Final answer:
Option B (Unchanged; decreased) is correct. In severe kyphoscoliosis, which is associated with restrictive lung disease, the FEV1/FVC ratio is typically unchanged while the forced vital capacity is decreased due to limited lung expansion.
Step-by-step explanation:
In patients with severe kyphoscoliosis, FEV1/FVC is expected to be unchanged and vital capacity to be decreased, which corresponds to option B. Unchanged; decreased. Kyphoscoliosis can lead to a restrictive lung disease, where the lung's capacity to expand is limited. In restrictive lung diseases, the FEV1/FVC ratio is typically normal or high because the lungs, although reduced in volume capacity, are still able to expel air reasonably fast. Conversely, the total volume that can be exhaled forcefully, the forced vital capacity (FVC), is reduced due to the restricted expansion of the lungs.
Lung fibrosis is an example of a condition that leads to a high FEV1/FVC ratio because the lungs become stiff and less pliable, making the lungs not compliant. In kyphoscoliosis and fibrosis, the lungs decrease in size, but in kyphoscoliosis, the FEV1/FVC ratio remains unchanged or is even higher than normal. Therefore, even though the total volume of air that can be exhaled is compromised, indicating a decrease in FVC, the expiratory flow rates remain relatively normal, therefore the ratio stays unchanged.