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Hypercarbia and Hypoxemia. 11.7.11. What happens to our cells if we don’t get enough O 2 ?. What happens to our cells if we don’t remove CO 2 ?. Why is P I O 2 150 mmHg if atmospheric PO 2 is 160 mmHg? . Causes of Hypoxemia. 1. 2. 3. 4. Diffusion impairment. . - PowerPoint PPT Presentation
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Hypercarbia and Hypoxemia11.7.11
What happens to our cells if we don’t get enough O2?
What happens to our cells if we don’t remove CO2?
tissue
CIRCULATION
CO2 O2
PIO2 = 150 mmHgPICO2 = 0.3 mmHg (0)
P aO
2 = 9
8 m
mH
gP a
CO
2 = 4
0 m
mH
g
CO2 O2
P vO
2 = 4
0 m
mH
gP v
CO
2 = 4
5 m
mH
g
PAO2 = 100 mmHgPACO2 = 40 mmHg
Subscripts:I = inhaledA = alveolara = arterialv = venous
Why is PIO2 150 mmHg if atmospheric PO2 is 160 mmHg?
Causes of Hypoxemia
1.
2.
3.
4.
Diffusion impairment
PAO2
PcapO2
T
A
.VO2 = K x A x (PAO2 – PaO2)/T
Diffusion impairment .VO2 = K x A x (PAO2 – PcapO2)/T
How does the rate of transport change with:
-Increased thickness, ie. with fibrosis?
-Decreased surface area, ie pneumonia?
-Decreased PcapO2, less O2 in the capillary blood?
V/Q Abnormalities
0Upper parts of the lung receive more/less blood supply than the lower parts (gravity).
0Upper parts of the lung also receive more/ less of the tidal volume.
V/Q Abnormalities
0The result is that the upper parts of the lung receive relatively more/less ventilation than they do blood flow, while the lower parts of the lung receive relatively more/less ventilation than they do blood flow.
Shunt
Definition:
Let’s take a short cut! But is it a good short cut?
ShuntWhich causes blood to go from the right to left heart without going through the lungs?
A. Foreign object (ie. Peanut)B. Bronchial circulationC. Pneumonia or abundant pusD. Foramen Ovale
ShuntBronchial circulation- only goes through the larger airways and does not reach the alveolar region
Foramen Ovale- system established in utero that may not close when the baby is born
Shunt
What happens with these two?
Foreign object (ie. Peanut)Pneumonia or abundant pus
Does hypoventilation cause hypoxemia or hypercarbia?
Hypoventilation
What things can cause hypoventilations?1.
2.
3.
4.
Hypercarbia
In addition to hypoventilation,
Think ALVEOLAR VENTILATIONThink DEAD SPACE
How to calculate alveolar ventilation?
What happens when you increase dead space?
VA = (VT V‑ D) x f
Dead Space
Name 3 things that cause changes in dead space.
Equipment
-Snorkel-Gas Mask-Ventilator
Deep Vein Thrombosis
How does DVT cause dead space?
Air can get in but gas exchange surface is destroyed.
