Final answer:
Pneumonia can affect the exchange of gases between the alveoli and capillaries in the lungs, leading to decreased oxygen levels and difficulty breathing.
Step-by-step explanation:
A respiratory infection such as pneumonia can affect the exchange of gases between the alveoli in the lungs and the capillaries surrounding them. Pneumonia causes inflammation and filling of the alveoli with fluid, which inhibits gas exchange. When the alveoli are filled with fluid, oxygen cannot diffuse from the alveoli into the capillaries, and carbon dioxide cannot diffuse out of the capillaries into the alveoli. This can lead to decreased oxygen levels in the bloodstream and difficulty breathing.