Too Tight

By Peter Galvin, MD

There are two main types of lung disease – obstructive and restrictive. In obstructive disease, the air sacs, or alveoli, in the lungs are destroyed, usually by a toxin inhaled into the lungs, for example cigarette smoke. This causes Chronic Obstructive Pulmonary Disease, better known as COPD or emphysema. A patient with COPD can expand the lungs but doesn’t have enough alveoli for proper gas exchange (oxygen and carbon dioxide), causing low oxygen levels (hypoxia) and shortness of breath (SOB). In restrictive lung disease, the lungs are stiffened and cannot expand sufficiently, usually due to scar tissue from lung inflammation. The alveoli are intact, but the patient cannot inhale enough air for proper gas exchange, causing hypoxia and SOB.

Interstitial lung disease (ILD) is a group of conditions that cause inflammation and scarring in the lungs, or restrictive lung disease. Patients with ILD typically have SOB with exertion that often progresses to SOB at rest. About 30% of those with ILD have cough, and some have flare-ups (exacerbations) that cause episodes of rapidly worsening SOB over several days to weeks. The most common type of ILD is idiopathic pulmonary fibrosis (IPF), which, as the name implies, has no known cause. Conditions associated with IPF include connective tissue diseases, such as rheumatoid arthritis or scleroderma; hypersensitivity pneumonitis, caused by environmental exposure to mold, fungus, or birds; medications, such as amiodarone, nitrofurantoin, bleomycin, and certain cancer immunotherapies; and infections, such as Covid-19.

The highest rate of ILD occurs in people aged 80 to 84 years, although the average age at diagnosis is 67 to 72 years. In the U.S., more than 650,000 people have ILD. Overall, ILD is more common in women, but IPF affects men about three times more often. A diagnosis of ILD is usually made based on symptoms, physical examination, and additional testing that typically includes chest CT scanning, pulmonary function testing (PFTs), blood tests to evaluate for inflammation, and sometimes a lung biopsy. Treatment depends on the cause and severity of the illness. Medications known to cause ILD should be discontinued, certain exposures should be avoided (mold, birds [especially pigeons]), and conditions associated with ILD should be treated. First-line treatment for IPF is medication to slow scarring (nintedanib, pirfenidone). Lung transplant may be considered for severe disease, although organ availability is limited, and many patients are excluded due to other medical conditions (diabetes, heart disease) and advanced age.

About 30% to 40% of those with ILD develop progressive scarring, which causes respiratory failure and is associated with an average survival of 2.5 to 3.5 years after diagnosis without lung transplant. Lung transplant can increase average survival time to 5.2 to 6.7 years after transplant. Pulmonary rehabilitation, and 8- to 12-week program of endurance training and education, improves symptoms, quality of life, and walking distance in patients with SOB from ILD. Pneumococcal, Covid-19, RSV, and flu vaccines are recommended, as is supplemental oxygen for those with hypoxia. End-of-life planning and palliative care services are important for those with respiratory failure. For those with severe disease who are not candidates for lung transplantation, mechanical ventilation should be avoided as it is associated with poor outcomes.

For more information go to the website of the National Heart, Lung, and Blood Institute at www.nhlbi.nih.gov

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