Respiratory disease

Respiratory diseases,orlung diseases,arepathologicalconditions affecting the organs and tissues that makegas exchangedifficult inair-breathinganimals. They include conditions of therespiratory tractincluding thetrachea,bronchi,bronchioles,alveoli,pleurae,pleural cavity,the nerves andmuscles of respiration.Respiratory diseases range from mild and self-limiting, such as thecommon cold,influenza,andpharyngitisto life-threateningdiseasessuch asbacterial pneumonia,pulmonary embolism,tuberculosis,acute asthma,lung cancer,andsevere acute respiratory syndromes,such asCOVID-19.Respiratory diseases can be classified in many different ways, including by the organ or tissue involved, by the type and pattern of associated signs and symptoms, or by the cause of the disease.

Respiratory disease
Micrographof an emphysematous lung;emphysemais a respiratory disease, strongly associated withsmoking.H&E stain.
Specialty	Pulmonology

The study of respiratory disease is known aspulmonology.Aphysicianwho specializes in respiratory disease is known as a pulmonologist, a chest medicine specialist, a respiratory medicine specialist, a respirologist or a thoracic medicine specialist.

Obstructive lung disease

Asthma,chronic bronchitis,bronchiectasisandchronic obstructive pulmonary disease(COPD) are allobstructive lung diseasescharacterised byairway obstruction.This limits the amount of air that is able to enter alveoli because of constriction of the bronchial tree, due to inflammation. Obstructive lung diseases are often identified because of symptoms and diagnosed withpulmonary function testssuch asspirometry.Many obstructive lung diseases are managed by avoiding triggers (such asdust mitesorsmoking), with symptom control such asbronchodilators,and with suppression of inflammation (such as throughcorticosteroids) in severe cases. One common cause of COPD includingemphysema,and chronic bronchitis, istobacco smoking,and common causes ofbronchiectasisinclude severe infections andcystic fibrosis.The definitive cause ofasthmais not yet known.

Restrictive lung diseases

Age-standardiseddisability-adjusted life year(DALY) rates from respiratory diseases by country (per 100,000 inhabitants).

Restrictive lung diseasesare a category of respiratory disease characterized by a loss oflung compliance,causing incomplete lung expansion and increased lung stiffness, such as in infants with respiratory distress syndrome. Restrictive lung diseases can be divided into two categories: those caused by intrinsic factors and those caused by extrinsic factors. Restrictive lung diseases yielding from intrinsic factors occur within the lungs themselves, such astissue deathdue to inflammation or toxins. Conversely, restrictive lung diseases caused by extrinsic factors result from conditions originating from outside the lungs such asneuromuscular dysfunctionand irregular chest wall movements.

Chronic respiratory disease

Chronic respiratory diseases are long-term diseases of the airways and other structures of the lung. They are characterized by a high inflammatory cell recruitment (neutrophil) and/or destructive cycle ofinfection,(e.g. mediated byPseudomonas aeruginosa). Some of the most common areasthma,chronic obstructive pulmonary disease,andacute respiratory distress syndrome.CRDs are not curable; however, various forms of treatment that help dilate major air passages and improveshortness of breathcan help control symptoms and increase the quality of life.

Telerehabilitation for chronic respiratory disease

The latest evidence suggests that primary pulmonary rehabilitation and maintenance rehabilitation delivered through telerehabilitation for people with chronic respiratory disease reaches outcomes similar to centre-based rehabilitation.While there are no safety issues identified, the findings are based on evidence limited by a small number of studies.

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

Classic steeple sign indicating croup

The upper airway is defined as all the structures connecting the glottis to the mouth and nose.The most commonupper respiratory tract infectionis thecommon cold.However, infections of specific organs of the upper respiratory tract such assinusitis,tonsillitis,otitis media,pharyngitisandlaryngitisare also considered upper respiratory tract infections.

Epiglottitisis a bacterial infection of the larynx which causes life-threatening swelling of theepiglottiswith a mortality rate of 7% in adults and 1% in children.Haemophilus influenzaeis still the primary cause even with vaccinations. Also Streptococcus pyogenes can cause epiglottitis. Symptoms include drooling, stridor, difficulty breathing and swallowing, and a hoarse voice.

Croup(Laryngotracheobronchitis) is a viral infection of thevocal cordstypically lasting five to six days. The main symptom is a barking cough and low-gradefever.On an X-ray, croup can be recognized by the "steeple sign", which is a narrowing of thetrachea.It most commonly occurs in winter months in children between the ages of 3 months and 5 years. A severe form caused by bacteria is called bacterial tracheitis.

