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179 Cards in this Set
- Front
- Back
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what is brownian mvt of gas molecules?
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random movement of gas molecules due to kinetic energy
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gas molecules undergo what?
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collisions
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where do collisions of gas molecules occur?
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1-intermolecular
2-w/ boundaries of system (gas cylinder, capillary membrane, alevolar membrane) |
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what is definition of pressure?
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force/area
-force exerted on gas particles |
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what is the origin of gas pressure?
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collision exert a force which is the origin of gas pressure
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what are the units of pressure?
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-mmHg (Torr)
-cmH2O -psi -Pa -atm |
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total gas pressure is proportional to what?
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the total concentration of gas molecules
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in a mixture of gases each gas exerts a pressure, the partial pressure of the gas is proportional to what?
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to its fractional concentration in the mixture
(Pgas=Fgas x Pt) |
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dissolved gas particles have what type of energy?
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kinetic energy
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what does Henry's law state?
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the partial pressure of a gas in solution is proportional to its concentration
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the solubility coefficient of Co2 is how many times that of O2?
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20x
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what is Fick's law?
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net diffusion of a gas occurs in response to a difference in gas partial pressure
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what are the 4 reasons the composition of aleolar gas is different from that of atmospheric air>?
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1-alveolar gas is only partially replaced by atmospheric air w/ each breath
2-oxygen is absorbed from alveolar gas 3-CO2 is added to alveolar gas 4-atmospheric air is humidified as it enters the resp system |
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FRC is 2300ml, how much new air is delivered to alveol w/ each normal breath?
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350ml
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why is it important that only 1/7th of total alveolar air is replaced w/ new air?
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it is important in preventing sudden changes in blood gas concentrations
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the alveolar partial pressure of oxygen is determined by the balance between what?
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1-oxygen delivery
2-oxygen absorption |
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for a person breathing normal atmospheric air at sea level, PAo2 cannot exceed what?
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150mmHg
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at a Co2 production/excretion rate of 200ml/min and alveolar ventilation rate of 4.2L/min what is alveolar Pco2?
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40mmHg
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PACo2 is inversly related to what?
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alveolar ventilation
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T or F atmospheric air is humidified as it enters the resp system.
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True
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what is the saturated VP of water at body temp?
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47mmHg
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humidification lowers the partial pressure of what?
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inspired Oxygen and Nitrogen
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what is the composition of expired gas?
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-combination of dead space gas and alveolar gas
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what are the structures separation alveolar gas from blood in teh alveolar capillaries called?
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the respiratory membrane (blood-gas barrier)
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what is the thickness of the blood-gas membrane?
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0.6um
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what is included in the respiratory membrane?
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-fluid lining alveolus (incl. surfactant)
-type I alveolar cells -epithelial basement membrane -interstitial space -capillary basement membrane -capillary endothelium |
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what is total surface area of resp. membrane?
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50-100m^2
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what is total amt of blood in the pulm capillaries at any time?
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60-140ml
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what are the factors affecting rate of gas diffusion across resp membrane?
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-thickness of resp membrane
-surface area of resp membrane -diffusivity of the gas in resp membrane -difference in gas partial pressure across the resp membrane |
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in relation to thickness of the membrane rate of diffusion is inversely related to what?
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thickness
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what can increase the thickness of membrane and impair gas exchange?
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-pulm interstitial edema
-fibrosis |
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rate of diffusion is directly related to what?
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surface area
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how is surface area reduced?
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by surgical removal of lung tissue
and certain pulm diseases (ex emphysema) |
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diffusivity is directly related to what and inversely related to what?
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directly r/t solubility
inversely r/t molecular weight of gas |
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Co2 diffuses through the membrane how much faster than oxygen and nitrogen?
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-20x faster than oxygen
-40x faster than nitrogen |
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what is the definition of the diffusion capacity?
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volume of a gas that diffuses across the membrane per minute in response to a partial pressure difference of 1mmHg
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what is diffusion capacity of O2 at rest?
