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26 Cards in this Set
- Front
- Back
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What is true of the respiratory exchange ratio? |
-It is the ratio of alveoli CO2 excretion to blood oxygen uptake. -R=VCO2/VO2 -Its value is normally approximately 0.8. |
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What statements apply to Fick's law? |
-Gas diffusion increases with increased membrane surface area. -Gas diffusion increases with increased pressure gradient. -Gas diffusion decreases if membrane thickness increases. |
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What law states that the amount of gas dissolving in a liquid is directly proportional to the gas partial pressure? |
Henry's Law |
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Diffusion of what gas will be limited by a defective alveolar capillary membrane? |
O2 |
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What is the main limiting factor for the oxygen transfer right? |
Perfusion |
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What are components of the diffusion path? |
-Capillary endothelium -Intracellular fluid bathing the hemoglobin molecule. -Red blood cell membrane -Aveolar epithelium -Surfactant layer lining the alveolar surface. |
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What conditions can increase the length of the diffusion path? |
-Fibrotic thickening of alveolar and capillary walls. -Fluid in the alveoli -Interstitial edema fluid |
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What condition has an inverse relationship with DLCOSB (Diffusing capacity of the lung for carbon monoxide in a single breath)? |
PAo2 |
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The DLCOSB is useful in differentiating emphysema from what other obstructive disease? |
Asthma |
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For a person breathing 21% oxygen what is the inspired oxygen partial pressure? |
Approximately 160 MMHG |
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What is the PA02 of a person breathing room air at sea level with PaC02 = to 40MMHG and an R = to 0.8? |
Approximately 100 MMHG |
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The rate of gas diffusion in the lung is inversely proportional to its molecular weight and directly proportional to what physical properties? |
Solubility |
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How many times faster does oxygen diffuse through a gas medium then CO2? |
1.2 times |
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C02 is how many times more soluble than o2? |
24 times |
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When our patients with thickened alveolar capillary membrane most likely to show evidence of oxygen diffusion impairment? |
During exercise |
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Oxygen equalibrium between the alveolus and capillary never occur because of thickened membranes, oxygen transfer is truly |
Diffusion limited |
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Why is CO the ideal gas for measuring the extent to which the alveolar capillary membrane itself impedes the diffusion rate? |
Because blood can absorb it at a greater rate than CO can diffuse across the alveolar capillary membrane, even under resting conditions. |
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Why is N2O the ideal gas for measuring the extent to which pulmonary blood contributes to the diffusion rate? |
Because it reaches maximal capacity almost instantly |
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What is the most common of resting hypoxemia? |
A mismatch between ventilation and blood flow |
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What is the mean DLCOSB range for healthy adults? |
20-30mL/min/mmhg |
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How do you obtain the diffusion capacity for oxygen? |
By multiplying DLC02 by 1.23 |
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What is the best explanation for the DLO2 being greater than the DLCOSB? |
O2 is more soluble than CO in the alveolar capillary membrane and the plasma and therefore diffuses more rapidly. |
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The DLCOSB is useful in differentiating emphysema from what other obstructive disease? |
Asthma or chronic bronchitis |
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According to the alveolar air equation, all other factors remaining constant PAO2 |
Increases |
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Administering fluid to a severely dehydrated hypotensive patient inproves diffusion capacity because |
Diffusion surface area is increased |
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We give patients with retained secretions humidified gas to breathe improving their ability to cough out secretions and open previously plugged airways, opening these airways improves diffusion capacity because |
Low ventilation perfusion ratio is corrected |
