Gas Transport Flashcards
In the oxyhemoglobin dissociation curve, when does the switch from the arterial to venous curve occur? venous to arterial?
arterial to venous: when blood goes to the systemic capallaries
venous to arterial: when blood loses CO2 (increase pH)
Why is the oxyhemoglobin dissociation curve shaped the way it is at the bottom and top?
Top: Because the relationship between partial pressure of O2 and O2 in blood is not linear. Becomes flater at top due to hemoglobin being saturated with oxygen
Bottom: cooperative binding of oxygen to hemoglobin (after first O2 binds, the rest are quick to bind)
True/False: Changes in alveolar partial pressure will affect O2 content
False
Why is the oxyhemoglobin curve so steep in the middle?
O2 release is highly sensitive to changes in O2 demands. A small change in partial pressure in tissue will make a quick response by the body (this is why when a muscle is active, it will receive O2 while other tissues won’t)
What is the definition of O2 capacity? Main determinant? Equation and UNITS! and the most common value
O2 capacity is the amount of oxygen the blood potentially could carry if hemoglobin were fully saturated and is determined by amount of hemoglobin.
Equation: O2 capacity= hemoglobin concentration X 1.34 ml O2/gm Hb
units: ml O2/dl blood
Common value: 20.1 ml 02/dl blood
What is the definition of O2 content of blood? Determinants and equation w/ units!
Defintion: amount of O2 in the blood depends on the O2 capacity, the percent saturation, plus a small contribution of dissolved O2
(Hb-bound O2 + dissolved O2)
Equation: Content O2= (percent saturation of hb X O2 capacity + (solubility of O2 X Partial pressure of O2)
Units: ml O2/100 ml of blood
How much of O2 is normally bound to hemoglobin? dissolved? and what is the significance of the extended oxyhemoglobin curve?
Hemoglobin: 98%
Dissolved: 2%
Amount of dissolved O2 is prop to the partial pressure of O2. At partial pressures over 100 torr, the boyd is 100% saturated w/ oxygen and large changes in PO2 won’t affect saturation
How would we be asked to solve for dissolved O2 on the exam?
Using the oxygen content equation
What is the solubility of O2 in the blood
0.003
When a patient is said to have a 98% oxygen saturation, is this referring to their oxygen content or capacity
Neither!
What 4 things shift the oxygen dissociation curve? how?
- increase CO2, right shift
- increase H+, right shift
- increase 2,3 DPG, right
- increase temp, right
What are the effects of a right shift of the curve on O2 affinity to Hb? What is occurring at the lungs and tissue? Which is a more prominent change?
- Right shift means a lower affinity of O2 to hemoglobin
- lungs: reducation in O2 taken up by blood (only a little bit. because curve is flat at top)
- tissue: large reduction in O2 capacity of Hb, thus O2 will be released (more prominent)
What is the role of 2,3 DPG?
bind to hemoglobin near binding site of O2 and decreases affinity (almost like an inhibitor)
What is changing in individuals w/ polycythemia and anemia? What is the result to the oxygen dissociation curve?
Polycythemia: increased Hb content. Upward shift
Anemia: lowered Hb content. Downward shift
What is the effect of CO to the oxygen dissociation curve? What two ways does it affect hemoglobin/oxgyen binding?
- leftward shift
1. CO competes w/ O2 for hemoglobin binding sites and has a 240 times greater affinity than O2 to hemoglobin
2. Allosteric effect on remaining sites, causing Hb affinity for O2 to increase (leftward shift) thus less O2 is released to the tissue
What is the most effective treatment for CO poisoning?
Give pure oxygen
-at higher oxygen concentrations, you get a faster response
CO binding to hemoglobin reduces the ____ of oxygen in the blood
capacity (reducing the amount of available hemoglobins)
What are the 4 types of hypoxias? 3 possible outcomes of hypoxia?
- Types: hypoxic, anemia, hypoperfusion, histotoxic
- Outcomes: revisibile tissue injury, irreversible tissue injury, death
What is occurring in hypoxic hypoxia? (mechanism) and diseases associated? (5)
Mechanism: low alveolar oxygen leading to low arterial oxygen and thus a lower driving force for prefusion and a low oxygen in the system.
Diseases: hypoventilation, diffusion impairments (fibrosis, edema), shunts, V/Q mismatch, or high altitude
What is occuring in anemic hypoxia? What usually stays the same?
Lowered O2 capacity due to lack of hemoglobin.
Same: arterial oxygen
What is occurring in hypoperfusion hypoxia? When does it occur?
