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62 Cards in this Set
- Front
- Back
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If atmospheric air is 79% nitrogen, what is the partial pressure of N in atmospheric air?
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.79 * 760 mmHg = 600 mmHg
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Suppose some air was composed of 4 gasses and was 100 mmHg. The partial pressure of gas 1 was 30, gas 2 was 40, gas 3 was 10. What is the partial pressure of gas 4?
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20 mmHg. the partial pressures have to add up to the total pressure of the air (100 in this case, 760 for atmospheric air)
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Fun, somewhat obvious fact: partial pressure of a gas is directly proportional to the concentration of the gas's molecules
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yea, that was pretty obvious
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Atmospheric oxygen has a partial pressure of 160 mmHg. What % is this of atmospheric air?
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160/760 = 21%
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Partial pressure of a gas in fluid is determined by what 2 factors?
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concentration and solubility coefficient
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A molecule that is very soluble in water will have a (higher or lower) partial pressure in blood?
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lower. once its dissolved, it exerts less of a force on other molecules, hence less pressure
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Henry's Law
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partial pressure = concentration of gas / solubility coefficient
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What is more soluble in water, oxygen or CO2?
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CO2
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What is more soluble in water, oxygen or carbon monoxide?
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oxygen
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Vapor pressure of water in the body?
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47 mmHg
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When dehumidified air is inhaled, why does evaporation occur?
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The new dry air has a low water vapor pressure. The water in the respiratory passages will humidify it due to the gradient
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Diffusion is directly proportional to ...
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pressure difference, area of diffusion surface, solubility of molecule
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Diffusion is inversely proportional to ...
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distance of diffusion, square root of Molecular weight (heavier moves slower)
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Expired air has (more or less) CO2 than atmospheric air?
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more
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Expired air has (more or less) O2 than atmospheric air?
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less
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Expired air has (more or less) H2O than atmospheric air?
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more water
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Why are nitrogen levels lower in expired air compared to atmospheric air (inspired air)? hint: we do not absorb nitrogen into the blood
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The humidification of water in the respiratory system raises the water pressure (to 47) and therefore dilutes all the other partial pressures. since all partial pressure add up to the same value (760), if one increases the rest must decrease. (CO2 also increases in expired air)
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after how many breaths is the residual volume completely replaced?
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over 16
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Why is it important that alveolar air is replaced slowly? through mechanisms like residual volume
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prevents sudden changes in gas concentration in the blood. gives a delay so the body can compensate for any gas changes
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alveolar pO2 is controlled by what 2 factors?
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rate of ventilation and rate of absorption into blood
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What is the maximum pO2 that can exist due to the basic principles of partial pressure?
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149. basic principles state that the sum of all partial pressure must = the total air pressure. pO2 can't go too high without lower the other values too much
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Alveolar pCO2 is (directly or inversely) proportional to ventilation rate?
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inversely. more CO2 buildup = lower ventilation rate
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Alveolar pCO2 is (directly or inversely) proportional to CO2 excretion from blood?
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directly. as CO2 exits the RBC, it enters the alveoli
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Expired air is a combination of alveolar air and _____
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dead space air
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Respiratory unit is made up of ...
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resp. bronchiole, alveolar duct, atria, alveoli
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Pulmonary capillaries are in close proximity and in high numbers and have been described as a "______"
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sheet of flowing blood
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all respiratory membranes are collectively called the ...
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pulmonary membrane
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6 layers Oxygen must pass from lung to RBC
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surfactant, alveolar epithelium, alveolar basement, interstitial fluid, capillary basement, endothelium
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Why don't oxygen and CO2 need to move through much plasma to enter the RBC?
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The RBC is in close contact with the endothelium
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What diseases cause thickness of respiratory membrane?
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edema (increased interstitial fluid), fibrous lungs,
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What diseases decrease surface area of respiratory membrane?
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COPD/emphysema,
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What is diffusing capacity defined as?
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volume of a gas that will diffuse through membrane each minute for a pressure difference of 1 mmHg
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Normal oxygen diffusing capacity
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21 ml/min/mm Hg
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If the normal oxygen diffusing capacity is 21 and there is normally a pressure difference of 11 mmHg between lungs and pulmonary blood, how much oxygen is diffusing per minute?
