Airway mucosal Function Flashcards
Week 8
Functions of airway mucous
Barrier to water loss
Barrier to microbial invasion
Clearance of inhaled foreign matter
Mucosal dehydration consequences
Increased viscosity and elasticity
Adherence to airway wall (decreased ability to clear)
What is the Pathogenesis of ALL common airway diseases?
Excessive mucous = impaired clearance
What are the 2 principal cells of surface epithelium?
Ciliated
Secretory (cara/club, goblet and serous)
Where do we fine submucosal glands?
Nose, trachea and bronchi
What conditions lead to excessive mucous and how?
Smoking, infection, oxidative stress and pathogenic factors
= secretory cell hypertrophy and goblet cell hyperplasia.
What is the dominant variable in determining mucus clearance?
ASL hydration
Why is it important for ASL to be hydrated?
- increases mucus transport rates (movement)
- maintains PCL depth so that cilia can beat
Mechanism of ASL secretion
Epithelial cell active ion transport:
Cl and HCO3 secretion –>
CFTR inhibits ENaC activity –>
Decreased Na reabsorption –>
CFTR stimulates 2Cl channels and a Cl/HCO3 exchanger –>
Na and water follow gradient in paracellular pathways –>
Increased ASL hydration and pH.
What are alveolar macrophages and what occurs if they die?
gulf and phagocytose foreign particles and deliver to mucociliary escalator, lymphatics and blood.
die: Release trypsin –> tissue damage (digests elastin)
What are the consequences of Primary Cilia Dyskineses?
Stagnation and accumulation of mucous (early onset refractory or recurrent airway infections)
Infertility: defect in flagella of spermatozoa and cilia of uterine tubes
What is the mechanistic change of COPD?
Increased airway resistance (obstruction)
What are the 3 main mechanisms of airway obstruction?
Conditions within lumen
Causes within wall of airway
Causes outside the airway
What are conditions within lumen that lead to airway obstruction?
Partial occlusion by excessive secretions
= Chronic bronchitis and P Oedema
Aspiration of foreign material
=Localised or complete occlusion
Retained post-op secretions
What are the causes within wall of airway that lead to airway obstruction?
Contraction of bronchial SM
=Asthma
Hypertrophy of mucous glands
=Chronic bronchitis
Inflammation or oedema of airway wall
=Chronic bronchitis and asthma
What are the causes outside the airway that lead to airway obstruction?
Destruction of lung parenchyma
=Emphysema
Localised compression of bronchus
=Enlarged lymph nodes or neoplasm
Peri bronchial oedema
What is COPD-BC?
Excessive production of mucus for most days for at least 3 months in a year for at least the last 2 successive years
COPD-BC pathogenesis
Chronic inflammation triggered by chronic irritation via inhaled substances or infection
treatment of COPD-BC
Liberal fluid intake (hydrates ASL and increases mucus clearance by decreasing mucous viscosity)
physiotherapy (move mucus)
postural changes
bronchodilators, anticholinergics, and corticosteroids
Characteristics of CF classes I-III.
Classic CF, early diagnosis
Increased sweat Cl
Pancreatic insufficiency
characteristics of CF classes IV-VI.
Late diagnosis
Sweat Cl near normal
Pancreatic sufficiency
CF Pathogenesis
Dehydrated ASL ( increased adherence and decreased PCL depth)
Mucous hypersecretion
Acidic ASL from decreased HCO3 transport
Clinical features of CF
Course crackles and bronchial auscultation
Consolidation
Fibrosis and cystic changes
Pulmonary function impact of CF.
Abnormal ventilation distribution
Increased alveolar-arterial difference
Decreased FEV unresponsive to bronchodilators
Increased has trapping
Decreased exercise tolerance
CF management
- antibiotics (treat antibiotics)
- physiotherapy and postural drainage
- mucolytic agents
- CFTR modulators
- lung transplant
what are the causes of Respiratory failure type 1
Ventilation/perfusion mismatch
Increased shunt
Diffusion impairment
Alveolar hypoventilation
Features of resp failure Type 2
Gas exchange failure
Hypoxemia w normocapnia or hypocapnia
PaO2 < 60mmHg
Features of Type 2 Resp Failure
Ventilatory failure
Hypoxemia w hypercarbia
PaO2 < 60mmHg and PaCO2 > 45mmHg
Causes of Type 2 resp failure
Decreased output from central resp centres (drug overdoes, anaesthesia)
Increased dead space (COPD)
Mechanical defect in chest wall (flail chest, kyphoscoliosis)
Inspiratory muscle fatigueq
