Embedded Files
1. A 3-year-old boy presents with a barking cough and inspiratory stridor. A lateral neck X-ray reveals subglottic narrowing (steeple sign). Which virus is the most likely cause?
A. Respiratory syncytial virus
B. Adenovirus
C. Parainfluenza virus
D. Influenza virus
Answer: C. Parainfluenza virus
Explanation: Parainfluenza virus (a paramyxovirus) is the most common cause of croup (laryngotracheobronchitis). Symptoms include a barking cough, stridor, and the classic steeple sign on imaging due to subglottic narrowing.
2. Which of the following cells is primarily responsible for producing surfactant in the lungs?
A. Type I pneumocyte
B. Type II pneumocyte
C. Alveolar macrophage
D. Clara cells
Answer: B. Type II pneumocyte
Explanation: Type II pneumocytes secrete surfactant to reduce alveolar surface tension and prevent collapse. They also proliferate in response to lung injury and can differentiate into type I cells.
3. What part of the airway has the highest resistance to airflow under normal conditions?
A. Terminal bronchioles
B. Alveolar ducts
C. Medium-sized bronchi
D. Trachea
Answer: C. Medium-sized bronchi
Explanation: Medium-sized bronchi generate the highest resistance due to turbulent airflow and relatively narrow diameter. Although smaller airways have smaller radii, their high total cross-sectional area reduces overall resistance.
4. A 64-year-old smoker has a chronic productive cough for over 3 months in each of the past 2 years. Which histological measurement supports the diagnosis?
A. A-a gradient
B. Reid index
C. Tiffeneau-Pinelli index
D. FEV1/FVC ratio
Answer: B. Reid index
Explanation: The Reid index is the ratio of the thickness of mucus glands to the thickness of the bronchial wall. An index >0.4 supports chronic bronchitis due to glandular hyperplasia.
5. Which of the following lung volumes cannot be measured using spirometry?
A. Vital capacity
B. Tidal volume
C. Inspiratory reserve volume
D. Residual volume
Answer: D. Residual volume
Explanation: Residual volume (RV) is the air remaining in the lungs after maximal expiration and cannot be directly measured by spirometry. It requires body plethysmography or gas dilution techniques.
6. A 55-year-old man with a history of emphysema has increased lung compliance. What causes this physiologic change?
A. Pulmonary fibrosis
B. Loss of alveolar elastic tissue
C. Increased surface tension
D. Increased capillary hydrostatic pressure
Answer: B. Loss of alveolar elastic tissue
Explanation: In emphysema, destruction of alveolar walls reduces elastic recoil and increases lung compliance. The lungs expand more easily, but deflation is impaired, leading to air trapping and hyperinflation.
7. A newborn is diagnosed with neonatal respiratory distress syndrome (NRDS). Which component of surfactant is deficient?
A. Lamellar bodies
B. Lecithin
C. Sphingomyelin
D. Dipalmitoylphosphatidylcholine (DPPC)
Answer: D. Dipalmitoylphosphatidylcholine (DPPC)
Explanation: DPPC is a critical phospholipid in surfactant that reduces alveolar surface tension. Its deficiency in premature infants leads to alveolar collapse and impaired gas exchange.
8. A 22-year-old man with cystic fibrosis is most likely to have chronic colonization by which organism in adulthood?
A. Haemophilus influenzae
B. Mycoplasma pneumoniae
C. Pseudomonas aeruginosa
D. Streptococcus pneumoniae
Answer: C. Pseudomonas aeruginosa
Explanation: Pseudomonas becomes the dominant pathogen in older children and adults with CF, contributing to chronic infection, biofilm formation, and progressive lung damage.
9. A patient with sarcoidosis presents with dyspnea and bilateral hilar lymphadenopathy. Which histological finding is most characteristic?
A. Caseating granulomas
B. Noncaseating granulomas
C. Eosinophilic infiltration
D. Fibrinoid necrosis
Answer: B. Noncaseating granulomas
Explanation: Sarcoidosis classically features noncaseating granulomas composed of tightly clustered epithelioid macrophages and giant cells. Caseating granulomas are typical of TB and fungal infections.
10. Which of the following best explains the clubbing seen in chronic lung disease?
A. Polycythemia-induced hypoxia
B. Platelet-derived growth factor from megakaryocytes
C. Hypercapnia-induced vasodilation
D. Hyperplasia of alveolar epithelium
Answer: B. Platelet-derived growth factor from megakaryocytes
Explanation: Clubbing is due to increased PDGF and VEGF released by megakaryocytes that bypass the pulmonary capillaries and lodge in peripheral circulation, stimulating angiogenesis and tissue proliferation.
