K Restrictive pulmonary diseases
Definition
Restrictive pulmonary disease is defined as any condition that interferes with normal lung expansion during inspiration. Typically, it includes disorders that increase the inward elastic recoil of the lungs or chest wall. Consequently, the alteration in pulmonary dynamics results in decreases in lung volumes and capacities and in lung or chest wall compliance. Some restrictive diseases produce ventilation abnormalities and V/Q mismatching, and others lead to impairment of diffusion. FEV1 and FVC are both decreased owing to a reduction in TLC or a decrease in chest wall compliance or muscle strength. However, the FEV1/FVC ratio is normal or elevated.
Incidence and prevalence
Statistics vary according to the acute intrinsic, chronic intrinsic, or chronic extrinsic nature of the restrictive disease.
Pathophysiology
Impairment-producing restrictive pulmonary diseases can be classified as (1) acute intrinsic, (2) chronic intrinsic, or (3) chronic extrinsic. Acute intrinsic disorders are primarily caused by the abnormal movement of intravascular fluid into the interstitium of the lung and alveoli secondary to the increase in pulmonary vascular pressures occurring with left ventricular failure, fluid overload, or an increase in pulmonary capillary permeability. Examples of acute intrinsic disorders include pulmonary edema, aspiration pneumonia, and ARDS. Chronic intrinsic diseases are characterized by pulmonary fibrosis. Conditions that produce fibrosis of the lung include idiopathic pulmonary fibrosis, radiation injury, cytotoxic and noncytotoxic drug exposure, O2 toxicity, autoimmune diseases, and sarcoidosis. Chronic extrinsic diseases can be defined as disorders that inhibit the normal lung excursion. They include flail chest, pneumothorax, atelectasis, and pleural effusions. They also include conditions that interfere with chest wall expansion, such as ascites, obesity, pregnancy, and skeletal and neuromuscular disorders.
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