Respiratory disease

Respiratory disease
Specialty	Pulmonology

Respiratory Disease is the term for diseases of the respiratory system. These include diseases of the lung, pleural cavity, bronchial tubes, trachea, upper respiratory tract and of the nerves and muscles of breathing. Respiratory diseases range from mild and self-limiting such as the common cold to life-threatening such as bacterial pneumonia or pulmonary embolism. They are a common and important cause of illness and death. In the US, Adults average between two and four colds a year, children between six and ten. One in seven people in the UK is affected by some form of chronic lung disease, most commonly chronic obstructive pulmonary disease and asthma. Respiratory disease is responsible for over 10% of hospitalizations and over 16% of deaths in Canada. The study of respiratory disease is known as pulmonology. A doctor who specializes in respiratory disease is known as a pulmonologist, a chest medicine specialist, a respiratory medicine specialist, a respirologist or a thoracic medicine specialist.

Symptoms

The symptoms of respiratory disease differ depending on the disease. Common symptoms are:

• Shortness of breath or dyspnea which usually occurs with exercise and can interfere with daily activities. In severe cases, shortness of breath can occur while resting.
• Cough with or without the production of sputum.
• Coughing blood (haemoptysis).
• Chest pain. This may or may not be pleuritic chest pain (that is pain that worsens with the movements of breathing).
• Noisy breathing, either wheeze or stridor.
• Somnolence.
• Loss of appetite.
• Weight loss.
• Cyanosis, a bluish discoloration of the lips, tongue or fingers.

In some cases respiratory disease is diagnosed without symptoms in the investigation of another disease or through a routine check. gnknfg,ngld

Diagnostic tests

Respiratory diseases may be investigated by performing one or more of the following tests

• Chest x-ray
• Pulmonary function test
• Computed tomography scan
• Culture of microorganisms from secretions such as sputum
• Bronchoscopy
• Biopsy of the lung or pleura
• Ventilation - perfusion scan
• Ultrasound scanning can be useful to detect fluid such as pleural effusion

Treatment

Treatment of respiratory disease depends on the particular disease being treated, the severity of disease and the patient. Lifestyle factors such as regular exercise and healthy nutrition are important in preventing and treating respiratory disease. Vaccination can prevent some respiratory diseases. In addition, the following treatments are often used for respiratory diseases:

• Medication, often given in an inhaled form
  • Corticosteroids
  • Bronchodilators
  • Antibiotics
  • Anticoagulants
  • Cancer chemotherapy
  • Immune suppressants
• Physiotherapy
• Oxygen
• Mechanical ventilation
• Radiotherapy
• Surgery
  • Removal of a cancer e.g. lobectomy, pneumonectomy
  • Pleurodesis
  • Lung volume reduction surgery
  • Lung transplantation

Respiratory diseases

Respiratory diseases can be classified in many different ways; by the organ involved, by the pattern of symptoms or by the cause of the disease.

Obstructive lung diseases

These are diseases of the lung where the bronchial tubes become narrowed making it hard to move air in and especially out of the lung.

Chronic obstructive pulmonary disease

Main article: Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive airways disease (COAD) or chronic airflow limitation (CAL), is a group of illnesses characterised by airflow limitation that is not fully reversible. The flow of air into and out of the lungs is impaired. This can be measured with breathing devices such as a peak flow meter or by spirometry. The term COPD includes the conditions emphysema and chronic bronchitis although most patients with COPD have characteristics of both conditions to varying degrees. Asthma being a reversible obstruction of airways is often considered separately, but many COPD patients also have some degree of reversibility in their airways.

In COPD, there is an increase in airway resistance, shown by a decrease in the forced expiratory volume in 1 second (FEV1) measured by spirometry. COPD is 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 often increased in COPD, as is the total lung capacity, while the vital capacity remains relatively normal. The increased total lung capacity (hyperinflation) can result in the clinical feature of a "barrel chest" - a chest with a large front-to-back diameter that occurs in some individuals with COPD. Hyperinflation can also be seen on a chest x-ray as a flattening of the diaphragm.

The most common cause of COPD is cigarette smoking. COPD is a gradually progressive condition and usually only develops after about 20 pack-years of smoking. COPD may also be caused by breathing in other particles and gasses.

The disagnosis of COPD is established through spirometry although other pulmonary function tests can be helpful. A chest x-ray is often ordered to look for hyperinflation and rule out other lung conditions but the lung damage of COPD is not always visible on a chest x-ray. Emphysema, for example can only be seen on CT scan.

