In assessing for major sources of infection in a COPD patient, the nurse focuses on:

Correct Answer: A

Rationale: The correct answer is A: Stasis of respiratory secretions. In COPD patients, stasis of respiratory secretions can lead to bacterial growth and increase the risk of infections like pneumonia. This is a common issue in COPD due to impaired mucociliary clearance. Choices B, C, and D are not directly related to sources of infection in COPD patients. Low body weight is more associated with malnutrition, postural hypotension with cardiovascular issues, and delayed antigen-antibody response with immune system deficiencies.

Correct Answer: D

Rationale: The correct answer is D. Oxygen is primarily carried by hemoglobin in red blood cells, not blood plasma. Hemoglobin binds to oxygen, forming oxyhemoglobin for transport. Option A is false because oxygen is more soluble in fluid than carbon dioxide. Option B is incorrect as oxygen diffuses slower than carbon dioxide due to its larger molecular size. Option C is true as the diaphragm is the main muscle involved in breathing, contracting to expand the lungs during inhalation.

Correct Answer: D

Rationale: The correct answer is D because in the lungs, during gas exchange, carbon dioxide (CO2) is removed from the blood and exhaled. This leads to a lower PCO2 in the alveoli compared to the capillaries. The concentration gradient drives the diffusion of CO2 from the capillaries to the alveoli. Options A and B are incorrect because the partial pressure of CO2 (PCO2) and oxygen (PO2) differ between the alveoli and capillaries due to gas exchange. Option C is also incorrect as PCO2 is lower in the alveoli to facilitate the removal of CO2 from the blood.

Correct Answer: A

Rationale: Correct Answer: A - Increase in volume of thoracic cavity and fall in lung pressure Rationale: 1. During inspiration, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity. 2. The external intercostal muscles also contract, lifting the ribcage and further expanding the thoracic cavity. 3. As thoracic cavity volume increases, lung pressure decreases, creating a pressure gradient that allows air to flow into the lungs. Summary: B: Fall in pressure inside the lungs - This is a consequence of the increase in thoracic cavity volume, not the cause of air entering the lungs. C: Increased volume of thoracic cavity - This is correct but does not explain how air enters the lungs. D: Muscular expansion of lungs - Lungs do not expand on their own; it is the thoracic cavity that expands to create the pressure gradient for air entry.

Correct Answer: A

Rationale: The correct answer is A: Medulla (pons). The medulla, located in the brainstem, controls involuntary functions like breathing. Specifically, the medulla contains the respiratory center, which regulates breathing rhythm and depth. During forced breathing, the medulla sends impulses to the voluntary muscles involved in breathing, such as the diaphragm and intercostal muscles. The pons, which is closely connected to the medulla, assists in regulating breathing patterns. The vagus nerve (B) is responsible for parasympathetic functions, not voluntary breathing. The cerebral hemispheres (C) are primarily involved in higher brain functions, not breathing regulation. The spinal cord (D) plays a role in transmitting signals between the brain and muscles but does not initiate voluntary breathing impulses.