The treatment of choice in a hemophilic bleeding into a knee joint would be:

Correct Answer: B

Rationale: Hemophilia joint bleed (e.g., factor VIII <1%) fresh frozen plasma (B) replaces clotting factors (e.g., 15 mL/kg raises VIII to 30%), stopping hemarthrosis. Transfusion (A) lacks factors. Bed rest (C) aids, not treats. Vitamin K (D) is for liver factors. Protamine reverses heparin. FFP's factor delivery is key, guiding nursing for infusion and joint care.

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.

Correct Answer: B

Rationale: The PAO2-PaO2 gradient measures the difference between alveolar oxygen (PAO2) and arterial oxygen (PaO2), normally small (~5-10 mmHg) due to efficient diffusion. In pulmonary fibrosis, thickened alveolar walls from scarring impair O2 diffusion, lowering PaO2 (e.g., 60 mmHg) while PAO2 (calculated via the alveolar gas equation, ~100 mmHg at sea level) remains closer to normal, widening the gradient (e.g., 40 mmHg). During exercise in a normal person, increased cardiac output and ventilation match perfusion, keeping the gradient minimal despite higher O2 demand. Anemia reduces oxygen-carrying capacity (low hemoglobin), not diffusion, so PaO2 approximates PAO2, maintaining a normal gradient. At 5000 meters, low atmospheric PO2 reduces both PAO2 and PaO2 proportionately (e.g., PAO2 ~50 mmHg, PaO2 ~45 mmHg), keeping the gradient small. Pulmonary fibrosis uniquely disrupts diffusion, causing the largest gradient, as fibrotic barriers hinder O2 transfer more than ventilation or perfusion issues.