All About Interstitial Lung Disease (ILD) - Dr Srinivas Rajagopala

Q1. What does the Lung Interstitium contain and do?

The Lung interstitium has small airways called bronchioles to bring in air to the alveolus; the alveolar membrane-a delicate membrane to exchange oxygen and carbon dioxide; thin blood vessels called capillaries to bring blood into and out of the lung; and the lymphatic vessels, which helps remove excess of fluid in this delicate space and has an important role in protection against infection.

It is extremely thin in health to permit easy oxygen and carbon dioxide exchange in health. Thickening of this vital area due to disease impairs gas exchange and is the main abnormality in ILDs, along with progressive loss of lung volume.

Interstitial lung disease (ILD) is a term that covers several lung diseases, many of which result in progressive and permanent scarring of our lungs, with irreversible loss of lung volume. The process starts in the part of the lung involved in gas exchange (called the alveolus) and its support structures (called the Interstitium).

This loss of lung available for its effective function will affect a person’s ability to breathe freely and affect the ability of the lungs to transfer enough oxygen into the bloodstream and carbon dioxide out of the body. Initial loss of lung volumes is tolerated by the immense reserve of the lung; when lung function is <80% of its baseline or lower, symptoms of exercise begin to appear.

Symptoms in activities of daily life appear only when 50% of lung volumes are affected. At 20-30% of usual lung capacity, the need for oxygen supplementation throughout the day and night to make up for the inability of the lungs to add oxygen into the body occurs.

At a further advanced stage, the need for ventilation (BiPAP) support appears and eventually leads to death if the primary cause is not halted or reversed. The course of an ILD can also be punctuated by episodes of “flares or exacerbations”, which can be due to infection, surgery, heart failure, blood clots or often, unexplained in nature (idiopathic). Acute exacerbations are common (6-9 per 100 patient-years) and are associated with worsening disease and deaths.

Q3. What causes Interstitial lung disease?

More than 400 separate causes can cause ILDs. The most common causes are connective tissue diseases (like rheumatoid arthritis, and scleroderma); smoking; occupational exposures (farming, silica, coal, asbestos, heavy metals); certain medications (antibiotics, heart medications, cancer treatments); home exposures (Pigeons, parakeets, love birds, mould) or recreational exposures (vaping) and it can be inherited (familial in origin).

One of the most common ILDs is Idiopathic pulmonary fibrosis (IPF). This is a form of abnormal lung repair due to life-long environmental exposures and typically occurs after 60 years of age.

Q4. What are the symptoms of Interstitial lung disease?

Symptoms are typically breathlessness and non-productive cough. Breathlessness is initially on heavy exercise, and slowly worsens to activities of daily living and then occurs during rest as the disease worsens. Other symptoms can include fever, weight loss, blood in sputum and chest pain.

Q5. How is an Interstitial lung disease diagnosed?

ILD is a complex medical condition. It is fairly easy to diagnose the presence of an ILD. It is more challenging and often complex to find the cause of the ILD, which is the crucial part. Some patients can be diagnosed by a good history taking and exposure assessment; some can be diagnosed by careful examination, blood tests and CT scans but most of them require careful discussion of their CT scans and a lung biopsy to diagnose the cause of the ILD.

Lung biopsies can be obtained by several methods, including bronchoscopy [cryo-lung biopsy and surgical lung biopsy (VATS)]. At the Kauvery Lung Centre, our approach is to discuss patients whose cause of ILD remains unclear in a multi-disciplinary discussion (MDD) consisting of experienced pulmonologists, radiologists, pathologists and rheumatologists. Our MDD meets monthly and earlier if required to provide patients with the least invasive, most advanced and effective courses of treatment, tailored to each patient’s specific needs

Q6. How is an Interstitial lung disease treated?

Treatment starts with the correct diagnosis of the cause. In earlier stages, if an exposure is identified and rectified, the disease process is almost completely reversible. As lung damage and shrinkage worsen, treatment may include steroids and drugs to suppress your immunity.

If fibrosis or lung scarring is advanced, anti-fibrotic are used to reduce further lung fibrosis. Unfortunately, these drugs cannot reverse fibrosis that has occurred and may, at best, slow the rate of further fibrosis. As lung failure ensues, oxygen therapy and rehabilitation become vital parts of therapy.

At this stage, when the patient is independent and able to walk and perform activities of daily living by himself, lung transplantation is considered if the disease is worsening steadily. This is important as the success of lung transplantation depends heavily on the stage at which it is performed.

When patients are bed bound and have breathlessness on even slight movement with significant weakness, it is best not to perform lung transplantation. Treatment focuses on improving breathlessness and cough with palliative intent.

Q7. How do I know if my lung function is stable or improving?

The trajectory of your disease will determine the intensity of treatment and also trigger referral for transplant and palliative services. This is determined by serial Spirometry, DLco, Oscillometry, six-minute walk tests and annual CT scans. CT scans are done yearly and have significant radiation exposure. Quantitative information is lacking with CT scans and relying only on CT scans can miss early disease worsening. In the first year, spirometry, DLco and walk tests are done every 3-4 months, then half yearly till disease stability.

ILDs are a serious and potentially life-threatening set of diseases. Treatment requires very specialized medical knowledge, equipment and patient support services. At the Kauvery Hospital Lung Centre, we have a dedicated exposure instrument to identify unrecognized exposures to reverse early ILDs and a highly experienced multi-disciplinary team that meets regularly to avoid lung biopsies or perform the least invasive type of biopsy, if it is needed.

Our state-of-the-art lung function lab can diagnose lung function accurately. We have extensive experience with immunosuppression and anti-fibrotic for ILDs, with a focus on minimizing their need. In the event that your ILD worsens on treatment or is advanced when we see you for the first time, our embedded lung transplant team will suggest the right time to test and undergo lung transplantation.

Lung ailments, especially serious ones, can be frightening for both patients and their families. Knowing that the care and treatment available at the Kauvery Lung Centre is the very best that is available will go a long way in easing anxiety which will, in turn, help to increase the effectiveness of the treatment.

Disclaimer: The views expressed in this article are of the author and not of Medical Dialogues. The Editorial/Content team of Medical Dialogues has not contributed to the writing/editing/packaging of this article.