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Respiration-Gases, Respiration-Gases Exercise Response O2 delivery=O2 content*CO -increase deliv by increasing CO or content Increase Blood O2 content in two ways: 1. Increase Hb-add packed RBCs 2. increase PO2 of alv. air-little effect, Respiration-Gases Gas Exchange Inhaled air warmed to body temp -more water vapor can be added -reduces vapor P of other gases -vapor P in airway same at all altitudes Dead space air-air in non-gas exchange passages-nose, trachea, bronchi/oles anatomical dead space-passages physiological-alvs w/ no vascular net, Venous Admixture-causes A-aPO2 grad. -systemic circ PO2 lower than PAO2 -due to 3 types of shunts:(ɱ%=problem) -shunt % increases w/ age 1.Anatomical (true/extra-alv) shunt -bronchial vv anast w/ pulm veins -return O2-poor blood w/ O2 rich (also include Thebesian vv.) 2.Physiological (alveolar)-V/Q mismatch -perfusion alv DNE ventilation of alv -VA/Q should equal 1 -if VA/Qə, gradient produced 3.Pathological (Diffusion limitation)- -fibrosis, edema -O2 more limited than CO2 -O2 diff greater w/ higher blood flow Ventilation Phenomena Upright Lung-bottom alvs get more air -more compliant on lung-comp curve -bottom alvs get 4x more blood -below level of heart, gravity -near base, slightly over-perfused PO2, PCO2ᡠmmHg, Respiration-Gases Gas Transport Buffering Hydration rxn-happens in RBC -over 50% of buffering CO2+H2O->H2CO3->H+ +HCO3 -with carbonic anhydrase -mainly in bicarb ion -bicarb leaves, Cl- enters -chloride shift, Hamburger Protein buffering-H+ jumps on imidazole group of His AA -Hb-35% of buffering -proteins-10%, PO4-5% Haldane effect-Hb w/out O2 can transport more CO2, Hypoxia-low O2 in blood/air/tissues Hypoxemia-low blood PO2 -sensed by chemoreceptors -stim. breathing Altitude Descent from high alt. 1.PA02 NL, so vent dec. ->CO2 inc.->acidosis b/c less HCO3- -so vent still up bc less HCO3-, more CO2 2.HCO3- levels normalize, 20:1 bicarb:CO2, Hyperventilation-vent exceeds metabolism PAO2 up, PACO2 down Hypovent-vent inadequate for metab. PAO2 down, PACO2 up ???? Vol%=mL gas/100mL blood =sol O2*100mL blood*PO2/760, Diffusion Fick's Law:dQ/dt=kA*dC/dL 0.25<Lɘ.4, increased w/ edema,fibrosis gases diff. thru gas, membrane, blood Graham's Law: r1/r2=sqrt(MM2/MM1) RBC acceptor-takes .25s to equlibrate gases CO2 diffuses 24x faster in blood 20x faster b/w alv and cap O2 w/ greater partial P difference -RBC Hb binds O2, maintain gradient lung dzs or edema can impede diff ->less O2, more CO2 in systemic exercise->more alvs perfused, VT up -more surface area for gas exchange Partial P diff maintained by: 1.alv. ventilation, 2.blood flow, 3. Hb Lung Diffusing Capacity (DL) -measure of lung conductance across alv-cap membranes -chemical attachment to Hb -[mL/min/torr] DLO2=flow(rate of transfer)/mean driving P DLO2=VO2/(mean PAO2-mean PcapO2) VO2=O2 uptake or consumption (mL/min) -use CO to measure accurately w/ PcapCO=0 DLO2=1.23*DLCO, Hb+4O2=Hb(O2)4=oxy-Hb affinity increases after each O2 binds -sigmoidal dissociation curve Pulm a. blood=40 torr O2, 14.8vol% Pulm v. blood=100 torr, 19.6vol% Sb02 (O2 saturation) increases by 23% -association part of curve is flat, high PO2 -long->same loading for abnormal PO2 -dissociation part-steepest part -small change in PO2, lots unloaded -transition around 60torr PO2 Bohr Effect Shift Dissociation Curve shift right->dec pH, inc. PCO2 inc. blood temp, 2,3-DPG -reduced affinity -mm. contraction left<-dec PCO2, [H+], inc.pH -increased affinity -shift has little effect on loading, Phys. response to exercise -⇑CO up to 6X-extra goes to sk. mm., lungs, heart, skin -⇑HR, ⇑BP->afterload ⇑->↓SV -⇑SV-blood shifted to venous return ↓art. resistance, ↑ven. capacitance -redistribute organ blood flow from gut to mm. -⇑minute ventilation VE up to 20X -due to proprioceptor/anticipation? -not PO2 or PCO2 changes -⇑alveolar ventilation up to 20X -CV system, not lungs, limits O2 deliv Lung changes VT, breathing freq. increase -more O2 in, more CO2 out -more elastic work by resp. mm. -faster air mvmt, ↑air resistance possible turb flow, airway compression -expiratory mm. help to increase freq -upper airway resistance increases, Respiration-Gases Gas Transport Oxygen -sol=0.023mL/100mL plasma -Vol%=0.3% (dissolved in plasma) -Vol%=19.6% in whole blood b/c RBCs carry 98% of blood O2 -NL adult-ᡄ bill RBCs, males more -RBC memb permeable to O2, CO2, H2) -anions more perm than cats, HCO3-, Cl- -Hb impermeable Hb-67000 amu, 2 alpha, 2 beta chains -holds 4 O2 molecules -g equiv. combining wt =16700g Hb/mol O2 =1.34mL O2/g Hb