08.12 - Gas Exchange, Oxygen Transport (Waters) - Questions Flashcards
Respiratory Quotient
Ratio of CO2 produced to O2 consumed
Respriatory Quotient depends on
what we eat and burn
Partial Pressure of inspired O2 vs dry air
159 vs 150
Henry’s Law
Cx = (alpha)Px [partial pressure x solubility]
How do we measure diffusing capacity of lung
Single breath inhalation of carbon monoxide
Diffusion rate of CO2 vs O2 in blood and tissue
CO2 diffuses 20 times faster than O2
Solubility of CO2 vs O2
CO2 is about 23 times that of O2
Partial Pressure of O2 in arterial system
100 mmHg
Partial Pressure of O2 in venous system
40 mmHg
Partial Pressure of CO2 in arterial system
40 mmHg
Partial Pressure of CO2 in venous system
46 mmHg
Partial Pressure of O2 in Alveolus
105 mmHg
Partial Pressure of CO2 in Alveolus
40 mmHg
What determines Alveolar PCO2
CO2 production in body/ Alveolar ventilation
If CO2 production is constant, then PACO2 is determined by
Alveolar Ventilation
How does cellular O2 consumption affect PAO2
Decreases, more O2 will leave alveoli and enter blood
Alveolar Gas Equation
PAO2 = PIO2 - PACO2/R
Definition of Hypoxemia
Arterial PO2 < 100mmHg
A - a gradient is a measure of
whether O2 has equilibrated b/t alveolar gas and pulmonary capillary blood
A - a gradient is useful for
examining causes of hypoxemia
Ratio of arterial PO2 to fraction of inspired air is used as a measure of
Acute Lung Injury
What is used as a measure of Acute Lung Injury
Ratio of Arterial PO2 to Fraction of Inspired Oxygen
Gas transfer is said to be ____-limited
Perfusion-limited, b/c all blood leaving capillary ahs reached equilibrium with the alveolar gas
CO transfer is ____-limited
Diffusion limited
What causes oxidation of Iron to Methemoglobin
Nitrites and Sulfonamides
T/F: Oxygen bound to Hb does not contribute directly to the PO2 of the blood
TRUE
Typical percent saturation of Hb as it leaves most tissue capillaries
75%
4 Causes of Decreased Hb affinity for O2
PCO2 up, pH down, Temp up, 2,3-DPG up
4 Causes of Increased Hb affinity for O2
PCO2 down, pH up, Temp down, Fetal Hb up, 2,3-DPG down
What increases 2,3-DPG
Metabolite of glycolytic pathway, increased in hypoxia –> Decrease affinity for O2
How does CO affect O2 affinity
Increase, making more difficult to release
3 mechanisms for CO2 transport in blood:
(1) Dissolved CO2; (2) Protein carbamylation, Carbaminohemoglobin; (3) Formation of Bicarb
Amount of CO2 dissolved in blood is determined by
Henry’s Law
How does CO2 bind to proteins in blood
binds to amine goups
Hamburger’s Phenomenon
(1) Diffusion of HCO3- back into plasma causes decr. In net neg charge in cell; (2) Cl- moves into cell; (3) Cl- drags H20 into cell, causing swelling
What causes Cl- shift in Hamburger’s Phenomenon
Band Three Protein, an anion exchange protein
How are H+ ions carried in venous blood
Remain in RBC’s buffered by deoxyHb
Rate limiting step of bicarb reaction
CO2 + H20 to H2CO3
Shape of CO2 vs O2 curve
O2 is s-shaped; CO2 is linear -> Changes in PCO2 over broad range will have same effect on CO2 content
Steepness of CO2 vs O2 curve
CO2 curve is much steeper –> Allows big changes in CO2 with changes in PCO2
Haldane Effect
Oxygenation of Hb decreases its ability to carry CO2 –> Shifts CO2 curve right
Ratio of excretion of HCO3 by the kidney relative to CO2 by the lung
[100mEq/day] / [10,000mEq/day]
pH in terms of HCO3 and CO2
pH = 6.1 + log[HCO3]/(0.03PCO2)
Small changes in Alveolar Ventilation have ____ effects on plasma pH
Pronounced
