Respiratory 23 Flashcards
What is Intrapleural pressure like at the bottom of the lungs?
Intrapleural pressure increases (becomes more negative) at the bottom of the lungs
How does Intrapleural pressure affect ventilation?
Because intrapleural pressure becomes more negative at the bottom of the lungs this increases ventilation to the botom of the lungs
Why do the bottom part of the. lungs receive more ventilation?
Because they are starting more deflated and expand more during inspiration
How can regional differences in lung perfusion be measured?
By injecting a patients with radioactive xenon and seeing the radioactivity in different parts of the lung
Where is perfusion in the lungs higher in an upright subject?
At the base of the lung
What does Perfusion depend on?
Gravity and Posture
What is ventilation and lung perfusion like at the bottom of a lung?
Both ventilation and perfusion are higher at the bottom of the lung
How is V/Q affected from the bottom to the top of the lung?
V/Q increases exponentially from the bottom to the top of the lung
What is the difference between blood flow and alveolar ventilation between the basal and apical lung?
Blood flow and alveolar ventilation are reduced in the apical lung compared to the basal lung
What is the Homeostatic mechanism for Ventilation-Perfusion matching?
Bronchoconstriction of one alveoli means there is less ventilation in the alveoli this will increase the PCO2 and decrease the alveolar PO2 reducing the diffusion from the alveoli to the capillary. This causes Vasoconstriction in the arterioles and blood is diverted to areas where ventilation is still effective
What is Pulmonary Hypoxic Vasoconstriction?
A homeostatic mechanism that causes vasoconstriction in arterioles in the lungs to divert blood flow when low PO2 is sensed in the alveoli
What happens if there is decreased blood flow to an area of the lung?
There will be an increase in alveolar PO2 and a decrease in alveolar PCO2. This induces bronchoconstriction and less air moves into the region with decreased blood flow and more to the region with increased blood flow
