Which respond to blood CO₂, not O₂ or H⁺ concentrations?

Correct Answer: A

Rationale: central chemoreceptors respond to blood CO₂ via CSF pH changes (CO₂ diffuses, forms H⁺), not directly to O₂ or H⁺. Choice B (carotid) and C (aortic) sense PO₂, PCO₂, and pH. Choice D (stretch) is mechanical. Located in the medulla, central receptors drive 70-80% of CO₂ response, insensitive to hypoxia, making A the specific match.

Correct Answer: D

Rationale: advancing age increases compliance (loss of elastic recoil, e.g., emphysema-like), not decreases. Choice A (LV failure) reduces it via edema (stiffer lungs). Choice B (atelectasis) decreases via collapse. Choice C (fibrosis) lowers it (scarring). Choice E (raised PCWP) mimics edema. Aging weakens lung elastin, raising compliance (e.g., 250 vs. 200 mL/cm Hâ‚‚O), distinguishing D as the exception.

Correct Answer: C

Rationale: nitrous oxide (N₂O) is perfusion-limited, not diffusion-limited its high solubility allows rapid equilibration (≈0.1 s) with pulmonary blood flow. Choice A is true; gases diffuse per Fick's law. ' DₗCO₂ ≈ 20x DₗO₂ (600 vs. 25 mL/min/mmHg) due to solubility. Choice D is accurate; CO, diffusion-limited, doesn't equilibrate in 0.75 s (high Hb affinity). Choice E (O₂ perfusion-limited) is true at rest. N₂O's uptake depends on flow, not diffusion barrier, making C the false statement.

Correct Answer: C

Rationale: Congestive heart failure (CHF) increases an adult's risk of acquiring the flu if exposed because it compromises cardiovascular and respiratory function, weakening the body's ability to resist infection. CHF reduces oxygen circulation, impairing immune responses, and fluid buildup in the lungs creates a fertile ground for viral replication and complications like pneumonia. Gallbladder disease and recent cholecystectomy (gallbladder removal) don't directly affect immunity or respiratory health, so they pose minimal flu risk. Deep vein thrombosis impacts blood clotting, not infection susceptibility. Adults with CHF, especially older ones, are more vulnerable to severe flu outcomes due to their chronic condition taxing the body's reserves. The nurse identifies CHF as the key risk factor, as it aligns with evidence linking cardiopulmonary conditions to higher flu morbidity, necessitating preventive measures like vaccination.

Correct Answer: A

Rationale: For 65-year-old Harold Jackson, the nurse teaches that the injectable flu vaccine might be less effective due to age-related immune decline, increasing his risk a key point to encourage vaccination despite this. Past influenza A (2009) doesn't guarantee immunity strains change yearly, and antibodies wane, so prior infection isn't protective now. The intranasal spray, a live vaccine, is contraindicated for those over 50 due to safety and efficacy concerns. Living at home versus a facility lowers exposure but not inherent risk flu circulates everywhere. The nurse emphasizes vaccination's role, even if less potent in seniors, as it still reduces severity and complications like pneumonia, critical for his age group, aligning with CDC recommendations for annual shots to mitigate flu's impact on older adults.