paralysis & Neuromuscular Crises: Botulism, Tetanus, Tick Paralysis & Myasthenic Crisis
21 Chapter 21: Gastrointestinal, Hepatic & Abdominal Emergencies
21.1 Acute Upper & Lower Gastrointestinal Bleeding in the ICU 21.2 Acute Liver Failure & Severe Acute Pancreatitis 21.3 Abdominal Compartment Syndrome & Acute Mesenteric Ischemia
22 Chapter 22: Luminal GI Emergencies & Complications of Cirrhosis
22.1 Esophageal, Gastric & Bowel Emergencies: Perforation, Obstruction, Ogilvie Syndrome & Colonic Ischemia 22.2 Complications of Cirrhosis: Alcohol-Associated Hepatitis, Hepatorenal Syndrome & Pulmonary Vascular Syndromes
23 Chapter 23: Trauma, Burns & Perioperative Critical Care
23.1 Polytrauma Resuscitation, Damage Control & Massive Transfusion 23.2 Severe Burn Injury, Inhalation Injury & Environmental Emergencies 23.3 Perioperative Critical Care for High-Risk Surgical Patients
24 Chapter 24: Thoracic Trauma, Environmental Injury & Obstetric Critical Care
24.1 Thoracic Trauma: Flail Chest, Pulmonary Contusion, Great Vessel & Tracheobronchial Injury 24.2 Environmental Injury: Drowning, Diving, Altitude, Heat, Cold, Electrical & Radiation 24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy
25 Chapter 25: Transplantation, Donor Management & Post-Cardiac Surgery Care
25.1 Solid Organ Transplant Recipients & Deceased Donor Management 25.2 Post-Cardiac Surgery Critical Care: Bleeding, Tamponade, Low Output & Vasoplegia
26 Chapter 26: Hematologic Emergencies, Toxicology, Critical Ultrasound & ICU Liberation
26.1 Hematologic Emergencies in the ICU: HIT, DIC, TMA & Anticoagulant Reversal 26.2 Critical Care Toxicology, Toxidromes & Specific Antidotes 26.3 Critical Care Point-of-Care Ultrasound (POCUS) 26.4 ICU Liberation, Analgosedation, Goals of Care & Critical Care Ethics
27 Chapter 27: Transfusion Medicine, Hematologic & Oncologic Disorders
27.1 Transfusion Medicine: Products, Thresholds, Reactions & Apheresis 27.2 Red and White Cell Disorders, Hemoglobinopathies, Factor Deficiencies & Hypercoagulable States 27.3 Oncologic Emergencies, Hematopoietic Cell Transplant Complications & Cellular Therapy Toxicity
28 Chapter 28: Clinical Pharmacology, Adverse Drug Reactions & Specific Poisonings
28.1 Pharmacokinetic Principles, Dose Adjustment & Drug Interactions in Critical Illness 28.2 Adverse Drug Reactions: Anaphylaxis, Severe Cutaneous Reactions & Hyperthermic Syndromes 28.3 Specific Poisonings: Sodium-Channel Blockers, Lithium, Valproate, Theophylline, Iron, Sulfonylureas & Methemoglobinemia
29 Chapter 29: Ethics, Research Methods, Administration & Abdominal Ultrasound
29.1 Advance Care Planning, Nonbeneficial Treatment, Informed Consent & Confidentiality 29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement 29.3 Abdominal, Vascular & Procedural Point-of-Care Ultrasound
29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement
Key Takeaways Explain This Topic AI
Number needed to treat is the reciprocal of the absolute risk reduction, so a relative reduction looks impressive while the absolute benefit can be small.
A trial can be statistically significant and clinically unimportant, and an underpowered trial can miss a true benefit; a p value above 0.05 is not evidence of no difference.
Positive and negative predictive values depend on disease prevalence, whereas sensitivity, specificity, and likelihood ratios do not.
