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![Pathogenesis
• The most widely cited mechanism of infectious bronchiectasis
is the “vicious cycle hypothesis,” in which susceptibility to
infection and poor mucociliary clearance result in microbial
colonization of the bronchial tree.
• The ensuing host response, immune effector cells
(predominantly neutrophils), neutrophilic proteases (elastase),
reactive oxygen intermediates (eg, hydrogen peroxide
[H2O2]), and inflammatory cytokines, creates transmural
inflammation, mucosal edema, cratering, ulceration, and
neovascularization in the airway](https://image.slidesharecdn.com/bronchiectasis-200801134915/75/Bronchiectasis-9-2048.jpg)
![Cont…
iv. inhalation of aerosolized antibiotics [e.g., tobramycin
inhalation solution (TOBI)] by select patients on a rotating
schedule (e.g., 30 days on, 30 days off) with the goal of
decreasing the microbial load without encountering
the side effects of systemic drug administration
v. Intermittent administration of IV antibiotics (e.g., “clean-
outs”) for patients with more severe bronchiectasis and/or
resistant pathogens. In addition, ongoing, consistent
attention to bronchial hygiene can promote secretion
clearance and decrease the microbial load in the airways.](https://image.slidesharecdn.com/bronchiectasis-200801134915/75/Bronchiectasis-32-2048.jpg)
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Bronchiectasis
Bronchiectasis is a condition characterized by the irreversible dilation of airways, categorized into cylindrical, varicose, and cystic forms, often resulting from both infectious and non-infectious causes. Clinical features include a persistent productive cough, sputum production, and breathlessness, with a diagnosis supported by imaging and sputum analysis. Treatment focuses on infection control, improving airway clearance, and managing exacerbations, with considerations for surgery or lung transplantation in advanced cases.
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Bronchiectasis
- 1.
- 2. Outline i. Introduction ii. Epidemiology iii.Aetiology iv. Pathogenesis v. Clinical presentation vi. Diagnosis. vii. Treatment
- 3. Introduction • Bronchiectasis refersto the congenital/acquired irreversible airway dilation that involves the bronchi/bronchioles in either a focal or a diffuse manner and that classically has been categorized as: i. Cylindrical or Tubular (the most common form) ii. Varicose, or cystic.
- 4. Epidemiology • Varies greatlywith the underlying etiology. • E.g., in CF often develop significant clinical bronchiectasis in late adolescence or early adulthood, although atypical presentations of CF in adults in their 30-40’s are also possible. In contrast, bronchiectasis resulting from MAC infection classically affects nonsmoking women older than age 50 years. • Incidence of bronchiectasis increases with age. • F>M • More in those with disadvantaged socio-economic status
- 5. Cont… • Highly prevalentwhere TB is prevalent: associated extrinsic compression of the airway by enlarged granulomatous lymph node and/or from development of intrinsic obstruction as a result of erosion of a calcified lymph node through the airway wall (e.g., broncholithiasis) • Increased incidence in those with malnutrition
- 6. Aetiology • Bronchiectasis canarise from infectious or noninfectious causes. • Up to 25–50% of cases the causes can not be identified (idiopathic) • Clues to the underlying aetiology are often provided by the pattern of lung involvement. i. Focal bronchiectasis = in a localized area of the lung and can be a consequence of obstruction of the airway—either extrinsic (e.g., due to compression by adjacent lymphadenopathy or parenchymal tumor mass) or intrinsic (e.g., due to an airway tumor or aspirated foreign body, a scarred/stenotic airway, or bronchial atresia from congenital underdevelopment of the airway).
- 7. Cont… ii. Diffuse bronchiectasis=widespread changes throughout the lung and often arises from an underlying systemic or infectious disease process and cigarette/tobacco smoking. • More of Central airways involvement: allergic bronchopulmonary aspergillosis (ABPA)which an immune- mediated process, also cartilage deficiency due tracheobronchomegaly (Mounier-Kuhn syndrome) and Williams-Campbell syndrome.
- 8. Cont… • More upperlung fields involvement: cystic fibrosis (CF) and postradiation fibrosis. • Lower lung fields involvement: chronic recurrent aspiration (e.g., due to esophageal motility disorders like those in scleroderma), end-stage fibrotic lung disease (e.g., traction bronchiectasis from idiopathic pulmonary fibrosis), or recurrent immunodeficiency-associated infections (e.g., hypogammaglobulinemia). • Predominantly Midlung fields MAC infections dyskinetic/ immotile cilia syndrome = Kartagener’s syndrome.
