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A child presents with noisy breathing when air is impeded as it flows past a narrow or partially obstructed airway. This disruption of airflow leads to wheezing, stridor, or stertor. There are many potential causes of noisy breathing, and a careful history and physical exam will facilitate accurate diagnosis.

Wheezing is a high-pitched, continuous, whistling sound heard over the chest. It occurs when exhaled air flows through narrowed or partially obstructed intrathoracic airways, most often the bronchioles. However, narrowing of larger airways can also lead to wheezing.1 An estimated 10–15% of all infants younger than 1 year have an episode of wheezing, and up to 25% of children younger than 5 years present at least once to seek medical attention for evaluation of wheezing.2

Stridor is a harsh, high-pitched, musical sound that is indicative of upper airway obstruction.3 It occurs most commonly during inspiration, but may be biphasic or expiratory on the basis of anatomic location of the narrowing. Stridor is an important clinical finding that warrants investigation, as the etiologies range from benign, self-limited disease to severe illness leading to a rapidly progressive airway obstruction.

Stertor is a low-pitched, grunting sound similar to snoring that is usually produced during inspiration. It is caused by upper airway obstruction from vibrations of tissue of the nasopharynx, oropharynx, or hypopharynx and exacerbated when laying in the supine position.3 The prevalence ranges from 3% to 27% in children.4



Wheezing typically indicates lower airway obstruction. In infants, acute bronchiolitis is the most common cause of an initial episode of wheezing. It results from a viral respiratory tract infection (respiratory syncytial virus, parainfluenza, adenovirus, human metapneumovirus) and usually occurs during winter months. If wheezing is recurrent or persistent, other causes should be considered such as serial viral respiratory infections, gastroesophageal reflux with pulmonary aspiration, and asthma. Recurrent wheezing over the age of 2 years, especially in the absence of viral infections, usually indicates a diagnosis of asthma. Less common causes of recurrent wheezing (Table 18-1) include cystic fibrosis; immunologic defects; congenital abnormalities of the lung, diaphragm, or branches of the aorta or pulmonary vessels (vascular rings); or other anatomic causes (Figure 18-1).

TABLE 18-1Diagnostic Tests and Expected Results in Children with Less Common Causes of Wheezing

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