Bronchiolitis

Bronchiolitis
Classification and external resources
A chest X-ray demonstrating lung hyperinflation with a flattened diaphragm and bilateralatelectasis in the right apical and left basal regions in a 16-day-old infant with severe bronchiolitis.
ICD-10	J21.
ICD-9	466.1
DiseasesDB	1701
MedlinePlus	000975
eMedicine	emerg/365
MeSH	D001988

Not to be confused with bronchitis.

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. This inflammation is usually caused by viruses.

Contents  [hide] 1 Causes 2 Diagnosis and Recovery 3 Treatment 3.1 Conservative measures 3.2 Bronchodilators 3.3 Hypertonic saline 3.4 Non effective 4 Complications 5 Prevention 6 See also 7 References 8 External links

[edit]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). (J21.0)

Other viruses which may cause this illness include metapneumovirus, influenza, parainfluenza,coronavirus, adenovirus, and rhinovirus.

The American Academy of Pediatrics has published a clinical practice guideline for theDiagnosis and Management of Bronchiolitis, including a review of the evidence and recommendations.

[edit]Diagnosis and Recovery

In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. The diagnosis is made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.

Testing for specific viral cause (e.g. RSV by nasopharyngeal aspirate) can be done but has little effect on management. In a systematic review, RSV testing by direct immunofluorescence testing on nasopharyngeal aspirate had a sensitivity of 61% and specificity of 89%.^[1]Identification of RSV-positive patients can be helpful 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).

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.

There is a possible link with later asthma: 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.

Bronchiolitis Obliterans occurs rarely in rheumatoid lung disease when small airway obstruction develops into a necrotizing bronchiolitis.

[edit]Treatment

There is no effective specific treatment for bronchiolitis. Therapy is principally supportive.^[2]

[edit]Conservative measures

Frequent small feeds are encouraged to maintain hydration as evidenced by good urine output, and sometimes oxygen may be required to maintain blood oxygen levels. Suction of the nasopharynx is often performed to maintain a clear airway. In severe cases the infant may need to be fed via a nasogastric tube or it may even need intravenous fluids. In extreme cases, mechanical ventilation (for example, using CPAP) might be necessary.

[edit]Bronchodilators

Bronchodilator drugs such as salbutamol/albuterol or ipratropium are no longer recommended, but many clinicians offer a trial dose to see if there is any benefit (especially if there is a family history of asthma, since it can be difficult to clinically distinguish bronchiolitis from a viral-induced asthma). Racemic epinephrine is another drug that is sometimes given.

[edit]Hypertonic saline

There is some interest in the use of hypertonic saline in bronchiolitis. Initially recommended for use in cystic fibrosis patients, it is speculated to increase hydration of secretions, thus facilitating their removal. ^[3] In a study of emergency room patients with bronchiolitis, a comparison of nebulized 3% saline/epinephrine with 0.9% saline/epinephrine showed no difference in effectiveness.^[4] However, in another study looking at the inpatient population, aerosolized 3% saline soln/1.5mg epinephrine was shown to reduce the length of hospital stay among non-asthmatic, non-severely ill infants with viral bronchiolitis as compared to aerosolized 0.9% saline soln/1.5mg epinephrine according to a randomized controlled trial. Length of stay for aerosolized 3% saline soln/1.5mg epinephrine was 3 +/- 1.2 days, which was significantly shorter (by 25%) than length of stay for patients treated with 0.9% saline soln/1.5mg epinephrine which was 4 +/- 1.9 days (p < 0.05).^[5]

[edit]Non effective

Ribavirin is an antiviral drug which has a controversial role in treating RSV infection. There is no proven benefit but it is used sometimes for infants with pre-existing lung, heart or immune disease. Antibiotics 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.^[6]

[edit]Complications

Middle ear bacterial infection

Development of asthma later (bronchial hyperactivity)

[edit]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 (amonoclonal 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 and other vulnerable groups is currently unknown

Introduction

Background

Bronchiolitis is an acute infectious disease of the lower respiratory tract that occurs primarily in young infants, most often in those aged 2-24 months.

Pathophysiology

Bronchiolitis is usually due to a viral infection of the small airways (bronchioles). Infection of bronchiolar respiratory and ciliated epithelial cells produces increased mucus secretion, cell death, and sloughing, followed by a peribronchiolar lymphocytic infiltrate and submucosal edema. The combination of debris and edema produces critical narrowing and obstruction of small airways.

