Restrictive Lung Disease
are a category of extrapulmonary, pleural, or parenchymal respiratory diseases that restrict lung expansion resulting in a decreased lung volume (reduced TLV), reduced RV, an increased work of breathing, and inadequate ventilation and/or oxygenation.
- o FEV1 reduced
- o FVC reduced (TLC <80% and reduced RV)
- o Therefore – FEV1/FVC = normal (or even slightly raised)
Restrictive lung diseases may be due to specific causes which can be intrinsic to the parenchyma of the lung, or extrinsic to it
- Asbestosispleural plaquesmesothelioma
- Radiation therapy fibrosis / radiation pneumonitis (within RT area, after 3/12 exposure in 10-15%)
- Certain drugs such as amiodarone, bleomycin and methotrexate.
- Rheumatoid Arthritis (RA nodules and pneumoconiosis [coal workers] = Caplan’s syndrome).
- Infant respiratory distress syndrome due to a deficiency of surfactant in the lungs
- Hypersensitivity pneumonitis (Extrinsic Allergic Alveolitis) due to an allergic reaction to inhaled particles.
- Acute respiratory distress syndrome (ARDS) – caused by…
- o Mechanical ventilation
- o Sepsis
- o Pneumonia
- o Shock
- o Aspiration
- o Trauma (especially pulmonary contusion)
- o Major surgery
- o Massive transfusions
- o Smoke inhalation
- o Drug reaction or overdose
- o Fat emboli and reperfusion pulmonary oedema after lung transplantation
- o Pulmonary embolectomy
Many cases of restrictive lung disease are idiopathic (have no known cause). Still, there is generally pulmonary fibrosis. Examples are:
- Idiopathic pulmonary fibrosis (IPF) / cryptogenic fibrosing alveolitis (CFA) = MOST COMMON RLD
- Idiopathic interstitial pneumonia, of which there are several types
- Eosinophilic pneumonia
- Lymphangioleiomyomatosis (LAM) = smooth muscle invades airways, 20-40yo, female, reticular nodular pattern of disease, cysts and pneumothorax.
- Pulmonary Langerhan’s cell histiocytosis = proliferation of LC’s from bone marrow, dyspnoea, pneumothorax, stellate nodules, birbeck granules, skin eruptions.
- Pulmonary alveolar proteinosis
Conditions specifically affecting the interstitium are called interstitial lung diseases.
- Neuromuscular diseases, including quadriplegia
- Nonmuscular diseases of the chest wall, e.g. kyphosis
- In disorders that are intrinsic to the lung parenchyma, the underlying process is usually pulmonary fibrosis (scarring of the lung).
- As the disease progresses, the normal lung tissue is gradually replaced by scar tissue interspersed with pockets of air.
- This can lead to parts of the lung having a honeycomb-like appearance.