ABSTRACT
Other lung conditions which primarily affect the overall size (volume) of the lungs cause what are known as restrictive defects. In these, the problem is one of shrinkage of the lung and loss of lung volume rather than narrowing of the airways. Hence, the FVC is decreased, and because the airways are not affected, the FEV1, although reduced in absolute terms, is not reduced in proportion to the vital capacity. Hence, the FEV1/FVC ratio is normal or may in fact be increased.