Normal O2 pressure and content. Slow flow of blood thus O2 is extracted before it gets to the tissue (longer travel time).
-During shock and arterial obstruction
What is occuring in histotoxic hypoxia?
Metabolic poisons affected O2 utilization for mitochondrial respiration
What makes up the total CO2 in the blood? (percents)
- Dissolved CO2= 5-10%
- Bicarbonate: 70-90%
- Carbamino compount: 5-10%
Of the components of total CO2 in the blood, what are their percentages of transport from the venous to arterial content?
Dissolved CO2: 10% transported
Bicarbonate: 60-69%
Carbamino: 21-30%
What is the bicarbonate equation? Rate determining step? Catalysts? Location?
CO2 + H20 –> H2CO3–> HCO3- + H+
First part is the rate determining step. (second part is fast)
Catalyst: carbonic anhydrase
What does the proton in the bicarbonate reaction do?
Binds to hemoglobin and thus reduces affinity of hemoglobin to oxygen (releases oxygen to the tissue to oxygenate)
What regulates CO2 content in the blood?
pressure of oxygen
What is the net affect of the Haldane effect? Basic idea
increases net Co2 transported to lungs by 50%
oxygenation of hemoglobin promotes dissociation of CO2 from hemoglobin
What are the two ways the haldane effect increases CO2 transport to the lung?
- Reverse bicarbonate reaction where free protons bind to bicarbonate to create CO2 to expel to lungs
- binds more readily to deoxy Hb than oxy Hb
What classifies someone as having cyanosis?
less than 5 gm/dl deoxyhb
What is on the y and x axis of the oxygen dissociation curve?
Y: oxygen saturation
X: partial pressure of oxygen
At normal pressure of the lung (100 torr) what is the oxygen saturation
98%
T/F we get the same saturation of oxygen at all parts of the lung
False, top gets a higher saturation (closer to 98) and bottom gets lower (closer to 90)
What part of the dissociation curve do highly metabolically active tissue go?
Lower parts because when they need oxygen, they will receive a larger amount
What is the oxygen content equation broken down into words?
(O2 capacity w/ oxygen saturation) + (dissolved oxygen)
Dissolved O2 content is directly proportional to?
PO2
O2 content depends on what?
- concentration of Hb
2. saturation
Why does pH shift the oxygen dissociation curve the way it does?
it shifts it right because at low pHs, tissues need oxygen. By shifting right, at a given partial pressure of O2, you will get more oxygen delivered to the tissue
In comparing anemic and CO bound to hemoglobin dissociation curves, what things are similar and what is different?
Similar: both have less hemoglobins available for binding
Different: CO curve is shifted left because allosertic affect (CO bound to hemo causes O2 to bind to the other 3 sites up it is trapped and now can’t be oxygenate tissue)
When is elevated COHb cause symptoms and when is it lethal?
From 10-30% CoHB: headache, nausea, CNS malfunction
Greater than 40 is lethal
What is anoxia?
A reduction in oxygen saturation occurs and thus further distant cells of the mitochondria do not receive oxygen
Do intracellullar structures further away from capillary receive larger/less/or the same oxygen saturation as tissue closer to capillary?
Less
Describe the mechanism of how a tissue receives oxygen
Elevated CO2 diffuses from the tissue into a RBC. The bicarbonate reaction occurs that leads to the formation of HCO3- and a proton. The proton reactions w/ a HbO2 species to form HHb + O2 (Bohr Effect). This free oxygen now goes back into the tissue to oxygenate it
What is a chloride shift?
Bicarbonate formed in the bicarbonate reaction leaves the RBC. To maintain electronuetrality, a chloride comes into the RBC.
Where will chloride plasma concentrations be greater, arterial or venous blood? whY?
Greater in the arterial blood.
Venous blood is deoxyenated so the chloride shift is occurring here (all the chloride is in the RBC and not the plasma)
Does dissolved CO2 have a bigger/smaller/similar effect than dissolved O2? Why?
bigger effect because it is more soluble
What is the Haldane Effect saying in terms of affinity of Hb to CO2 (from youtube video)?
O2 is affecting the affinity of Hb to CO2/H+
In a haldane effect graph, what structure is represented in lower parts of the graph? higher?
Lung (low CO2 system)
tissue (high CO2 content)
What is the net result of increased oxygen to the Haldane effect graph? How?
Shifts it to the right and increases CO2 delivery to the lung.
-Oxygen binds Hb, so HHb is reduced and you have free protons hanging around. These protons go and conduct the reverse bicarbonate reaction and thus create CO2 that can be expelled from lung
