ATI LPN
NCLEX PN Questions Respiratory System Questions
Question 1 of 5
Vol Above FRC Which area represents the work to overcome airway resistance?
Correct Answer: C
Rationale: In a pressure-volume loop, work to overcome airway resistance is the area during inspiration where pressure exceeds elastic recoil, typically AECFA (choice C). ABCEA (choice A) includes total inspiratory work (elastic + resistive). ABCFA (choice B) overestimates resistance by including elastic work. ABCDOA (choice D) represents expiratory work, not inspiratory resistance. OAFCDO (choice E) is unrelated. During inspiration from FRC, the curve from A (FRC) to E (peak pressure) reflects effort against resistance and elastic forces; C (end-inspiration) marks full volume. The triangle AECFA isolates resistive work, as pressure above the elastic recoil line (A to C) is due to airflow resistance. This aligns with respiratory mechanics, where resistive work depends on flow and airway caliber, making C the correct area.
Question 2 of 5
Which abolishes automatic respiration? Destruction of:
Correct Answer: A
Rationale: destroying pre-Bötzinger complexes abolishes automatic respiration, as they generate the inspiratory rhythm in the medulla. Choice B (ventral group) modulates inspiration/expiration; damage impairs but doesn't stop rhythm. Choice C (dorsal group) drives inspiration; loss disrupts but doesn't abolish automaticity. Choice D (pons section) alters patterns (e.g., apneusis) via pneumotaxic/apneustic loss, not cessation. Choice E (rostral transection) preserves medullary function. The pre-Bötzinger complex, a pacemaker cluster, initiates breathing via spontaneous firing, driving phrenic and intercostal activity. Lesion studies confirm its destruction halts rhythm, unlike accessory regions. Thus, A is the critical site for automatic respiration's abolition.
Question 3 of 5
Regarding the glottis:
Correct Answer: B
Rationale: glottal abductors (posterior cricoarytenoids) contract early in inspiration to widen the glottis. Choice A is false; adductor paralysis (e.g., vocal cord) causes weak voice, not stridor (abductor issue). Choice C is true; abductor paralysis narrows the glottis, risking aspiration. Choice D is wrong; both adductors and abductors are vagus-innervated (recurrent laryngeal), not hypoglossal. Choice E is partially true but not absolute. Abductors, vagus-driven, open the glottis pre-inspiration, ensuring airflow. This timing, critical for ventilation, makes B the accurate statement.
Question 4 of 5
A patient with a right to left shunt: Mixed venous oxygen content = 15 ml/100 ml, Pulmonary capillary Oâ‚‚ content = 20 ml/100 ml, Arterial Oâ‚‚ content = 18 ml/100 ml. What fraction of total cardiac output passes through the shunt?
Correct Answer: D
Rationale: shunt fraction (Qs/Qt) = 40%. Using Qs/Qt = (CcOâ‚‚ - CaOâ‚‚) / (CcOâ‚‚ - CvOâ‚‚), where CcOâ‚‚ = 20, CaOâ‚‚ = 18, CvOâ‚‚ = 15 ml/100 ml: Qs/Qt = (20 - 18) / (20 - 15) = 2 / 5 = 0.4 (40%). Choice A (10%), B (20%), C (30%) underestimate; E (50%) overestimates. Right-to-left shunt mixes venous blood (low Oâ‚‚) with pulmonary capillary blood (high Oâ‚‚), reducing arterial Oâ‚‚ content. The formula quantifies this bypass, showing 40% of cardiac output skips oxygenation, matching D.
Question 5 of 5
The amount of Oâ‚‚ in blood with a PaOâ‚‚ of 100 mmHg is:
Correct Answer: B
Rationale: dissolved O₂ at PaO₂ = 100 mmHg is ≈0.3 mL/100 mL (solubility = 0.003 mL/mmHg/100 mL · 100 = 0.3). Choice A (0.003) is a typo or misunit. Choice C (3 mL) includes Hb-bound O₂ (≈19 mL with Hb 15 g/dL, SaO₂ 97%), not just dissolved. Choice D (3 mL/mL) is absurdly high. Total O₂ content is ≈20 mL/100 mL, but dissolved fraction is minor; B specifies this accurately per Henry's law.