Transport of Gases (CO2, O2, dissociation curves) Flashcards
________ is d\t or a function of oxygen tension (partial pressure).
Hgb saturation
What is P50 and what is the normal value for it?
The partial pressure of oxygen at which Hgb is 50% saturated with oxygen.
normal is 26-28mmhg
What SO2 corresponds to PO2’s of 40 and 60mmHg?
remember 40, 50, 60= 70, 80, 90
70%=40mmHg
90%=60mmHg
What is the significance of the flat portion of the oxyHgb dissociation curve?
facilitates the unloading of oxygen by blood…. b\c in the flat portion of the curve, large changes in partial pressure of oxygen in arterial blood (PaO2) produce only small changes in oxygen saturation
What is the significance of the steep portion of the oxyHgb dissociation curve?
facilitates unloading of oxygen at tissues b\c large amounts of oxygen are unloaded from Hgb (large decrease in oxygen saturation) in response to small changes in the partial pressure of oxygen
Name the factors that cause a rightward shift in the oxyHgb dissociation curve. (using “RIGHTS”)
"R"ightward shift "I"ncreased PCO2 Increased 2, 3, DP"G" "H"ydrogen ions increased (decreased pH) "T"emperature increases "S"ickle cell (HbS)
P50 ______ when there is a rightward shift.
increases
P50 ______ when there is a leftward shift.
decreases
The ______ refers to the shift in oxyHgb dossociation curve in response to an increase or decreased PCO2.
Bohr effect
*studied factors that shift the curve right or left. Bohr assessed how a change in CO2 shifts the curve.
Administration of opioids shifts the oxyHgb dissociation curve right or left?
Right–> produces resp depression, so CO2 accumulates and the curve shifts rightward
Name the comprehensive list of factors that cause a rightward shift in the oxyHgb dissociation curve.
- increased temp
- decreased pH (increased H+ concentration)
- increased PCO2
- increased 2, 3 DPG
- maternal Hgb
- sickle cell (HbS)
Name the comprehensive list of factors that cause a leftward shift in the oxyHgb dissociation curve.
- decreased temperature
- increased pH (decreased H+ concentration)
- decreased PCO2
- decreased 2, 3, DPG
- fetal Hgb (HbF)
- carboxyhemoglobin
- methemoglobin
A rightward shift facilitates _____.
unloading
A leftward shift facilitates ______.
loading
Explain the normal process of the utility of the Bohr effect involved with the transport of gases (CO2 and O2).
blood travels through the capillaries in the systemic circuit, CO2 and acids diffuse into the blood from the tissue cells—> tissue metabolism causes an increase in temperature–> rightward shift–> O2 unloading is facilitated (for a given PO2, the blood holds less O2)
blood then diffuses through capillaries in the pulmonary circuit, CO2 then diffuses out of the blood to the alveoli–> curve shifts leftward, facilitating the loading of O2 (a given PO2, the blood holds more O2 when the oxyHgb curve shifts left)
Is oxygen release from hemoglobin to the tissues increased or decreased by acidosis?
increased; acidosis causes a rightward shift facilitating the unloading of O2 to the tissues–> increasing O2 delivery to the tissues
Total O2 carrying capacity of the blood is the sum of what two values?
hgb bound to O2 and dissolved Hgb
Who’s law explains O2 dissolved in the blood?
Henry’s
dissolved oxygen= 0.003 x PO2
Most of the contribution to the O2 carrying capacity of the blood is from _______.
Hb bound O2
dissolved O2 only makes up a small portion
dissolved oxygen = ________ x ________
0.003 x PO2
How much oxygen is dissolved in arterial blood if PaO2 is 90mmHg?
dissolved O2: 0.003 x 90= 0.27
What is the difference in PO2 and PaO2?
nothing–> for the exam purpose
Calculate the increase in dissolved oxygen in the arterial blood if PaO2 increases from 50mmHg to 300mmHg.
50 x 0.003= 0.15
300 x 0.003= 0.9
0.15-0.9= 0.75
the increase in dissolved O2 is 0.75mL O2/100mL blood
_______ liquids to dissolve gas, _______ liquids to dissolve solids.
cool; heat
What is 0.003 in the dissolved O2 equation?
solubility coefficient
O2 is carried in blood in two forms: ________ and _______
Hgb bound and dissolved
In a young, healthy individual, normal arterial blood (PaO2-100mmHg) has ______ mL O2/100mL blood dissolved and ______ mL O2/100mL blood bound to hemoglobin (98.5% SaO2; 15g Hg/100mL blood).
