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15 Cards in this Set
- Front
- Back
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Explain the oxygen cascade in the body
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The partial pressure of O2 in the air is about 159 Torr. As soon as it gets in the airways the partial pressure drops to 149 Torr due to humidification. In the air the PO2. Later when the air mixes with alveolar air the partial pressure drops to 104 Torr before diffusing into the blood at this pressure.
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What is the effect of normal anatomical shunts on the PO2 in the blood.
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After the blood passes the alveoli normal anatomical shunts further reduce the PO2 to about 94 Torr.
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What are the 3 main factors affecting alveolar gasses?
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1. Quantity and quality of gases delivered by diffusion
2. Rater of diffusion of the gases between the alveoli and the capillary bed. 3. Cardiac output or pulmonary blood flow which removes O2 and adds CO2 to the alveoli. |
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Composition of air on Earth is?
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78% Nitrogen
21% Oxygen 0.03% Carbon Dioxide |
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How does the barometric pressure relate to the gases on Earth?
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The Pb depends on the Earth's gravitational field. At higher altitudes there is less pressure but the fractional content of gases remains the same.
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How to calculate PO2 in the atmosphere?
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PO2 = FO2 * Pb
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Water vapor effect on gases?
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Water vapor will bring down the barometric pressure but not the percent of gases. The PH2O will increase with heat.
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What is the effect of water vapor on PO2?
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The PH2O at 37C is 47 Torr. So the PO2 in the body drops
PO2 = 0.21 * (760-47) PO2 = 149 Torr |
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Functional Residual Capacity(FRC)
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Volume of air left in the lungs after passive expiration. A low or elevated FRC is often the sign of respiratory disease.
High FRC could be indicative of emphysema(lungs as a paper bag) and Low FRC could be indicative of interstitial pulmonary fibrosis(lungs hard like a rock). |
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Obstructive and restrictive lung disorders
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An obstructive disorder is a problem with the airways while a restrictive disorder is a problem with the lungs.
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Alveolar gas equation
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Relate the alveolar pressure of oxygen to the fraction you are able to respire.
PaO2=PiO2(Pb - Ph2o[1-FiO2]/R) The R value indicates the amount of fats(.7), carbs(1), and proteins(.8) you eat. The lower the R value the lower the PaO2 because there is more PaCO2 in the lungs. |
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Minute Volume/ Ventilation
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# of breaths/min * Tidal volume
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Cardiac output
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the total blood flow Q = stroke volume * beats/min
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Ficks Law
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Diffusion rate
Qdot = KA(C1-C2)/L |
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Why is there a Pressure difference in blood and the atmosphere
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The Ptotal in blood can be less than the Pb because blood is a closed system. Uptake of O2 by the tissues causes a larger drop in pressure than excretion of CO2.
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