PSC1002/L15 Ventilation Flashcards
Define elasticity.
Ability of tissue to return to its original state when stretched
Describe PIP between breaths.
Intrapulmonary pressure = atmospheric pressure
Describe PIP during inspiration.
Lung volume increases
PIP decreases
Describe PIP during expiration.
Lung volume decreases
PIP increases
Give the 3 primary physical factors that influence the overall effectiveness of pulmonary ventilation.
Airway resistance
Alveolar surface tension
Lung compliance
What is airway resistance determined by? (4)
Length of system
Airway diameter
Flow
Viscosity of gas
Which of the airways has the highest resistance?
Bronchi
Give 3 conditions which increase the resistance of airways.
Inflammation
Increased mucus secretion
Presence of tumour
Describe central control of the bronchial tone. (2)
Parasympathetic innervation of airways
Bronchoconstriction increases resistance
Describe non-neural control of airways. (2)
Sympathetic B2 receptors present on SM activated by adrenergic agonists
Bronchodilation decreases resistance
Describe the gas-water boundary of the alveoli. (2)
Water molecules form H-bonds
Gases non-polar and no not form H-bonds
When is surface tension at its highest and why? (2)
When alveoli are at their smallest diameter during expiration
Increased ST resists ability of alveolus to inflate
What is the law of LaPlace? (2)
Small alveoli will be more difficult to inflate than larger alveoli
Surfactant reduces surface tension
What does a high amount of unopposed surface tension cause in alveoli?
Collapse during expiration (atelectasis)
How does surfactant disrupt the cohesive force of H-bonding in water? (2)
Contains proteins and phospholipids
Polar and non-polar end
What does surfactant allow alveoli to do and where is it more concentrated because of this? (2)
Remain partially open even during expiration
In smaller alveoli to increase stability
Define lung compliance.
The ability of the chest wall/lungs to stretch/distend
What affects lung compliance? (3)
Alveolar surface tension
Distensibility of elastic tissue of lung
Ability of chest wall to move or stretch during inspiration
How does emphysema affect lung compliance? (2)
Shift to left
Increased lung compliance
How does fibrosis affect lung compliance? (2)
Shift to right
Decreased lung compliance
What is forced vital capacity (FVC)?
Maximum inspiration followed by maximum expiration as fast as possible
What if FEV1?
Forced expiratory volume in 1 second
First second of forced expiration
What is a normal FEV1/FVC value?
80%
What effect does restrictive lung disease have on FVC and FEV1?
FVC reduced
FEV1 close to normal
What effect does obstructive lung disease have on FVC and FEV1?
FVC close to normal
FEV1 reduced