0.3mL dissolved; 19.8mL bound
What is the maximum oxygen carrying capacity of arterial blood in a young, healthy person breathing room air?
20.4mL; 20.1mL bound (100% saturation) and 0.3mL dissolved
Therapy with 100% O2 will produce much greater increases in oxygen content of blood if ________.
if the Hgb was poorly saturated prior to the admin of O2
- pulmonary disease (pulm edema, deadspacing)
- poor perfusion in relation to ventilation respond well
- pt with shunt (poor ventilation in relation to perfusion) are less responsive
Oxygen hemoglobin dissociation curve is a _______ shaped curve. The steep portion occurs when PO2 is ______.
S shaped; <60
It is important to remember that most of the O2 carried in the blood is combined with hemoglobin. Only a small portion of the total amount of oxygen in blood is dissolved. This is an application of ______ law.
Henry’s
To calculate the amount of O2 bound to hemoglobin, you need to know:
the amount of oxygen carried by each gram of fully saturated hemoglobin = _________
the normal concentration of Hemoglobin = ________
and the % saturation (ex: 90%)
1.34mL O2 per g Hgb
15g Hb per 100mL blood
What is the equation to calculate bound hemoglobin?
bound Hgb= 1.34 x 15 x % sat
so for 90% saturation= 1.34 x 15 x 0.9= 18.1 mL O2/dl
Since you know the equation for dissolved Hgb is PO2 x 0.003…. what is the total amount of O2 carried by blood when it is 90% saturated?
1.34 x 15 x 0.9= 18.1 (bound) 90% is ~ 60mmHg PO2, so: 60 x 0.003= 0.18 then just add: 0.18 + 18.1= 18.28 mL O2/100mL blood
If SvO2 is 70%, how much oxygen is dissolved in venous blood?
so if SvO2 is 70%, PvO2 is 40mmHg;
so, 0.003 x 40= 0.12 mL O2/100mL
The CO2 dissociation curve shifts _____ and to the _____ when PO2 decreases, and shifts _____ and to the _____ when PO2 increases.
The CO2 dissociation curve shifts UP and to the LEFT when PO2 decreases, and shifts DOWN and to the RIGHT when PO2 increases.
What effect does opioid administration have on the blood CO2 dissociation curve?
opioids shift the CO2 dissociation curve up and to the left b\c of the decrease in PaO2 secondary to opioid induced respiratory depression
The _______ describes how a change in partial pressure of oxygen (PO2) in the blood influences the blood CO2 dissociation curve.
Haldane effect
A shift in the CO2 dissociation curve leftward facilitates _______.
loading of CO2 into the blood (at the tissues)
A shift in the CO2 dissociation curve rightward facilitates _______.
unloading of CO2 (blood to alveoli)
_____ % of CO2 in the plasma is in the form of ______. Total amount of CO2 that is _______ is _______%
70% of CO2 in plasma is HCO3-
total amount of CO2 that is HCO3= is 90%
CO2 is carried in the blood:
1) in _____ form
2) as ______
3) chemically bound to ______
CO2 is carried in the blood:
1) in dissolved form
2) as bicarbonate
3) chemically bound to proteins (to plasma proteins and Hgb)
What are the two main byproducts of ATP?
CO2 and H2O (mitochondria)
Dissolving gases= ______ law
Diffusing gases= ______ law
dissolving = Henry (dissolved O2) diffusing = Fick's
Explain the general process of conversion of CO2 to bicarbonate in red blood cells.
CO2 diffuses from the metabolizing cell into plasma down a gradient—> gets hydrated (CO2 + H2O)—> forms carbonic acid (H2CO3–> weak acids like to give up a H+—> Le Chatliers principle “if you are not in equilibrium, Le Chatlier is here”–> dissociates to HCO3 and H+–> HCO3 diffuses out of the RBC down a concentration gradient (70% of CO2 is in plasma)–> Cl- diffuses into the RBC as HCO3- diffuses out (Hamburger shift)
The exchange of Cl- for HCO3- is the chloride shift, which is also referred to as the ______.
Hamburger shift
How do you calculate the amount of CO2 dissolved in blood?
multiply PCO2 x 0.067 (Henry’s law applies)
