Domain I is the largest on the examination: 50 of the 140 scored items. It tests whether you can gather the right information, interpret what it means, and decide what to do next — the chart, the bedside assessment, the procedures you perform to collect data, what the results tell you, and which diagnostic steps to recommend. Almost every question here is a small clinical story: data in, judgment out.
I.A · Evaluate Data in the Patient Record
I.A.1 · Patient history
Start with the record before you touch the patient. The history of present illness tells you why they are here; the orders tell you what is prescribed and what has been held; medication reconciliation catches the home drugs the admission orders missed; progress notes show the trajectory; DNR status and advance directives set the boundaries of what you may do; and the social, family, and medical history supplies the risk factors. How it is tested: a stem gives you a fragment of the chart and asks what matters most, or it plants a trap — a discontinued order you must not follow, a DNR you must honor, a home medication that explains the presentation. The trap is skimming: the one line you skip is the one the question turns on.
I.A.2 · Physical examination relative to the cardiopulmonary system
Read the documented cardiopulmonary examination the way you would perform it: inspection, palpation, percussion, auscultation, and the vital signs that frame them. The record's examination narrows your differential before you repeat it at the bedside. How it is tested: the stem quotes examination findings and asks what they suggest or what to assess next. The trap is treating the documented examination as current — always verify at the bedside, because cardiopulmonary status changes fast.
I.A.3 · Lines, drains, and airways
Note every line, drain, and airway in the record and confirm each at the bedside: chest tubes (and whether they are to water seal or suction, and whether they are tidaling or bubbling), vascular lines (arterial lines give beat-to-beat pressure and sampling access; central lines carry vasoactive drugs), and artificial airways (type, size, depth, cuff status). How it is tested: a chest radiograph or a bedside finding asks whether a line or tube is malpositioned, or a stem asks what a tidaling chest tube tells you. The trap is assuming position from the procedure note — verify against the film and the patient.
I.A.4 · Laboratory results
The outline names five laboratory groups: CBC (anemia reduces oxygen-carrying capacity; leukocytosis suggests infection), electrolytes (potassium and magnesium disturb cardiac rhythm; sodium and chloride track with acid–base status), coagulation studies (they matter before bronchoscopy, arterial puncture, or any invasive step), sputum culture and sensitivities (they direct antimicrobial therapy), and cardiac biomarkers (they distinguish cardiac from respiratory causes of dyspnea). How it is tested: a laboratory value is embedded in a vignette and you must decide whether it changes the plan. The trap is a normal value planted to distract you from the abnormal one.
I.A.5 · Blood gas analysis and hemoximetry results
This is the most-tested single data type in Domain I. Read every arterial blood gas in the same order: pH first, then PaCO2, then HCO3, then PaO2 and oxygenation. MedlinePlus lists the normal ranges your interpretation hangs on: pH 7.35–7.45, PaCO2 35–45 mmHg, HCO3 22–26 mEq/L, PaO2 75–100 mmHg, and oxygen saturation 95–100%. A pH below 7.35 is acidosis; above 7.45 is alkalosis. When the pH and the PaCO2 move in opposite directions, the disorder is respiratory; when pH and HCO3 move in the same direction, it is metabolic. Hemoximetry (CO-oximetry) goes further than a standard gas: it measures dyshemoglobins such as carboxyhemoglobin and methemoglobin, which a calculated saturation will miss. How it is tested: you get numbers and must name the disorder, judge compensation, or pick the next action. The trap is reading PaO2 as the acid–base story — oxygenation and acid–base are separate questions answered by separate numbers. Worked interpretation drills are in Appendix B.
I.A.6 · Pulmonary function testing results
Spirometry, lung volumes, and DLCO each answer a different question. Spirometry (FVC, FEV1, and their ratio) separates obstruction from restriction. Lung volumes tell you whether total lung capacity is reduced (restriction) or increased (hyperinflation). DLCO measures gas transfer across the alveolar–capillary membrane and falls in emphysema, fibrosis, and pulmonary vascular disease. How it is tested: a pattern of results asks for the category of defect, or a single DLCO value asks what it reflects. The trap is over-reading one number — interpret the pattern, not the value.
