Airway obstruction is a blockage that limits the flow of air into and out of the lungs. The lower airway encompasses structures deep within the chest: the trachea (windpipe), the bronchi (larger tubes branching off the trachea), and the smaller bronchioles and tiny air sacs called alveoli within the lungs. This article focuses on the common causes of lower airway obstruction in children.
Understanding Lower Airway Obstruction in Children
The lower airway begins at the trachea, dividing into two main bronchi that lead to each lung. These then branch into smaller bronchioles, which ultimately lead to the alveoli where oxygen and carbon dioxide exchange occurs. When any part of this system narrows or blocks, it increases airflow resistance, making breathing difficult. Lower airway obstructions are often more noticeable during exhalation.
Children are particularly susceptible to lower airway obstruction due to their unique anatomy. Their airways are naturally smaller in diameter and shorter, meaning even a small amount of swelling or mucus can cause significant narrowing. The cricoid cartilage, a ring of cartilage, is the narrowest point in a young child’s airway, making it especially vulnerable to obstruction.
Acute Conditions Leading to Obstruction
Acute conditions causing lower airway obstruction in children have a sudden onset and often require immediate medical attention.
Bronchiolitis
Bronchiolitis is a common viral infection, most frequently caused by Respiratory Syncytial Virus (RSV), affecting infants and young children. This infection leads to inflammation, swelling, and increased mucus production in the bronchioles, causing them to narrow and obstruct airflow. The accumulation of mucus plugs the bronchioles, resulting in air trapping and difficulty breathing.
Foreign Body Aspiration
Foreign body aspiration occurs when an inhaled object becomes lodged in the airway. Common items include small, round foods like peanuts or grapes, and non-food items such as small toys. These objects can cause partial or complete blockage, with the right main bronchus being a common site for lodging.
Anaphylaxis
Anaphylaxis, a severe allergic reaction, can cause rapid lower airway obstruction. During anaphylaxis, the body releases chemicals that cause the airways to constrict and swell. This bronchoconstriction and airway edema quickly reduce the passage for air, leading to severe breathing difficulties. These reactions are medical emergencies requiring immediate intervention.
Chronic Conditions Leading to Obstruction
Some conditions lead to persistent or recurring lower airway obstruction over time.
Asthma
Asthma is a chronic inflammatory condition of the airways. In children with asthma, the airways become inflamed, swell, and produce excess thick mucus. The muscles surrounding these inflamed airways can also tighten, a process called bronchospasm, further narrowing the air passages. This causes recurrent episodes of coughing, wheezing, and shortness of breath.
Cystic Fibrosis
Cystic Fibrosis is a genetic disorder that impacts the respiratory system by affecting mucus production. Individuals produce abnormally thick and sticky mucus throughout their bodies, including in the airways. This viscous mucus accumulates in the bronchi and bronchioles, clogging them. The persistent mucus buildup leads to chronic obstruction and fosters bacterial infections.
Bronchopulmonary Dysplasia (BPD)
Bronchopulmonary Dysplasia (BPD) is a chronic lung disease primarily affecting premature infants who required prolonged respiratory support. This condition results from lung injury and abnormal lung development, leading to structural changes in the airways. These changes include airway remodeling, where the small airways become narrowed. Infants and children with BPD often experience increased airway resistance and reduced lung function, contributing to persistent airflow obstruction.