The main form of long term management involves the use of inhaled bronchodilators (specifically beta agonists and anticholinergics) and inhaled corticosteroids. Many patients eventually 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 although lung function can partially recover if the patient stops smoking. Smoking cessation is an essential aspect of treatment. Pulmonary rehabilitation programmes involve intensive exercise training combined with education and are effective in improving shortness of breath. Severe emphysema has been treated with lung volume reduction surgery with some success in carefully chosen cases. Lung transplantation is also performed for severe COPD in carefully chosen cases.

Alpha 1-antitrypsin deficiency is a fairly rare genetic condition that results in COPD (particularly emphysema) due to a lack of the antitrypsin protein which protects the fragile alveolar walls from protease enzymes released by inflammatory processes.

Asthma

Main article: Asthma

Asthma is an obstructive lung disease where the bronchial tubes (airways) are extra sensitive (hyperresponsive). The airways become inflamed and produce excess mucus and the muscles around the airways tighten making the airways narrower. Asthma is usually triggered by breathing in things in the air such as dust or pollen that produce an allergic reaction. It may be triggered by other things such as an upper respiratory tract infection, cold air, exercise or smoke. Asthma is a common condition and affects over 300 million people around the world. Asthma causes recurring episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning.

Asthma is diagnosed by the characteristic pattern of symptoms. A peak flow meter can record variations in the severity of asthma over time. Spirometry, a measurement of lung function, can provide an assessment of the severity, reversibility, and variability of airflow limitation, and help confirm the diagnosis of asthma.

Asthma is treated by identifying and removing the triggers that set it off, if possible. The main form of long term management involves the use of inhaled corticosteroids. Inhaled bronchodilators, particularly beta agonists are used to relieve and control symptoms by reducing muscle spasm around the airways. An alternative way to control mild asthma is with a leukotriene antagonist tablet.

Other obstructive lung diseases

• Cystic fibrosis is an inherited disorder of the CFTR gene, a chloride ion channel. The lack of this channel causes reduced water content of secretions. This affects the mucus secreted as part of the lung's defence and creates sticky, viscous mucus. This makes the lungs more susceptible to infection, inflammation and mucous plugging.
• Bronchiectasis
• Bronchiolitis
• Allergic bronchopulmonary aspergillosis

In many parts of the world, the most common cause of obstructive lung disease is lung scarring after tuberculosis infection.

Restrictive lung diseases

Restrictive lung diseases (also known as interstitial lung diseases) are characterised by a loss of lung compliance, causing incomplete lung expansion and increased lung stiffness. 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.

The main symptoms are shortness of breath and cough.

In restrictive lung disease, both the FEV1 and FVC are reduced so the FEV1/FVC ratio is normal or even increased in contrast to obstructive lung disease where this ratio is reduced. The values for residual volume and total lung capacity are generally decreased in restrictive lung disease.

Restrictive lung diseases may be due to a specific cause such as:

• Asbestosis caused by long-term exposure to asbestos dust.
• Radiation fibrosis, usually from the radiation given for cancer treatment.
• Certain drugs such as amiodarone, bleomycin and methotrexate.
• As a consequence of another disease such as rheumatoid arthritis.
• Hypersensitivity pneumonitis due to an allergic reaction to inhaled particles.
• Acute respiratory distress syndrome (ARDS), a severe lung condition occurring in response to a critical illness or injury.
• Infant respiratory distress syndrome due to a deficiency of surfactant in the lungs of a baby born prematurely.

Many cases of restrictive lung disease are idiopathic (have no known cause). Examples are:

• Idiopathic pulmonary fibrosis
• Idiopathic interstitial pneumonia, of which there are several types
• Sarcoidosis
• Eosinophilic pneumonia
• Lymphangioleiomyomatosis
• Pulmonary Langerhan’s cell histiocytosis
• Pulmonary alveolar proteinosis

Respiratory tract infections

Infections can affect any part of the respiratory system. They are traditionally divided into upper respiratory tract infections and lower respiratory tract infections.

Upper respiratory tract infection

The most common upper respiratory tract infection is the common cold however infections of specific organs of the upper respiratory tract such as sinusitis, tonsillitis, otitis media, pharyngitis and laryngitis are also considered upper respiratory tract infections.

Lower respiratory tract infection

The most common lower respiratory tract infection in is pneumonia, a lung infection. Pneumonia is usually caused by bacteria, particularly ''Streptococcus pneumoniae'' in Western countries. Worldwide, tuberculosis is an important cause of pneumonia. Other pathogens such as viruses and fungi can cause pneumonia for example severe acute respiratory syndrome and pneumocystis pneumonia. A pneumonia may develop complications such as a lung abscess, a round cavity in the lung caused by the infection or an empyema, the spread of the infection to the pleural cavity.