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21ml x min^-1 x mmHg^-1
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what is maximum amt of oxygen diffusion capacity?
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65ml x min^-1 x mmHg^-1
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what occurs at 65ml/min of O2 diffusion?
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1-opening of dormant capillaries
2-better ventilation-perfusion matching |
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what is Co2 diffusion capacity extimated to be?
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-400-450 ml/min/mmHg at rest and max 1200-1300ml/min/mmHg
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at rest what is the transit time of blood in the pulm capillary ?
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0.75 sec
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what is Po2 of blood entering the capillary?
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40mmHg (mixed venous)
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what is PAo2 of blood entering capillary?
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100mmHg
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diffusion equilibrium occurs when?
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by the time blood has moved about 1/3 the length of capillary (0.25 sec)
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when can diffusion impairment occur?
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1-pt w/ thickened resp membrane (fibrosis)
2-exercise at high altitude, esp in pt w/ thickened resp membrane |
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what is Pco2 of blood entering pulmonary capillary?
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45mmHg (mixed venous)
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what is PAco2 ?
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40mmHg
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diffusion impairment may create a difference btwn end-capillary what?
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Pco2 and PAco2
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diffusion equilibrium normally occurs for what?
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oxygen and carbon dioxide
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what is uptake of oxygen by pulmonary capillary blood driven by?
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difference in Po2 btwn alveolar gas and capillary blood
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what is PAo2?
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100-104mmHg
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what is Po2 of mixed venous blood entering the capillary?
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40mmHg
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blood leaving the lungs and traveling to the left side of the heart has a Po2 of what?
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95-100mmHg due to shunt flow of the bronchial circulation and poorly ventilated and nonventilated alveoli
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how is oxygen transported in the blood?
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bound to Hgb in RBC
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what is chemistry of hgb?
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-4 subunits combine to form Hb molecule
-each subunit heme grp is bound to polypeptide globin |
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what Hb is most common?
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HbA
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the heme grp contains what that can bind oxygen molecule?
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Fe++
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each Hb molecule can bind a maximum of how many oxygen molecules?
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4
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what is normal blood Hb concentration?
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15g/100ml
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1 gram of pure Hb can combine w/ how many ml of oxygen?
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1.39ml
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at a Pao2 of 95-100mmHg oxygen saturation of Hb is 97 to 98% and the quantity of oxygen bound to Hb is how many ml?
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19.5ml/100ml blood
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at mixed venous Po2 of 40mmHg oxygen saturation of Hb is what %?
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75%
-and quantity of oxygen bound to Hb is 14.5ml/100ml blood |
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what is the significance of the flat upper portion of the oxyhb dissoc. curve?
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some protection against hypoexemia
-even at Pao2 of 70mmHg, Hb saturation is more than 90% |
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what is significance of steep lower portion of OH dissoc curve?
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permits unloading of large amts of oxygen to the tissues as Po2 falls to 40mmHg in the systemic capillaries
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what is frequently used indicator of the position of the curve along the x-axis?
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P50
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what is normal value of P50?
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27mmHg
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what are some factors that shift the OH dissoc curve to the right?
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-increased Pco2 and hydrogen ion conc in blood (acidemia)
-increased RBC 2,3 DPG -hyperthermia -inhaled anesthetics |
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what does a shift of the curve to the right mean?
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P50>27mmHg
facilitate oxygen unloading and may permit normal oxygen supply to cells despite reduced tissue perfusion |
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what does a shift in the curve to the left mean?
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P50 <27mmHg
-impair oxygen unloading; increased tissue perfusion may be necessary to provide adequate oxygen supply to cells |
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what are some examples that can shift the OH dissoc curve to the left?
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-alkalosis
-hypothermia -decreased 2,3 DPG -carboxyhgb |
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what is the equation given for the oxygen concentration of the blood?
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Co2= (1.39 x Hb x sat/100) + 0.003 Po2
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what is the normal arteriovenous oxygen content difference?
