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41 Cards in this Set

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what are the normal arterial blood values of:

-pH
-PaCO2 (arterial pressure)
-PaO2
-HCO3
pH=7.35-7.45
PaCO2 = 35-45 (~40)
PaO2 = >70 mmHg (age-dependent)
HCO3 = 22-26 (~24)
what's the difference b/w alveolar ventilation (VA) and dead space ventilation (VD)?
VA = amt of air that reaches the alveoli and takes part in gas exchange

VD = amt of air that DOESN'T take part in gas exchange

(Out of one breath about 150 mL is dead space ventilation, and 350 mL is for alveolar ventilation. Disorders of the lung change this ratio…)
a LOW/HIGH PaCO2 (<35) signifies hyperventilation
low; bc all the CO2 is getting breathed out of the arterial circulatory system faster than normal
a LOW/HIGH PaCO2 (>35) signifies hypoventilation
high; bc all the CO2 is not getting the chance to be breathed out of the arterial circulatory system as normal
the lower the ventilation (VA), the LOWER/HIGHER that CO2 is found in the arterial blood circulation (PaCO2)
higher; REMEMBER that PaCO2 is inversely related to alveolar ventilation
name some factors that cause increased PaCO2
most of the time, it's alveolar hypoventilation due to increased dead space (VD). most of the time, this is seen in COPD

you can also have decreased minute volume (VE) via CNS depression (brain problem leading to respiratory rate decreasing)
name some common causes of decreased PaCO2
of course, it's due to alveolar hyperventilation (PALEPAM):

- pain
- anxiety
- liver failure
- early sepsis
- pulmonary embolism
-acute asthma
-metabolic acidosis
what does the alveolar gas equation help you do clinically?
by measuring the PaCO2, you can plug in this # into the EQ and find out the estimated PAO2 (alveolar O2). then you can take this number and subtract the measured PaO2 (arterial O2) to give you the A-a difference. now the A-a difference basically tells you how much air is actually getting into the arterial supply from the alveoli and can signal potential ventilation/perfusion mismatching (normal A-a difference = 10-12). so if A-a difference is 18, then you've got ventilation/perfusion (V/Q) mismatch!!! COOL...!!!
explain when V/Q = infinity. what could be the underlying cause?
Where V/Q = infinity, this is pulmonary embolism, so there is no blood perfusing the lung
explain when V/Q = 0. what could be the underlying cause?
shunting due to anything that blocks the alveoli. this could occur with severe pneumonia, for example.
T or F. the part of the lung that receives the best ventilation are the upper lobes.
False!! The lower lobes get the best ventilation. However the ratio (V/Q) is highest in the upper lungs bc there’s more ventilation there than perfusion. The lower lobes have more ventilation and perfusion absolutely.
where is V/Q the highest in the lungs?
upper lungs, near the apex (since ventilation is highest there)
T or F. the older you get, the A-a difference gets bigger.
T, arterial pressure O2 gradually goes down as you age
the most accurate estimation of A-a difference is when pt is breathing:

a. tank oxygen
b. room air
B. basically, check blood gases of the pt when they are breathing room air in order to properly calculate alveolar gas EQ to find out A-a difference
arterial blood gases tell us information about which 3 processes?
alveolar ventilation
oxygenation
acid-base balance
partial pressure of oxygen (PaO2) is:

a. oxygen molecules found in alveolar spaces
b. oxygen molecules dissolved in plasma AND bound to Hb
c. oxygen molecules dissolved in plasma and NOT bound to Hb
d. none of the above
C.
arterial oxygen saturation (SaO2) is:

a. % heme binding sites saturated with oxygen
b. number of oxygen molecules found in plasma AND bound to Hb
c. number of oxygen molecules foudn in plasma NOT bound to Hb
d. none of the above
A
arterial oxygen content (CaO2) is:

a. amount of free oxygen dissolved in plasma
b. amount of oxygen bound to Hb AND oxygen dissolved in plasma
c. amount of oxygen bound to Hb only
d. none of the above
B
partial pressure of oxygen (PaO2) is:

a. oxygen molecules found in alveolar spaces
b. oxygen molecules dissolved in plasma AND bound to Hb
c. oxygen molecules dissolved in plasma and NOT bound to Hb
d. none of the above
C.
SaO2 > ___% is usually ok!
90%
arterial oxygen saturation (SaO2) is:

a. % heme binding sites saturated with oxygen
b. number of oxygen molecules found in plasma AND bound to Hb
c. number of oxygen molecules foudn in plasma NOT bound to Hb
d. none of the above
A
what is the cut off for O2 sat, where below it, you need to calculate the blood gas (measure PaCO2 and PaO2)
below 90%
arterial oxygen content (CaO2) is:

a. amount of free oxygen dissolved in plasma
b. amount of oxygen bound to Hb AND oxygen dissolved in plasma
c. amount of oxygen bound to Hb only
d. none of the above
B
SaO2 > ___% is usually ok!
90%
what is the cut off for O2 sat, where below it, you need to calculate the blood gas (measure PaCO2 and PaO2)
below 90%
which of the following shift the oxygen dissociation curve to the RIGHT:

a. low temperature
b. high pH
c. high pCO2
d. low PaO2
C. (right = think "muscles")
which of the following shifts the oxygen dissociation curve to the LEFT:

a. low temperature
b. high pH
c. high pCO2
d. two of the above (name 'em!)
A, B (left = think "lungs)
define hypoxemia vs. hypoxia
hypoxemia = low oxygen in blood and plasma (low CaO2, PaO2, SaO2)

hypoxia = decreased OXYGEN DELIVERY to the tissues
in cyanide poisoning, are you hypoxic, hypoxemic, or both?
only hypoxic. you'll have normal oxygen in blood and plasma, but hypoxic at the level of the tissues
what two underlying causes could give you hypoxemia but normal A-a difference?
- low oxygen content in atmosphere (aka. low barometric pressure)
- hypoventilation
most common cause of hypoxemia
V/Q mismatch
what are 3 main causes of hypoxia?
- hypoxemia (severe anemia, CO intoxication)
- reduced oxygen delivery to tissues (reduced cardiac output)
- reduced tissue oxygen uptake (mitochondrial poisoning, left shift of oxygen dissociation curve)
name the conditions for metabolic acidosis in terms of pH, HCO3, and PaCO2.
dec pH
dec HCO3 (primary)
dec PaCO2 (compensatory)
name the conditions for respiratory alkalosis in terms of pH, HCO3, and PaCO2
inc pH
dec PaCO2 (primary)
dec HCO3 (compensatory)
which acid/base disorder would give you hyperventilation?
metabolic acidosis (to try to decrease PaCO2 as fast as possible to compensate the loss of HCO3 in the blood. this is all, of course, in response to the acidemia that is at the underlying cause)
a pt who is hypoventilating is likely to have which acid/base disorder?
metabolic alkalosis
what two causes can give you metabolic acidosis with a normal anion gap?
diarrhea
renal tubular acidosis

these both willl causes concentration of Cl to be increased to replace HCO3
how do you calculate serum anion gap?

what is its normal value?
Na - (Cl + HCO3)

nl = 12 +/- 4
what does an increased serum anion gap mean?
that the conc of an unmeasured anion (ie. phophate, lactate, etc) is increased to replace HCO3 (as opposed to Cl)
pt with diarrhea will most likely have what kind of acid/base disorder and why? would they have anion gap increased and why?
metabolic acidosis (bc you're losing a lot of bicarb through pooping it all out)

no increase in AG (bc you're compensating this loss with increased conc of Cl)
you find out a pt has metabolic acidosis, whatsyour next step?
calculate anion gap