Which of the following abnormality is seen in a preoperative pulmonary function test, done in a patient with severe kyphoscoliosis?

Kyphoscoliosis is a combination of excessive anteroposterior and lateral curvature of thoracic spine. The major pathophysiologic effect of severe kyphoscoliosis are restrictive lung disease and ventillation perfusion imbalance resulting in chronic hypoventilation, hypoxic vasoconstriction pulmonary aery hypeension and cor pulmonale. Pulmonary function test shows a decrease in vital capacity and total lung capacity and an increase in residual volume, resulting in an increased residual volume/total lung capacity. Flow is reduced only in propotion to the reduction in vital capacity. Ref: Pulmonary Function Testing and Cardiopulmonary Stress Testing By Vincent C. Madama, 2nd Edition, Page 102; Chest Medicine: Essentials of Pulmonary and Critical Care Medicine By Ronald B. George, 5th Edition, Pages 440-1