With reference to homeostasis and the respiratory system, can you explain why Abraham has become short of breath?

SCENARIO A (max 500 words & 10 marks)

Abraham (43 years old) has been feeling unwell the last few days. His initial symptom was a productive cough, and he then developed a temperature which today you measure at 38.9°c. He has been managing to work, but in the last 24 hours has started to feel quite short of breath. He has received a diagnosis of pneumonia.