Regarding gas exchange in the lungs:

Correct Answer: B

Rationale: DₗO₂ rises from ≈25 to 65 ml/min/mmHg in exercise via increased surface area and perfusion. Choice A is false; pulmonary capillary PaO₂ (≈100 mmHg) exceeds aortic (≈95 mmHg) due to shunts. Choice C is wrong; beryllium poisoning and sarcoidosis reduce DₗO₂ via fibrosis. Choice D is true; fibrosis impairs CO₂ diffusion, causing retention. Choice E is false; decreased PDGF doesn't cause fibrosis increased does. Exercise triples DₗO₂, enhancing O₂ uptake (e.g., VO₂ max), making B the accurate physiological change.

Correct Answer: D

Rationale: mean pulmonary artery pressure (mPAP) is ≈15 mmHg in a healthy adult (systolic ≈25, diastolic ≈8). Choice A (2 mmHg) is far too low, below venous levels. Choice B (5 mmHg) underestimates pulmonary circulation. Choice C (8 mmHg) is diastolic, not mean. Choice E (25 mmHg) is systolic, not mean. mPAP reflects low-resistance pulmonary flow (≈1/10 systemic), driven by right ventricular output. Catheterization data confirm 15 mmHg as normal, distinguishing it from systemic pressures (≈100 mmHg mean), making D the precise value.

Correct Answer: A

Rationale: asthma doesn't inherently increase compliance (lung stiffness), but options like emphysema (chronic asthma complication) do via loss of elastic recoil (compliance rises, e.g., 300 mL/cm Hâ‚‚O). Choice B (edema) decreases compliance (stiffer lungs). Choice C (hypertension) affects vessels, not compliance directly. Choice D (atelectasis) and E (fibrosis) reduce compliance (collapse, scarring). Asthma's acute bronchoconstriction doesn't alter compliance, but chronic changes mimic emphysema's high compliance, making A the relative increase among options.

Correct Answer: D

Rationale: FEV₁ is ≈80% of FVC in healthy adults (FEV₁/FVC ratio ≈ 0.75-0.85). Choice A (50%) suggests obstruction (e.g., COPD). Choice B (60%) and C (70%) are low for normals. Choice E (90%) is high, nearing restriction. FEV₁ (forced expiratory volume in 1 s) reflects airway patency; FVC (forced vital capacity) is total expirable volume. A ratio of 80% indicates normal flow, making D standard.

Correct Answer: A

Rationale: Bohr's method calculates physiological dead space (VD = VT · (PaCO₂ - PECO₂) / PaCO₂), not anatomic (Fowler's N₂ washout does). Choice B is true (≈150 mL). ' deep breaths stretch airways. Choice D is accurate (≈2 mL/kg). Choice E (conducting zone) is true. A's methodological error makes it the exception.