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How does gas move across the system?
simple diffusion
Where is PO2 the smallest?
In the cell
What is normal PO2 in the alveoli?
100mmHg
What is normal PO2 in the air?
159mmHg
What is normal PO2 in cells?
~5mmHg
What are normal gas ranges in the lungs?
O2= 20.95%, 159mmHg
N2= 78.08%, 593mmHg
Argon= 0.93%, 7mmHg
CO2= 0.03%, 0.23mmHg
Trace elements= 0.01%, 0.76mmHg
PO2 gradient is what compared to the CO2 gradient?
they are in reverse of each other
PACO2 will increase with an increased what?
VCO2
what is normal CO2 production?
200mL/min
What is the equation for PACO2?
PACO2= (VCO2 x 0.863)/Va
What is the primary determinant of PAO2?
PIO2 (Pressure of inspired O2)
What is PAO2 diluted by in the lungs?
water vapor and CO2
What is normal PH20 in alveoli?
47
What is the hightest PIO2 on RA (room air) at sea level?
110-120
What is equation for PAO2?
PAO2= FIO2 x (PB-PH2O) - (PACOR/Q)
What is normal R/Q or respiratory exhange ratio?
0.8
What does PB stand for and how is it expressed?
Barometric Pressure expressed as mmHg
When is the R/Q dropped?
If FIO2 is greater than or equal to 60mmHg
What is normal ATM at seal level?
760mmHg (14.7psi)
What is determined by Daltons law? How is it expressed?
PAN2= PB-(PAO2+PACO2+PH2O)
What prevents PACO2 from decreasing any further below 15-20mmHg
Nerual control mechanisms and an increased WOB
What is the sum of PaO2+PaCO2?
140 on R/A
What will an increase in VA cause?
Decreased PaCO2 and increased PO2
Diffuison occurs along what?
Pressure gradients
What are the barriers to diffusion?
A/C membrane and RBC membrane
What are the three main barriers for the A/C membrane?
  • Alveolar epithelium
  • Interstitial space and its structures
  • Capillary endothelium
How many times faster than O2 does CO2 diffuse?
20x
How many times faster than O2 does CO diffuse?
200x
Hemoglobins affinty for CO is ____ more than it is for O2? This is also the reason why people die from CO poisoning.
200x
How long is pulmonary blood normally exposed to alveolar gas?  During execise?
  • 0.75s
  • it may fall 0.25s
What will damage in diffusion barriers do?
It will hinder diffusion or slow it down
When does normal equilibration occur in diffusion?
in 0.25s
When may there be inadequate time for equilibration?
With a diffusion defect or exposure time < 0.25seconds
Why is PaO2 normally 5-10mmHg less than PAO2?
The pressure of anatomic shunts or diffusion defects
What can limit diffusion time?
  • High fever
  • septic shock
  • increased QT
What drains poorly oxygenated blood into arterial circulation which lowers CaO2 and SaO2?
Bronchial and thesbian veins?
What are the two ways O2 is carried in plasma?
Dissolved in plasma and combined with hemoglobin?
How much O2 can be dissolved in 1mL of plasma at 37°C and 760mmHg?
0.003mL
What is the equation for the amount of O2 dissolved in the blood?
0.003xPaO2
In a HBO chamber at 2280mmHg there is how much O2?
There is 6mL/dL which is enough to comply most tissue at rest.
With normal PaO2 of 100 how much O2 is dissolved?
0.3Ml/dL
When breathing 100% O2 there is how much PaO2?
670mmHg
How much of O2 in the tissues is carried by Hb?
~70%
How much O2 does 1g/Hb carry?
1.34mL/O2
When bound to Hb O2 does not exert what?
Pressure
What is Hb saturation?
Percentage of Hb carrying O2 comapred to the total Hb
What is normal SaO2?
95-100%
Flat portion of HbO2 curve occurs with what?
SaO2>90%
Flat portion of HbO2 curve represents what?
Normal operating range for arterial blood
Normal range for arterial blood is?
60mmHg
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