I.A.7 · 6-minute walk test results
The 6-minute walk measures functional exercise capacity and, with pulse oximetry, exercise-induced desaturation. It is used to qualify patients for long-term oxygen, to follow disease progression, and to judge response to therapy. How it is tested: a desaturation on exertion asks what to recommend — usually oxygen titration with exercise. The trap is treating distance as the only result; the oximetry tracing during the walk is often the point.
I.A.8 · Imaging study results
Read the chest radiograph systematically: quality first (positioning, penetration, inflation), then lines, tubes, and drains, then the heart, then the lungs. The outline lists the findings to recognize — pneumothorax, consolidation, pleural effusion, pulmonary edema, pulmonary artery size, and the diaphragm, mediastinum, and trachea. CT adds detail for nodules, emboli, and interstitial disease; ultrasound and echocardiography assess effusions and cardiac function at the bedside; PET stages lung cancer; the ventilation/perfusion scan evaluates suspected pulmonary embolism. How it is tested: a described film asks for the abnormality or the next step. The trap is the satisfying single finding — keep reading the whole film.
I.A.9 · Maternal and perinatal/neonatal history
Three data points anchor every neonatal vignette. The Apgar score is a quick test performed on the baby at 1 and 5 minutes after birth; five categories — breathing effort, heart rate, muscle tone, reflexes, and skin color — are each scored 0, 1, or 2. The 1-minute score reflects how the baby tolerated birth; the 5-minute score reflects how the baby is doing outside the womb and the response to resuscitation. Gestational age sets expectations: most neonatal respiratory distress syndrome occurs in babies born before 37 to 39 weeks, and risk rises as gestation falls. The L/S (lecithin/sphingomyelin) ratio estimates fetal lung maturity from amniotic fluid. How it is tested: a vignette gives gestation and Apgar and asks what to anticipate or what the score means. The trap is treating the Apgar as a resuscitation trigger by itself — it describes, while the baby's current condition directs.
I.A.10 · Sleep study results
The apnea-hypopnea index (AHI) is the headline number of a sleep study: apneas plus hypopneas per hour of sleep. A higher AHI means more severe sleep-disordered breathing and drives decisions about CPAP or bilevel titration. How it is tested: an AHI value asks about severity or the next step. The trap is confusing AHI with the oxygen desaturation index — count events versus depth of desaturation are different measurements.
I.A.11 · Trends in monitoring results
Single values diagnose; trends decide. Follow fluid balance (intake versus output, daily weights), vital signs, intracranial pressure, ventilator liberation parameters, and pulmonary mechanics over time. Noninvasive trends — pulse oximetry, capnography, transcutaneous monitoring — and cardiac monitoring (ECG, hemodynamic parameters) are read the same way: direction and rate of change matter more than any one number. How it is tested: two sets of values, hours apart, ask whether the patient is improving and what to do. The trap is reacting to the latest number instead of the slope.
I.A.12 · Determination of a patient's pathophysiological state
This is the synthesis step the whole domain builds toward: take the history, the examination, the laboratories, the gases, the imaging, and the trends, and name what is happening — hypoxemic versus hypercapnic respiratory failure, obstructive versus restrictive disease, cardiogenic versus noncardiogenic edema, compensated versus uncompensated acid–base disorder. The outline lists the conditions candidates must recognize, from COPD, asthma, and pneumonia through ARDS, pulmonary embolism, heart failure, and the neonatal conditions. How it is tested: a full vignette asks for the best interpretation. The trap is anchoring on the first abnormal value — assemble the whole picture before you name it.
I.B · Perform Clinical Assessment
I.B.1 · Interviewing the patient
Assess level of consciousness and orientation, emotional state, and ability to cooperate — an uncooperative or obtunded patient changes what procedures are safe. Ask about pain, shortness of breath, sputum production, and exercise tolerance in the patient's own words. Take a smoking history in pack-years and ask about environmental exposures (dusts, fumes, birds, molds). Review activities of daily living to grade functional limitation, and assess learning needs — literacy, preferred learning style, and social or cultural factors — because the teaching plan depends on them. How it is tested: the stem describes the interview and asks what it reveals or what to ask next. The trap is skipping the learning-needs assessment and then wondering why the teaching failed.
