Correct Answer: B

Rationale: Chest tubes are used to drain air and fluid from the chest cavity to prevent complications such as pneumothorax or cardiac tamponade after surgery. Choice A is incorrect as chest tubes are not used to increase tidal volumes. Choice C is incorrect as chest tubes do not maintain positive intrapleural pressure; instead, they assist in removing excess air or fluid. Choice D is incorrect as chest tubes do not regulate pressure on the pericardium and chest wall; they primarily aid in drainage.

Correct Answer: B

Rationale: Chest tubes are necessary after open-heart surgery to facilitate the drainage of air and fluid from the chest cavity. These tubes help prevent complications such as pneumothorax (accumulation of air in the pleural space) or cardiac tamponade (build-up of fluid in the pericardial sac), which can be serious postoperative issues. Options A, C, and D are incorrect because chest tubes are primarily used for draining purposes and not for increasing tidal volumes, maintaining positive intrapleural pressure, or regulating pressure on the pericardium and chest wall.

Correct Answer: A

Rationale: Abdominal swelling is a classic presentation and often the first noticeable sign of a Wilms tumor. This occurs due to the tumor mass in the kidney, leading to abdominal distension. Weight gain (Choice B) is less likely as a presenting symptom compared to abdominal swelling. Hypotension (Choice C) is not typically associated with a Wilms tumor unless complications like bleeding or shock occur. Increased urinary output (Choice D) is not a typical finding for Wilms tumor; instead, patients may present with hematuria or urinary symptoms.

Correct Answer: A

Rationale: In this scenario, the infant is presenting with signs of respiratory distress, as evidenced by the increased work of breathing. Lowering the extremities can help reduce the workload on the diaphragm and improve respiratory mechanics. This action can be beneficial in optimizing the infant's breathing before considering more invasive interventions. Option B, initiating positive pressure ventilations, should be considered if the infant's condition deteriorates further and not as the first step. Option C, placing a nasopharyngeal airway and increasing oxygen flow, is not indicated as the primary intervention for increased work of breathing. Option D, listening to the lungs with a stethoscope, may provide additional information but is not the most urgent action needed in this situation.

Correct Answer: D

Rationale: Preparing a toddler for a CT scan involves providing a simple explanation of the procedure to reduce anxiety and help the child understand what will happen. This approach helps establish trust and cooperation, making the experience less frightening for the child. Shaving the head, starting an IV infusion, or administering a sedative are not typically part of the preparation for a CT scan in a toddler and may not be necessary or appropriate in this scenario.