repiratory gases, etc
what is the normal respiratory exchange ratio and how to find it?
0.8 CO2 excreted/O2 consumed
what is a normal A-a gradient?
10. If it's smaller there is no problem, but if larger there is a problem because it's saying oxygen is coming into the alveoli but not the artery
what partial pressure of inspired oxygen should be used when breathing ambient air at sea level?
150 mm Hg
what percent is oxygen in the air?
21%
what percent is CO2 in the air?
<1%
What happened to a patient's alveolar ventilation to cause his partial pressure of arterial CO2 to go from normal 40 to 80?
Alveolar ventilation decreased. This can be from overdose on barbiturates
What is the partial pressure and percent of oxygen and CO2 in alveolar air at sea level?
O2: 100 (13.2%) CO2: 40 (5.3%)
What is the partial pressure of oxygen and CO2 in inspired air?
O2: 120 CO2: 27
What is the partial pressure of oxygen and CO2 in mixed venous blood?
O2: 40 CO2: 45
What is the partial pressure of oxygen and CO2 in tissue cells at rest?
O2: 40 CO2: 45
What is the partial pressure of oxygen and CO2 in arterial blood?
O2: 90-100 CO2: 40
what is the partial pressure of arterial O2 if the partial pressure of arterial CO2 is 40 mm Hg?
PAO2= PiO2- (PaCO2/R) PAO2= 150- (40/0.8) =100 mm Hg
provide the alveolar gas equation
Partial pressure of alveolar oxygen= partial pressure of inspired oxygen - (Partial pressure of alveolar CO2/R) + F Keep in mind you can't measure the partial pressure of alveolar CO2 so the next best thing is using partial pressure of arterial CO2 in its place. Also F is a correcting factor we can ignore for now
what percent is Nitrogen in the air?
about 79%
which of those has a decreased partial pressure of arterial O2?
all of them
what equation can you use to calculate the partial pressure of oxygen in the alveoli?
alveolar air equation
what do you use to calculate the partial pressure of gas in the air?
dalton's law. The sum of all gases in a in a mixture is equal to atmospheric pressure
if your partial pressure of arterial CO2 goes up and the diffusion capacity (DL) goes down then you have a _____ problem
diffusion
which of those just mentioned has a normal A-a gradient?
high altitude and hypoventilation
before using the alveolar air equation you have to find out what ______ is. How do you calculate that?
inspired oxygen. You have to calculate inspired oxygen before using alveolar air equation to calculate the partial pressure of the air in the alveoli. First, you know to calculate inspired oxygen you have to take into account the water vapor, which turns out to be 50 mm Hg. Subtract that 50 from the atmospheric pressure (760) to get 710. The multiply that by 0.21 which is the percent (21%) that oxygen is in the air. This equals 149. Partial pressure of inspired oxygen= 0.21 * (760-50)= 149 mm Hg
how do you find the partial pressure of each of the gases in air?
multiply their percentage by the atmospheric pressure which is 760 Nitrogen: 0.79*760=600.4 oxygen: 0.21*760=159.6 CO2: 0*760=0
can absolute shunts be improved with supplemental oxygen?
no
will a left to right shunt have an effect on the A-a gradient?
no. right to left will though left to right shunt does not cause hypoexemia
What is the partial pressure and percent of oxygen and CO2 in humidified inspired air?
o2: 150 (19.62%) CO2: 0 (0%)
What is the partial pressure and percent of oxygen and CO2 in atmospheric dry air at sea level
partial pressure O2: 160 (21%) partial pressure CO2: 0 (0%)
what's an example of a right to left shunt?
patent foramen ovale
out of high altitude, hypventilation, diffusion defecit, low V/Q ratio, and right to left shunt, which one will have limited help from supplemental O2?
right to left shunt will have limited helpfulness from the supplemental O2, while the other four situations can benefit from the supplemental O2
what could cause an increase in the A-a gradient for O2?
shunt diffusion limitation low V/Q ratio
if you see a decrease in partial pressure of arterial CO2 but no change in diffusion capacity (DL) you have ______.
shunting
will the following things increase, decrease, or not change the A-a gradient? diffusion deficit, low V/Q ratio, right to left shunt
these all decrease A-a gradient
why are there differences in the partial pressure of O2 in the air, inspired air, and alveolar air?
water vapor which is a gas O2 is constantly being removed from alveoli CO2 is constantly being added to alveoli
can a shunt like state be improved with supplemental oxygen?
yes.