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5ml/100ml blood
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values of arteriovenous oxygen content difference greater than 5ml/100ml suggest what?
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reduced cardiac output
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what may a value of arteriovenous oxgyen content difference of < 5ml/100ml blood be caused by?
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arteriovenous shunts; may occur during hyperdynamic sepsis
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CO can combine w/ hb to form what?
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carboxyhgb
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the affinity of CO for Hb is what?
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240times that of oxygen for Hb
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small amts of CO can tie up lg amts of Hb and do what?
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reduce oxygen loading
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COHb shifts oxyhgb dissoc curve which direction?
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to the left; interfering w/ oxygen uploading
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what is intracellular Po2?
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20mmHg
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interstitial Po2 is what?
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40 mmHg
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intracellular Pco is what?
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46mmHg
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what is interstitial Pco2?
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45mmHg
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Pco2 of arterial blood entering the tissues is what?
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40mmHG
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how is Co2 transported in the blood?
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1-CO2 dissolved in plasma
2-Bicarbonate ion 3-carbaminohemoglobin |
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the amt of Co2 dissolved obey's what law?
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Henry's law
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at venous blood Pco2 of 45mmHg the amt of dissolved CO2 is about how many ml and what is alpha?
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2.7ml/100ml
alpha= 0.06ml Co2/100ml blood/mmHg |
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approx how much of blood Co2 is transported dissolved in plasma water?
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7%
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Co2 in the blood reacts w/ what inside RBC's to form what?
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water to form carbonic acid
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what enzyme is the Co2 to carbonic acid reaction catalyzed by?
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carbonic anyhydrase
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carbonic acid ionized to yield what?
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hydrogen and bicarbonate ions
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Hydrogen is buffered by what?
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Hb
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HCO3 diffuses out of RBC in exchange for what?
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Cl
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approximately 70% of blood Co2 is transported how?
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as bicarbonate
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Co2 reacts reversibly with what to form carbaminoHgb?
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terminal amine grp of Hb molecule
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how much of Co2 is transported in carbaminohemoglobin form?
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23%
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Pco2 of blood entering the pulmonar capillary is what?
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45mmHG
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Alveolar Pco2 is what?
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40mmHg
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the carbon dioxide dissociation curve relates what?
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Co2 in the blood to Pco2
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Co2 unloading in the lung is facilitated by what?
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oxygen loading
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the what effects shifts the Co2 dissociation curve what direction?
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Haldane effect shifts curve to right
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hydrogen bound to Hb are displaced and combine with what to form what?
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w/ bicarbonate to form carbonic acid---Co2 and water
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haldane effect works in the opposite direction in the tissue capillaries as it does in the lungs so it shifts the Co2 curve which direction?
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to the left; oxygen unloading shifts the Co2 curve to the left
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what effect does the haldane effect have on Co2 that can be released from blood in the lungs and taken by the the blood in the tissues?
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it is doubled
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the respiratiory exchange ratio or resp quotient (R) is the ratio of what?
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Co2 production to oxygen consumption
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about how many ml of Co2 per 100ml is transported from the tissues to the lungs?
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4ml Co2 per 100ml
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Co2 excretion is normally about what percent of oxygen uptake and the R is what?
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80% R is 0.8
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the actual value of R depends on what?
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metabolic substrates being utilized for cellular ATP production
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if a person were using only CHO for metabolism R would be what?
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1.0
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if a person were using only fatty acids for metabolism R would be ?
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0.70
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For a person consuming a normal diet consisting of CHO, fat, and protein R would be?
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0.8
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the main pulmonary artery extends from where?
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right ventricle
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what kind of blood does the main pulm artery receive from where?
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mixed venous blood pumped by the right ventricle
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the main pulmonary artery divides into what and supplies what?
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divides into right and left pulmonary branches which supply the left and right lungs
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pulmonary arteries follow what segmentation?
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tracheobronchial segmentation down to the terminal bronchioles
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what are thin-walled vessels with relatively large diameters and little smooth muscle?
