Overinflation and Congenital Lobar Emphysema

Kevin Kuriakose, MD, FAAP

Overinflation

Introduction/Etiology/Epidemiology

•Overinflation consists of distended air spaces; however, it is often reversible.

•The terms overinflation and hyperinflation have been used interchangeably in medical practice. Both terms refer to distended air spaces that appear as excessive inflation of the lung parenchyma at presentation.

•Potential etiologic origins for overinflation include

—Intrinsic airway factors

▪Asthma and bronchiolitis

▪Cystic fibrosis

▪Aspiration of zinc stearate powder or other chemicals and irritants

▪Foreign bodies

▪Endobronchial tumors

▪Severe bronchomalacia

—Extrinsic airway factors

▪Mediastinal tumors

▪Pulmonary vascular abnormalities

•Unilateral hyperlucent lung is a localized overinflation in 1 lung or lobe, which includes

—Obstructive overinflation

—Pulmonary venolobar syndrome (also known as scimitar syndrome)

—Congenital lobar emphysema (CLE)

Pathophysiology

•Partial obstruction of the airway results in distention of air spaces distal to the obstruction.

•Key points that distinguish overinflation from other forms of hyperlucency of the lungs include

—Hyperinflated normal alveoli

—Alveoli or lung parenchyma communicating with the respiratory tree

—Overinflation that is usually reversible once the underlying cause is addressed

•Symptoms

—Dyspnea

—Shortness of breath or difficulty exhaling

—Patients may present with no symptoms or with symptoms only on exertion

•Signs at physical examination

—Increased respiratory rate

—Prolonged expiratory phase

—Hyperresonance on percussion

—Retractions

Differential Diagnosis

•Pulmonary emphysema

•Congenital cystic adenomatoid malformation

•Pulmonary sequestration

•Pneumothorax

Diagnostic Considerations

•Chest radiography or thin-section computed tomography (CT) performed with or without contrast material may demonstrate

—Localized hyperlucency on radiographs or localized hyperattenuation on CT images

▪Based on the size of the hyperlucency or hyperattenuation, images may show

~Mediastinal shift

~Flattening of the ipsilateral diaphragm

—Pulmonary vascular markings

▪The presence or absence of markings can help distinguish the diagnosis among the differential diagnoses.

•Bronchoscopy can be used to visualize an abnormality of the airway that is causing partial obstruction, resulting in a check valve effect, where airflow is unidirectional.

•A ventilation-perfusion scan can be used to identify a perfusion defect.

Management

•Respiratory distress or clinically significant respiratory symptoms will require supportive care.

•Treat the underlying cause of the overinflation.

—Clinically significant respiratory symptoms may require surgical intervention.

—Caution must be taken when intubating and using mechanical ventilation or positive pressure.

—Clinically significant signs and symptoms may require further evaluation and management prior to air travel.

•Prognosis is typically good to excellent, because overinflation is often reversible.

•Factors that decrease prognosis are dependent on the underlying cause of overinflation and any sequelae.

When to Refer

•Refer the patient to a specialist for recurrent or persistent bilateral diffuse hyperinflation secondary to an illness (eg, bronchiolitis, asthma).

•Unilateral or localized overinflation with or without symptoms necessitates referral.

•Multidisciplinary teams may include the following pediatric subspecialists:

—Pulmonologist

—Ear, nose, and throat specialist and/or surgeon

—Cardiologist

—Infectious diseases specialist

When to Admit

•Respiratory symptoms that progressively worsen

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