Interstitial Lung Disease

Interstitial lung disease (ILD) describes a wide range of lung diseases. About 200 disorders, most of which causes progressive scarring of the lung tissues exists. The scarring brought about by the interstitial lung disease affects an individual’s breathing ability and ability to get oxygen into the bloodstream. These disorders are grouped together because of the clinical similarities in their apparent chest radiographic appearance, presentations, and physiological features. There are two broad categories of ILD i.e. diseases which have no known cause (idiopathic ILD), and diseases having a known cause or those that occur along other diseases. Types of idiopathic ILD include the nonspecific interstitial pneumonitis (NSIP), acute interstitial pneumonitis (AIP) and respiratory interstitial pneumonia (LIP) (Meyer, 2011).

Although the causes of ILD remain unknown, both environmental and genetic factors contribute to its development. Some therapeutic drugs, such as amiodarone, methotrexate and radiation also cause lung disease. Treatment of cancers through radiation therapy in the chest (breast cancer) also predisposes an individual to interstitial lung diseases (Kumar, 1996). Risk factors, such as exposure to dust, gender, age; race and cigarette smoking have also been identified. The antigen processing and presentation develop the immune response seen in the disease.

Pathophysiology

The interstitium is a space found between the blood capillaries and space in the alveoli. The interstitium supports the delicate relation between the alveoli and the capillaries hence allowing efficient gas exchange. The interstitium also allows close apposition of gas and capillaries with minimal fibroblasts, connective tissue matrix and inflammatory cells, such as macrophages (Nathan, 2008).

The lung may experience injury from an exposure to an autoimmune- mediated inflammation or a systemic connective tissue disease, such as rheumatoid arthritis. It may also experience unknown injury from idiopathic pulmonary fibrosis. In case of these injuries, the lungs respond through self repair. However, in case the repair does not occur or if it’s not perfect, the lungs risk experiencing permanent damage. The increased interstitial tissue in this case, replaces the normal capillaries, healthy interstitium and the alveoli. These injuries cause profound impairment in the lung physiology. A decrease in the lung function consequently increases the rate of breathing (Muller et. al.)

Diagnosis

The unusually large number of disorders that are categorised here, challenges the diagnosis of interstitial lung disease. The symptoms and signs of many diseases also have similar symptoms to ILD. Several tests are carried out before making a definitive diagnosis. Imaging tests, such as chest X-ray, computerized tomography (CT), and echocardiogram are used. An echocardiogram uses sound waves to visualize and show the functioning of the heart. It provides the physician with the information about the heart size and evaluates the functioning of the heart chambers and the valves. An echocardiogram can evaluate the amount of pressure that is present in the right ventricle of the heart. The CT scanners, on the other hand, uses computers to produce cross sectional images of internal structures by combining X-ray images taken from different angles (Behr & Ryu, 2008). The chest X-rays are mostly used to track the progression of the interstitial lung disease.

Pulmonary function tests are also used for definitive diagnosis. These tests measure the intake and release of air by the lungs the movement of gases such as oxygen from the atmosphere into the body’s circulation. They involve the use of oximetry, spirometry and exercise stress test. In oximetry, a small device placed on the finger is used to measure the saturation of blood oxygen. Spirometry tests show how much air the patients’ lungs can hold and the speed at which the air can be expelled. Through the obtained results, a broad range of lung diseases can be diagnosed. The exercise stress test out on a treadmill is used to monitor the lung function of an active patient. The obtained results are compared against the known normal values of healthy individuals. If the results deviate strongly from the normal, they indicate the possible presence of lung diseases (Nathan, 2008).

The lung tissue analysis is done by examining lung tissue (biopsy) in a laboratory with the help of an electronic microscope. The tissue sample to be analysed may either be from surgical biopsy, bronchoalveolar lavage or bronchoscopy. Bronchoscopy is a test that is carried out to view the airways and diagnose lung disease. It is done by the use of a bronchoscope. This is a device that is inserted into the lungs, and it shows images of the inside of the lungs. A bronchoscope can either be flexible or rigid, but it has a width of less than half an inch. It is passed via the nose, the mouth or through the trachea into the lungs. Once inside the lungs, remarkably small tissue samples are picked, which are then used for analysis. The method is convenient, but the tissue samples obtained are at times too small for accurate diagnosis (Wagner, et. al, 2007)

