ATI LPN
Introduction of Respiratory System NCLEX Questions PN Questions
Question 1 of 5
A healthy young adult breathing 100% oxygen will have:
Correct Answer: D
Rationale: mixed venous PO₂ (PvO₂) is ≈50 mmHg on 100% O₂. With FiO₂ = 1.0, PaO₂ rises to ≈650 mmHg (PIO₂ = 760 - 47 ≈ 713 mmHg, minus A-a gradient). O₂ content increases (dissolved O₂ ≈ 2 ml/100 ml + Hb-bound), but tissues extract ≈5 ml/100 ml O₂, dropping PvO₂ to 50-55 mmHg (SaO₂ near 100%). Choice A (40 mmHg) is normal air breathing. Choice B (713 mmHg) is arterial, not venous. Choice C (650 mmHg) overestimates venous saturation. D reflects the balance of high arterial O₂ and tissue uptake.
Question 2 of 5
Which are the most important for minute-by-minute control of ventilation?
Correct Answer: A
Rationale: central chemoreceptors (medulla) dominate minute-by-minute ventilation, sensing CSF pH (CO₂-driven, 70-80% of response). Choice B (carotid) and C (aortic) contribute <20% (O₂, CO₂, pH), critical in hypoxia. Choice D (stretch) fine-tunes via Hering-Breuer reflex. Central receptors adjust breathing rate/depth to maintain PaCO₂ ≈ 40 mmHg, responding within seconds to CO₂ shifts, making A the primary controller.
Question 3 of 5
All of the following are features of acclimatisation to high altitude EXCEPT:
Correct Answer: C
Rationale: high altitude causes pulmonary vasoconstriction (hypoxic response), not vasodilation. Choice A is true; 2,3-DPG shifts the curve right. ' angiogenesis increases capillaries. Choice D is accurate; polycythemia boosts Hb. Choice E (breathing capacity) rises. Vasoconstriction matches V/Q, countering hypoxia, making C the exception.
Question 4 of 5
Fick's law states that:
Correct Answer: B
Rationale: Fick's law states gas diffusion rate (V) = (A · D · (P1-P2)) / T, where A is area, D is diffusion constant, P1-P2 is pressure gradient, and T is thickness. Choice A is the alveolar ventilation equation, not Fick's. Choice C is the pH definition, unrelated. Choice D is Boyle's law (gas volume-pressure). Choice E is a temperature ratio misstep. Fick's law governs O₂ and CO₂ transfer across the alveolar-capillary membrane, emphasizing area and gradient (e.g., DₗO₂ ≈ 25 mL/min/mmHg), inversely proportional to thickness. B accurately captures this principle, critical for lung gas exchange calculations.
Question 5 of 5
Which of the following DOES NOT constrict pulmonary arterioles?
Correct Answer: D
Rationale: isoproterenol (β₂-agonist) dilates pulmonary arterioles, not constricts. Choice A (adrenaline) constricts via α-receptors (β₂ dilates, but α dominates in lung). Choice B (thromboxane B₂) constricts (stable metabolite). Choice C (noradrenaline) constricts (α-effect). Choice D (prostaglandin F2α) constricts. Isoproterenol's β₂-stimulation reduces resistance, aiding flow, distinguishing E as the non-constrictor.