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Mizzou MPP 3202 - Chapter 18

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PowerPoint PresentationFigure 18.1Slide 3SensorsTable 18.2 Normal Blood Values in Pulmonary MedicineFigure 18.2Causes of Low Alveolar PO2Pathological examples for low alveolar PO2Diffusion and Solubility Influence Gas ExchangeFigure 18.4a-cFigure 18.4d (6 of 6)Slide 12Figure 18.5Figure 18.7a (1 of 3)Figure 18.7b (2 of 3)Figure 18.7c (3 of 3)Figure 18.8Figure 18.9 ESSENTIALS – Oxygen-hemoglobin Binding CurvesSlide 19Carbon Dioxide TransportFigure 18.11Regulation of VentilationSlide 23Protective Reflexes Guard the LungsSlide 25© 2013 Pearson Education, Inc.Gas Exchange and TransportChapter 18Figure 18.1PULMONARY GAS EXCHANGE AND TRANSPORTCO2 enters alveoliat alveolar-capillaryinterface.AirwaysAlveoli of lungsCO2O2O2O2O2O2CO2CO2CO2CO2CellsATP NutrientsSystemiccirculationPulmonarycirculationCO2 is trans-ported dissolved,bound tohemoglobin, oras HCO3.CO2 diffusesout of cells.Cellularrespirationdeterminesmetabolic CO2production.Oxygen diffusesinto cells.Oxygen is trans-ported in blooddissolved in plasmaor bound tohemoglobin insideRBCs.Oxygen enters theblood at alveolar-capillary interface.Hypoxia = a state of too little oxygen – results from impaired diffusion in lungs or inadequate oxygen transport in bloodHypoxia often (but not always) accompanied by hypercapnia (elevated carbon dioxide levels)Sensors•To avoid hypoxia and hypercapnia, the body responds to three regulated variables–Oxygen–Carbon dioxide–pH© 2013 Pearson Education, Inc.Table 18.2 Normal Blood Values in Pulmonary MedicineSystemicblood“Blood Gases”Figure 18.2GASES DIFFUSE DOWN CONCENTRATION GRADIENTSCO2O2O2CO2Dry air  760 mm HgPO2  160 mm HgPCO2  0.25 mm HgAlveoliPulmonarycirculationPO2  100 mm HgPCO2  40 mm HgPO2  40 mm HgPCO2  46 mm HgPO2  100 mm HgPCO2  40 mm HgVenous blood Arterial bloodPO2  40 mm HgPCO2  46 mm HgSystemiccirculationAerobic metabolism consumesO2 and produces CO2.CellsCauses of Low Alveolar PO2•Inspired air has abnormally low oxygen content–Altitude is major factor influencing atmospheric oxygen•Alveolar ventilation is inadequate–Decreased lung compliance–Increased airway resistance–CNS depression– Alcohol poisoning– Drug overdose© 2013 Pearson Education, Inc.Pathological examples for low alveolar PO2•Pathological changes–Decrease in amount of alveolar surface area–Emphysema (smokers)–Increase in thickness of alveolar membrane–Fibrotic lung diseases–Increase in diffusion distance between alveoli and blood–Pulmonary edema© 2013 Pearson Education, Inc.__ Asthma – bronchoconstriction reduces alveolar ventilationDiffusion and Solubility Influence Gas Exchange•Constants (normally!!)–Surface area –Membrane thickness–Diffusion distance–Temperature•Concentration gradient –Primary factor affecting gas exchange© 2013 Pearson Education, Inc.Figure 18.4a-cOxygen solubilityInitial state: no O2 in solution Oxygen dissolves. At equilibrium, PO2 in air and water are equal. Low O2solubility means concentrations are not equal.PO2  100 mm HgPO2  100 mm Hg[O2 ]  5.20 mmol/L[O2 ]  0.15 mmol/LPO2  100 mm HgPO2  0 mm HgGas solubility affects amount of dissolved gas that can be carried by plasmaOxygen solubility is low  very little oxygen can be carried dissolved in plasmaFigure 18.4d (6 of 6)FIGURE QUESTIONWhen CO2 is at equilibrium at the same partial pressure(100 mm Hg), more CO2 dissolves.