Respiratory IV Transport of O2 and CO2 Flashcards
how is oxygen carried physically and chemically in the body
physically dissolved in blood and chemically combined to hemoglobin
how is carbon dioxide physically and chemically carried in the body
physically dissolved in blood, chemically combined to blood proteins as carbamino compounds and as bicarbonate
what do the partial pressure of the gases include
the gases that are dissolved in the plasma
what happens to the gradient when cells utilize more oxygen than normal
the gradient increases which increases flow of oxygen from the blood to the tissues
what is the tissue PO2 a function of
-the rate of O2 transport to the tissues in blood (blood flow)
- the rate at which the tissues use O2
what does increased blood flow and/or increased metabolism result in with O2
more O2 delivery to the tissues
what is the pressure in arteries of O2, CO2, and SO2
-O2: 95
-CO2: 40
- SO2: 97%
what is the pressure in the capillaries of O2 and CO2
-O2: 40
CO2: 46
what is the pressure in the veins of O2, CO2, and SO2
-O2: 40
-CO2: 46
-SO2: 75%
without hemoglobin what would CO need to be in L/min to transport sufficient oxygen to meet the needs of the tissues at rest
83.3 L/min
how much of the total oxygen content is dissolved in plasma
2%
how much O2 reversibly binds to hemoglobin inside of the RBC
98%
describe the hemoglobin molecule
2 alpha subunits and 2 beta subunits and each bind 1 molecule of O2
what state must iron be in to bind O2
ferrous state
what does the amount of oxygen bound to hemoglobin depend on
-plasma O2
- number of binding sites in RBCs
what does the number of binding sites in RBCs depend on
the Hb amount per RBC
how many Hb molecules does 1 RBC contain
1 million
what is the concentration of oxygen in the arterial blood (definition)
ml of O2 carried by oxyhemoglobin plus ml of O2 carried dissolved in plasma
what is the average g of Hb / 100 mL of blood
15 g Hb/100 mL blood
what is the average partial pressure of oxygen in arterial blood
95 mmHg
what is the average CaO2 ( number)
19.782 ml O2/100 mL blood
what does 2,3-BPG do
binds to beta subunits of deoxy hemoglobin and decreases its O2 affinity which causes more oxygen unloading
what is positive cooperativity
at a high PO2 hemoglobin’s affinity for O2 is highest
when does a major drop off in % O2 saturation of hemoglobin occur
60 mmHg
what is the bohr effect
the oxyhemoglobin dissociation curve shifts to the right
what is a right shift/bohr effect caused by
-increased H+ ions
- increased CO2
- increased temperature
- increased BPG
what does a right shift in the oxyhemoglobin dissociation curve indicate
decreased affinity between hemoglobin and oxygen
when do levels of 2,3- BPG increase
with exercise, hypoxia from high altitude, pregnancy, and chronic lung disease
what is the normal blood pH
7.4
what is a left shift in the oxyhemoglobin dissociated curve caused by
- decreased PCO2
- increased pH
- decreased temperature
- decreased 2,3- BPG
what does a left shift indicate about oxygen/Hb affinity
- increased affinity
- O2 is less likely to dissociate from Hb
how much of a greater affinity does CO have for Hb than O2 does to Hb
250x
what is the effect of CO bound to Hb
increased Hb’s affinity for O2 (left ward shift in curve)
if CaO2 is greatly reduced, what happens to PaO2
could be normal
what is the treatment for CO poisoning
-pure oxygen
- 5% CO2
what is the common presentation of CO poisoning
-cherry red skin
- flu like symptoms
- headache
- neurologic symptoms
what are the 3 variants of Hb
-methemoglobin
- hemoglobin F ( fetal)
- hemoglobin S (sickle cell)
what happens in methemoglobin
-heme with Fe3+ (ferric) has lower O2 affinity and causes heme groups in the same Hb molecule with heme in the Fe2+ (ferrous) state to have higher affinity for bound O2 so net effect is less O2 release from Hb and less delivery to tissues
what can methemoglobin occur due to
G6PDH deficiency or exposure to local anesthetics such as prilocaine or benzocaine
describe the structure of hemoglobin F
2 alpha chains and 2 gamma chains
describe the affinity of hemoglobin F to O2
higher affinity for oxygen than adult Hb because it doesnt contain the beta chain that binds to 2,3-BPG
describe the structure of Hb S and what causes it
-normal alpha and beta units
- caused by one amino acid change
- when deoxygenated, RBCs form sickle shapes and obstruct small vessels
describe Hb S affinity for O2 compared to normal adult Hb
O2 has lower affinity
what is the oxygen content in methemoglobin compared to normal oxyhemoglobin
decreased by 50% so about 10
what is hypoxemia
low PaO2
what is hypoxia
low tissue O2
what causes hypoxemia
-decreased FiO2
-hypoventilation
- diffusion defects
- V/Q defects
describe the A-a gradient in decreased FiO2, hypoventilation, diffusion defects, and V/Q defects
-decreased FiO2: normal
-hypoventilation: normal
- diffusion defects: increased
- V/Q defects: increased
when is supplemental O2 helpful in hypoxemia causes
in every case
what can hypoxia be caused by
hypoxemia, decreased cardiac output, anemia
what are the PCO2 values in the alveoli, arteries, capillaries and veins
- alveoli: 40
-arteries: 40
-capillaries: 46
0veins: 46
does hemoglobin transport CO2
yes
what can CO2 be transported as in the blood and what are the percentages of each
-dissolved CO2: 7%
- carbamino-hemoglobin: 23%
- bicarbonate: 70%
what is the volume of transport of CO2 in the blood
4 ml CO2 / 100 mL blood
which is the slowest of the transport mechanisms of CO2 in blood
carbaminohemoglobin
which is the fastest of the transport mechanisms of CO2 in blood
bicarbonate
describe the carbaminohemoglobin transport mechanism
CO2 forms a loose, reversible bond with hemoglobin on terminal amine groups
describe the bicarbonate transport mechanism
In RBCs, carbonic anhydrase rapidly forms carbonic acid from H2O and CO2 which in turn dissociates into H+ and HCO3-
- H+ combines with hemoglobin for buffering and HCO3- moves into plasma in exchange for Cl-
what is the haldane effect in systemic capillaries
deoxygenated Hb promotes increased binding of CO2 to Hb
what would happen to PaCO2 if there were no carbonic anhydrase
it would increase by double
what is the effect of CO2 with Hb at lower O2 concentrations
CO2 is more likely to combine with Hb and Hb buffers more H+
what is the haldane effect in pulmonary capillaries
oxygenated Hb promotes dissociation of CO2 from Hb