Tonsillitisis swelling of the tonsils by a bacterial or viral infection. This inflammation can lead to airway obstruction. From tonsillitis can come a peritonsillar abscess which is the most common upper airway infection and occurs primarily in young adults. It causes swelling in one of the tonsils, pushing theuvulato the unaffected side.Diagnosis is usually made based on the presentation and examination. Symptoms generally include fever, sore throat, trouble swallowing, and sounding like they have a "hot potato" in their mouth.

Lower respiratory tract infection

The most common lower respiratory tract infection ispneumonia,an infection of the lungs which is usually caused by bacteria, particularlyStreptococcus pneumoniaein Western countries. Worldwide,tuberculosisis an important cause of pneumonia. Other pathogens such asvirusesand fungi can cause pneumonia, for examplesevere acute respiratory syndrome,COVID-19andpneumocystis pneumonia.Pneumonia may develop complications such as a lung abscess, a round cavity in the lung caused by the infection, or may spread to thepleural cavity.

Poor oral care may be a contributing factor to lower respiratory disease, as bacteria from gum disease may travel through airways and into the lungs.

Upper and lower respiratory tract infection

Primary ciliary dyskinesiais a genetic disorder causing the cilia to not move in a coordinated manner. This causes chronic respiratory infections, cough, and nasal congestion. This can lead to bronchiectasis, which can cause life-threatening breathing issues.

Tumors

Malignant tumors

Malignant tumors of the respiratory system, particularlyprimary carcinomas of the lung,are a major health problem responsible for 15% of all cancer diagnoses and 30% of all cancer deaths. The majority of respiratory system cancers are attributable tosmoking tobacco.

The majorhistologicaltypes of respiratory system cancer are:

• Small cell lung cancer
• Non-small cell lung cancer
  • Adenocarcinoma of the lung
  • Squamous cell carcinoma of the lung
  • Large cell lung carcinoma
• Other lung cancers (carcinoid,Kaposi's sarcoma,melanoma)
• Lymphoma
• Head and neck cancer
• Pleuralmesothelioma,almost always caused by exposure toasbestosdust.

In addition, since many cancers spread via the bloodstream and the entire cardiac output passes through the lungs, it is common for cancermetastasesto occur within the lung.Breast cancermay invade directly through local spread, and through lymph node metastases. After metastasis to theliver,colon cancerfrequently metastasizes to the lung.Prostate cancer,germ cell cancer andrenal cell carcinomamay also metastasize to the lung.

Treatment of respiratory system cancer depends on the type of cancer. Surgical removal of part of a lung (lobectomy,segmentectomy,orwedge resection) or of an entire lungpneumonectomy), along with chemotherapy andradiotherapy,are all used. The chance of surviving lung cancer depends on the cancer stage at the time the cancer is diagnosed, and to some extent on thehistology,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 tumors

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

• Pulmonaryhamartoma
• Congenital malformations such aspulmonary sequestrationandcongenital cystic adenomatoid malformation(CCAM).

Pleural cavity diseases

Pleural cavity diseases includepleural mesotheliomawhich are mentioned above.

A collection of fluid in the pleural cavity is known as apleural 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.

Apneumothoraxis 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. Atension pneumothoraxis 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 disease

Pulmonary vascular diseases are conditions that affect thepulmonary circulation.Examples are:

• Pulmonary embolism,ablood clotthat 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 (travel through the blood stream) 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– caused by invasive medical procedures).
• Pulmonary arterial hypertension,elevated pressure in the pulmonary arteries. Most commonly it isidiopathic(i.e. of unknown cause) but it can be due to the effects of another disease, particularly COPD. This can lead to strain on the right side of the heart, a condition known ascor pulmonale.
• Pulmonary edema,leakage of fluid from capillaries of the lung into thealveoli(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 asgranulomatosis with polyangiitisandGoodpasture's syndrome.

Neonatal diseases

Pulmonary diseases also impact newborns and the disorders are often unique from those that affect adults.

Infant respiratory distress syndromemost commonly occurs in less than six hours after birth in about 1% of all births in the United States.The main risk factor is prematurity with the likelihood of it occurring going up to 71% in infants under 750g.Other risk factors include infant of a diabetic mother (IDM), method of delivery, fetal asphyxia, genetics,prolonged rupture of membranes(PROM), maternal toxemia,chorioamnionitis,and male sex. The widely accepted pathophysiology of respiratory distress syndrome is it caused by insufficient surfactant production and immature lung and vascular development. The lack of surfactant makes the lungsatelectaticcausing a ventilation to perfusion mismatch, lowered compliance, and increased air resistance. This causes hypoxia and respiratory acidosis which can lead topulmonary hypertension.It has a ground glass appearance on an x-ray. Symptoms can include tachypnea, nasal flaring, paradoxical chest movement, grunting, and subcostal retractions.