Decreased ventilation of portions of the lung causes ventilation/perfusion mismatching, resulting in hypoxia. During the expiratory phase of respiration, further dynamic narrowing of the airways produces disproportionate airflow decrease and resultant air trapping. Work of breathing is increased due to increased end-expiratory lung volume and decreased lung compliance. Recovery of pulmonary epithelial cells occurs after 3-4 days, but cilia do not regenerate for about 2 weeks. The debris is cleared by macrophages.

Infection is spread by direct contact with respiratory secretions. In the United States, epidemics last 2-4 months beginning in November and peaking in January or February. While 93% of cases occur between November and early April, sporadic cases may occur throughout the year. Attack rates within families are as high as 45% and are higher in daycare centers. Rates of hospital-acquired infection range from 20-47%. Previous infection with the common etiologic viruses does not confer immunity. Reinfection is common.

Frequency

United States

Annual incidence is 11.4% in children younger than 1 year and 6% in those aged 1-2 years. The illness accounts for 4500 deaths and 90,000 hospital admissions per year. Prevalence may be higher in urban areas.

In children aged 2 years, approximately 95% have serologic evidence of past infection with the predominant causative agent, respiratory syncytial virus (RSV). Unfortunately, presence of antibodies to RSV does not confer immunity.

International

RSV is an important respiratory pathogen worldwide. The frequency of bronchiolitis in developed countries appears to be similar to that in the United States. Epidemiologic data for underdeveloped countries are incomplete. Peak incidence of bronchiolitis usually occurs during winter months in temperate climates and during the rainy season in tropical climates. In the United States, the peak occurs in February. Morbidity and mortality may be higher in less developed countries because of poor nutrition and lack of resources for supportive medical care.

Mortality/Morbidity

Significant morbidity is unusual.

• Hospitalization is required in up to 2% of cases; most of those patients are younger than 6 months. These patients account for as many as 17% of all infant hospitalizations. Hospitalization is significantly more likely at altitudes above 2500 meters (8000 ft). Mechanical ventilation is required for 3-7% of admitted patients.
• The mortality rate is 1-2% of all hospitalized patients and 3-4% for patients with underlying cardiac or pulmonary disease.
• Most deaths occur in infants younger than 6 months.

Race

• Race and socioeconomic status may affect the frequency of contracting bronchiolitis.
• Lower socioeconomic status may increase the likelihood of hospitalization. Hospitalization rates are higher in Native American, Alaskan, and Hispanic populations, but it is not clear if this is due to more severe infection or a lower threshold for admission.

Sex

Bronchiolitis occurs as many as 1.25 times more frequently in males than in females.

Age

• Although infection with etiologic agents may occur at any age, the clinical entity of bronchiolitis includes only infants and young children. Seventy-five percent of cases of bronchiolitis occur in children younger than 1 year, and 95% in children younger than 2 years. Incidence peaks in those aged 2-8 months.

Clinical

History

• History and physical examination form the primary basis for the diagnosis of bronchiolitis.
• Early symptoms are those of a viral upper respiratory tract infection (URI), including mild rhinorrhea, cough, and sometimes low-grade fever.
• Adults, older children, and many infants do not progress beyond this stage of URI.
• For the 40% of infants and young children who progress to lower respiratory tract involvement, paroxysmal cough and dyspnea develop within 1-2 days.
• Other common symptoms include the following:
  • Fever
  • Increased work of breathing
  • Wheezing
  • Cyanosis
  • Grunting
  • Noisy breathing
  • Vomiting, especially post-tussive
  • Irritability
  • Poor feeding or anorexia

Physical

Most patients with bronchiolitis have the following signs:

• Tachypnea, often at rates over 50-60 breaths per minute (most common physical sign)
• Tachycardia
• Fever, usually in the range of 38.5-39°C
• Mild conjunctivitis or pharyngitis
• Diffuse expiratory wheezing
• Nasal flaring
• Intercostal retractions
• Cyanosis
• Inspiratory crackles
• Otitis media
• Apnea, especially in infants younger than 6 weeks
• Palpable liver and spleen from hyperinflation of the lungs and consequent depression of the diaphragm

Causes

RSV is the most common pathogen (85%), but other organisms occasionally produce a similar clinical picture.

• Adenovirus (11%) occasionally causes a similar syndrome with a more virulent course.
• Epidemics of bronchiolitis due to parainfluenza virus usually begin earlier in the year and tend to occur every other year.
• Other less common etiologic agents include the following:
  • Mycoplasma pneumoniae
  • Enterovirus
  • Influenza virus
  • Rhinovirus
  • Chlamydia pneumoniae
  • Human metapneumovirus¹
• Ear, nose, or mouth inoculation
• Exposure to an adult with a URI
• Daycare exposure (significant)
• Idiopathic