Surgical biopsy, compared to bronchoscopy, is a more invasive procedure that harbours potential complications since it involves surgery. It is, however, preferred to bronchoscopy since it is the only way to obtain tissues large enough for accurate diagnosis. The Incisions made in the ribs allow surgical instruments and cameras are inserted into the lungs. This enables the surgeon to view the lungs on a video monitor, while removing tissue samples from the lungs. The obtained lung tissues are then observed via a microscope and compared with normal specimens. In bronchoalveolar lavage, salt water is injected into a section of the lungs through a bronchoscope and then immediately sucked out (Meyer, 2011). The solution sucked out is a mixture that contains cells from various air sacs and the salt water. This technique allows for the sampling of a larger area of the lung, compared to the other two lung tissue analysis procedures (Nathan, 2008).

Treatment

The adverse effects of ILD, such as lung scarring cannot be reversed. There is still no treatment that is known to curb the progression of the disease. The treatments that are currently available only improve the symptoms temporarily and reduce the development of the disease. All these  treatments aim at improving the patient’s quality of life rather than curing the interstitial lung diseases. The treatment of the interstitial lung disease is heavily dependent on the cause of the disease e.g. If an autoimmune disease is the cause of the disease, anti-inflammatory drugs, such as corticosteroids or other drugs that can suppress the immune systems are prescribed. Some of the other drugs used to suppress the immune system, include methotrexate and cyclosporine (Kumar, 1996)).

Pulmonary rehabilitation is also used as a form of treatment. Pulmonary rehabilitation aims at improving the lives of patients living with ILD and helps them live better lives. This is made possible by improving their daily functioning through nutritional counselling, emotional support, physical exercises (to improve endurance) and breathing techniques (that improve lung efficiency).

Patients suffering from advanced respiratory diseases may exhibit depression, anxiety and serious difficulties coping with lung disease. These patients are taken through regular education sessions, where they are given key patient information. They are also educated on panic control and stress reduction methods. Other techniques used in pulmonary rehabilitation include posture techniques and diaphragmatic breathing. A nutritional assessment can be carried out to indicate the extent of the ILD. When the nutritional state is established, that ensures that the patient enjoys maximum nutritional status (Wagner et. al, 2007).

A low oxygen concentration in blood (hypoxemia) is common in interstitial lung disease. Therefore, oxygen therapy is used as another form of treatment. This refers to the administration of oxygen gas to a patient as a means of medical intervention. It can be done by the use of gas masks filled with oxygen gas or by filling incubators with oxygen in the case of infants. The best source for oxygen in most patients is liquid oxygen since it provides adequate flow rates. Oxygen therapy makes breathing and exercise easier. Although it is not capable of stopping the damage of the lungs, it can prevent and lessen the complications from the low oxygen levels in the blood. Oxygen therapy has also been shown to improve sleep and reduce blood pressure in the right side of the heart (Behr & Ryu, 2008).

Transplantation of the lung is known to be the only therapy that prolongs a patient`s life. Most of the interstitial lung disease patients are old. They have increased chances of chronic rejection of the transplant followed by death.

Prevalence

The interstitial lung disease was once thought to be a rare disease, but continued epidemiologic investigations have shown that the occurrence of the disease is more rapid than previously thought. These studies show that 80.9 per 100,000 men and 67.2 per 100,000 women suffer from the interstitial lung disease in the USA. The same study showed that 31.5 new cases are diagnosed per 100,000 men per year and 26.1 new cases per 100,000 women per year (Nathan, 2008). Of all the wide range of the interstitial lung diseases, the most common and prevalent are; sarcoidosis, occupational and environmental associated disease, pulmonary fibrosis and connective tissue associated interstitial disease.

The disease is prevalent in adults, although it also occurs in children. Individuals between the age of 40 and 70 years old tend to develop idiopathic pulmonary fibrosis, whereas young people tend to develop interstitial diseases, such as sarcoidosis, autoimmune associated lung diseases and pulmonary langerhans cell histiocytosis. In the idiopathic pulmonary fibrosis, the emergence of fibrosis occurs earlier. Idiopathic pulmonary fibrosis has been diagnosed in individuals of different racial and ethnic groups throughout the world. Reports have also suggested that Caucasians are more prone to idiopathic pulmonary fibrosis, and they also exhibit higher mortality rates due to the same compared to the African Americans (Meyer, 2011).

