Pediatric Lower Airway Obstruction

Asthma

Key Concepts

No single asthma score has been universally adopted to assess the degree of illness or treatment responses. However, most scores include some combination of respiratory rate, degree of wheezing, inspiratory-to-expiratory ratio, use of accessory muscles, and oxygen saturation.
Chest x-ray (CXR) is not required for wheezing children, even for those who are febrile, are wheezing for the first time, or require hospitalization. CXR is indicated for those with a history of choking, focal chest findings, extreme distress, subcutaneous emphysema, diagnostic uncertainty relative to respiratory illness, or with clinical findings suggestive of a cardiac etiology.
Albuterol delivered by metered-dose inhalers with spacers (MDI-S) is as effective as that delivered by nebulizers for children with acute asthma. The mode of delivery is largely chosen on the basis of cost and ability to achieve the goal of three treatments within the first hour of care. Per the 2007 National Heart Lung and Blood Institute guidelines, a high dose (4–12 puffs) of a short-acting beta-agonists (SABAs) metered-dose inhaler (MDI) with a spacer has “equivalent bronchodilation” to nebulized treatment.
Levalbuterol does not lead to better emergency department (ED) outcomes compared with racemic albuterol. Racemic albuterol, at a substantially lower cost, should remain the drug of choice for children with acute asthma exacerbations.
Dexamethasone is as effective as prednisone in the ED treatment of acute asthma. Dexamethasone is associated with fewer doses, less vomiting, and greater compliance.
Continuously nebulized albuterol, corticosteroids, magnesium sulfate, and parenteral SABA are cornerstones of therapy for moderately to severely ill children with asthma.

Foundations

Background and Importance

A recent national survey found that one in 12 children had asthma; however, the prevalence among non-Hispanic black children was 16%. Asthma is associated with significant morbidity, with approximately 17% of children with asthma requiring emergency department (ED) or Urgent Care management and 5% needing to be hospitalized annually

Anatomy, Physiology, and Pathophysiology

Asthma is a lower airway disease marked by bronchoconstriction, mucosal edema, and pulmonary secretions. Upper respiratory infections (URIs) associated with copious rhinorrhea, a common trigger of an asthma exacerbation, may significantly increase airway resistance in young children. Because children have compliant chest walls and horizontally located ribs, their ability to use the thorax to increase tidal volume is limited; thus, ventilation is highly dependent on diaphragmatic movement. Also, as functional residual lung capacity increases with age, minute ventilation is largely rate-dependent in young children and may quickly lead to fatigue. An infant younger than 12 months has an oxygen consumption index that is double that of an adult. Increased airway resistance and a compliant chest wall predispose infants to tachypnea, increased work of breathing, and increased oxygen consumption. As a result, the infant with respiratory distress may rapidly develop hypoxemia, precipitating bradycardia and cardiopulmonary arrest.

Clinical Features

All acutely wheezing children arriving for ED care should be attached to a cardiorespiratory monitor and have oxygen saturation determined by pulse oximetry. For children with hypoxia, supplemental oxygen should be provided while the emergency clinician begins the clinical assessment.

History

To initiate appropriate therapy quickly, based on the degree of illness, a concise history should be obtained upon patient arrival, followed by a physical examination that focuses on the cardiopulmonary system. An abbreviated history should include questions about the child’s age, duration and severity of symptoms, recent medication use, and hospitalizations, including the need for intensive care unit (ICU) care or intubation. The parents should be able to relate how the severity of this attack compares with that of previous exacerbations. A history of difficulty sleeping, eating, or speaking suggests a moderate to severe exacerbation. Names, doses, and frequency of asthma medications, as well as preexisting conditions, should be documented.

After starting therapy, a more comprehensive history should include questions about asthma triggers, such as URIs, cigarette smoke, allergies, and exercise. Frequent ED visits or hospitalizations due to asthma may indicate poorly controlled asthma. The impact of asthma on the child’s life may be gauged by the monthly frequency of daytime or nighttime symptoms, including cough, as well as missed days of school or restricted activity. A child with persistent asthma marked by frequent symptoms should be receiving daily anti-inflammatory therapy. Family and social histories should focus on asthma, cystic fibrosis, or atopic disease, and on the adequacy of support systems at home.

Physical Examination

The targeted examination includes assessing vital signs, mental status, and cardiopulmonary systems. A child who is anxious, restless, or lethargic may be hypoxic. The oxygen saturation, sometimes referred to as the “fifth vital sign,” should be determined soon after ED arrival for any child with respiratory distress, and supplemental oxygen should be provided for values 92% or less. No single asthma score has been universally adopted to assess the degree of illness or treatment responses. However, most scores include some combination of respiratory rate, degree of wheezing, inspiratory-to-expiratory ratio, use of accessory muscles, and oxygen saturation. These scores can assist in assessing the pretreatment degree of illness and tracking the response to therapy.

Assessing the work of breathing should include a careful inspection of the chest and neck; rarely, an associated pneumomediastinum or pneumothorax will produce subcutaneous air. Severely ill children may have wheezing that is audible without a stethoscope or have no wheezing (“silent chest”) due to critically limited aeration. Asymmetric wheezing suggests pneumonia, pneumothorax, or a foreign body. More anxiety-provoking parts of the examination, such as otoscopy, should be delayed until treatment is well underway.

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