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What the ratio of alveolar CO2 excretion (VCO2) to blood oxygen uptake (VO2) called?
The respiratory exchange ratio =0.8
What is the normal PA02 for a person breathing room air at seal level, with a PaCO2 equal to 40 torr and Respiratory Exchange Ratio at normal value?
According to Fick's Law that if the Vgas increases if there are increases in what?
surface area, gas diffusivity or diffusion pressure gradient
How many time faster does O2 diffuse through a gas medium over CO2 and why?
It diffuses 1.7 times faster due to its lighter molecular weight
When combining Graham's Law and Henry's law CO2 diffuses across the alveolar capillary membrane about how much faster than O2?
Henry's Law states what regarding gas dissolving in a liquid?
It is directly proportional to the gas' partial pressure.
When there are defects in the Alveolar capillary membrane what will happen long before CO2 is limited in diffusion?f
It will limit O2 diffusion
The rate of diffusion is rapid at first when the partial pressure gradient across the alveolar capillary membrane is greatest. What will happen to the diffusion rate as partial pressure gradient diminishes?
The diffusion rate will continue to slow until at equilibrium diffusion will cease.
During the last two thirds of travel through the pulmonary capillary what occurs?
under normal circumstances no diffusion occurs
What can happy when a healthy person exercises vigorously at a high altitude, where atmospheric PO2 is very low?
The diffusion gradient my be so low that oxygen cannot cross the alveolar capillary membrane quickly enough to establish equilibrium during a shortened transit time.
Patients with thickened alveolar capillary membranes are mostly to show evidence of O2 when?
What is it called when O2 transfer never reaches equilibrium between the alveolus and capillary because of thickened membranes?
What is the ideal gas for the measurement of gas diffusion and why?
Carbon monoxide because the blood can absorb it at a greater rate than it can diffuse across the alveolar capillary membrane even at rest.
What gas when inhaled reaches it maximum capacity almost instantly in the pulmonary capillary blood?
N2O - Nitrous oxide
What are the nine steps in the pathway from the alveolus to capillary?
1. Surfactant layer that is lining the alveolar surface
2. the alveolar epithelium
3 the basement membrane of the alveolar epithelium
4. extremely thin interstitial space
5 the basement membrane of the capillary endothelium
6. The capillary endothelium
8. The red cell membrane
9. intracellular fluid bathing the hemoglobin molecule
What abnormal conditions can increase the diffusion path length?
1. Fibrotic thickening of alveolar and capillary walls
2. interstitial edema fluid, separating alveolar and capillary membranes
3. fluid alveoli
4. interstitial fibrotic processes that thicken the interstitial space.
5. dilated, engorged capillaries, which allow red cells to flow side by side.
What is the major cause of resting hypoxemia?
a mismatch between ventilation and blood flow (V/Q mismatch)
What is the standard accepted normal range for healthy adults in the upright position?
20-30 mL/min/mm Hg
To obtain the diffusion capacity of the lung for oxygen (DlO2) it must be multiplied by what number?
What kind of PAO2 is associated with a lower DlCO and why?
A higher PAO2 is associated with a lower DlCO because in the blood, O2 competes with CO for binding sites on the hemoglobin molecule.
DlCO is useful in differentiating between what?
emphysema from other obstructive diseases not associated with destroyed alveolar architecture such as chronic bronchitis and asthma.
One hundred percent saturation does not imply that the blood O2 content is normal. This statement implies what?
Saturation percent is not a measure of oxygen or hemoglobin concentration.
What is the conventionally accepted value for hemoglobin's oxygen-carrying capacity?
1.34 mL of O2 per gram of hemoglobin.
How much oxygen will hemoglobin allow from whole blood to carry?
Approximately 20 mL per 100 mL of blood at the normal arterial PaO2 of 100 torr.
How much more will hemoglobin allow from plasma alone rather than whole blood to carry oxygen?
67 times more
How much oxygen will a cardiac output (Q) of 5 L/min deliver to the body's tissue each minute?
What is the SO2 when the PO2 is 27 torr, blood temp is 37 degrees C, the pH is 7.40, and the PCO2 is 40 torr?
What are some factors that might decrease hemoglobin's affinity for oxygen?
1. increased blood PCO2
2. decreased blood pH
3.increased body temp
4. increased blood levels of 2,3-DPG
What is the decreased affinity of oxygen, right curve shift cause by high PCO2 known as?
The Bohr effect
If a patient receives large transfusions of banked blood that is stored for several days can theoretically do what?
impair oxygen release to the tissues
What are factors that can affect oxygen delivery (O2 DEL) to the tissues?
1. hemoglobin concentration
2. arterial hemoglobin saturation with oxygen (automatically taking PaO2 into account.
3. Cardiac Output
The cardiopulmonary system delivers approximately how much of oxygen to the tissues each minute at rest?
Why does slow moving blood give up more oxygen to tissues?
It spends more tiime in contact with the tissue. This causes the blood leaving the capillaries to have relatively low oxygen content.
What is the point which O2 DEL fails to satisfy the tissue demands of oxygen fails called? What can happen when it falls below that point?
The point is referred to "critical oxygen delivery threshold." If it fall below that point it can cause tissue hypoxemia and lactic acid accumulation.This marks a transition from aerobic to anaerobic metabolism throughout the body.
In relation to the critical oxygen delivery threshold what has been found when blood transfusions were administered?
patients do not increase their oxygen availability to the tissues. There is an association to increased mortality, independent of the diseases severity. Transfusions may increase O2 delivery but are generally not associated with increased tissue oxygen consumption and may even be linked to tissue hypoxia.
Most observers do not perceive cyanosis until when?
the average desaturated hemoglobin concentration in the capillaries is at lease 5 g per 100 mL of blood.
In acute CO poisoning what is extremely important in displacing the CO from the hemoglobin molecule?
Administering 100% oxygen
Fetal Hemoglobin (Hb) has a high affinity for oxygen. How can you explain this?
The organic phosphate 2,3-DPG does not bind with HbF. HbF and adult hemoglobin (HbA) without 2,3-HPG have similar left-shifted HbO2 equilibrium curves.
Sickle cell hemoglobin is much less soluble that HbA in the deoxygenated state. What tends to happens to HbS in the red blood cell on deoxygenation?
tends to crystalize. This changes the red cell to a biconcave to a curved, sickle shape.
What can happen to sickle-shaped cells?
The cells are fragile and subject to rupture. The shape also causes to tangle with other sickle cells and they clump together to form thromboemboli.
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