Environmental hazards, such as asbestos induce interstitial lung disease and persons who are constantly exposed to these hazards, have higher incidences of the disease. Lifestyle behaviours, such as cigarette smoking enhance an individual's susceptibility to the disease. Interstitial pulmonary fibrosis develops more in the case of constant exposure to metal and wood dusts. Finally, the prevalence of the interstitial lung disease is thought to be influenced by genetics with about 8 percent of familial cases being attributed to a single set of genes (Behr & Ryu, 2008).

Clinical Manifestations

Interstitial Lung Disease is a heterogeneous group of disorders characterized by alveolar and septal thickening, fibroblast proliferation and collagen deposition. If the process of fibroblast proliferation remains unchecked, it leads to pulmonary fibrosis. Interstitial lung diseases bring about related problems, such as the right sided heart failure (cor pulmonale), respiratory failure and pulmonary hypertension (Wagner et. al, 2007).

The right sided heart failure is a condition, where the right ventricle of the heart fails due to an increased pumping pressure. This pressure needed to push the blood through the obstructed pulmonary. In the pulmonary hypertension, blood flow to the lungs is restricted by scar tissues found in the lungs blood vessels. The prevention of the flow of blood increases the pressure of blood in the pulmonary arteries hence the name pulmonary hypertension (Muller et. al, 2004).

Aetiology

The interstitial lung disease affects the lungs in different ways. The walls of the alveoli in the lungs become inflamed, and lung tissue is damaged. Fibrosis also occurs in the interstitium. Fibrosis usually causes a permanent damage to tissue and hence reduces the ability of the alveoli to breathe and carry oxygen. The adjacent alveoli also experience a similar fate, when they are destroyed by the formation of scar tissue. The symptoms vary from mild to severe among different patients (Meyer, 2011).

Prevention

Considerable breakthroughs have been made in the understanding of interstitial lung disease. However, curing and eliminating this disease has not been achieved leaving prevention as the only possible option of curbing the disease. Prevention is done on a basis of first understanding the leading causes of interstitial lung disease. Once the causative agents have been identified, efforts can be made to avoid exposing individuals to them (Kumar, 2011).

Hypersensitivity pneumonitis is caused by dust and mold, and hence these two should be avoided to prevent oneself from the disease. Idiopathic diseases have no known causes and are hard to prevent. Smoking exposes an individual to lung diseases and thus quitting smoking is also recommended as a means of preventing ILD. Once respiratory infections set in, patient becomes more prone to the symptoms of interstitial lung disease vaccination against diseases, such as pneumonia and flu can be carried out to prevent the latter two from expressing themselves (Nathan, 2008).

People who are exposed to occupational hazards e.g. coal miners, sand blasters and ship workers can practise another prevention strategy. These individuals are in constant exposure to known causes of lung disease in their workplaces. Therefore, these workers are subjected to constant lung disease checkups to allow for early detection. Individuals working in these careers are encouraged to take long breaks in their jobs to avoid constant exposure to the causative agents of interstitial lung disease.

Constant radiation and chemotherapy to the chest predisposes an individual to lung diseases. These two treatments should be kept at the lowest possible levels and only used when there are no other treatment methods. Interstitial lung disease has been shown to be more prevalent in adults than in children. This is mainly because of its slow development nature. It has also been observed that continued exposure to high levels of therapeutic oxygen for more than forty eight hours can harm the lungs. This should be avoided to reduce the exposure of an individual to causative agents of Interstitial Lung disease (Muller et. al, 2004).

Many people with interstitial lung disease learn to cope with the disease, but it also can eventually lead to death. This is dependent on the disease type, and how far the disease has progressed without treatment. Many different types of treatments that help slow the progression of lung dysfunction down exist. Early detection of the disease helps to curb its further proliferation by applying the treatment and preventive measures discussed earlier. Interstitial lung disease is known to cause complications, such as right sided heart failure and respiratory failure, which are life threatening (Wagner et. al, 2007). Its emergence and or spread should be curbed at all costs.