Correct Answer: A

Rationale: The correct answer is A: Avoiding the administration of high levels of oxygen for extended periods. Oxygen toxicity can occur when high levels of oxygen are given for a prolonged period. It is important to monitor and adjust the oxygen levels as needed to prevent toxicity. Choice B is incorrect because administering a sedative to slow the respiratory rate does not directly prevent oxygen toxicity. Choice C is incorrect as removing the nasal cannula during the night can compromise the client's oxygenation. Choice D is incorrect as running oxygen through a hydration source does not prevent oxygen toxicity; instead, it may introduce risks associated with the hydration source.

Correct Answer: C

Rationale: The correct answer is C. Partial thromboplastin time (PTT) is the laboratory value that should be monitored to evaluate the effectiveness of heparin therapy. PTT reflects the intrinsic pathway of coagulation and is specifically sensitive to heparin's anticoagulant effects. Monitoring the PTT helps ensure that the client is within the therapeutic range to prevent clot formation without increasing the risk of bleeding. Choices A, B, and D are incorrect because while they are important laboratory values in other contexts, they are not specifically used to monitor the effectiveness of heparin therapy.

Correct Answer: B

Rationale: The correct answer is B: 'It prevents the blood from clotting.' Warfarin works by inhibiting the synthesis of vitamin K-dependent clotting factors in the liver, thereby preventing the formation of blood clots. Choice A is incorrect because warfarin does not dissolve existing blood clots but prevents new ones from forming. Choice C is partially correct but not as specific as choice B in explaining how warfarin works. Choice D is unrelated to the mechanism of action of warfarin and is incorrect.

Correct Answer: B

Rationale: The correct answer is B because a client with lupus erythematosus can be safely transferred to the antepartal unit as this condition does not pose a significant risk to other patients or staff. Choices A, C, and D should not be recommended for transfer to the antepartal unit due to the potential risks they may pose to pregnant women and their unborn babies. Chronic hepatitis B, rubella, and herpes lesions of the vulva can be contagious and harmful in the perinatal setting.

Correct Answer: C

Rationale: The correct action for the nurse to take first when a client with COPD reports difficulty breathing while receiving oxygen is to check the client's oxygen saturation level. This helps in determining the adequacy of oxygenation and identifying the cause of the breathing difficulty. Increasing the oxygen flow rate (Choice A) may not be appropriate without knowing the current oxygen saturation level. Instructing the client to breathe deeply and cough (Choice B) may not address the immediate need for oxygen assessment. Placing the client in a high-Fowler's position (Choice D) can help with breathing but should come after ensuring proper oxygenation.