Bronchiectasis - Respiratory Care Pathophysiology (Ch.16)

Bronchiectasis - Study Notes (Ch. 16)

• Definition

  • Bronchiectasis is characterized by chronic dilation and distortion of one or more bronchi as a result of extensive inflammation and destruction of bronchial wall components (cartilage, blood vessels, elastic tissue, smooth muscle).
  • Often limited to a lobe or segment and frequently found in the lower lobes.
  • Smaller bronchi are predominantly affected.
  • Mucociliary clearance mechanism is impaired.

• Three forms of bronchiectasis

  • Cylindrical (Tubular)
  • Varicose (Fusiform)
  • Cystic (Saccular) — most severe

• Anatomic imaging (Fig. 13-1; summary)

  • Varicose bronchiectasis (irregular, beaded appearance)
  • Cylindrical bronchiectasis (uniform dilation)
  • Cystic (saccular) bronchiectasis (broad, bulbous dilations at the ends)
  • Common associated findings: excessive bronchial secretions and atelectasis

• Etiology and epidemiology

  • Most causes involve a combination of bronchial obstruction and infection.
  • Incidence (non–CF bronchiectasis) in the US: 4.2\ ext{per} \ 100{,}000 in young adults.
  • Causes categorized as:
  • Acquired bronchial obstruction
  • Congenital anatomic defects
  • Immunodeficiency states
  • Abnormal secretion clearance
  • Miscellaneous disorders (e.g., alpha-1 antitrypsin deficiency)

• Anatomic alterations of the lungs

  • Chronic dilation and distortion of bronchial airways
  • Excessive production of foul-smelling sputum
  • Bronchospasm
  • Hyperinflation of alveoli (air-trapping)
  • Atelectasis and parenchymal fibrosis
  • Hemorrhage secondary to bronchial arterial erosion

• Causes of bronchiectasis (expanded)

  • Acquired bronchial obstruction: foreign body (peanuts, chicken bone, teeth), mucoid impaction, tumors, COPD
  • Congenital anatomical defects that may cause obstruction
  • Immunodeficiency states
  • Abnormal secretion clearance
  • Cystic Fibrosis: causes 50 ext{\%} of bronchiectasis in the US
  • Kartagener’s syndrome: triad of bronchiectasis, dextrocardia, and rhinosinusitis; defective cilia
  • Account for about 20 ext{ extperthousand} of all congenital bronchiectasis
  • Miscellaneous disorders (see table 14-1)

• Diagnosis

  • High-resolution computed tomography (HR-CT)
  • Spirometry to determine whether bronchiectasis is primarily obstructive or restrictive
  • Arterial blood gas (ABG) to assess severity (mild, moderate, severe)

• Obstructive vs. restrictive bronchiectasis

  • Disease can produce obstructive, restrictive, or mixed patterns.
  • Obstructive: majority of airways are partially obstructed.
  • Restrictive: majority of airways are completely obstructed; distal alveoli collapse and atelectasis.
  • If disease is limited to a small portion of the lung, typical clinical manifestations may be absent.

• Clinical manifestations

  • Increased respiratory rate (RR), heart rate (HR), and blood pressure (BP)
  • Accessory muscle use
  • Pursed-lip breathing (more common in obstructive physiology)
  • Increased anteroposterior (A-P) diameter (often in obstructive disease)
  • Cyanosis
  • Digital clubbing
  • Peripheral edema, venous distension, enlarged/tender liver
  • Cough with sputum production, hemoptysis
  • Sputum characteristics: large amounts of foul-smelling sputum; a 24-hour collection may separate into 3 layers

• Chest assessment findings (by pattern)

  • Primarily obstructive
  • Decreased tactile and vocal fremitus
  • Hyperresonant percussion note
  • Diminished breath sounds
  • Wheezing
  • Crackles
  • Primarily restrictive (areas of atelectasis/consolidation)
  • Increased tactile/vocal fremitus
  • Bronchial breath sounds
  • Crackles
  • Whispered pectoriloquy
  • Dull percussion

• Pulmonary function test findings — obstructive pattern (moderate to severe bronchiectasis)

  • Spirometry: FVC ↓, FEV1 ↓, FEV1/FVC ↓, FEF25-75 ↓, FEF50% ↓, FEF200-1200 ↓, PEFR ↓, MVV ↓
  • Lung volumes: VT (tidal volume) may be normal or ↓; IRV ↓ or normal; ERV ↓ or normal; RV ↑; VC ↓ or normal; IC ↓ or normal; FRC ↑ or normal; TLC ↑ or normal; RV/TLC ↑ or normal
  • Note: Hyperinflation is common with obstructive disease; overall pattern tends toward air-trapping

• Pulmonary function test findings — restrictive pattern (moderate to severe bronchiectasis)

  • Spirometry: FVC ↓, FEV1 ↓, FEV1/FVC ratio may be normal or ↑, FEF25-75 ↓, FEF50% ↓, FEF200-1200 ↓, PEFR ↓, MVV ↓
  • Lung volumes: VT ↓, IRV ↓, ERV ↓, RV ↓ or normal, VC ↓, IC ↓, FRC ↓ or normal, TLC ↓, RV/TLC ratio ↓ or normal

• Arterial blood gases (ABG)

