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19 Cards in this Set
- Front
- Back
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What is the normal oxygen content in the blood
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Total=20ml/100ml, Dissolved=.3ml/100ml, Bound=19.4/100
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what is the difference between blood gas partial pressure and blood gas contents
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Pressure=kinetic energy of the dissolved gas, component that is freely diffusable; Content=total amount of gas including bound+free
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What is the Bohr effect?
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An increase in PCO2 or an increase in [H+] decrease Hb affinity for oxygen leading to more oxygen release
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What is the relationship between P50 and oxygen affinity
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P50 is the pressure of O2 when Hb is 50% saturated. A higher P50 means a lower oxygen affinity because it takes a higher pressure to saturate the Hb
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WHy is a shift in Hb Oxygen affinity beneficial during exercise or high altitud
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Shifting the affinity allows the oxygen to dissociated at a higher pressure, this maintains a high pressure gradient for the released oxygen to diffuse into the tissue. If the curve did not shift, the PO2 would have to decrease signficantly before the oxygten would release and there would be less of a pressure gradient left to push the oxygen into the tissue.
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How would anemia affect the delivery of O2
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The total oxygen content is reduced so the PO2 in the capillary blood must decrease more than normal to deliver the same amount of O2
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Name 4 factors that determine end systemic capillary PO2. How do these change during exercise
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1. metabolic rate of tissue 2. aterial O2 content 3. Hemoglobin affinty for O2 4. rate of capillary blood flow, during exercise metablic rate increases but arterial O2 content does not change, to ensure delivery of enough oxygen, Hb affinity for oxygen decreases and capillary blood flow increases
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HOw is CO carried in the blood
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70% as HCO3, 25% bound to Hb, 5% dissolved
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What is the function of carbonic anhydrase
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CO2+H2O=>H2CO3=> H+ +HCO3-, the enzyme increases the rate of the reaction to ensure that enough CO2 is carried away from the tissues.
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Describe the Chloride shift
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refers to the movement of HCO3 out of red blood cells in exchange for Cl moving in. RBCs on the venous end will have a higher chloride content, maintains electroneutrality and keeps intracellular [HCO3] low to facilitate release of CO2
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What is the Haldane effect
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binding of oxygen with Hb causes Hb to become a stronger acid and release H+ ions. This release facilitates the displacement of CO from the blood into the alveoli by 1) the more acidic Hb has less tendency to bind CO2 so more CO2 is displaced to the blood 2)supplying H ions to bind with HCO3- to reverse the CA reaction . The reverse happens in the tissues (release of oxygen from Hb makes it a weaker acid, it binds CO2 better and less H+ ions are available so HCO3- is favored)
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What is the significance of the respiratory quotient? Why is it not always 1?
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VCO2/VO2, when only carbs are used for energy there is no difference in arterial-mixed venous CO2/O2 content because for every 1 O2 used, a CO2 is liberated. In contrast, when fat is utlizied the respiratory quotient is 0.7 as less CO2 is libereated than O2 used
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WHy Does PO2 change more (60) than PCO2 (5) from aterial to mixed venous
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relfects a difference in dissociation curves
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Despite a nearly 40% decrease in PaO2, a person can have only a small decrease in O2 content. Why is this so?
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Over a range of 100mgHg to about 60, the oxygen dissociation curve is realtivley flat so a high content can be sustained over a wide range of pressures
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Why would a patient with CPOD complain of dyspnea but a person with anemia would not?
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Dyspnea is a result of a low PaO2 which increases the drive to breath. In the patient with emphysema, the low PaCo2 and decreases saturation will cause dyspnea despite a nearly normal oxygen content (note the flat portion of the O2 dissociation curve). In contrast a patient with anemai will have a normal PaO2 and will not experience dyspnea despite a signficantly reduced O2 content. Main point-note the difference between pressure and content, dyspnea is the result of low pressure NOT low content.
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Why would it be an ineffective treatment to administer 100% O2 to an anemic patient.
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The anemic patient has a normaly PaO2 because the lungs are functioning normally .The probelm is a low oxygen content due to low Hb. 100% O2 merley increases the oxygen pressure but cannot increse oxygen content if there is insufficent Hb
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Why is administering 100% O2 an effective treatment for COPD
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Pts with COPD can have low PaO2 because of a diffusion problem. Increasing the PiO2 increases the PAO2 and can thus provide more of a drive to increase PaO2.
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Why can a hyperventilated lung compensate and maintain a normal PaCO2 but not a normal PaO2?
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The two gases are operating on different points of the dissocition curve. PaCO2 can be maintained because of the linear dissocition. PaO2 cannot be maintained because of the steep shape of the curve lower than 60mmHg
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What are the normal values of oxygen and CO2 in arterial and mixed venous blood
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oxygen-arterial=95, mixed venous=40; CO2- arterial=40. mixed venous=45
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