Gas Exchange Physiology

 Deeper you go under water, does the water pressure increase or decrease? Increase Higher you climb the Himalayas, does the air pressure increase or decrease? Decrease Is atmospheric pressure higher in Denver or Mesa? Mesa, because we are lower in altitude vs Denver is high up there What is the atmospheric pressure near sea level? 760 mmHg Is pressure greatest at lowest or highest altitude? Lowest What is the fractional concentration of oxygen in air? 21% What is the fractional concentration of nitrogen in air? 78% What is the fractional concentration of carbon dioxide in air? 0.03% -- effectively zero! True/False: atmospheric air is simply just oxygen gas and nothing else False; atmospheric air is a mixture of gasses—nitrogen, oxygen and some carbon dioxide What is the equation for partial pressure? Partial pressure = total pressure x fractional concentration of gas What is Dalton’s Law? Total pressure is sum of partial pressure of gas mixtures What is the partial pressure of oxygen in atmospheric air? PO2= 760 mmHg x 0.21= 159.6 mmHg Atmospheric pO2 is _____ tracheal pO2 Greater than True/false: Water vapor is present in the trachea so water vapor displaces atmospheric air, thereby reducing tracheal pO2 True At 37C, aka body temp, what is the amount of water vapor in the airway? 47 mmHg Water vapor in humidified tracheal air is in which state? Gaseous How would you calculate pO2 in the trachea? Must subtract water vapor in the airway, which is 47 mmHgTracheal pO2= (760-47) x 0.21 = 150 mmHg Why is pO2 in trachea calculated differently from pO2 in atmosphere? Because respiratory system releases water vapor into the airways and this water vapor exerts partial pressure within the airway, so atmospheric air is displaced Why is water vapor in the airways important? Water vapor prevents epithelial tissue of airways from getting dried out while breathing Tracheal pO2 is ____ alveolar pO2 Greater than Why is alveolar pO2 less than Tracheal pO2? Because alveoli exchange gas with blood, so there is less oxygen in the alvoli as compared to trachea Tracheal pCO2 is _____ alveolar pCO2 Less than Gas exchange occurs by _______, not ________. Diffusion; active transport Venous pO2 entering the alvoeli is about _____. 40 mmHg After gas exchange has taken place between the blood and alveoli, what is the partial pressure of O2 in arterial? In alveoli? Equal in both (100 mmHg in textbook picture) What is the pCO2 between alveoli and arterial blood after gas exchange? Equal, just like pO2 are equal in both after gas exchange Venous pO2 (before gas exchange) is ____, and arterial pO2 (after gas exchange) is ____. 40; 100 mmHg Venous pCO2 (before gas exchange) is ___, and arterial pCO2 (after gas exchange) is___. 46; 40 mmHg How come there is a greater difference (60 mmHg) between arterial and venous pO2, than there is a difference (6 mmHg) between arterial and venous pCO2, before and after gas exchange? Because CO2 is more soluble in liquid so it does not exert much partial pressure True/false: gases behave according to their partial pressures, not their concentrations. True Henry’s Law: Concentration of gas in solution = partial pressure gradient x solubility What does Henry’s Law actually mean in Catherine’s head? Basically saying that concentration of gas in solution is dependent on how soluble that gas is, so the more soluble the gas, the greater the concentration of it in solution True/ False: free floating gasses contribute to partial pressure True What role does hemoglobin play in terms of O2 partial pressure in blood? Hgb increase the amount of O2 that our blood can hold without changing arterial pO2. This is because oxygen that are in the hemoglobin does not contribute to the partial pressure of arterial blood, only free O2 molecules contribute to the pressure gradient, allowing the blood to carry more O2 at once ____ molecules contribute to partial pressure gradient. Free floating What is Fick’s law of diffusion describe? Rate of diffusion increases when partial pressure gradient increasesRate of diffusion is proportional to partial pressure gradient, surface area and solubility What is the relationship between the rate of diffusion and molecular weight? Inversely proportional What is the relationship between the rate of diffusion and thickness of the barrier? Inversely proportional What is the relationship between the rate of diffusion and partial pressure gradient? Directly proportional What is the relationship between the rate of diffusion and surface area? Directly proportional What is the relationship between the rate of diffusion and