In medicine, compliance and elasticity are different ways to describe how stretchy, springy or flexible something is. The more compliant the lungs are, the more they are able to stretch in response to a force, and the lower the compliance, the less they stretch in response. Lung diseases that impair compliance stop the lungs from expanding as easily so more force is required to get them to expand to a given volume. Two classes of lung disease cause decreased compliance: restrictive interstitial lung diseases and diseases associated with fluid in the lungs.
Idiopathic Pulmonary Fibrosis
In idiopathic pulmonary fibrosis, normal lung tissues are replaced by fibrous scar tissue that does not expand like normal elastic fibers. The cause of this disease is unknown, and it tends to occur most in people ages 50 to 70. Symptoms include decreased exercise tolerance, shortness of breath, dry cough and possibly chest pain. A number of tests establish the diagnosis, including pulmonary function tests, which measure the force produced to inhale and exhale, imaging such as CT scans and biopsies of the lungs. There is presently no cure, but symptoms can be helped with drugs to suppress the immune system, oxygen and lung rehabilitation.
Pneumoconiosis is a disease caused by the long-term inhalation of dust or minerals, such as in mines; it is also called environmental lung disease. Examples of chemical dusts that cause this disease include asbestos, carbon, silica, coal and beryllium. The dusts settle in the lung, and nodules of scar tissue infiltrate these areas. People with the disease generally do not have symptoms, but in severe cases they may have shortness of breath and cough. Diagnosis is typically made by imaging by CT scan. There is no cure, so prevention is the best approach.
Acute Respiratory Distress Syndrome
Acute respiratory distress syndrome, or ARDS, is a syndrome in which fluids and protein fill the lungs, making it difficult to deliver oxygen to the blood. ARDS has many causes, including bad bacterial infections or viral infections, serious trauma, pancreatitis, smoke inhalation, near drowning, shock and others. It causes severe shortness of breath and labored breathing. Tests include imaging, blood tests of the gases such as carbon dioxide and oxygen in the lungs and ruling out heart problems as the cause of fluid in the lungs. Treatment involves mechanical ventilation with supplemental oxygen, fluid management and treatment of the underlying condition or conditions.
Many other disease can restrict compliance of the lungs. Some of these include connective tissue diseases such as some forms of lupus and rheumatoid arthritis, infections such as tuberculosis or other pneumonias and side effects of certain drugs such as the chemotherapeutic bleomycin.