Diseases of the Respiratory System...
Respiratory disease is an umbrella term for diseases of the lung, bronchial tubes, trachea and pharynx . These diseases range from mild and self-limiting (coryza/common cold) to life-threatening (e.g. bacterial pneumonia, pulmonary embolism ect.).
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 affecting either upper or lower respiratory tract (most commonly used in the context of infectious respiratory disease), parenchymal and vascular lung diseases.
Chronic Obstructive Pulmonary Disease
Chronic Obstructive Pulmonary Diseases (COPD) are characterized by an increase in airway resistance, shown by a decrease in Peak Expiratory Flow Rate (PEFR; measured in spirometry). 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:
- Acute bronchitis
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 generally irreversible (unless lung transplantation is performed) although lung function can partially recover if the patient stops smoking.
Restrictive Lung Disease
Restrictive Lung Diseases (RLD) are characterized by a loss of airway compliance, causing incomplete lung expansion. This change manifests itself in a reduced Total Lung Capacity, Inspiratory Capacity and Vital Capacity.
Notable restrictive lung diseases include:
- Fibrosis,Sarcoidosis,Pleural effusion
- Hypersensitivity, pneumonitis,Asbestosis
- Pleurisy, Lung Cancer, Infant respiratory distress syndrome (IRDS)
- Acute respiratory distress syndrome (ARDS)
- Neurologic diseases affecting the ability of the body to alter respiration rate, including spinal cord injury
- Mechanical diseases affecting pulmonary musculature, including myasthenia gravis
- Severe acute respiratory syndrome (SARS)
The basic functional units of the lung, the alveoli, are referred to as the lung parenchyma. Diseases such as COPD are characterized 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.
Notable parenchymal diseases include:
- COPD (emphysema and chronic bronchitis)
- Acute lung injury (ALI) and Acute respiratory distress syndrome (ARDS)
- Pulmonary fibrosis
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
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, near 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:
- Pulmonary oedema (most commonly due to congestive heart failure)
- Pulmonary embolism/Chronic venous thromboembolic disease
- Pulmonary hypertension (as a sequela of congestive heart failure or diseases of the lung parenchyma, or due to genetic causes)
- Hepatopulmonary syndrome
- Lymphangitic spread of metastatic cancer
Infectious Respiratory Disease
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: Upper respiratory tract infection, including strep throat and the common cold; and Lower respiratory tract infection, including pneumonia and pulmonary tuberculosis.
"Respiratory tumor" can refer to either malignant (cancerous) or benign masses within the lungs or lung parenchyma.
Malignant respiratory tumors
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 that can affect lung tissue.
Malignant respiratory tumors include the following: Non-small cell lung cancer Small cell lung cancer Carcinoid tumor of the lung Mesothelioma, a cancer originating on the mesothelium outside the lung.
Benign respiratory tumors include the following:
- Tuberculosis cysts
- Pulmonary hamartoma
Congenital malformations such as pulmonary sequestration and congenital cystic adenomatoid malformation (CCAM).
Benign lesions may not require treatment, although certain cases may predispose towards infection, or may interfere with normal lung function.
The definitive treatment of benign respiratory masses 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 masses. Even in the case of metastases to the lung, palliative excision or complete pneumonectomy may be warranted in certain unique circumstances.
Other Respiratory diseases
There are many other disorders that affect the lung and respiratory system.Auto-immune disorders such as vasculitis (e.g. as in Wegener's Granulomatosis and Goodpasture's syndrome) attack the blood vessels in the lung, causing pulmonary haemorrhage. Clinically, this can manifest as the expulsion of blood from the airway (haemoptysis).
Disorders in swallowing, or conditions resulting in gastric reflux can cause aspiration pneumonia.
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A comprehensive list of diseases related to the respiratory system, may be found at ICD-10 Chapter 10 Block J00-J99. ~