RS5 Causes of Hypoxemia Flashcards
(26 cards)
What are the 3 determinants of pulmonary vascular resistance?
Gravity
Lung volume
Hypoxic vasoconstriction
Describe the hydrostatic pressure differences in the lung
It goes low to high (top to bottom). The bottom of the lungs have the greatest hydrostatic pressure
Systemic arteries ___ in response to perfusion with blood low oxygen
dilate
Pulmonary arteries ____ in response to alveolar hypoxia but not to perfusion with blood low in oxygen
constrict
Deadspace unit
Normal ventilation
No pefusions
The alveoli is working great, but the capillary is not
Shunt unit
No ventilation (no alveolar function)
Perfusion (blood vessel is fine)
Silent unit
Neither vent or perf
Draw the 4 types of V:P relationships
In the healthy adult, a PaO2 above ___mmHg is considered normal while breathing room air at sea level
80
What are the 2 exceptions to normal PaO2?
Newborn infant 50-70mmHg
Subtract 1mmHg for every year over 60years of age
Normal PaCo2 ___-___mmHg
35-45mmHg
Hyperventilation PaCo2
<35mmHg
Hypoventilation PaCo2
> 45mmHg
Expected values
PaO2 = __mmHg
PaCo2 = ___mmHg
100
40
Hypoxemia
A decrease in the partial pressure of oxygen in the arterial blood PaO2 < 80mmHg
What are the 5 causes of hypoxemia PaO2 < 80mmHg
Hypoventilation
Diffusion impairment
Ventilation-perf relationship
Reduction of inspired O2
Shunt
Alveolar Air Equation
PAO2 = PIO2 - PACo2/R
Diffusion impairment
The equilibrium does not occur between the PO2 in the pulmonary capillary blood and alveolar gas
V:P inequality
vent and blood flow are mismatched in various regions of the lung with the result that gas transfer becomes inefficient
VA =
Q =
alveolar ventilation
perfusion (blood flow)
VA/Q values for Deadspace, normal, and shunt
Deadspace: infinity
1
Shunt: 0
Reduction of inspired PO2
The alveolar PO2 and thus the arterial PO2 will be decreases
Shunt
Blood reaches the arterial system without passing through ventilated regions
How can we distinguish between the 5 causes of hypoexmia?
A-ADO2
