In considering a patient with Duchenne's muscular dystrophy (DMD), which of the following are likely to be DECREASED except?
A. Vital capacity
B. Maximum inspiratory force
C. Maximum expiratory force
D. Residual volume to Total Lung Capacity ratio (RV/TLC)
The answer is D. The important point is that the VC is decreased. A RESTRICTIVE lung defect. Pulmonary function testing (PFTs) usually shows decreased maximum inspiratory and expiratory pressures, decreased peak flows, and decreased VC (restrictive defect) caused by muscle weakness. Although they may have a normal pulse oximetry, their pulmonary function is unlikely to be normal. They also may have an impaired cough and may have difficulty mobilizing secretions.