Bronchiolitis

Question 1

What is bronchiolitis?

Answer 1

Bronchiolitis is an acute inflammatory injury of the bronchioles that is usually caused by a viral infection (most commonly respiratory syncytial virus). This condition may occur in persons of any age, but severe symptoms are usually evident only in young infants.

Question 2

What are the signs and symptoms of bronchiolitis?

Answer 2

Because bronchiolitis primarily affects young infants, clinical manifestations are initially subtle, such as the following:

May become increasingly fussy and have difficulty feeding during the 2 to 5-day incubation period [1]

Low-grade fever (usually < 101.5°F); possible hypothermia in infants younger than 1 month [2]

Increasing coryza and congestion

Apnea: May be the presenting symptom in early disease

Question 3

What are the signs and symptoms of severe bronchiolitis?

Answer 3

Severe cases of bronchiolitis may progress over 48 hours to the following signs and symptoms:

Respiratory distress with tachypnea, nasal flaring, retractions

Irritability

Possibly cyanosis

Question 4

What are physical findings characteristic of bronchiolitis?

Answer 4

The diagnosis of bronchiolitis is based on clinical presentation, the patient’s age, seasonal occurrence, and findings from the physical examination, which may reveal the following:

Tachypnea

Tachycardia

Fever (38-39°C)

Retractions

Fine rales (47%); diffuse, fine wheezing

Hypoxia

Otitis media

Question 5

What tests are commonly performed in the evaluation of bronchiolitis?

Answer 5

Commonly used tests in the evaluation of patients with bronchiolitis include the following:

Rapid viral antigen or nucleic acid amplification testing of nasopharyngeal secretions for respiratory syncytial virus

Arterial blood gas analysis

White blood cell count with differential

C-reactive protein level

Pulse oximetry

Blood cultures

Urine analysis, specific gravity, and culture

Cerebrospinal fluid analysis and culture

Serum chemistries

Electrocardiography or echocardiography should be reserved for those few children who display arrhythmias or cardiomegaly.

Question 6

What is the focus of treatment of bronchiolitis in young children?

Answer 6

Among numerous medications and interventions used to treat bronchiolitis, thus far, only oxygen appreciably improves the condition of young children. [7] Therefore, therapy is directed toward symptomatic relief and maintenance of hydration and oxygenation.

Question 7

What is included in supportive care for bronchiolitis?

Answer 7

Supportive care for patients with bronchiolitis may include the following:

Supplemental humidified oxygen

Maintenance of hydration

Mechanical ventilation

Nasal and oral suctioning

Apnea and cardiorespiratory monitoring

Temperature regulation in small infants

Question 8

What is the role of necrosis of the respiratory epithelium in the pathophysiology of bronchiolitis?

Answer 8

Necrosis of the respiratory epithelium is one of the earliest lesions in bronchiolitis and occurs within 24 hours of acquisition of infection. [12] Proliferation of goblet cells results in excessive mucus production, whereas epithelial regeneration with nonciliated cells impairs elimination of secretions. Lymphocytic infiltration may result in submucosal edema.

Question 9

What is the role of cytokines and chemokines in the pathophysiology of bronchiolitis?

Answer 9

Cytokines and chemokines, released by infected respiratory epithelial cells, amplify the immune response by increasing cellular recruitment into infected airways. Interferon and interleukin (IL)–4, IL-8, and IL-9 are found in high concentrations in respiratory secretions of infected patients.

Question 10

What is the pathophysiology of bronchiolitis?

Answer 10

The inflammation, edema, and debris result in obstruction of bronchioles, leading to hyperinflation, increased airway resistance, atelectasis, and ventilation-perfusion mismatching. Bronchoconstriction has not been described. Infants are affected most often because of their small airways, high closing volumes, and insufficient collateral ventilation. Recovery begins with regeneration of bronchiolar epithelium after 3-4 days; however, cilia do not appear for as long as 2 weeks. Mucus plugs are instead predominantly removed by macrophages.

Question 11

What are the signs and symptoms of bronchiolitis?

Answer 11

Because bronchiolitis primarily affects young infants, clinical manifestations are initially subtle. Infants may become increasingly fussy and have difficulty feeding during the 2 to 5-day incubation period. [1] A low-grade fever, usually less than 101.5°F, and increasing coryza and congestion usually follow the incubation period. In older children and adults, as well as in up to 60% of infants, respiratory syncytial virus (RSV) infection is generally confined to the upper airway and does not progress further.

Over a period of 2-5 days, RSV infection progresses from the upper to the lower respiratory tract, and this progression leads to the development of cough, dyspnea, wheezing, and feeding difficulties. When the patient is brought to medical attention, the fever has usually resolved. Infants younger than 1 month may present as hypothermic. [2] Severe cases progress to respiratory distress with tachypnea, nasal flaring, retractions, irritability, and, possibly, cyanosis.