  • Mild to moderate bronchiectasis (acute stage): Acute alveolar hyperventilation with hypoxemia (acute respiratory alkalosis)
  • pH ↑, PaCO2 ↓, HCO3− ↓, PaO2 ↓, SaO2/SpO2 ↓
  • Severe stage: Chronic ventilatory failure with hypoxemia (compensated respiratory acidosis)
  • pH near normal or ↓, PaCO2 ↑, HCO3− ↑, PaO2 ↓, SaO2/SpO2 ↓
  • Time course figure (PaO2 and PaCO2 trends) illustrates how airway disease evolves from acute hyperventilation to chronic ventilation abnormalities
  • Note: Acute ventilatory changes can be superimposed on chronic ventilatory failure; clinicians must recognize two dangerous ABG patterns:
  • Acute alveolar hyperventilation on chronic failure: possible impending acute ventilatory failure
  • Acute ventilatory failure (acute hypoventilation) on chronic failure

• Abnormal laboratory tests and procedures

  • Increased hematocrit and hemoglobin
  • Elevated white blood cell count if acutely infected
  • Sputum examination cultures often show:
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Pseudomonas aeruginosa
  • Anaerobic organisms

• Radiologic findings

  • Chest radiograph (general):
  • Obstructive pattern tendencies: translucent (dark) lung fields; depressed/flattened diaphragms; long/narrow heart; possible cardiac enlargement with heart failure; areas of consolidation/atelectasis; tram-tracks due to bronchial wall thickening
  • Restrictive pattern tendencies: atelectasis and consolidation; infiltrates suggesting pneumonia; increased opacity
  • Tram-tracking sign: dilated bronchial walls create parallel linear markings
  • Signet ring sign (noted in cystic fibrosis): radiologic hallmark on imaging
  • Typical radiographs include examples of cylindrical, varicose, and cystic bronchiectasis with corresponding volume loss and changes in lung architecture

• Radiologic patterns and examples (imaging terminology)

  • Helium/airway topology images demonstrate basal involvement with volume loss and tram-tracking
  • Cylindrical bronchiectasis: parallel, non-tapering airways extending toward the periphery
  • Varicose bronchiectasis: irregular, beaded appearance of bronchi
  • Cystic (saccular) bronchiectasis: clustered, sac-like dilations often in lower lobes

• General management of bronchiectasis

  • Core goals:
  • Controlling pulmonary infections
  • Controlling airway secretions
  • Preventing complications

• Respiratory care protocols

  • Oxygen therapy as needed to maintain adequate saturations
  • Bronchopulmonary hygiene (airway clearance techniques)
  • Lung expansion therapies (deep breathing, coughing, incentive spirometry)
  • Aerosolized medication therapy
  • Mechanical ventilation (as indicated by clinical status)
  • Other medications: Expectorants; Antibiotics (guided by sputum culture)

• Practical and clinical implications

  • Early and accurate differentiation between obstructive and restrictive patterns guides therapy (airway clearance strategies, inhaled therapies, and ventilation planning).
  • Regular monitoring of ABG and O2 saturation is essential due to risk of acute on chronic ventilatory failure.
  • Sputum culture-directed antibiotics help manage chronic infection and prevent exacerbations; Pseudomonas involvement necessitates specific antibiotic strategies.
  • Imaging findings (HR-CT) are critical for diagnosis and for monitoring disease progression and response to therapy.
  • Management emphasizes preventing infections, preserving lung function, and maintaining quality of life through pulmonary rehab and airway clearance.

• Foundational and real-world relevance

  • In CF patients, bronchiectasis is a major complication; the “signet ring” sign on imaging is a recognized CF marker.
  • Kartagener’s syndrome (primary ciliary dyskinesia) highlights the role of ciliary function in airway clearance and bronchiectasis development.
  • Understanding bronchiectasis patterns (obstructive vs restrictive) informs prognosis and tailored rehabilitation programs.

• Key terminology to remember

  • Bronchiectasis: chronic dilatation/distortion of bronchi
  • Tram-tracking: bronchial wall thickening pattern on radiographs
  • Signet ring sign: radiologic sign often associated with CF-related bronchiectasis
  • Obstructive vs restrictive physiology: determines spirometry patterns and ABG implications

• Summary takeaways

  • Bronchiectasis involves chronic airway dilation with mucus plugging and repeated infection, frequently affecting lower lobes and small airways.
  • It presents in multiple forms (cylindrical, varicose, cystic) with varying severity and radiologic features.
  • Diagnosis relies on HR-CT, spirometry, and ABG to define pattern and severity.
  • Management focuses on infection control, airway clearance, and lung expansion, with oxygen, bronchodilators, and antibiotics as needed.
  • ABG and laboratory findings help stage disease and detect acute on chronic deterioration; radiology provides essential structural context.

• Important formulas and numerical references

  • Incidence of non–CF bronchiectasis: 4.2\ ext{per} \ 100{,}000
  • Proportion due to Cystic Fibrosis in the US: 50\%
  • Common sputum finding patterns: 24-hour sputum may separate into 3 layers (gross observation)

• Connections to broader topics

  • Relationship between chronic infection, inflammation, and airway remodeling as a pathophysiologic mechanism for bronchiectasis
  • Role of mucus clearance defects (ciliary disorders) in chronic lung disease
  • Importance of imaging modalities (HR-CT) in evaluating small-airway diseases beyond bronchitis, COPD, and interstitial lung disease

• Ethical and practical implications

  • Shared decision-making about long-term antibiotic use and potential resistance
  • Access to respiratory therapy (hygiene techniques, rehabilitation) and home oxygen therapy when needed
  • Need for regular monitoring to adjust therapies and prevent hospitalizations due to exacerbations