- 9. Pathogenesis • The mostwidely cited mechanism of infectious bronchiectasis is the “vicious cycle hypothesis,” in which susceptibility to infection and poor mucociliary clearance result in microbial colonization of the bronchial tree. • The ensuing host response, immune effector cells (predominantly neutrophils), neutrophilic proteases (elastase), reactive oxygen intermediates (eg, hydrogen peroxide [H2O2]), and inflammatory cytokines, creates transmural inflammation, mucosal edema, cratering, ulceration, and neovascularization in the airway
- 10. Cont… • Some organisms,such as Pseudomonas aeruginosa, exhibit a particular propensity for colonizing damaged airways and evading host defense mechanisms. • Impaired mucociliary clearance can result from inherited conditions such as CF or dyskinetic cilia syndrome, and it has been proposed that a single severe infection (e.g., pneumonia caused by Bordetella pertussis or Mycoplasma pneumoniae) can result in significant airway damage and poor secretion clearance.
- 11. Cont… • The presenceof the microbes incites continued chronic inflammation, with consequent damage to the airway wall, continued impairment of secretion and microbial clearance, and ongoing propagation of the infectious- inflammatory cycle. • Moreover, it has been proposed that mediators released directly from bacteria can interfere with mucociliary clearance
- 12. Cont… • Classic studiesof the pathology of bronchiectasis from the 1950s demonstrated significant small-airway wall inflammation and largerairway wall destruction as well as dilation, with loss of elastin, smooth muscle, and cartilage. • It has been proposed that inflammatory cells in the small airways release proteases and other mediators, such as reactive oxygen species and proinflammatory cytokines, that damage the larger-airway walls… chronic inflammation destroy the elastin and cartilage which causes dilation and weakening of the bronchial walls
- 13. Cont… • Furthermore, theongoing inflammatory process in the smaller airways results in airflow obstruction. • It is believed that antiproteases, such as α1 antitrypsin, play an important role in neutralizing the damaging effects of neutrophil elastase and in enhancing bacterial killing. • In addition to emphysema, bronchiectasis has been observed in patients with α1 antitrypsin deficiency.
- 14. Cont… • Proposed mechanismsfor noninfectious bronchiectasis include immune-mediated reactions that damage the bronchial wall (e.g., those associated with systemic autoimmune conditions such as Sjögren’s syndrome and rheumatoid arthritis). • Traction bronchiectasis refers to dilated airways arising from parenchymal distortion as a result of lung fibrosis (e.g., postradiation fibrosis or idiopathic pulmonary fibrosis).
- 15. Clinical features • Mostcommon clinical presentation = persistent productive cough with ongoing production of thick, mucopurulent tenacious sputum. • Hemoptysis • Dyspnoea • Wheezing (bases of the lung) • Chest pain
- 16. Physical findings • Cachexia •Crackles and wheezing on lung auscultation • ??Clubbing of the digits = sometimes. • Mild to moderate airflow obstruction is often detected on pulmonary function tests, overlapping with that seen at presentation with other conditions, such as COPD. Acute exacerbations of bronchiectasis are usually characterized by changes in the nature of sputum
- 17. Diagnosis • Suggestive hxof persistent chronic cough and sputum production • Physical exam paying attention to the Respiratory system exam • Sputum for Gram stain, culture and sensitivity, AFB, GeneXpert • Bronchoalveolar lavage (BAL) fluid sample • FBP • Spirometry: reduced or normal FVC, low FEV1 and low FEV1/FVC ratio • Imaging i. CXR ii. CT Chest iii. Bronchoscopy
- 18. Radiology • CXR: nonspecific however presence of “tram tracks” can be seen • Chest CT = more specific for bronchiectasis = imaging modality of choice for confirming the diagnosis. CT findings include airway i. Dilation (detected as parallel “tram tracks” or as the “signet-ring sign” ii. lack of bronchial tapering iii. Bronchial wall thickening in dilated airways, inspissated secretions (e.g., the “tree-in-bud” pattern), or cysts emanating from the bronchial wall (especially pronounced in cystic bronchiectasis)
- 21. Rx • Rx ofinfectious bronchiectasis is directed at the control of active infection and improvements in secretion clearance and bronchial hygiene so as to decrease the microbial load within the airways and minimize the risk of repeated infections. • Antibiotic therapy: targeting the causative or presumptive pathogen (with H. influenzae and P. aeruginosa isolated commonly) should be administered in acute exacerbations, usually for a minimum of 7–10 days. • MAC strains are the most common NTM pathogens, and the recommended regimen of a macrolide combined with rifampin and ethambutol.