Exception from informed consent research requires a life-threatening condition, no feasible way to obtain prospective consent, community consultation, public disclosure, and an independent data monitoring committee.
Intention-to-treat analysis preserves randomization and is the primary analysis for superiority trials, while per-protocol analysis is used to support noninferiority conclusions.
Last updated: October 2026
Reading an ICU Trial
Effect measures :
Absolute risk reduction (ARR) = = = control event rate − - − treatment event rate.
Relative risk reduction (RRR) = ARR / control event rate = \text{ARR} / \text{control event rate} = ARR / control event rate .
Number needed to treat (NNT) = 1 / ARR = 1 / \text{ARR} = 1/ ARR .
Odds ratio approximates relative risk only when the outcome is uncommon.
Hazard ratio describes the instantaneous rate over time and comes from time-to-event analysis.
Worked example: mortality falls from 40% to 32%. The ARR is 8 percentage points, the RRR is 20%, and the NNT is 1 / 0.08 = 12.5 1/0.08 = 12.5 1/0.08 = 12.5 , so about 13 patients must be treated to prevent one death. The same 20% relative reduction applied to a 2% baseline mortality gives an ARR of 0.4 percentage points and an NNT of 250 . Always convert to absolute terms.
Design vocabulary :
Randomization balances known and unknown confounders; allocation concealment prevents gaming assignment; blinding prevents differential care and outcome assessment.
Intention-to-treat analyzes patients as randomized and preserves the benefit of randomization; it is conservative for superiority trials. Per-protocol analysis is biased by differential dropout but is needed to support noninferiority claims, where a sloppy trial can create a false appearance of equivalence.
Noninferiority margin : the largest acceptable difference, specified in advance. A result is noninferior only if the confidence interval excludes that margin.
Composite outcomes can be driven by their least important component; look at each element.
Surrogate endpoints (oxygenation, a biomarker) often fail to predict patient-centered outcomes, as inhaled nitric oxide in ARDS demonstrated.
Subgroup analyses are hypothesis-generating unless pre-specified with an interaction test.
Stopping early for benefit overestimates effect size.
Pragmatic and cluster-randomized designs, stepped-wedge trials, and platform trials with Bayesian adaptive randomization (REMAP-CAP) are increasingly common; understand that adaptive designs report posterior probabilities rather than single p values.
External validity : screened-to-enrolled ratios, exclusion criteria, and usual care in the control arm determine whether the result applies to your patient.
Statistical concepts :
Type I error (alpha) is a false positive; type II error (beta) is a false negative. Power = 1 − β = 1 - \beta = 1 − β .
Confidence intervals convey precision and plausible effect sizes; a wide interval crossing 1.0 cannot exclude meaningful benefit or harm.
A p value above 0.05 does not demonstrate equivalence ; many ICU trials are underpowered for mortality.
Choose tests appropriately: t test for two normally distributed means, ANOVA for more than two, Mann-Whitney U or Wilcoxon for non-normal data, chi-square or Fisher exact for proportions, log-rank for survival curves, and logistic or Cox regression for adjustment.
Mortality definitions matter : ICU, hospital, 28-day, 60-day, and 90-day mortality are not interchangeable, and discharge practices distort hospital mortality.
Diagnostic Test Characteristics
Metric Definition Behavior
Sensitivity True positives / all with disease Independent of prevalence; a highly sensitive test, when negative, rules out
Specificity True negatives / all without disease Independent of prevalence; a highly specific test, when positive, rules in
- Positive predictive value True positives / all positives Falls as prevalence falls
- Negative predictive value True negatives / all negatives Rises as prevalence falls
- Positive likelihood ratio Sensitivity / (1 − specificity) Above 10 is strongly confirmatory
- Negative likelihood ratio (1 − sensitivity) / specificity Below 0.1 is strongly exclusionary
- Area under the ROC curve Discrimination across thresholds 0.5 is useless, 1.0 is perfect
This is why a D-dimer is useful in low-probability patients (high sensitivity, high negative predictive value in low prevalence) and useless in high-probability patients, and why screening a low-prevalence ICU population generates false positives.
