Respiratory Disorders Practice Questions
20 free Respiratory Disorders practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
A 62-year-old man with a 40-pack-year smoking history presents with chronic productive cough and dyspnea. His FEV1/FVC ratio is reduced. Which pathologic change is most characteristic of chronic bronchitis?
- A Destruction of alveolar walls
- B Smooth muscle hypertrophy
- C Mucus gland hyperplasia
- D Loss of elastic recoil
Correct answer: Mucus gland hyperplasia
Chronic bronchitis is defined by chronic productive cough with mucus gland enlargement and increased goblet cells. This leads to airway narrowing and obstructive physiology.
A 25-year-old woman presents with wheezing, chest tightness, and cough triggered by exposure to pollen. Which of the following best explains the early phase of her asthma attack?
- A Neutrophil-mediated inflammation
- B IgE-mediated mast cell degranulation
- C Delayed macrophage recruitment
- D Progressive loss of elastic fibers
Correct answer: IgE-mediated mast cell degranulation
Early-phase asthma involves IgE-mediated mast cell degranulation, leading to bronchoconstriction, mucus secretion, and airway edema. This produces acute symptoms.
A COPD patient has a markedly decreased diffusion capacity (DLCO). Which subtype of COPD is this most consistent with?
- A Chronic bronchitis
- B Emphysema
- C Asthma
- D Bronchiectasis
Correct answer: Emphysema
Emphysema destroys alveolar walls, decreasing surface area available for gas exchange. This significantly reduces DLCO.
A 7-year-old with asthma has a pulsus paradoxus during an acute exacerbation. What is the mechanism?
- A Acute right ventricular failure
- B Negative intrathoracic pressure swings
- C Massive acute pulmonary embolism
- D Severe aortic valve stenosis
Correct answer: Negative intrathoracic pressure swings
Severe asthma increases intrathoracic pressure swings, causing exaggerated decrease in systolic BP during inspiration (pulsus paradoxus).
A 58-year-old man with emphysema has hyperinflated lungs. Which physiologic change explains this?
- A Increased airway resistance
- B Increased alveolar surface area
- C Decreased elastic recoil
- D Decreased lung compliance
Correct answer: Decreased elastic recoil
Loss of elastic recoil in emphysema causes air trapping and hyperinflation. Compliance is increased, not decreased.
A patient with severe asthma has normal DLCO. This finding supports the diagnosis because:
- A Alveolar walls remain intact
- B Air trapping reduces diffusion
- C Bronchioles collapse permanently
- D Mucus plugs thicken the alveolar membrane
Correct answer: Alveolar walls remain intact
Asthma affects airways but not alveoli, so DLCO is typically normal or increased. This helps distinguish asthma from emphysema.
A patient develops ARDS after sepsis. Which physiologic abnormality defines ARDS?
- A Increased lung compliance
- B Non-cardiogenic pulmonary edema
- C Bronchial hyperreactivity
- D Decreased alveolar ventilation
Correct answer: Non-cardiogenic pulmonary edema
ARDS is caused by diffuse alveolar damage, leading to leaky capillaries and pulmonary edema without heart failure. Compliance is reduced.
A COPD patient retains CO₂ chronically. Which compensation is expected?
- A Metabolic acidosis
- B Metabolic alkalosis
- C Respiratory alkalosis
- D Normal bicarbonate
Correct answer: Metabolic alkalosis
Chronic CO₂ retention causes respiratory acidosis, and the kidneys compensate by increasing bicarbonate, producing metabolic alkalosis.
A 34-year-old woman with asthma shows a reversible drop in FEV1 after methacholine challenge. Methacholine acts by:
- A Stimulating β2 adrenergic receptors
- B Blocking M3 cholinergic receptors
- C Stimulating muscarinic receptors
- D Blocking peripheral histamine receptors
Correct answer: Stimulating muscarinic receptors
Methacholine is a muscarinic agonist that induces bronchoconstriction. Increased airway responsiveness helps diagnose asthma.
A 70-year-old smoker presents with dyspnea and pursed-lip breathing. Which mechanism improves his expiratory airflow?