Question 12

What are characteristic physical findings of bronchiolitis?

Answer 12

Examination often reveals the following:

Tachypnea

Tachycardia

Fever (38-39°C)

Retractions

Fine rales (47%)

Diffuse, fine wheezing

Otitis media

Question 13

What is the basis for the diagnosis of bronchiolitis?

Answer 13

The diagnosis is made on the basis of age and seasonal occurrence, tachypnea, and the presence of profuse coryza and fine rales, wheezes, or both upon auscultation of the lungs. Some practitioners exclude RSV infection in the absence of coryza.

Question 14

What is the best predictor of illness in bronchiolitis?

Answer 14

Hypoxia is the best predictor of severe illness and correlates best with the degree of tachypnea (>50 breaths/min). The degree of wheezing or retractions correlates poorly with hypoxia. First-time infections are usually most severe; subsequent attacks are generally milder, particularly in older children.

Question 15

What is the presentation of apnea in bronchiolitis?

Answer 15

Apnea occurs early in the course of the disease and may be the presenting symptom, especially in those younger than 2 months of age or those born prematurely. Nonobstructive central apnea occurs during quiet sleep and is associated with increases in the apnea index (the percentage of time the baby spends apneic), apnea attack rate (the number of episodes of apnea per unit time), and apnea percentage (the distribution of episodes of apnea in a given sleep state).

Question 16

How are asthma and bronchiolitis differentiated?

Answer 16

Bronchiolitis and asthma have similar symptoms and signs, and some concern exists that patients with asthma could be misdiagnosed with bronchiolitis. The pathology of bronchiolitis involves edema of the airway wall rather than bronchoconstriction (as in asthma).

Question 17

How is bronchiolitis managed?

Answer 17

Since no definitive antiviral therapy exists for most causes of bronchiolitis, management of these infants should be directed toward symptomatic relief and maintenance of hydration and oxygenation. Although numerous medications and interventions have been studied for the treatment of bronchiolitis, at present, only oxygen appreciably improves the condition of young children with bronchiolitis and many other medical therapies remain controversial.

Question 18

What is the initial management of bronchiolitis?

Answer 18

Patients should be made as comfortable as possible (held in a parent’s arms or sitting in the position of comfort). Administer saline nose drops and perform nasal and oral suctioning. Deep oral and nasal suctioning is not routinely needed. Carefully monitor the patient for apnea. Pay attention to temperature regulation in small infants. [8]

Cardiorespiratory monitoring is essential. Pulse oximetry is a helpful tool; hypoxia is common. It is vital to have a clear picture of the patient’s clinical respiratory status and the severity of disease. The ability to maintain adequate hydration should be assessed by observing the patient’s oral intake. Many dyspneic infants have difficulty taking a bottle.

Although young infants have the unique ability to breathe and swallow simultaneously, the risk of aspiration is significant when the respiratory rate is higher than 60 breaths/min. Fever and hyperpnea may contribute to excessive fluid losses. For these reasons, infants who are hospitalized with bronchiolitis require careful fluid monitoring and provision of nasogastric or intravenous (IV) fluids when hyperpnea precludes safe oral feeding.

An early effort should be made to isolate or cohort patients who are confirmed or likely to have RSV infection, especially from other patients at risk for severe disease. Institute standard and contact isolation precautions to prevent nosocomial transmission.

Question 19

What is the indication for oxygen supplementation in the management of bronchiolitis?

Answer 19

Administer supplemental humidified oxygen, if necessary, to maintain a transcutaneous oxygen saturation higher than 90%. Unger and Cunningham found that oxygen supplementation is the prime determinant of length of hospitalization. [7] The use of high-flow nasal cannulas may reduce intubation rates in infants with bronchiolitis. [147]

A multicenter, randomized, controlled trial conducted in Australia that included 1472 patients reported that among infants with bronchiolitis and hypoxemia who were treated outside an ICU (in an emergency department or general floor setting), those who received high-flow oxygen therapy early in their course of management had significantly lower rates of escalation of care due to treatment failure than those in the group that received standard oxygen therapy (12% in the high-flow group compared to 23% in the standard-therapy group).

Question 20

How is dehydration treated in patients with bronchiolitis?

Answer 20

Infants with bronchiolitis are mildly dehydrated because of decreased fluid intake and increased fluid losses from fever and tachypnea. Accordingly, it is vital to maintain adequate hydration. The goal of fluid therapy is to replace deficits and to provide maintenance requirements. Avoid excessive fluid administration, because this may promote interstitial edema formation, particularly if a component of inappropriate antidiuretic hormone release is present. [98]

Oral therapy is preferred. Parenteral therapy may be necessary in those patients who are unable to take fluids by mouth or who have a respiratory rate higher than 70 breaths/min. Patients with apneic episodes should have access to IV hydration.