I.B.2 · Performing inspection
Start with general appearance: distress, cyanosis, posture, and work of breathing. Examine the airway — patency, Mallampati classification, tracheal position — before any airway intervention. Note cough and the amount and character of sputum. In the neonate, note the Apgar score and gestational age as the frame for everything else. Check skin integrity: pressure ulcers and stoma sites are found by looking, and they change positioning and device plans. How it is tested: inspection findings ask for the next assessment or the likely problem. The trap is the dramatic finding that distracts from the dangerous one — noisy breathing gets attention, silent obstruction kills.
I.B.3 · Palpating to assess
Feel the pulse for rate, rhythm, and intensity; feel for accessory muscle use; compare the chest for asymmetrical movement; and assess tactile fremitus, crepitus, tenderness, tactile rhonchi, and tracheal deviation. Increased fremitus over consolidation, decreased movement and hyperresonance over pneumothorax, crepitus over subcutaneous air — palpation confirms what inspection suggests. How it is tested: a palpation finding asks what it indicates. The trap is palpating through the gown and missing it — technique matters, and so does the question's assumption that you used it.
I.B.4 · Performing diagnostic chest percussion
Percuss to map resonance: hyperresonance over pneumothorax or hyperinflation, dullness over effusion or consolidation. Percussion is a confirmatory step, quick and equipment-free, and the examination expects you to know what each note means. How it is tested: a percussion note in a vignette asks for the underlying condition. The trap is treating percussion as obsolete — on the examination it still counts.
I.B.5 · Auscultating to assess
Listen to breath sounds (normal, diminished, bronchial, adventitious — crackles, wheezes, rhonchi, stridor, pleural friction rub), heart sounds and rhythm, and blood pressure. Stridor is upper airway; wheezes are lower airway; crackles are small airways and alveoli opening. A silent chest in a severe asthmatic is worse than a wheezy one — air movement is the message. How it is tested: a described sound asks for its meaning or location. The trap is naming the sound instead of answering what it means for the patient.
I.B.6 · Reviewing a chest radiograph
Assess quality first — patient positioning (rotation), penetration, and lung inflation — because a poor film creates false findings. Then confirm the presence and position of airways, lines, and drains; look for foreign bodies; assess heart size and position; and identify cardiopulmonary abnormalities — pneumothorax, consolidation, pleural effusion, pulmonary edema, pulmonary artery size — and the diaphragm, mediastinum, and trachea. How it is tested: the stem describes the film and asks what is wrong or what to do. The trap is reading the lungs before checking the tubes — a malpositioned endotracheal tube outranks an infiltrate.
I.C · Perform Procedures to Gather Clinical Information
I.C.1 · 12-lead ECG
Place the leads correctly, confirm calibration, and obtain a tracing free of artifact. The 12-lead ECG screens for ischemia, arrhythmia, and right-heart strain — all of which mimic or accompany respiratory disease. How it is tested: the stem asks what the procedure requires or what artifact to correct. The trap is limb-lead reversal, which manufactures pathology.
I.C.2 · Noninvasive monitoring
Apply pulse oximetry, capnography, and transcutaneous monitors correctly and know what degrades each signal: motion and poor perfusion for oximetry, leaks and secretions for capnography, sensor temperature and site for transcutaneous. These monitors trend; they do not replace blood gases when precision matters. How it is tested: a faulty reading asks for the cause or the fix. The trap is treating the number — recheck the sensor before you treat the patient.
I.C.3 · Peak flow
Measure peak expiratory flow with maximal effort, the best of three attempts, and compare with the patient's personal best. Peak flow tracks asthma control day to day and grades exacerbation severity in the moment. How it is tested: a peak-flow value as a percentage of personal best asks about severity or action. The trap is comparing with predicted instead of personal best.
I.C.4 · Mechanics of spontaneous ventilation
Measure tidal volume, minute volume, maximal inspiratory pressure (MIP, the negative inspiratory force), and vital capacity to judge whether the patient can sustain spontaneous breathing. These are the liberation parameters: adequate volumes and a strong negative inspiratory force argue the patient may wean; shallow rapid breathing argues otherwise. How it is tested: values ask whether the patient is ready for a spontaneous breathing trial. The trap is one good number — readiness is a pattern across parameters, not a single pass.
I.C.5 · Blood gas sample collection
Collect arterial samples correctly: appropriate site and technique, heparinized syringe, expel air, cap, mix, and analyze promptly or ice the sample. Venous samples answer different questions than arterial ones — know which you hold. How it is tested: a handling error asks how the result changes (air bubbles raise PaO2; delay raises PaCO2). The trap is analyzing a venous sample as if it were arterial.
