L13 Mechanics of Ventilation Flashcards
rate of airflow is inversely proportional to what?
airway resistance
due to cross sectional area
Resistance in lower always (small bronchi) is higher or lower than that of the upper airways ?
Lower. Combined cross sectional area is larger in small airways
What is the airflow rate equation
Airflow rate= pressure gradient (Delta P)/ airway resistance (R)
What is the upper airway’s defence mechanisms against collapse?
levator nasealis to flare nostrils
Tensor muscles of pharyngeal walls
Abduction of arytenoid cartilages
Tracheal cartilages
What are some pathological disorders of the upper airways structures than can cause airflow restriction?
facial nerve paralysis DDSP elongated SP Laryngeal hemiplegia Collapsing trachea
How does the lower airway adjust itself
bronchoconstriciton (para)
dilation (sympathetic)
what prevents collapse of the lower airway?
the transmural pressure gradient between the pleural cavity and the lumen of the airways.
What is pulmonary compliance
the ease at which the lung expands within the thorax, thus a measure of distensibility
What dz cause a decrease of pulmonary compliance?
pulmonary fibrosis, decreased CT etc.
What is lung elasticity
the degree of recoil from a stretched state
What confers lung elasticity ?
elastic CT
the surface tension of the fluid lining alveoli
Why is pulmonary surfactant important?!
crucial for lung elasticity!!
Reduces the attraction between water molecules
keeps lungs dry
Why is it important to reduce the attraction of water molecules in the alveoli
would increase surface tension
would increase the lung’s ability to collapse by decreasing its compliance
What does Laplace’s law describe? How does surfactant work to help the lung in terms of this?
the smaller the radius, the higher the collapsing pressure.
A smaller radii means that surfactant molecules would be even closer together…. essentially meaning that they are more greatly reducing surface tension!
