ATI LPN
Exam Questions on Respiratory System Questions
Question 1 of 5
Regarding gas exchange in the lungs:
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.
Question 2 of 5
Regarding pulmonary blood flow:
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.
Question 3 of 5
Which responds quickly to chemicals injected into the pulmonary circulation?
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.
Question 4 of 5
The calibre of extra-alveolar vessels is primarily determined by:
Correct Answer: C
Rationale: extra-alveolar vessel caliber (e.g., arterioles, venules) is primarily determined by lung volume, expanding with inflation (radial traction). Choice A affects alveolar capillaries (Zone 2/3). Choice B (artery pressure) influences flow, not caliber directly. Choice D (output) and E (fluid) are secondary. As volume rises (e.g., FRC to TLC), vessel resistance drops, distinguishing C as the mechanical driver.
Question 5 of 5
Which of the following is INCORRECT?
Correct Answer: A
Rationale: HbS shifts the O₂ curve right (lower affinity, P₅₀ up), not left, due to altered structure (valine for glutamic acid). Choice B is true (Bohr effect). Choice C is correct (CO affinity ≈240x O₂). Choice D is accurate; COHb left-shifts remaining Hb's curve. HbS's sickling enhances O₂ unloading, contradicting A's left shift, making it false.