Exam 2 - Pulmonary lecture 2 Flashcards
What does dependent mean regarding the lungs?
Having a greater effect from gravity; being closer to the earth
What force opposes the intrapleural pressure?
Elastic recoil or transpulmonary pressure
What must be the relationship between intrapleural and elastic recoil pressure to allow for inspiration and expiration?
Elastic recoil > Intrapleural = Expiration
Intrapleural > Elastic recoil = Inspiration
What is the formula to calculate alveolar pressure?
PA = PIP + PTP
What is another term for elastic recoil pressure?
Transpulmonary Pressure
What is the formula for transpulmonary pressure?
PTP = PA - PIP
How is transpulmonary pressure related to lung volumes?
Transpulmonary pressure is the pressure available to fill the lungs - direct relationship
When PTP is high there should be high lung volumes
When PTP is low there should be low lung volumes
What are the top 2 variables that passively influence PVR?
- Gravity
- Lung volumes
At what lung capacity is PVR the lowest?
Why?
Functional Residual Capacity (FRC)
We spend most of our time in this volume, so it makes sense that resistance would be lowest during the volume we have most often
What happens to PVR as we gain or lose volume from FRC?
PVR increases in both directions
PVR in small alveolar vessels are most effected by ?
Alveolar volume
PVR in larger extraalveolar vessels are most effected by?
Intrapleural pressure
When PIP is more negative, it stretches and widens out the vessel, lowering PVR
The opposite occurs when PIP is more positive
What is PVR in extraalveolar vessels at low and high lung volumes?
Low lung volumes - PVR is high (PIP is more positive)
High lung volumes - PVR is low (PIP is more negative)
Explain why PVR goes up in extraalveolar vessels when volumes get closer to RV?
To get to RV, we have to forcefully expire which increases PIP - narrowing the vessels and increasing their resistance
What happens to PVR in alveolar capillaries with increased alveolar volume?
PVR increases because the alveolar capillaries which are imbedded in the alveolar walls become elongated and more narrowed = increased PVR
How does right heart CO effect PVR?
- When RH CO is higher, PVR decreases
- This is because the pulmonary vessels are highly compliant and will stretch out decreasing PVR
- Also, an increased CO will recruit more areas of the lungs which also decreases reistance
Are we using all of our alveoli all the time?
No, we may only be using 1/3 for normal breathing
What are the passive factors that influence PVR?
What active factors increase PVR?
These things cause constriction of pulmonary vessels
HEAT - mediators
What active factors decrease PVR?
These things cause vasodilation of pulmonary vessels
What is normal atmoshpheric pressure at sea level?
760 mmHg or torr and 1 atm
How does elevation effect atmospheric pressure?
Low altitudes have higher pressures
High altitudes have lower pressures
What concentration are N2, O2, and CO2 in the atmosphere?
N2 = 79%
O2 = 21%
CO2 = 0.04 %
These concentrations do not change with altitude
How can you calculate a gases partial pressure?
Partial pressure = Total pressure (atmospheric) x [gas]