- A Increasing total airway resistance
- B Increasing expiratory back-pressure
- C Decreasing anatomic dead space
- D Reducing inspiratory muscle effort
Correct answer: Increasing expiratory back-pressure
Pursed-lip breathing increases airway back-pressure during expiration, preventing airway collapse in emphysema. This improves ventilation.
A patient with chronic bronchitis has secondary polycythemia. What is the cause?
- A Increased EPO from chronic hypoxia
- B Primary bone marrow failure
- C Chronic carbon monoxide poisoning
- D Systemic iron overload
Correct answer: Increased EPO from chronic hypoxia
Chronic hypoxia in COPD stimulates the kidneys to produce more EPO. This increases RBC production, causing secondary polycythemia.
A patient with acute asthma shows hyperinflated lungs on x-ray. What mechanism causes this?
- A Loss of alveolar elastic recoil
- B Air trapping from narrowed bronchioles
- C Diffuse interstitial fibrosis
- D Alveolar wall rupture
Correct answer: Air trapping from narrowed bronchioles
Bronchoconstriction and mucus obstruct expiration, leading to air trapping. This causes hyperinflation in asthma exacerbations.
A patient develops ARDS after inhaling toxic fumes. Which microscopic finding is characteristic?
- A Caseating granulomas
- B Hyaline membrane formation
- C Curschmann spirals
- D Charcot–Leyden crystals
Correct answer: Hyaline membrane formation
ARDS features diffuse alveolar damage and formation of hyaline membranes. This disrupts gas exchange.
Which cytokine plays a major role in neutrophil recruitment in ARDS?
- A IL-4
- B IL-17
- C TNF-α
- D IL-5
Correct answer: TNF-α
TNF-α and IL-1 are key mediators of neutrophil recruitment in ARDS. They trigger inflammatory cascade and endothelial injury.
A patient with longstanding emphysema has a barrel-shaped chest. Which physiologic change contributes to this?
- A Increased elastic recoil
- B Loss of alveolar septa
- C Reduced residual volume
- D Reduced total lung capacity
Correct answer: Loss of alveolar septa
Loss of alveolar septa decreases elastic recoil and increases lung compliance, causing hyperinflation and barrel chest.
A patient with asthma has thickened basement membranes and smooth muscle hypertrophy on biopsy. What does this indicate?
- A Emphysema
- B Airway remodeling
- C ARDS
- D Bronchiolitis obliterans
Correct answer: Airway remodeling
Chronic asthma leads to airway remodeling, characterized by thickened basement membranes, smooth muscle hypertrophy, and goblet cell hyperplasia.
A patient with COPD has increased anterior–posterior chest diameter. Which pulmonary function test is most likely reduced?
- A TLC
- B RV
- C FEV1
- D FRC
Correct answer: FEV1
COPD decreases FEV1 due to airflow obstruction. Lung volumes (TLC, RV, FRC) are typically increased due to air trapping.
A patient with severe ARDS requires mechanical ventilation. Which strategy reduces ventilator-associated lung injury?
- A High tidal volume ventilation
- B Low tidal volume ventilation
- C High FiO₂ ventilation
- D Zero PEEP
Correct answer: Low tidal volume ventilation
Low tidal volume ventilation reduces overdistension of alveoli and prevents ventilator-associated lung injury in ARDS.
A patient with asthma develops elevated eosinophils. Which protein is released by eosinophils that damages epithelial cells?
- A Myeloperoxidase
- B Major basic protein
- C Elastase
- D Histamine
Correct answer: Major basic protein
Major basic protein from eosinophils damages airway epithelium in atopic asthma. It contributes to airway inflammation.
A COPD patient has chronic hypercapnia. What is the main drive for respiration in such cases?
- A Central chemoreceptors sensing CO₂
- B Peripheral chemoreceptors sensing O₂
- C Mechanoreceptors
- D Juxtacapillary (J) receptors
Correct answer: Peripheral chemoreceptors sensing O₂
Chronic hypercapnia blunts central chemoreceptor response, so hypoxemia sensed by peripheral chemoreceptors becomes the main respiratory drive.