11. A 34-year-old woman at high altitude develops respiratory alkalosis. What is the underlying mechanism?
A. Increased oxygen consumption
B. Increased PaCO₂
C. Hypoventilation
D. Hypoxic stimulation of peripheral chemoreceptors
Answer: D. Hypoxic stimulation of peripheral chemoreceptors
Explanation: At high altitude, low oxygen tension stimulates peripheral chemoreceptors (in the carotid body), leading to hyperventilation and subsequent respiratory alkalosis (↓PaCO₂, ↑pH).
12. A patient with chronic bronchitis is expected to have which spirometry finding?
A. Decreased FVC, normal FEV₁/FVC
B. Normal FVC, increased FEV₁/FVC
C. Normal FEV₁, increased TLC
D. Decreased FEV₁, decreased FEV₁/FVC
Answer: D. Decreased FEV₁, decreased FEV₁/FVC
Explanation: Chronic bronchitis is an obstructive disease with reduced FEV₁ and a lowered FEV₁/FVC ratio (<70%). TLC may be normal or increased due to air trapping.
13. A pulmonary embolism results in which of the following arterial blood gas findings?
A. Increased PaCO₂
B. Normal A-a gradient
C. Respiratory acidosis
D. Decreased PaCO₂
Answer: D. Decreased PaCO₂
Explanation: Pulmonary embolism causes V/Q mismatch and hypoxemia, triggering hyperventilation and resulting in a decreased PaCO₂ (respiratory alkalosis) early on.
14. Which type of hypoxemia is most responsive to supplemental oxygen?
A. Diffusion impairment
B. Shunt
C. Anemia
D. Low inspired oxygen
Answer: D. Low inspired oxygen
Explanation: Hypoxemia due to low inspired oxygen (e.g. high altitude) improves significantly with supplemental O₂. In contrast, right-to-left shunts do not respond well, since blood bypasses ventilated alveoli.
15. A 50-year-old male with COPD has increased PaCO₂ and bicarbonate. What is the most likely acid-base status?
A. Acute respiratory acidosis
B. Chronic respiratory acidosis with compensation
C. Respiratory alkalosis
D. Metabolic alkalosis
Answer: B. Chronic respiratory acidosis with compensation
Explanation: COPD patients retain CO₂ (respiratory acidosis). Over time, the kidneys compensate by increasing bicarbonate reabsorption, leading to a compensated chronic respiratory acidosis.
16. A patient is treated with a drug that inhibits phosphodiesterase, leading to bronchodilation. What is the drug?
A. Salmeterol
B. Ipratropium
C. Theophylline
D. Cromolyn
Answer: C. Theophylline
Explanation: Theophylline is a methylxanthine that inhibits phosphodiesterase, increasing intracellular cAMP and promoting bronchodilation. It also has anti-inflammatory effects but a narrow therapeutic index.
17. A child with nasal polyps and recurrent respiratory infections likely has which genetic condition?
A. Kartagener syndrome
B. Alpha-1 antitrypsin deficiency
C. Cystic fibrosis
D. Primary immunodeficiency
Answer: C. Cystic fibrosis
Explanation: CF is caused by CFTR mutations leading to thick mucus, chronic infections, and nasal polyps. Kartagener syndrome causes situs inversus and infertility but is less commonly associated with polyps.
18. Which of the following is a key pathophysiologic mechanism in asthma?
A. Neutrophil-mediated tissue damage
B. IL-1-induced fibrosis
C. Th2-mediated eosinophilic inflammation
D. Type IV hypersensitivity
Answer: C. Th2-mediated eosinophilic inflammation
Explanation: Asthma is driven by Th2 cells releasing IL-4, IL-5, and IL-13, which promote IgE production and eosinophil recruitment. This leads to bronchial hyperreactivity and reversible obstruction.
19. A 65-year-old man with silicosis is at increased risk for which infection?
A. Klebsiella pneumoniae
B. Mycobacterium tuberculosis
C. Aspergillus fumigatus
D. Pneumocystis jirovecii
Answer: B. Mycobacterium tuberculosis
Explanation: Silica particles impair macrophage phagolysosome formation, increasing the risk of TB. Silicosis shows upper lobe nodular opacities and “eggshell” calcification of hilar nodes.
20. Which of the following changes occurs with a left shift in the oxygen-hemoglobin dissociation curve?
A. Decreased affinity for oxygen
B. Facilitated oxygen delivery to tissues
C. Lower oxygen saturation at a given PaO₂
D. Increased hemoglobin affinity for oxygen
Answer: D. Increased hemoglobin affinity for oxygen
Explanation: A left shift means hemoglobin holds onto oxygen more tightly (increased affinity). Causes include alkalosis, hypothermia, decreased 2,3-BPG, and fetal hemoglobin.
Page updated
Google Sites
Report abuse