Bronchopulmonary Dysplasiais a condition that occurs after birth usually frommechanical ventilationand oxygen use. It happens almost exclusively in pre-mature infants and is characterized by the alveoli, and lung vasculature becoming inflamed and damaged. Complications from BPD can follow a patient into adulthood. As a child they may experience learning disabilities, pulmonary hypertension, and hearing problems. As an adult, there is an increased likelihood for asthma and exercise intolerance.

Meconium Aspiration Syndromeoccurs in full term or post-term infants who aspiratemeconium.Risk factors include a diabetic mother, fetal hypoxia, precipitous delivery, and maternal high blood pressure.Its diagnosis is based on meconium stained amniotic fluid at delivery and staining on the skin, nails, and umbilical cord. Aspiration can cause airway obstruction, air-trapping, pneumonia, lung inflammation, and inactivated surfactant. It presents as patchy atelectasis and hyperinflation on an x-ray with apneumothoraxof pneumomediastinum also possible.

Persistent Pulmonary Hypertension of the Newborn(PPHN) is a syndrome that occurs from an abnormal transition to extra-uterine life. It is marked by an elevated pulmonary vascular resistance and vasoconstriction causing a right-to-left shunt of the blood through theforamen ovaleorductus arteriosus.There are three main causes of PPHN are parenchymal diseases such as meconium aspiration syndrome, idiopathic, and hypoplastic vasculature like in a diaphragmatic hernia. It will eventually resolve in most infants.This is the only syndrome that inhaled nitric oxide is approved for by the FDA.

Pulmonary interstitial emphysema

Transient Tachypnea of the Newbornis caused by the retention of alveolar fluid in the lungs. It commonly occurs in infants who are delivered viacaesarean sectionwithout the onset of labor because absorption of amniotic fluid in the lungs has not yet commenced. Other risk factors are male sex,macrosomia,multiple gestations, and maternal asthma. It usually presents with tachypnea and increased work of breathing. On an x-ray diffuse infiltrates, interlobar fissures, and sometimespleural effusionscan be seen. It is a diagnosis of exclusion because of its similarity to other diseases and frequently CPAP is used to help push the lung fluid into the pulmonary vasculature.

Pulmonary interstitial emphysemais the condition of air escaping overdistended alveoli into the pulmonary interstitium. It is a rare disease that occurs most often in premature infants, even though it is possible to appear in adults.It often presents as a slow deterioration with the need for increased ventilatory support. Chest x-ray is the standard for diagnosis where it is seen as linear or cystic translucencies extending to the edges of the lungs.

Bronchiolitisis the swelling and buildup of mucus in the bronchioles. It is usually caused byrespiratory syncytial virus(RSV), which is spread when an infant touches the nose or throat fluids of someone infected.The virus infects the cells causing ciliary dysfunction and death. The debris, edema, and inflammation eventually leads to the symptoms.It is the most common reason for admission of children under the age of one year. It can present widely from a mild respiratory infection to respiratory failure. Since there is no medication to treat the disease, it is only managed supportively with fluids and oxygen.

Diagnosis

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

• Biopsyof the lung or pleura
• Blood test
• Bronchoscopy
• Chest X-ray
• CT scan,includinghigh-resolution computed tomography
• Culture of microorganismsfrom secretions such as sputum
• Ultrasoundscanning can be useful to detect fluid such aspleural effusion
• Pulmonary function test
• Ventilation–perfusion scan

Epidemiology

Deaths from respiratory diseases per million persons in 2012

19–125

126–169

170–196

197–225

226-–75

276–308

309–365

366–440

441–593

594–1,227

Respiratory disease is a common and significant cause of illness and death around the world. In the US, approximately one billioncommon coldsoccur each year.A study found that in 2010, there were approximately 6.8 million emergency department visits for respiratory disorders in the U.S. for patients under the age of 18.In 2012, respiratory conditions were the most frequent reasons for hospital stays among children.

In the UK, approximately 1 in 7 individuals are affected by some form of chronic lung disease, most commonlychronic obstructive pulmonary disease,which includesasthma,chronic bronchitisandemphysema. Respiratory diseases (including lung cancer) are responsible for over 10% of hospitalizations and over 16% of deaths in Canada.

In 2011, respiratory disease with ventilator support accounted for 93.3% of ICU utilization in the United States.