Which of the following will decrease diffusion?

Correct Answer: D

Rationale: All factors (D) reduce diffusion . Fick's law: rate = D × A × ΔP / d. Decreased area (A, e.g., emphysema, Q59) cuts A (70 m^2 to 35 m^2). Fluid (B, pulmonary edema, Q55) thickens d (0.2 μm to 1 μm). Pressure coefficient' (C) likely means ΔP lowering it (e.g., 60 to 30 mmHg) slows flow. Each halves diffusion (e.g., O2 from 250 mL/min); combined, they compound loss. D's inclusivity unlike A's single factor matches physiology's multifactorial model.

Correct Answer: A

Rationale: CO2 diffuses easier than O2 (A). CO2's solubility (0.57 mL/mmHg/dL) outstrips O2's (0.024), 20x faster despite O2's gradient (60 vs. 6 mmHg, Q20). O2's diffusing capacity (B, false) is lower (21 vs. 400 mL/min/mmHg) due to binding limits. Exercise shortens equilibrium time (C, true), but not length capillaries stay 0.75 s. ABGs hold (D, false, PaO2 ~95 mmHg). A's ease unlike B's reversal fits Fick's law, per physiology.

Correct Answer: B

Rationale: Alveolar proteinosis features diffuse lung changes with mottling and reticulation (B) on imaging surfactant-filled alveoli create a tree-in-bud' or crazy paving' pattern, reflecting its pathology. Pulmonary lavage (A) uses saline, not heparin (an anticoagulant), to clear proteinaceous material, making A false. Vital capacity (C) drops, not normal, due to alveolar filling reducing lung volumes restrictive pattern on spirometry. Thus, D (A & C) and E (all) fail; B alone holds. This rare condition, often tied to dust exposure or autoimmunity, impairs gas exchange, and lavage is therapeutic, not heparin-based, a distinction critical in pulmonology and treatment planning.

Correct Answer: D

Rationale: Average vital capacity (VC) total air exhaled after maximal inhalation is 4-5 liters (D) in healthy adults (e.g., ~4.8 L men, 3.2 L women), varying by age, sex, height. Options 600 cc (A) and 300 cc (B) are tidal volumes or fractions far too low. 10-20 liters (C) exceeds human lung capacity (total ~6 L). 2.5-3 liters underestimates normal VC, closer to inspiratory reserve. VC, measured via spirometry, reflects lung function; 4-5 L aligns with physiologic norms, key in assessing restrictive (low VC) versus obstructive diseases in pulmonary diagnostics.

Correct Answer: B

Rationale: Markedly decreased diffusion capacity for CO (DLCO) (B) indicates non-operability in lung cancer poor gas exchange (e.g., DLCO <40% predicted) predicts post-resection respiratory failure. Decreased compliance (A), V/Q mismatch (C), hypoventilation (D), or pulmonary hypertension impair function but aren't primary surgical contraindications DLCO directly assesses alveolar-capillary integrity. Low DLCO, from tumor or emphysema, limits resection tolerance, key in preoperative pulmonary function testing for surgical planning in chest oncology.