Human Subjects Protection
IRB review is required for research involving human subjects. The IRB evaluates risk-benefit balance, subject selection equity, informed consent adequacy, privacy and confidentiality protections, and monitoring plans.
Core documents and principles : the Nuremberg Code, the Declaration of Helsinki, and the Belmont Report (respect for persons, beneficence, justice), implemented in the United States through the Common Rule (45 CFR 46) and FDA regulations.
Consent in the ICU : most patients lack capacity, so legally authorized representative consent is used, with deferred consent from the patient on recovery where permitted.
Exception from informed consent (EFIC) for emergency research requires all of:
A life-threatening condition for which available treatments are unproven or unsatisfactory.
Prospective consent is not feasible within the therapeutic window.
The research offers the prospect of direct benefit .
Community consultation and public disclosure before and after the trial.
An independent data monitoring committee .
Attempts to contact a representative within a defined therapeutic window.
Vulnerable populations (pregnant people, prisoners, children, those with impaired decision-making) have additional protections.
Conflicts of interest must be disclosed; clinical trial registration before enrollment and reporting of results are expected.
Quality improvement versus research : QI aimed at improving local care with existing knowledge generally does not require IRB review, but systematic investigation designed to produce generalizable knowledge does. When in doubt, ask the IRB.
Quality Improvement and Patient Safety
Methods :
Model for improvement : aim, measures, changes, then Plan-Do-Study-Act cycles.
Lean reduces waste; Six Sigma reduces variation; high-reliability organization principles emphasize preoccupation with failure and deference to expertise.
Measures : structure (staffing, equipment), process (bundle compliance, time to antibiotics), outcome (mortality, CLABSI rate), and balancing measures that detect unintended harm.
Run charts and statistical process control (control) charts distinguish common cause variation from special cause variation; a sustained shift of points on one side of the median signals real change. A simple before-after comparison with a p value cannot separate a trend from an intervention effect.
Risk-adjusted benchmarking (APACHE, SAPS, SOFA-based models) allows comparison across units, with observed-to-expected mortality ratios.
Safety tools :
Checklists and bundles (central line insertion, ventilator, sepsis) reduce harm when coupled with culture change, as the Keystone ICU project demonstrated.
Root cause analysis is retrospective; failure mode and effects analysis is prospective.
Incident reporting and a just culture that distinguishes human error, at-risk behavior, and reckless behavior.
Structured handover (for example, I-PASS) reduces communication-related error, the leading contributor to sentinel events.
Rapid response systems and early warning scores target deterioration outside the ICU.
Error taxonomy : a near miss reaches no patient, an adverse event causes harm, and a sentinel event causes severe harm or death and triggers mandatory review. A never event (such as wrong-site surgery or a retained foreign body) should never occur.
ICU Organization and Administration
Staffing and structure : high-intensity physician staffing models and daytime intensivist coverage are associated with better outcomes; mandatory overnight in-house intensivist staffing did not improve mortality in a randomized trial. Nurse-to-patient ratios and the presence of clinical pharmacists and respiratory therapists affect outcomes.
Tele-ICU extends specialist oversight to units without on-site intensivists.
Triage and capacity : prioritize by likely benefit, use objective admission and discharge criteria, and plan for surge with crisis standards of care developed in advance, including a triage team separate from bedside clinicians.
Reimbursement and documentation : critical care time billing requires documented time devoted to the critically ill patient; severity of illness documentation affects risk adjustment and benchmarking.
Regulatory context : CMS Conditions of Participation, Joint Commission standards, public reporting, and value-based purchasing programs that penalize certain hospital-acquired conditions and readmissions.
Burnout and the clinician workforce : high prevalence in critical care, with moral distress a specific driver; mitigation includes workload management, ethics support, and team debriefing.