Bronchiolitis
Encyclopedia
Bronchiolitis is inflammation of the bronchiole
Bronchiole
The bronchioles or bronchioli are the first airway branches that no longer contain cartilage or glands in their submucosa. They are branches of the bronchi.The bronchioles terminate by entering the circular sacs called alveoli.- Structure :...

s, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses. Treatment is typically supportive but may involve the use of nebulized epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

 or hypertonic saline.

Signs and symptoms

In a typical case, an infant under two years of age develops cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...

, wheeze
Wheeze
A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed, or airflow velocity within the respiratory tree must be heightened...

, and shortness of breath over one or two days. The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze.

Causes

The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus (RSV, also known as human pneumovirus). Other viruses which may cause this illness include metapneumovirus
Metapneumovirus
Human metapneumovirus is a negative single-stranded RNA virus of the family Paramyxoviridae and is closely related to the avian metapneumovirus subgroup C. It was isolated for the first time in 2001 in the Netherlands by using the RAP-PCR technique for identification of unknown viruses growing...

, influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

, parainfluenza, coronavirus
Coronavirus
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31...

, adenovirus, and rhinovirus
Rhinovirus
Human rhinoviruses are the most common viral infective agents in humans and are the predominant cause of the common cold. Rhinovirus infection proliferates in temperatures between 33–35 °C , and this may be why it occurs primarily in the nose...

.

Studies have shown there is a link between voluntary caesarean
Caesarean section
A Caesarean section, is a surgical procedure in which one or more incisions are made through a mother's abdomen and uterus to deliver one or more babies, or, rarely, to remove a dead fetus...

 birth and an increased prevalence of bronchiolitis. A recent study by Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....

's Telethon Institute for Child Health Research
Telethon Institute for Child Health Research
Established in 1990 by former Australian of the Year Professor Fiona Stanley, the Telethon Institute of Child Health Research in Western Australia is a multidisciplinary research centre with more than 500 staff, post-graduate students and visiting scholars, working collaboratively to improve the...

 has shown an 11% increase in hospital admissions for children delivered this way.

Diagnosis

The diagnosis is typically made by clinical examination. Chest X-ray
Chest X-ray
In medicine, a chest radiograph, commonly called a chest X-ray , is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures...

 is sometimes useful to exclude pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

, but not indicated in routine cases.

Testing for the specific viral cause can be done but has little effect on management and thus is not routinely recommended. In a systematic review, RSV testing by direct immunofluorescence testing on nasopharyngeal aspirate had a sensitivity of 61% and specificity of 89%. Identification of those who are RSV-positive can help for:
  • disease surveillance
  • grouping ("cohorting") patients together in hospital wards as to prevent cross infection
  • predicting whether the disease course has peaked yet
  • reducing the need for other diagnostic procedures (by providing confidence that a cause has been identified).


There is a possible link with later asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

: possible explanations are that bronchiolitis causes asthma by inducing long term inflammation, or that children who are destined to be asthmatic are more susceptible to develop bronchiolitis.

Rarely, bronchiolitis obliterans
Bronchiolitis obliterans
Bronchiolitis obliterans , also called obliterative bronchiolitis and constrictive bronchiolitis , is a rare and life-threatening form of non-reversible obstructive lung disease in which the bronchioles are compressed and narrowed by fibrosis and/or inflammation...

 occurs, that is, when bronchitis presents with concomitant non-reversible obstruction due to the bronchiole
Bronchiole
The bronchioles or bronchioli are the first airway branches that no longer contain cartilage or glands in their submucosa. They are branches of the bronchi.The bronchioles terminate by entering the circular sacs called alveoli.- Structure :...

s (small airway branches) becoming compressed and narrowed by fibrosis
Fibrosis
Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This is as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue...

 (scar tissue) and/or inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

. This form of bronchiolitis is life-threatening and has various causes.

Prevention

In general, prevention of bronchiolitis relies on measures to reduce the spread of the viruses that cause respiratory infections (that is, handwashing, and avoiding exposure to those symptomatic with respiratory infections).

Premature infants, and others with certain major cardiac and respiratory disorders, can receive passive immunization with Palivizumab
Palivizumab
Palivizumab is a monoclonal antibody produced by recombinant DNA technology. It is used in the prevention of respiratory syncytial virus infections...

 (a monoclonal antibody against RSV). This form of passive immunization therapy requires monthly injections every winter. Whether it could benefit infants with lung problems secondary to muscular dystrophies
Muscular dystrophy
Muscular dystrophy is a group of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.In the 1860s, descriptions of boys who...

 and other vulnerable groups is currently unknown

Management

Therapy for bronchiolitis is primarily supportive. Nebulized epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

 may decrease the need for hospitalization while nebulized hypertonic saline appears to be effective in improving clinical outcomes and shortening the duration of hospital stay. All other medications do not have evidence to support their use.

Non effective

Ribavirin
Ribavirin
Ribavirin is an anti-viral drug indicated for severe RSV infection , hepatitis C infection and other viral infections. Ribavirin is a prodrug, which when metabolised resembles purine RNA nucleotides...

 is an antiviral drug which does not appear to be effective for bronchiolitis. Antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s are often given in case of a bacterial infection complicating bronchiolitis, but have no effect on the underlying viral infection. Corticosteroids have no proven benefit in bronchiolitis treatment and are not advised. DNAse has not been found to be effective.

Complications

Middle ear bacterial infection

Development of asthma later (bronchial hyperactivity)

Epidemiology

90% of the patients are aged between 1 and 9 months old. Bronchiolitis is the most common cause of hospitalization up to the first year of life. It is epidemic in winters.

External links

  • Bronchiolitis. Patient information from NHS Direct
    NHS Direct
    NHS Direct is the health advice and information service provided by the National Health Service for residents and visitors in England, with advice offered 24 hours a day, every day of the year through telephone contact on the national 0845 46 47 number, web based symptom checkers at and via...

      from the Scottish Intercollegiate Guidelines Network
  • Diagnosis and Management of Bronchiolitis from the AAP
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