I.C.6 · Blood gas analysis and hemoximetry
Run the analyzer with quality control, and use CO-oximetry when dyshemoglobins are suspected — carbon monoxide poisoning and methemoglobinemia are invisible to standard two-wavelength oximetry. A normal calculated saturation with a poisoned patient is the classic miss. How it is tested: a scenario asks which measurement to order. The trap is the reassuring pulse oximeter in carbon monoxide poisoning — carboxyhemoglobin reads as oxyhemoglobin.
I.C.7 · Oxygen titration with exercise
Titrate supplemental oxygen during exertion — typically the 6-minute walk — to keep saturation in the target range, because resting needs underestimate exertional needs. Document the flow that holds saturation with activity; that flow becomes the exertional prescription. How it is tested: desaturation on exertion asks what to do. The trap is titrating to rest and discharging to exertion.
I.C.8 · Cardiopulmonary calculations
Know what each calculation answers: the alveolar–arterial oxygen gradient P(A–a)O2 quantifies gas-exchange efficiency; dead-space to tidal-volume ratio VD/VT quantifies wasted ventilation; the P/F ratio (PaO2/FiO2) grades hypoxemia severity; the oxygenation index (OI) incorporates mean airway pressure. You do not need to derive them from first principles on examination day, but you must know which to reach for and what a worsening value means. Worked examples are in Appendix B. How it is tested: a value asks for its meaning or the trend. The trap is computing when the question asks for interpreting.
I.C.9 · Hemodynamic monitoring
Zero the transducer at the phlebostatic axis, level it, and read arterial and pulmonary artery pressures with their waveforms. Hemodynamics separate cardiogenic from noncardiogenic pulmonary edema and guide fluids and vasoactive drugs. How it is tested: a damped or misplaced waveform asks for the cause or correction. The trap is reading numbers off an unzeroed transducer.
I.C.10 · Pulmonary compliance and airways resistance
Compliance is volume change per pressure change — it falls when lungs stiffen (ARDS, fibrosis, pulmonary edema). Resistance is pressure change per flow — it rises when airways narrow (bronchospasm, secretions, kinked tube). Static compliance comes from the plateau pressure; dynamic compliance includes resistance. How it is tested: a change in compliance or resistance asks for the cause. The trap is blaming the lung when the tube is kinked — check the circuit before the physiology.
I.C.11 · Plateau pressure
Measure plateau pressure with an end-inspiratory hold — no flow, no resistance, so the pressure reflects the alveoli. It is the sum of elastic pressure and PEEP, determined at the bedside via an inspiratory hold. Rising plateau pressure means falling compliance or rising volume; it is the number you watch to keep ventilation lung-protective. How it is tested: a plateau value asks what it means or what to do. The trap is reading peak pressure as plateau — peak includes resistance, plateau does not.
I.C.12 · Auto-PEEP determination
Detect auto-PEEP (intrinsic PEEP, air trapping) with an end-expiratory hold: when the expiratory valve stays closed and flow has stopped, the measured pressure is trapped gas. Auto-PEEP raises intrathoracic pressure, drops venous return, and makes triggering harder. Causes are high minute ventilation, short expiratory time, and obstructive disease. How it is tested: a scenario asks how to measure it or what causes it. The trap is adding external PEEP to match it without understanding why it formed.
I.C.13 · Spontaneous breathing trial (SBT)
Conduct the SBT with the patient monitored — typically low-level pressure support or a T-piece/CPAP trial — and watch for failure signs: rapid shallow breathing, desaturation, tachycardia, hypertension or hypotension, agitation, diaphoresis. The SBT answers one question: can this patient sustain spontaneous ventilation? How it is tested: SBT results ask whether to extubate or continue weaning. The trap is passing the trial on paper while the patient fails at the bedside — the numbers serve the clinical picture, not the reverse.
I.C.14 · Apnea monitoring
Set apnea alarms for the at-risk patient — premature neonates, post-anesthesia, and anyone with central or obstructive apnea — and confirm the monitor detects both airflow and effort so central and obstructive events are distinguished. How it is tested: an alarm scenario asks what the monitor is telling you. The trap is alarm fatigue — every apnea alarm gets assessed.