Airway Resistance and Flow Flashcards
What are the components of resistance to airflow?
Lung tissue viscous resistance (10-20%)
Airway resistance (80-90%)
How do you calculate airflow?
Airflow (V) = PB - PA / Raw
Which system has more resistance (cardiac or respiratory)?
Cardiac has more resistance
20 - 30x greater resistance
How do you measure airway resistance?
Raw = PB - PA / V
Where is the major sites of resistance in the respiratory system?
Pharynx - Larynx (40-50%)
Below Larynx in trachea and bronchi down to 7th generation(30-40%)
Airways > 2mm diameter
What is the structure of the airways (trachea and bronchiole) ?
Trachea:
Ciliated epithelium
Cartilage ring
Constant resistance
Bronchiole:
Smooth muscle
ciliated epithelium
Variable resistance.
How is airway resistance controlled?
Airway smooth muscle tone - bronchodilation/constriction
Mucus build up
lung volume - increased transairway pressure and radial traction.
What effect would sympathetic innervation of bronchiole smooth muscle have?
Bronchodilation
Caused by beta receptor agonists, adrenaline, cholinergic antagonists and hypercapnia (High CO2)
What effect would parasympathetic innervation of bronchiole smooth muscle have?
Bronchoconstriction
Caused by cholinergic agonists, beta receptor antagonists, inflammatory mediators (histamine/leukotrienes) and Hypocapnia (low CO2)
What is the effect on breathing by constricting the bronchioles?
increase in airway resistance
Increases the work of breathing.
How can airway resistance changed be measured?
Peak flow measurements
Pulmonary function test (PFT) by spirometry
What are the determinants of peak expiratory flow?
Airway resistance
Generating a pressure gradient
What happens when there is normal elastic recoil of the alveoli and normal airway resistance?
Normal airflow
What happens when there is normal elastic recoil of the alveoli and increased airway resistance?
Decreased airflow
What happens when there is decreased elastic recoil of the alveoli and normal airway resistance?
Decreased airflow
