Alveolar Gas Exchange Flashcards
What is the principle function of the lungs and thorax?
respiration
What does gas exchange depend on?
ventilation, profusion, barriers (air-liquid interface)
The lung gas exchange begins at the level of (blank)
respiratory bronchiole
What does fick’s law tells us?
diffusion is proportional to surface area and inversely proportional to thickness of surface
In normal lungs is greater at the (Blank) and becomes progressively less towards the (blank).
In supine position this effect is (blank(
base
apex
less
Intrapleural pressure is more negative at the (blank) or compared to the bottom
top
The change in ventiliation per unit volume is greater at the (blank) than the (blank).
base
apex
Blood flow decreases from the (blank) as compared to ventilation which is less step but still decreases from (blank) of lung
bottom to the top
bottom to top
In the upright position there is a linear decrease of blood flow from the base to the apex, and (blank) from hilum to outer peripheral lung near pleura.
decreases
It is the alteration and abnormalities of the V/q rations that causes what?
hypoxia and disease states (ideal is v=q or a v/q=1)
What is the normal range of PaO2 (arterial)
70-100
Is PAO2 equal to PaO2?
no
decreased PaO2= (blank)
hypoxemia
What are basic causes of hypoxemia?
decreased PAO2 hypoventilation reduced FiO2 or low atmospheric pressure venitlation-perfusion mismatch diffusion defects right to left shunt
The higher the altitude the lower the (blank)
barometric pressure and PIO2
What is the alveolar gas equation?
PAO2=PIO2 or FIO2(Pb-Ph20)-PCO2/R
What is a normal P(A-aO2) or A-a gradient or PAO2-PaO2 difference?
3-15 on room air
How can you have hypoxemia due to hypoventilation?
you have decreased PAO2 an PaO2 even with normal A-a difference, just means both are low
As you decrease alveolar ventilation, your PACO2 will (blank)
increase
What causes hypoxemia due to hypoventilation?
sedation, neuromuscular diseases, muscle disorders, pharmacologic blockade, high spinal cord lesions, Brainstem infarction/trauma
If you have an abnormal A-a gradient what does this tell you?
If you have a normal A-a gradient but low PaO2 and PAO2 what does this tell you?
intrinsic lung problem
problems with respiration (breathing messed up)
How can you tell a person is brain death?
give pure oxygen to 100% point, stop giving it to them and watch to see if they take a breath, their CO2 should increase significantly if they have brain death. You take an ABG and check CO2 levels, if high=brain death
(blank) V/Q ratio indicates increased dead space ventilation or increased Vd (there is ventilation to non-perfused lung units->happens with pulmonary emboli)
high
COPD can do what to your ventilation and profusion? What is your VQ ratio?
reduce it (destroy alveolar membrane and induce hypoxic vasoconstriction) less than 1 and this person is unhealthy
The thin and abundant surface area of the NORMAL alveolar-capillary membrane is very well suited for (blank) of gas.The air-liquid interface normally avidly allows (blank). Thickness of RBC can is a barrier for (blank).
diffusion
diffusion
diffusion
When the alveolar-capillary membrane is compromised you can get what? What will this cause?
fluid-pulmonary edema diffuse pneumonitis fibrosis (scarring disease) bronchoalveolar destruction HYPOXIA
What are these: Right to left shunts: Intra-cardiac shunts (hole in cardiac chamber) -Patent foramen -Atrial septal defects -Ventricular septal defects -Congenital heart disease Extra-cardiac shunts -Pulmonary AVMs (arteriovenous malformations) -A-V fistulas
shunts that cause hypoxemia
In a right to left shunt what happens to your V/Q ratio?
it approaches zero because your profusion is normal but you are bypassing your alveoli so you are having no ventilation
Point is that in a right to left shunt there is minimal effect on (blank) but dramatic effect on (blank)
PaCO2
PaO2
In a normal healthy person, the physiological shunt is rarely over (blank)
4%.
What is hypoxemia?
Lower than normal PaO2 for a person’s age
Low CaO2
What are tools to approach a patient with?
hypoxemia ABG values PaO2 PaCO2 Calculated PAO2 P(A-a)O2 difference
