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Respiratory disease is an umbrella term for diseases of the lung, bronchial tubes, trachea and throat . These diseases range from mild and self-limited(coryza -or common cold) to being life-threatening,(bacterial pneumonia, or pulmonary embolism for example).
Respiratory diseases can be classified as either obstructive (i.e. conditions which impede the rate of flow into and out of the lungs, for example asthma) or restrictive (i.e. conditions which cause a reduction in the functional volume of the lungs, for example pulmonary fibrosis).
Respiratory disease can be further classified as either upper or lower respiratory tract (most commonly used in the context of infectious respiratory disease), parenchymal and vascular lung diseases.
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Chronic Obstructive Pulmonary Diseases (COPD) are characterised by an increase in airway resistance, shown by a decrease in Peak Expiratory Flow Rate (PEFR; measured in spirometry) and Forced Expiratory Volume in 1 Second (FEV1), but more specifically defined as a forced expiratory volume in 1 second to forced vital capacity ratio (FEV1/FVC) that is less than 0.7. The Residual Volume, the volume of air left in the lungs following full expiration, is greatly increased in COPD, as is the total lung volume, while the vital capacity remains relatively normal, leading to the clinical sign of chest over-inflation in patients with severe disease. Many individuals with COPD present with "barrel chest" - a deformity of outward rib displacement due to chronic over-inflation of the lungs,also, in severe COPD, a flattening of the diaphragm can be seen on chest radiograph.
The following conditions have characteristics of obstructive lung disease:
However, COPD generally refers specifically to emphysema and chronic bronchitis, although most patients with COPD have characteristics of both conditions to varying degrees.
COPD is a known complication of cigarette smoking, and generally develops after 120 pack-years. (1 pack-year corresponds to smoking 1 pack of cigarettes a day for 1 year)
Diagnosis is established through pulmonary function testing, specifically spirometry, although it is often treated empirically when suspected clinically. Chest x-ray is often ordered to rule out other pulmonary conditions. Hyperinflation is often seen, but is non-specific.
The mainstay of chronic management consists of the administration of inhaled bronchodilators (specifically beta agonists and anticholinergics) and inhaled corticosteroids. Many patients require oxygen supplementation at home. In severe cases that are difficult to control, chronic treatment with oral corticosteroids may be necessary, although this is fraught with significant side-effects.
COPD is generally irreversible (unless lung transplantation is performed) although lung function can partially recover if the patient stops smoking.
Restrictive Lung Diseases (RLD) are characterised by a loss of airway compliance, causing incomplete lung expansion (i.e. via increased lung \'stiffness\'). This change manifests itself in a reduced Total Lung Capacity, Inspiratory Capacity and Vital Capacity.
In contrast to OPD, RLD values for Tidal Volume, Expiratory Reserve Volume, Functional Residual Capacity and Respiratory Volume are unchanged. The FEV1 and FCV for a patient with RLD will be decreased however FEV1/FVC ratio will be normal or increased for a RLD patient[1].
Notable restrictive lung diseases include:
The basic functional units of the lung, the alveoli, are referred to as the lung parenchyma. Diseases such as COPD are characterised by destruction of the alveoli and are therefore referred to as parenchymal lung diseases.
Signs of parenchymal lung disease include, but are not limited to, hypoxemia (low oxygen in the blood), hypercapnoea (high carbon dioxide in the blood), and abnormal DLCO tests.
Chest x-ray will show patchy opacification of the lung fields due to radio-opaque material (exudates and debris) occupying the normally air-filled alveoli. If detail of the lung parenchyma is desired, high-resolution computed tomography (hi-res CT) is performed. Definitive diagnosis can be obtained by performing flexible bronchoscopy with bronchoalveolar lavage and/or transbronchial lung biopsy. In select cases, percutaneous lung biopsy may need to be performed.
Chronic complications of parenchymal lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale).
As can be seen from the overlap in categories, parenchymal diseases can be either restrictive, obstructive or both.
Notable parenchymal diseases include:
Infectious entities that affect the lungs ((such as pneumonia or pulmonary tuberculosis) generally also damage the lung parenchyma and may have permanent sequelae due to fibrosis and scarring.
Vascular lung disease refers to conditions which affect the pulmonary capillary vasculature. Alterations in the vasculature manifest in a general inability to exchange blood gases such as oxygen and carbon dioxide, in the vicinity of the vascular damage (other areas of the lung may be unaffected).
Signs of vascular lung disease include, but are not limited to, hypoxemia (low oxygen in the blood) and hypercapnoea (high carbon dioxide in the blood).
Chronic complications of vascular lung disease include reduced respiratory drive, right ventricular hypertrophy, and right heart failure (cor pulmonale).
Notable vascular lung diseases include:
Infectious Respiratory Diseases are, as the name suggests, typically caused by one of many infectious agents able to infect the mammalian respiratory system (for example the bacterium Streptococcus pneumoniae).
The clinical features and treatment options vary greatly between infectious lung disease sub-types as each type may be caused by a different infectious agent, with different pathogenesis and virulence. Features also vary between:
"Respiratory tumour" can refer to either malignant (cancerous) or benign masses within the lungs or lung parenchyma.
Malignant respiratory tumours : Respiratory neoplasms are abnormal masses of tissue within the lungs or parenchyma whose cell of origin may or may not be lung tissue (many other neoplasms commonly metastasize to lung tissue). Respiratory neoplasms are most often malignant, although there are non-malignant neoplasms which can affect lung tissue.
Malignant respiratory tumours include the following:
Since the entire cardiac output passes through the lungs during the cardiac cycle, it is a common place to find metastases. Breast cancer may invade directly through local spread, and through lymph node metastases. Colon cancer, after metastasizing to the liver, will then frequently metastasize to the lung. Prostate cancer and renal cell carcinoma may also metastasize to the lung.
Benign respiratory tumours: tuberculosis cysts, pulmonary hamartoma, congenital malformations such as pulmonary sequestration and congenital cystic adenomatoid malformation (CCAM).
Both malignant and benign pulmonary neoplasms are detected on chest x-ray, often obtained for some other unrelated indication, and typically appear as pulmonary nodules.
Benign lesions may not require treatment, although certain cases may predispose towards infection, or may interfere with normal lung function. Definitive treatment usually consists of surgical excision (except in the case of small cell lung cancer), although radiation therapy and neoadjuvant chemotherapy are frequently employed for treatment of malignant tumours. Even in the case of metastases to the lung, palliative excision or complete pneumonectomy may be warranted in certain unique circumstances.
There are many other disorders that affect the lung and respiratory system. Auto-immune disorders such as vasculitis,( Wegener\'s Granulomatosis, Goodpasture\'s syndrome, for example) attack the blood vessels in the lung, causing pulmonary hemorrhage. Disorders in swallowing,or gastric refluxing can cause aspiration pneumonia.
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia