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11*21 = 230 mL/min
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During exercise, what causes an increase in oxygen diffusing capacity?
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opening new capillaries at the lung apex (Zone 2 to Zone 3 as diastolic pressure increases), better ventilation/perfusion ratio
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Why does there not need to be a large difference in pCO2 in alveoli and in pulmonary blood?
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It diffuses so rapidly (due to increased solubility, 20x oxygen) that it doesn't need large gradients to move
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Oxygen diffusing capacity cannot be measured directly. Why?
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We cannot accurately calculate pulmonary capillary pressure. We need this value to determine how much oxygen is being diffused
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Since oxygen diffusing capacity cannot be directly measured, what do we measure instead?
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Carbon monoxide diffusing capacity
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How do we use carbon monoxide diffusing capacity to estimate oxygen diffusing capacity?
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Breath in some CO (known amount), subtract however much is exhaled (since all the CO that wasn't exhaled was certainly taken into the blood, since CO combines with Hb so rapidly). multiply by 1.23
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When estimating oxygen diffusing capacity with CO capacity, why do we multiply by 1.23?
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oxygen's diffusion coefficient is 1.23x CO's
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Why is Carbon monoxide a good gas to use to estimate any molecules diffusion rate?
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CO is taken directly into hemoglobin form alveoli, so we can determine how fast something gets from alveoli to the Hb. then we can adjust for the diffusion coefficient of the molecules
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Ventilation refers to ...
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rate of air entering alveoli
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Perfusion refers to ...
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rate of gas exchange from alveoli to Hb
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Formula for ventilation perfusion ratio?
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Va/Q. Va is ventilation, Q is blood flow
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A ventilation- perfusion ratio of 0 indicates ...
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there is no ventilation, air is not getting into the lungs
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A ventilation- perfusion ratio of infinity indicates ...
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there is no perfusion, oxygen is not getting into the blood
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When ventilation/ perfusion = 0, the pCO2 and pO2 of alveolar air will equilibrate to what values?
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that of venous blood. pCO2 = 45, pO2 =40
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When ventilation/perfusion = infinity, the pCO2 and pO2 of alveolar air will equilibrate to what values?
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pO2 will become maximum as the body is trying to get max air in (max pO2 is 149). pCO2 = 0, this can only come from the blood, we don't inhale CO2. if there is no perfusion (V/Q= infinity), no CO2 form blood is getting into the alveoli
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Normal alveolar air has what pO2 and pCO2 values?
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pO2 = 104, pCO2 = 40
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What is a physiological shunt?
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An area where there is decreased ventilation causes blood to flow through and remain deoxygenated. V/Q approaches 0
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High physiological shunt means...
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high amount of blood remains deoxygenated as it moves through the pulmonary system. bad ventilation
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What is physiological dead space?
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Areas where ventilation occurs, but no perfusion. V/Q approaches infinity
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The bottom of the lung has a (high or low) V/Q ratio?
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low. there is less ventilation in the bottom of the lungs
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The apex of the lung has a (high or low) V/Q ratio?
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high. there is less blood flow to the apex due to hydrostatic pressure during diastole (zone 2 circulation)
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The apex of the lung exhibits (physiological shunt or dead space)
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dead space
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The bottom of the lung exhibits (physiological shunt or dead space)?
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shunt. less air gets down there so V/Q approaches 0
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V/Q approaching 0 indicates?
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physiological shunt
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V/Q approaching infinity indicates?
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dead space
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The apex of the lung exhibits (physiological shunt or dead space)
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dead space. air gets in, but doesn't perfuse due to hydrostatic pressure and zone 2 circulation during diastole
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During excersize, how does the V/Q ratio become more optimal?
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circulation to the apex increases= higher Q value = decreasing dead space
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Why do smoking patients with emphysema/COPD have areas of severe shunting and severe dead space?
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smoking obstructs bronchioles to decrease ventilation in some areas and COPD causes decreases alveolar wall area so there is less perfusion
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Why is pCO2 partial pressure lower than the pCO2 of
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it is more soluble. solubility decreases partial pressure
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