Interstitial Lung Disease: Symptoms and Treatment

The lungs are primarily responsible for providing oxygen and removing oxygen from the blood. This organ is able to work efficiently because of the presence of microscopic sacs called alveoli. The walls of the alveoli are one cell thick and containing tiny blood vessels. Exchange of gas occurs through these thin membranes. Formation of scar tissue or fibrosis in the lung tissue leads to a reduction in the ability of lung to efficiently exchange gas between the blood and air. Diseases causing such fibrosis are termed as Interstitial Lung Disease (ILD).

Causes for ILD

Lung scarring can be caused by an abnormal healing response to an injury in the lung. The abnormal healing leads to thickening of the wall of alveoli making exchanges of gas difficult. Different factors have been attributed to be the cause of abnormal scarring. They are:

• Exposure to toxins like asbestos, silica dust, bird dropping, radiation and grain duct
• Adverse drug reaction to medications like some chemotherapeutic drug, amiodarone, rituximab, ethambutol.
• Autoimmune disease like sarcoidosis, Sjogren’s syndrome, scleroderma.
• Uncontrolled gastro esophageal reflux disease increases the risk of ILD
• Smoking increases the risk of ILD.

Symptoms of ILD

ILD presents with non specific symptoms like dry cough and shortness of breath on exertion.

Diagnosis of ILD

Diagnosing ILD has two components; determination of the extent of damage to the lungs and identifying the cause of scarring. After recording a detailed history of your symptoms and previous exposures to noxious substances, your doctor will like to hear the breath sounds with the help of a stethoscope. Your doctor will also do a thorough physical examination to find clues regarding the possible cause of scarring in your lungs. After this your doctor might request a few tests to confirm the diagnosis. The tests are:

• Blood tests to look for specific proteins or antibodies found in autoimmune disorders responsible for causing fibrosis in lungs
• CT scan: this procedure provides your doctor with high resolution images of your lung, made with the help of x rays. It is generally the first step towards the diagnosis of ILD
• Echocardiography: an ultrasound producing probe is placed on the heart to examine its structures. With the help of this probe, you doctor can estimate the pressure in the right side of your heart, which directly correlates with the extent of fibrosis in the lungs
• Oximetry: a small probe is placed over your finger or your ear to measure the level of oxygen in your blood. Low levels of oxygen point may point towards fibrosis in the lungs
• Spirometry and diffusion capacities: these are a series of tests for which you will be asked to blow through a tube connected to a machine. This machine can measure the maximum rate at which you can exhale, the maximum capacity of your lungs and the extent to which oxygen diffuses from the lungs into the blood stream
• Lung biopsy: a small sample of lung is obtained for microscopic examination.

Complications of ILD 

ILD causes an increase in resistance to blood flow through the lungs and a reduction in the diffusion of gases to and from the lungs. Complications associated with this disease are:

• Right sided heart failure: increase in resistance to blood flow in the artery leads to an increase load on the right ventricle. Eventually the right ventricle succumbs to increased strain leading to right sided heart failure
• Pulmonary hypertension: an increase in resistance to flow of blood through the blood vessels in lungs due to fibrosis
• Respiratory failure: dangerously low levels of oxygen in the blood accompanied by increased resistance to blood flow through lung in ILD can lead to life threatening conditions unless immediate medical care is provided.

Treatment of ILD

Scarring caused by ILD is irreversible. Presently there are no drugs in the market that can completely stop the progression of ILD. The goal of the treatment of ILD consists of slowing the progression of the disease and relieving symptoms. The treatment options are:

• Medications like corticosteroids with other immune-suppressing drugs to reduce the rate of scarring in the lungs. Depending on the cause of ILD this regimen may slow the progression or nearly stabilise the disease
• Uncontrolled gastro esophageal reflux disease is one of the causes of ILD. Control of acid production with drugs like H₂ receptor antagonists and proton pump inhibitors help in slowing the progression of the disease
• New drugs like pirfenidone and nintedanib are prescribed for patients with unknown cause of fibrosis. These drugs cause significant side effects and it is advisable to discuss them with your doctor before initiating the treatment
• Oxygen therapy: receiving supplemental oxygen helps in improving your sleep and makes breathing and exercising easy for you. It also reduces the risks of complications due to low oxygen levels.

Resources

• www.lung.org