Secondary polycythemia is seen in all of the following, except:

Correct Answer: B

Rationale: Secondary polycythemia hypoxia-driven RBC rise occurs in hypernephroma (A erythropoietin), emphysema (C low Oâ‚‚), AV aneurysms (D shunting), and cyanotic heart disease (E chronic hypoxia), but not peptic ulcer (B) GI bleeding causes anemia, not polycythemia. Hypoxia's erythropoietic trigger is key, guiding nursing for underlying cause workup.

Correct Answer: B

Rationale: Anemia of renal insufficiency low erythropoietin (B e.g., <100 mU/mL) from kidney failure slows RBC production, with reduced marrow transit (e.g., 5-7 days). Iron block (A) is chronic disease. Normocytic (C) describes, not causes. Blood loss (D) is unrelated. EPO deficiency is key, guiding nursing for EPO therapy.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Surfactant, produced by type II alveolar cells, is a phospholipid mixture that reduces surface tension in alveoli, stabilizing them and aiding lung function. Normally, high surface tension from water molecules at the air-liquid interface promotes alveolar collapse, but active surfactant lowers this tension, decreasing the tendency of lungs to collapse (atelectasis). Reduced surface tension also lessens the work of breathing by making lung expansion easier and decreases lymph flow in the lung, as less fluid is forced into the interstitium due to lower alveolar pressure gradients. However, lung compliance the ease with which lungs expand increases with active surfactant, not decreases. Compliance is inversely related to surface tension; when tension drops, the lungs become less stiff, improving their ability to stretch per unit of pressure. Thus, lung compliance is the exception, as it rises while the other factors diminish, reflecting surfactant's critical role in maintaining alveolar stability and efficient ventilation.

Correct Answer: D

Rationale: Diffusion of gases like O2 and CO2 across the alveolar-capillary membrane follows Fick's law: Rate = (A × D × ΔP) / d. Decreased surface area (A), as in emphysema, reduces the available exchange area, lowering diffusion. Increased fluid in the lung (e.g., pulmonary edema) increases diffusion distance (d), as fluid thickens the barrier, impeding gas transfer and often adding proteinaceous debris that further slows diffusion. Decreased pressure coefficient' likely intends partial pressure gradient (ΔP); reducing this (e.g., via hypoventilation) weakens the driving force for diffusion. All these factors surface area, distance, and gradient when altered as described, decrease diffusion rate. The diffusion coefficient (D) isn't directly mentioned, but the combined impact of the listed changes aligns with clinical scenarios (e.g., edema causing hypoxemia). Since each independently and collectively impairs diffusion, all contribute to a reduced gas exchange efficiency, critical for oxygenation and CO2 removal.