- 23. Bronchial hygiene • Enhancingsecretion clearance in bronchiectasis: i. Hydration and mucolytic administration: mucolytic dornase (DNase) is recommended routinely in CF-related bronchiectasis but not in non-CF bronchiectasis due to lack of efficacy and potential harm in the non-CF population ii. Aerosolization of bronchodilators iii. Hyperosmolar agents (e.g., hypertonic saline) iv. Chest physiotherapy (e.g., postural drainage, traditional mechanical chest percussion via hand clapping to the chest, or use of devices such as an oscillatory positive expiratory pressure flutter valve or a high-frequency chest wall oscillation vest).
- 24. Anti-inflammatory therapy • Hasbenefit in bronchiectasis and may improve dyspnea, decreased need for inhaled β-agonists, and reduced sputum production. • Inhaled/Oral glucocorticoids. • Do not significantly improve lung function or bronchiectasis exacerbation rates have been observed • ABPA: prolonged course of treatment with the oral antifungal agent itraconazole and oral corticosteroids
- 25. Refractory cases • Surgerycan be considered, with resection of a focal area of suppuration. • In advanced cases, lung transplantation if the patient is a candidate
- 26. Complications • Recurrent respiratoryinfections • Microbial resistance due to prolonged/repeated antibiotic use • Toxicity from repeated antibiotics use • Hemorrhage into bronchial tree resulting into hemoptysis • Cor pulmonale • Lung abscess
- 27. Bronchiectasis exacerbation • Increasedsputum over baseline, thicker sputum, low grade fever, increased of shortness of breath and pleuritic chest pain. • Most of these patients will need to be admitted • Most commonly due to acute bacterial infections • Of concern is P. aeruginosa infection which can be lethal
- 28. Rx of exacerbation •O2 therapy titrated to 90% • Routine labs, sputum cultures for Pseudomonas, Mycoplasma • Broad spectrum antibiotics: if CF, assume Pseudomonas • Beta agonists bronchodilators • Chest physiotherapy, Pulmonary toilet (can use spirometry)/bronchial hygiene • Expectorants can be given
- 29. Prognosis • Outcomes ofbronchiectasis vary widely with the underlying etiology and may also be influenced by the frequency of exacerbations and (in infectious cases) the specific pathogens involved.
- 30. Prevention • Vaccination ofpatients with chronic respiratory conditions (e.g., influenza and pneumococcal vaccines) • Reversal of an underlying immunodeficient state (e.g., by administration of gamma globulin for immunoglobulin- deficient patients) • Smoking cessation. • After resolution of an acute infection in patients with recurrences (e.g., ≥3 episodes per year), the use of suppressive antibiotics to minimize the microbial load and reduce the frequency of exacerbations has been proposed, although there is less consensus with regard to this approach in non-CF-associated bronchiectasis than there is in patients with CF-related bronchiectasis.
- 31. Cont… • Possible suppressivetreatments include i. Administration of an oral antibiotic (e.g., ciprofloxacin) daily for 1–2 weeks per month ii. Use of a rotating schedule of oral antibiotics (to minimize the risk of development of drug resistance) iii. Administration of a macrolide antibiotic daily or three times per week (with mechanisms of possible benefit related to non-antimicrobial properties, such as anti-inflammatory effects and reduction of gram-negative bacillary biofilms)
- 32. Cont… iv. inhalation ofaerosolized antibiotics [e.g., tobramycin inhalation solution (TOBI)] by select patients on a rotating schedule (e.g., 30 days on, 30 days off) with the goal of decreasing the microbial load without encountering the side effects of systemic drug administration v. Intermittent administration of IV antibiotics (e.g., “clean- outs”) for patients with more severe bronchiectasis and/or resistant pathogens. In addition, ongoing, consistent attention to bronchial hygiene can promote secretion clearance and decrease the microbial load in the airways.
- 33. References • Harrison's Principlesof Internal Medicine; 18Th Edition • UpToDate