solubility? Directly proportional At the same partial pressures, which diffuse faster, O2 or CO2?CO2, because CO2 is more soluble How does emphysema affect gas exchange? Reduces it because of reduced surface area due to destruction of alveoli True/False: Rate of diffusion changes, gas levels in blood remain the same False; gas levels in blood change too In fibrotic lung disease, how is the rate of diffusion affected? Slowed down because of thickened alveolar membrane as a result of decreaed lung compliance How is the rate of diffusion affected in pulmonary edema? Reduces it because of increased distance between the alveoli and arterial bloodArterial pO2 is lowBut pCO2 in arterial may be normal because of CO2 solubility in water, the distance ain’t no thang for CO2 What happens with the rate of diffusion in asthmatic patients? Increased airway resistance, decreases airway ventilation, so pO2 is low in both alveoli and arterial What are two ways that gases behave during gas exchange? Diffusion limited (slow equilibration)Perfusion limited (fast equilibration) Is diffusion limited fast or slow equilibration? Slow Is perfusion limited fast or slow equilibration? Fast What is perfusion limited gas exchange? Partial pressure gradient is not maintained Gas exchange limited by the amount of blood that perfuses the alveoli What are example of gasses that undergo perfusion limited gas exchange? NO, CO2, O2 (resting) – these gasses quickly equilibrate between alveoli and pulm capillaries, eliminating the partial pressure What is diffusion limited gas exchange? Occurs when the partial pressure gradient is maintained, so gas exchange is limited What are example of gasses and condition that would undergo diffusion limited gas exchange? Oxygen during strenuous exercise, CO, emphysema and pulmonary fibrosis Why is carbon monoxide diffusion limited? Because it is sticky for hemoglobin and binds to it, resulting it less free floating CO that contribute to partial pressure gradient True/false: anything that reduces the rate of diffusion could create diffusion-limited gas exchange if the partial pressure fails to equilibrate True Is alveolar air replaced slowly or quickly? Slowly What happens to the blood delivered to the lungs when we exhale? Does it still get oxygenated? Yes it still gets oxygenated because alveolar air is replaced slowly Air remains in the alveoli and still gets to be oxygenated True/False: arterial pO2 DOES change with the respiratory cycle FALSE; artier pO2 does NOT change with respiratory cycle, arterial pO2 remains constant during inhalation and exhalation Arterial pO2 does/does not vary during respiratory cycle DOES NOT The faster we breathe, the _____ alveolar air gets replaced with fresh air. Faster When we breathe fast, what happens to alveolar pCO2 and pO2? Alveolar pCO2 goes downAlveolar pO2 goes upBecause air gets replaced with fresh air faster True/false: CO2 enters the alveoli from inhaled breath False, there is NO CO2 entering from atmospheric air (essentially 0 CO2 in atm) Where does alveolar pCO2 come from? Blood; after gas exchange with blood, determined by metabolic rate of tissues How is the amount of CO2 that leaves the alveoli determined? By how fast air is moved into and out of the alveoli – aka alveolar ventilation How to calculation alveolar ventilation? Alveolar pCO2= metabolic rate (VCO2)/ alveolar ventilation (Va) What is the relationship between alveolar pCO2 and alveolar ventilation? Inversely proportional In the alveolar ventilation vs alveolar pCO2 graph, what happens to the curve when metabolic rate is doubled? Right shift Can arterial pCO2 be used to estimate alveolar pCO2? Yes kinda, but not super accurate Should approximate each other since gas exchange between those two How is alveolar pO2 measured? Alveolar gas equation: Alveolar pO2= PiO2 – PaCO2/ RIn English: tracheal pressure of O2 (pO2 enter/inspired)– arterial pCO2/ respiratory quotient What should the alveolar-arterial gradient (A-a gradient) be when it is fully equilibrated? 0 What can the A-a gradient be useful for? Distinguishing hypoxemia What could hypoxemia with high A-a gradient indicate? Oxygen is not effectively moving from alveoli to blood What could hypoxemia with normal A-a gradient indicate? Alveolar and arterial oxygen are equilibrating but there is hypoventilation or low atmospheric oxygen Does exhaled air have the same composition as alveolar air? No, because not all inhaled air participate in gas exchange, some are trapped in conduction zone Authorlykthrnn ID345342 Card SetGas Exchange Physiology DescriptionPulmonary Midterm Updated2019-02-13T19:45:24Z Show Answers