This blood gas picture reveals which of the following? PH=7.52, pCO2=20 mmHg, pO2=120 mmHg, bicarb =16 mmol/

Correct Answer: B

Rationale: The blood gas (pH = 7.52, pCO₂ = 20 mmHg, pO₂ = 120 mmHg, HCO₃⁻ = 16 mmol/L) indicates respiratory alkalosis with partial renal compensation (choice B). pH > 7.45 shows alkalosis; low pCO₂ (20 mmHg, normal 35-45) suggests hyperventilation as the cause (respiratory). HCO₃⁻ (16 mmol/L, normal 22-26) is reduced, indicating renal compensation kidneys excrete bicarbonate to offset pH rise, though not fully (partial). Choice A (metabolic alkalosis) requires high HCO₃⁻ (e.g., vomiting), not low. Choice C (metabolic acidosis) fits low pH and HCO₃⁻, not here. Choice D (respiratory acidosis) needs high pCO₂. High pO₂ (120 mmHg) aligns with hyperventilation. This pattern low pCO₂ driving alkalosis, kidneys adjusting HCO₃⁻ confirms B as the diagnosis.

Correct Answer: C

Rationale: O₂ is perfusion-limited at rest (equilibrates in 0.25 s vs. 0.75 s transit), intermediate between N₂O (perfusion-limited) and CO (diffusion-limited). Choice A is false; N₂O, highly soluble, is perfusion-limited uptake depends on flow. Choice B is wrong; CO, low solubility, is diffusion-limited. ' diffusing capacity (Dₗ) is proportional to area, inversely to thickness (Fick's law). Choice E is true; transit time is ≈0.25 s at rest. O₂'s rapid equilibration at rest shifts to diffusion limitation in exercise or disease, but C accurately reflects its resting state.

Correct Answer: D

Rationale: medium-sized bronchi (2-4 mm diameter) are the primary resistance site due to turbulent flow and cumulative cross-sectional area peak. Choice A (trachea) and B (main bronchi) have low resistance (large diameter). Choice C (large bronchi) contributes less. Choice E (bronchioles) has high total area, reducing resistance. Per Poiseuille's law, resistance peaks where radius narrows before area increases, making D the major site.

Correct Answer: C

Rationale: regional pulmonary blood flow differences (apex to base) arise from hydrostatic pressure gradients (West zones). Choice A is false; increased arterial pressure (Pa) reduces resistance via vessel distension. Choice B is true; hypoxia (low POâ‚‚) causes vasoconstriction, but isn't the question's focus. Choice D is wrong; in Zone 1 (apex), PA > Pa > Pv, stopping flow. Gravity increases Pa and Pv from apex (Zone 1, minimal flow) to base (Zone 3, high flow), with resistance adjusting inversely. C accurately describes this vertical distribution.

Correct Answer: D

Rationale: J (juxtacapillary) receptors in alveolar walls respond rapidly to pulmonary capillary chemicals (e.g., edema, emboli), causing dyspnea. Choice A (central) senses CSF pH, not pulmonary blood. Choice B (carotid) and C (aortic) monitor systemic arterial changes. Choice D (stretch receptors) responds to lung inflation. J receptors, vagally innervated, detect interstitial changes instantly, unlike systemic chemoreceptors, making F the precise match.