[CO2 ]  5.20 mmol/LPCO2  100 mm HgPCO2  100 mm Hg[CO2 ]  3.00 mmol/LIf arterial blood has a PO2 of 95 mm Hg and aPCO2 of 40 mm Hg, what are the oxygen andCO2 concentrations (in mL gas/L blood)?Physiologists also express dissolved gases inblood using the following equation: for oxygen is (0.03 mL O2/L blood)/mm Hg PCO2 for CO2 is (0.7 mL CO2/L blood)/mm Hg PCO2[Gas ]diss   [Pgas]Carbon dioxide is 20 times more soluble in water than oxygen isGAS TRANSPORTIN THE BLOODFigure 18.5Slide 1More than 98% of the oxygen in blood is bound to hemoglobinin red blood cells, and less than 2% is dissolved in plasma. ARTERIAL BLOOD O2 O2 dissolved in plasma (~Red blood cell O2 + Hb HbO2 > 98%AlveolusAlveolarmembraneCapillaryendotheliumTransportto cellsCellsHb + O2 HbO2 O2 O2 dissolvedin plasmaUsed incellularrespirationFIGURE QUESTIONHow many cell membranes will O2 cross in itspassage between the airspace of the alveolusand binding to hemoglobin?PO2) < 2% © 2013 Pearson Education, Inc.Hemoglobin transports most of the oxygen in the bloodFigure 18.7a (1 of 3)Oxygen transport in blood withouthemoglobin. Alveolar PO2  arterial PO2PO2  100 mm HgAlveoliO2 moleculePO2  100 mm HgArterialplasmaOxygen dissolves in plasma.O2 content of plasma  3 mL O2/L bloodO2 content of redblood cells  0Total O2 carryingcapacity3 mL O2/L bloodFigure 18.7b (2 of 3)Oxygen transport at normalPO2 in blood with hemoglobinO2 content of plasma  3 mL O2/L bloodO2 content of redblood cellsTotal O2 carryingcapacity 197 mL O2/L blood200 mL O2/L bloodPO2  100 mm HgRed blood cells with hemoglobin are carrying98% of their maximum load of oxygen.PO2  100 mm HgFigure 18.7c (3 of 3)PO2  28 mm HgOxygen transport at reduced PO2 in blood with hemoglobinPO2  28 mm HgO2 content of plasma  0.8 mL O2/L bloodO2 content of redblood cells 99.5 mL O2/L blood100.3 mL O2/L bloodRed blood cells carrying 50% oftheir maximum load of oxygen.Total O2 carryingcapacityFigure 18.8The amount of oxygenbound to Hb depends on% Saturationof HbPlasma O2The amount ofhemoglobinTotal number ofHb binding sitesHb contentper RBCNumberof RBCswhich determineswhich determinescalculated fromFigure 18.9 ESSENTIALS – Oxygen-hemoglobin Binding CurvesPO2 determines oxygen- hemoglobin bindingSeveral Factors Influence Oxygen-Hb BindingpHTemperaturePCO22,3-DPG (2,3-diphosphoglycerate)Changes in hemoglobin structure (fetal Hb)Decreased pH, increased temperature, increased PCO2decrease oxygen bound to hemoglobinCarbon Dioxide Transport•Dissolved: 7%•Converted to bicarbonate ion: 70%•Bound to hemoglobin: 23% –Hemoglobin also binds H–Hb and CO2: carbaminohemoglobin© 2013 Pearson Education, Inc.Figure 18.11CARBON DIOXIDE TRANSPORTMost CO2 in the blood has been convertedto bicarbonate ion, HCO3.CO2 diffuses out of cells into systemiccapillaries.Only 7% of the CO2 remains dissolvedin plasma.Nearly a fourth of the CO2 binds tohemoglobin, forming carbaminohemoglobin.70% of the CO2 load is converted tobicarbonate and H.


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Mizzou MPP 3202 - Chapter 18

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