Obstructive Ventilatory Defect Flashcards
How is airway resistance calculated?
Alveoli pressure divided by flow.
What happens to airway resistance with an obstructive ventilatory defect?
Resistance increases.
What is the flow rate?
Unit of air passing per minute.
How is there viscosity in the air?
Flow creates force between air molecules, which causes the viscosity.
When is the viscosity air seriously changed?
During drowning.
What is the difference between laminar and turbulent flow?
Turbulent flow is when air does not flow in a straight line - air fluctuates and vibrates the walls of the tube, causing vibrations. This does not occur with laminar flow.
Why is airway resistance higher in the trachea than in the alveoli?
Because it has a lower surface area than the alveoli.
What happens to the FEV1/FVC ratio with an obstructive defect?
It decreases to below 70% of expected.
What is the main difference between an obstructive and restrictive defect?
Obstructive is an increase in airway, restrictive is a decrease in compliance of lungs.
How can the airway resistance if bronchioles be increased?
Bronchioles are usually held open by outward pressure of alveoli - if alveoli are effected, bronchioles will collapse.
How do inflammatory mediators control airways?
Histamine and arachidonic acid metabolites cause bronchoconstriction.
What do inflammatory mediators come from?
Mast cells.
What is the neuronal control of airways?
Parasympathetic nerves release acetylcholine to cause bronchoconstriction, by increasing calcium ion concentrations. No sympathetic nerve activity.
How do hormones influence airways?
Adrenaline acts at beta-2 receptors to cause relaxation of bronchiole muscles.
What is the musociliary escalator?
Wafting of mucus containing dirt by cilia in the airways. Non specific defence mechanism.
