This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
18 year old girl with rheumatic carditis, with mitral insufficiency. Which of the following will be seen? 
Select and explain. 
A. Increased peak expiratory flow rate, B. Increased vital capacity, C. Increased residual volume, D. Decreased functional residual capacity
D: Decreased functional residual capacity
Answer: D: Decreased functional residual capacity 
Explanation: Decreased functional residual capacity [Ref Harrison 17th/e p. 224. 2251 Severe mitral regurgigation leads to increase in left atrial pressure which in trun leads to increased puhnonaly venous pressure and capillary pressure. Any cardiac abnormality that leads to an increase in pulmonary venous pressure shifts the balance of forces between the capillary and interstitium. Hydrostatic pressure is increased and fluid exits the capillary at an increased rate resulting in interstitial and in more severe cases alveolar edema. Interstitial edema produces restrictive lung disease so there will be decrease in functional residual capacity.