ATI LPN
NCLEX PN Questions Respiratory System Questions
Question 1 of 5
Regarding control of ventilation
Correct Answer: D
Rationale: peripheral chemoreceptors (carotid and aortic bodies) respond to decreased arterial pOâ‚‚, driving ventilation in hypoxia. Choice A is false; the apneustic centre is in the lower pons, not medulla (medulla houses DRG/VRG). Choice B is wrong; central chemoreceptors (medulla) detect CSF pH changes from COâ‚‚, not Oâ‚‚. Choice C is true; aortic body chemoreceptors sense pH drops (acidosis), stimulating breathing. Choice E is false; pOâ‚‚, not COâ‚‚, is the primary arterial driver under normal conditions COâ‚‚ via central chemoreceptors dominates. Peripheral chemoreceptors' sensitivity to low pOâ‚‚ (e.g., <60 mmHg) complements COâ‚‚/pH control, critical in hypoxemia (altitude, disease). This specificity and location make D the accurate statement in ventilatory control.
Question 2 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 3 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 4 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.
Question 5 of 5
Which show sustained activity with lung inflation?
Correct Answer: D
Rationale: pulmonary stretch receptors (airway smooth muscle) show sustained firing during lung inflation (Hering-Breuer reflex), inhibiting inspiration. Choice A (central) senses chemical changes, not volume. Choice B (carotid) and C (aortic) monitor blood gases. Slow-adapting stretch receptors signal via vagus, prolonging activity with sustained volume, unlike rapidly adapting receptors, making D the match.