PULMONARY 04: VENTILATION Flashcards
What is the relationship between partial pressures and total pressures of a gaseous system?
The partial pressures and volumes of a system are equal to the total pressures and volumes of a given system
Do conducting airways participate in gas exchange
no
Do partial pressures of gasses change in the conducting zones?
No, they aren’t participating in gas exchange
At what point do partial pressures of gasses begin changing?
At the alveoli
What is the alveolar gas equation?
Partial pressure of oxygen in the alveoli is equal to:the specific
Atmospheric pressure minus humidity pressure , multiplied by the specific amount of oxygen in the atmosphere. From all of this, you subtract the partial pressure of CO2 in the alveoli divided R, which is the ratio of CO2 eliminated to O2 consumed ; standard R is about 0.8 but can change with metabolism
What is the relationship between CO2 and alveolar ventilation?
Inverse; you know this because if the alveoli are being ventilated the CO2 should be expelled
What effect does gravity have on ventilation?
Gravity means there is greater ventilation in the base rather than the apex
How can we measure anatomical dead space?
Fowler’s method; breathe in pure oxygen and determine when you start detecting nitrogen (which should have been in lungs from previous breath)
What is physiological dead space?
Anatomical dead space + alveolar dead space
What is alveolar dead space?
Alveoli which are ventilated by not pefused
How do we measure physiological dead sace?
You hhave someone breathe in pure oxygen, but instead of looking at oxygen in the readout you’re interested in CO2 coming out of expired air. Then you compare this to co2 in the blood. If there is a higher ppco2 in the blood and whwat you are exhaling, this tells you there is something wrong with blood CO2 getting into alveolar co2.
This means there are areas which are being entlated, but not perfused
what is the composition of the atmosphere?
Mostly nitrogen (79%) and oxygen (21%)
Atmospheric pressure of oxygen
160mmHg
What is the respiratory quotient (R)
The ratio of CO2 eliminated to O2 consumed
An R of 1 means our tissue produced one molecule of CO2 for every O2 consumed
Alveolar CO2 is proportional to what
CO2 production
What is the single breath nitrogen test
You have someone breathe in 100% oxygen
Then they breahte it out
At first you just have oxygen coming out
Then as you get into further into the airways you have ntirogen coming out as well. Eventually where there is uniform ventilation this will plateau. But as you force more air out and get to areas that aren’t uniformally ventilated this rises to include more nitrogen
