Restrictive disease is a condition marked most obviously by a reduction in total lung capacity. A restrictive ventilatory defect may be caused by a pulmonary deficit, such as pulmonary fibrosis (abnormally stiff, non-compliant lungs), or by non-pulmonary deficits, including respiratory muscle weakness, paralysis, and deformity or rigidity of the chest wall.
In pulmonary tests, an individual with a restrictive ventilatory defect demonstrates a low total lung capacity, a low functional residual capacity, and a low residual volume. While his forced vital capacity (FVC) may be quite low, his forced expiratory volume in one second divided by the forced vital capacity (FEV1/FVC) is often normal or greater than normal due to the increased elastic recoil pressure of the lung.
Because large drops in pleural pressure are required to inflate the lungs, deep breaths are difficult for individuals with restrictive defects, and they tend to breathe shallowly and rapidly.