Idiopathic pulmonary fibrosis
Idiopathic pulmonary fibrosis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Idiopathic pulmonary fibrosis (IPF) is a chronic and usually fatal interstitial pulmonary disease. About 50% of patients with IPF die within 5 years of diagnosis. Once thought to be a rare condition, it’s now diagnosed with much greater frequency. IPF has been known by several other names over the years, including cryptogenic fibrosing alveolitis, diffuse interstitial fibrosis, idiopathic interstitial pneumonitis, and Hamman-Rich syndrome.
Causes and incidence
IPF is the result of a cascade of events that involve inflammatory, immune, and fibrotic processes in the lung. However, despite many studies and hypotheses, the stimulus that begins the progression remains unknown. Speculation has revolved around viral and genetic causes, but no good evidence has been found to support either theory. However, it’s clear that chronic inflammation plays an important role. Inflammation develops the injury and the fibrosis that ultimately distorts and impairs the structure and function of the alveolocapillary gas exchange surface.
IPF is slightly more common in men than in women and is more common in smokers than in nonsmokers. It usually affects people ages 50 to 70.
Signs and symptoms
The usual presenting symptoms of IPF are dyspnea and a dry, hacking, and typically paroxysmal cough. Most patients have had these symptoms for several months to 2 years before seeking medical help. End-expiratory crackles, especially in the bases of the lungs, are usually heard early in the disease. Bronchial breath sounds appear later, when airway consolidation develops. Rapid, shallow breathing occurs, especially with exertion, and clubbing has been noted in more than 40% of patients. Late in the disease, cyanosis and evidence of pulmonary hypertension (augmented S 2 and S3 gallop) commonly occur. As the disease progresses, profound hypoxemia and severe, debilitating dyspnea are the hallmark signs.
Diagnosis
Diagnosis begins with a thorough patient history to exclude a more common cause of interstitial lung disease.
CONFIRMING DIAGNOSIS Lung biopsy is helpful in the diagnosis of IPF. In the past, an open lung biopsy was the only acceptable procedure, but now biopsies may be done through a thoracoscope or bronchoscope.
Histologic features of the biopsy tissue vary, depending on the stage of the disease and other factors that aren’t yet completely understood. The alveolar walls are swollen with chronic inflammatory cellular infiltrate composed of mononuclear cells and polymorphonuclear leukocytes. Intra-alveolar inflammatory cells may be found in early stages. As the disease progresses, excessive collagen and fibroblasts fill the interstitium. In advanced stages, alveolar walls are destroyed and are replaced by honeycombing cysts.
Chest X-rays may show one of four distinct patterns: interstitial, reticulonodular, ground-glass, or honeycomb. Although chest X-rays are helpful in identifying the presence of an abnormality, they don’t correlate well with histologic findings or pulmonary function tests (PFTs) in determining the severity of the disease. They also don’t help distinguish inflammation from fibrosis. However, serial X-rays may help track the progression of the disease.
High-resolution computed tomography scans provide superior views of the four patterns seen on routine X-ray film and are used routinely to help establish the diagnosis of IPF. Research is currently under way to determine whether the four patterns of abnormality seen on these scans correlate with responsiveness to treatment.
PFTs show reductions in vital capacity and total lung capacity and impaired diffusing capacity for carbon monoxide. Arterial blood gas (ABG) analysis and pulse oximetry reveal hypoxemia, which may be mild when the patient is at rest early in the disease but may become severe later in the disease. Oxygenation will always deteriorate, usually to a severe level, with exertion. Serial PFTs (especially carbon monoxide diffusing capacity) and ABG values may help track the course of the disease and the patient’s response to treatment.
Treatment
Although it can’t change the pathology of IPF, oxygen therapy can prevent the problems related to dyspnea and tissue hypoxia in the early stages of the disease process. The patient may require little or no supplemental oxygen while at rest initially, but he’ll need more as the disease progresses and during exertion.
No known cure exists. Corticosteroids and cytotoxic drugs may be given to suppress inflammation but are usually unsuccessful. Recently, interferon-gamma-1B has shown some promise in treating the disease.
Lung transplantation may be successful for younger, otherwise healthy individuals.
Special considerations
❑ Explain all diagnostic tests to the patient, who may experience anxiety and frustration about the many tests required to establish the diagnosis.
❑ Monitor oxygenation at rest and with exertion. The physician may prescribe one oxygen flow rate for use when the patient is at rest and a higher one for use during exertion to maintain adequate oxygenation. Instruct the patient to increase his oxygen flow rate to the appropriate level for exercise.
❑ As IPF progresses, the patient’s oxygen requirements will increase. He may need a nonrebreathing mask to supply high oxygen percentages. Eventually, maintaining adequate oxygenation may become impossible despite maximum oxygen flow.
❑ Most patients will need oxygen at home. Make appropriate referrals to discharge planners, respiratory care practitioners, and home equipment vendors to ensure continuity of care.
❑ Teach breathing, relaxation, and energy conservation techniques to help the patient manage severe dyspnea.
❑ Encourage the patient to be as active as possible. Refer him to a pulmonary rehabilitation program.
❑ Monitor the patient for adverse reactions to drug therapy.
❑ Teach the patient about prescribed medications, especially adverse effects. Teach the patient and his family members infection prevention techniques.
❑ Encourage good nutritional habits. Small, frequent meals with high nutritional value may be necessary if dyspnea interferes with eating.
❑ Provide emotional support for the patient and his family as they deal with the patient’s increasing disability, dyspnea, and probable death.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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