CRE Patient Assessment & Diagnosis 3 — Questions and Answers
Question 1: A patient is being assessed for nocturnal hypoventilation. Which study is most definitive to diagnose obesity hypoventilation syndrome (OHS)?
- Overnight pulse oximetry alone
- Polysomnography with transcutaneous CO2 monitoring
- Daytime ABG showing PaCO2 > 45 mmHg with BMI ≥ 30 (Correct answer)
- Chest X-ray with cardiomegaly
Correct answer: Daytime ABG showing PaCO2 > 45 mmHg with BMI ≥ 30
OHS is diagnosed by daytime hypercapnia (PaCO2 > 45 mmHg) in an obese patient (BMI ≥ 30) without other explanatory cause.
Question 2: On chest radiograph, which finding is most consistent with a large pleural effusion?
- Hyperinflation with flattened diaphragms
- Opacification of the costophrenic angle with tracheal deviation away from the affected side (Correct answer)
- Bilateral diffuse interstitial infiltrates
- Mediastinal widening
Correct answer: Opacification of the costophrenic angle with tracheal deviation away from the affected side
A large pleural effusion causes opacification and blunting of the costophrenic angle, with mass effect shifting the trachea away from the effusion.
Question 3: Which finding on pulmonary function testing suggests a fixed upper airway obstruction such as tracheal stenosis?
- Scooped-out expiratory flow-volume curve
- Flattening of both the inspiratory and expiratory limbs of the flow-volume loop (Correct answer)
- Elevated TLC with reduced DLCO
- Reduced FEV1/FVC with normal TLC
Correct answer: Flattening of both the inspiratory and expiratory limbs of the flow-volume loop
Fixed upper airway obstruction produces plateau (flattening) on both the inspiratory and expiratory limbs of the flow-volume loop.
Question 4: A patient with suspected pulmonary hypertension undergoes a right heart catheterization. Which mean pulmonary arterial pressure (mPAP) confirms the diagnosis?
- ≥ 15 mmHg
- ≥ 20 mmHg (Correct answer)
- ≥ 25 mmHg
- ≥ 30 mmHg
Correct answer: ≥ 20 mmHg
Current guidelines (updated 2022) define pulmonary hypertension as a mean PAP ≥ 20 mmHg at rest during right heart catheterization.
Question 5: When assessing a patient's breathing pattern, Kussmaul respirations are most characteristic of which condition?
- Opiate overdose
- Diabetic ketoacidosis (Correct answer)
- CNS injury at the pons
- Congestive heart failure
Correct answer: Diabetic ketoacidosis
Kussmaul respirations are deep, rapid breaths driven by the body's attempt to compensate for metabolic acidosis, as seen in diabetic ketoacidosis.
Question 6: Which maneuver during spirometry testing best distinguishes variable extrathoracic obstruction from variable intrathoracic obstruction?
- Slow vital capacity maneuver
- Bronchodilator reversibility testing
- Comparison of the inspiratory vs. expiratory limb plateau on the flow-volume loop (Correct answer)
- Diffusion capacity measurement
Correct answer: Comparison of the inspiratory vs. expiratory limb plateau on the flow-volume loop
Variable extrathoracic obstruction flattens the inspiratory limb, while variable intrathoracic obstruction flattens the expiratory limb of the flow-volume loop.
Question 7: A patient with a chronic cough has a chest CT showing central airway dilation with mucus plugging and recurrent infections. Which diagnosis is most consistent?
- Emphysema
- Bronchiectasis (Correct answer)
- Pulmonary sarcoidosis
- Hypersensitivity pneumonitis
Correct answer: Bronchiectasis
Bronchiectasis is characterized by permanent dilation of bronchi with mucus retention and recurrent bacterial infections.
CRE Patient Assessment & Diagnosis 3
A patient is being assessed for nocturnal hypoventilation.
Which study is most definitive to diagnose obesity hypoventilation syndrome (OHS)?