All of the following shift the oxygen dissociation curve to the right EXCEPT

Correct Answer: C

Rationale: Carbon monoxide (CO, choice C) doesn't shift the Oâ‚‚ dissociation curve right, making it the exception. Decreased pH (choice A), increased temperature (choice B), and increased pCOâ‚‚ (choice D, repeated as E) all reduce Hb-Oâ‚‚ affinity (Bohr effect), shifting the curve right to favor Oâ‚‚ unloading. CO binds Hb with high affinity, forming COHb, which left-shifts the curve for unbound Hb, increasing Oâ‚‚ affinity and impairing release opposite to a right shift. Acidosis (A), heat (B), and COâ‚‚ (D) enhance tissue Oâ‚‚ delivery, adaptive in exercise or hypoxia. CO's toxic effect mimics high Oâ‚‚ saturation, masking hypoxia, and doesn't aid unloading. Thus, C's distinct leftward action excludes it from right-shift factors.

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: C

Rationale: lung surface area (≈70-100 m²) is ≈30 times the skin's (≈2 m² in adults). Choice A (3x, ≈6 m²) is too low. Choice B (10x, ≈20 m²) underestimates. Choice D (100x, ≈200 m²) overestimates. Choice E is false. The alveolar expanse, via 300 million units, maximizes gas exchange, making C accurate.

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.