Respiratory tumours

Tumours of the respiratory system are either malignant or benign.

Malignant tumours

Malignant tumours, or cancers of the respiratory system, particularly lung cancers, are a major health problem responsible for 15% of all cancer diagnoses and 29% of all cancer deaths. The majority of respiratory system cancers are attributable to smoking tobacco.

The major types of respiratory system cancer are:

• Small cell lung cancer
• Non-small cell lung cancer
  • Adenocarcinoma
  • Squamous cell carcinoma
  • Large cell undifferentiated carcinoma
• Other lung cancers (carcinoid, Kaposi’s sarcoma, melanoma)
• Lymphoma
• Head and neck cancer
• Mesothelioma, usually caused by exposure to asbestos dust.

In addition, since many cancers spread via the bloodstream and the entire cardiac output passes through the lungs, it common for cancer metastases to occur the lung. Breast cancer may invade directly through local spread, and through lymph node metastases. After metastasis to the liver, colon cancer frequently metastasizes to the lung. Prostate cancer, germ cell cancer and renal cell carcinoma may also metastasize to the lung.

Treatment of respiratory system cancer depends on the type of cancer. Surgery (usually removal of part of the lung, a lobectomy or an entire lung, a pneumonectomy), chemotherapy and radiotherapy are all used. The chance of surviving lung cancer depends on the cancer stage at the time the cancer is diagnosed and is only about 14-17% overall. In the case of metastases to the lung, treatment can occasionally be curative but only in certain, rare circumstances.

Benign tumours

Benign tumours are relatively rare causes of respiratory disease. Examples of benign tumours are:

• Pulmonary hamartoma
• Congenital malformations such as pulmonary sequestration and congenital cystic adenomatoid malformation (CCAM).

Pleural cavity diseases

Pleural cavity diseases include empyema and mesothelioma which are mentioned above.

A collection of fluid in the pleural cavity is known as a pleural effusion. This may be due to fluid shifting from the bloodstream into the pleural cavity due to conditions such as congestive heart failure and cirrhosis. It may also be due to inflammation of the pleura itself as can occur with infection, pulmonary embolus, tuberculosis, mesothelioma and other conditions.

A pneumothorax is a hole in the pleura covering the lung allowing air in the lung to escape into the pleural cavity. The affected lung “collapses” like a deflated balloon. A tension pneumothorax is a particularly severe form of this condition where the air in the pleural cavity cannot escape, so the pneumothorax keeps getting bigger until it compresses the heart and blood vessels, leading to a life threatening situation.

Pulmonary vascular diseases

Pulmonary vascular diseases are conditions that affect the pulmonary circulation. Examples of these conditions are

• Pulmonary embolism, a blood clot that forms in a vein, breaks free, travels through the heart and lodges in the lungs (thromboembolism). Large pulmonary emboli are fatal, causing sudden death. A number of other substances can also embolise to the lungs but they are much more rare: fat embolism (particularly after bony injury), amniotic fluid embolism (with complications of labour and delivery), air embolism (iatrogenic).
• Pulmonary arterial hypertension, elevated pressure in the pulmonary arteries. It can be idiopathic or due to the effects of another disease, particularly COPD. This can lead to strain on the right side of the heart, a condition known as cor pulmonale.
• Pulmonary edema, leakage of fluid from capillaries of the lung into the alveoli (or air spaces). It is usually due to congestive heart failure.
• Pulmonary hemorrhage, inflammation and damage to capillaries in the lung resulting in blood leaking into the alveoli. This may cause blood to be coughed up. Pulmonary hemorrhage can be due to auto-immune disorders such as Wegener's Granulomatosis and Goodpasture's syndrome.

Disorders of breathing mechanics

The brain co-ordinates breathing and sends messages via nerves to the muscles of respiration. The muscles produce the movements of breathing. Disorders of the brain’s control of breathing, the nerves or the muscles of respiration can affect the respiratory system. Common disorders of breathing mechanics are:

• Obstructive sleep apnea
• Central sleep apnea
• Amyotrophic lateral sclerosis
• Guillan-Barre syndrome
• Myasthenia gravis

Obesity is often associated with sleep apnea and can cause either an obstructive or a restrictive pattern on spirometry. Obesity reduces the movement of the chest wall which can, in extreme cases, result in the obesity-hypoventilation syndrome, a cause of respiratory failure.