Overview

Bronchiectasis is a chronic, heterogeneous disorder caused by repeated bouts of infection and inflammation that cause permanent dilation of the medium and medium-large airways.
– Damage can be focal or diffuse, depending on the cause and extent of the damage.
– Etiologies:
Obstruction, which causes focal bronchiectasis, and can be due to tumor masses or foreign bodies in the bronchi.
Infections, often bacterial; common pathogens include Pseudomonas aeruginosa, Haemophilus influenzae, and Non-tuberculosis mycobacteria.
Immune deficiencies
Autoimmune disorders; for example, bronchiectasis is associated with inflammatory bowel disease and rheumatoid arthritis.
Allergic bronchopulmonary aspergillosis; as its name suggests, this form of bronchiectasis is caused by an allergic reaction to the common mold aspergillus;
Genetic conditions, including cystic fibrosis, alpha-1-anti-trypsin deficiency, and primary ciliary dyskinesia (aka, Kartagener syndrome) – these disorders are associated with increased mucus production, neutrophilic damage, and impaired muco-ciliary functions, respectively.
**Asthma and/or COPD
– Many cases of bronchiectasis are idiopathic.

Bronchiolitis is a common affliction of children younger than two years of age; it occurs as result of respiratory infections.

BRONCHIECTASIS:

• Most patients have cough with prominent sputum production.
  – The sputum itself is often described as thick and “tenacious.”
• Hemoptysis may also occur, and is the result of airway neovascularization and rupture.
• Lung crackles and rhonchi
• Some patients wheeze
• Historically, bronchiectasis was associated with digit clubbing, in which the ends of the digits are enlarged and rounded; however, this is less commonly reported, today. The mechanistic link between bronchiectasis and digit clubbing is uncertain.
• Some patients have so-called “dry” bronchiectasis – this is often associated with nontuberculous mycobacterial infection, and is characterized by less sputum production.
• Exacerbations are defined as worsening symptoms that last two days or longer, and require changes in treatment approach.
  – Exacerbations are especially problematic because they cause additional bronchial damage.
• Complications can lead to hypoxemia, due to airway obstruction, and even pulmonary hypertension and right heart failure.
• Treatments:
  – Airway clearance techniques
  – Exercise
  – Macrolides and other antibiotics
  – Hyperosmolar and mucolytic agents that transform mucus to facilitate clearance
  – Anti-inflammatory drugs

Pathogenesis: A Vicious Cycle

• Impaired mucociliary clearance and retention of airway secretions, which creates an environment vulnerable to chronic infections.
• Chronic infections results in chronic inflammation with neutrophilic and T-cell infiltration.
• These inflammatory cells release cytokines that cause tissue destruction and airway remodeling
• Over time, this degradation of the bronchial wall produces dilation.
• And, chronic infection and inflammation further impair mucociliary clearance.

Pause for a moment and consider where and how some of the causes of bronchiectasis promote this cycle: cystic fibrosis increases mucus production; infection, especially by antibiotic-resistant bacteria, cause chronic and harmful inflammation, and immune deficiencies fail to clear infections effectively.

• Despite the fact that medium-sized airways are dilated in bronchiectasis, they can also become obstructed by recurrent inflammation and infection and mucus accumulation.
• Furthermore, smaller, downstream airways, which significantly impact airflow, can become obstructed by the inflammation and infections.
  – Thus, the complications we discussed earlier, including hypoxemia and right heart failure, can occur.

###Bronchiolitis

• Common in children under two years of age.
• It is most often caused by RSV, though rhinovirus and parainfluenza virus can also cause bronchiolitis.
• Pathogenesis: bronchiolitis occurs when the small bronchial tubes become inflamed, necrotic, and, subsequently, narrowed by mucus and debris.
  – As a result, that some alveoli collapse because air cannot be delivered to them, whereas low-oxygen air is trapped in other alveoli.
• Signs and symptoms:
  – Infants can experience fever, congestion or runny nose, coughing, and wheezing. Indicate that cyanosis, particularly of the lips and nail beds, can occur as the result of reduced oxygen levels.
  – Other signs of bronchiolitis include: rapid, shallow breathing and/or apnea, with wheezing and crackling.
  – Infants struggling to breath may grunt and, as a result of accessory muscle involvement and straining, retractions may be observed – look for “sucking in” of the skin around the base of the neck as the infant struggles to bring in air.
  – Due to congestion and obstructed breathing, infants may also have difficulty bringing in foods and liquids, which can lead to dehydration.