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pulmonary arteries
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what is a dense network of vessels in the alveolar walls?
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pulmonary capillaries
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the pulmonary venous system transports what?
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oxygenated blood to the left atrium; four main veins empty into the left atrium
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what has a reservoir function?
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pulmonary veins
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where does the lymphatic system begin?
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w/ blind-ended lymphatic capillaries that originate in the interstitial space of the lung
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what do lymphatic capillaries do?
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continually remove and collect fluid, protein, and foreign particles from the lung interstitium
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lymph flow is directed where?
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the right lymphatic duct and from there to the venous side of the systemic circulation
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what is the pulmonary artery pressure systolic pressure?
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25mmHg
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what is the pulmonary artery pressure diastolic pressure?
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8 mmHg
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what is the pulmonary artery pressure mean pulmonary arterial pressure?
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15mmHg
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what is the pulmonary artery pressure pulse pressure?
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17mmHg
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the low pressures in the pulmonary arterial system are consistent with what?
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1-properties of the right ventricle
2-properties of the pulmonary arteries |
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regional differences in pulm arterial pressures are due to what?
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hydrostatic pressure
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what is pulm capillary pressure estimated to be?
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7mmHg
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pulm venous pressure, left atrial pressure, and LVEDP can be estimated by what?
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pulm arter wedge pressure
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modest increases in left atrial pressure have what kind of effect on pulm arterial and capillary pressures?
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little effect
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lg increases in what can increase pulm artery pressure and pulm capillary pressure?
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left atrial pressure
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pulm edema is likely when left atrial pressure rises above what?
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25-30mmHg
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pulm vascular resistance (PVR) is determined by what passive factors?
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1-levels of pulm arterial and venous blood pressures
2-lung volume |
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an increase in pulm arterial or venous blood pressure does what to PVR?
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decreases; through distention and recruitment of pulm capillaries
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what is the J-shaped or U shaped curve?
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relationship btwn lung volume and pulmonary vascular resistance
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PVR increases or decreases relative to that at FRC?
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increases
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at rest the lungs contain about how many ml of blood?
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450ml; 70ml of that is contained in pulm capillaries
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what can greatly increase pulm blood volume and pulm vascular pressures?
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left heart failure and mitral valve dysfunction
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PVR is largely active or passive?
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passive
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what does HPV stand for?
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hypoxic pulmonary vasoconstriction
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what is HPV?
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-a protective mechanism
-if alveolar Po2 is reduced (<70mmHg) ctx of sm muscle occurs in sm arterioles in hypoxic area reducing blood flow to the area |
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what is the mech of vasoconstriction w/ HPV?
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-do not depend on nervous input
-occurs in isolated lung -occurs when arterial Po2 is kept high, despite low alveolar Po2 |
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what is thought to be the PAo2 sensor?
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mitochondrial electron transport chain in arteriolar sm muscle
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what is the fxn of HPV?
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-diversion of blood flow away from poorly ventilated alveoli to areas that are better ventilated
-its a mech to avoid ventilation-perfusion mismatch and possible hypoxemia |
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the pulm arteries have what type of receptors?
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-alpha and beta-adrenergic receptors
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T or F the autonomic nervous system exerts little influence on pulmonary arterial resistance.
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True
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what nervous system can sometimes strongly constrict the pulmonary veins and displace blood to the systemic circulation?
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sympathetic nervous system (ex w/ hemorrhage or shock)
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What are some other factors that influence PVR?
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-hypercapnia and acidemia cause pulm vasoconstriction and enhance HPV
-vasoconstrictors; serotonin, leukotrienes -vasodilators: nitroprusside, nitric oxide, ca ch blockers |
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P(cm H20)=ht of column in cm; so a column of blood 100cm in ht has hydrostatic pressure of what?
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100cmH20 at its base (100cmH2O=73.5mmHG)
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in an adult lung the distance from the apex to the base is how many cm?, and thus the hydrostatic pressure = how many cmH20?
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30cm, 30cmH20
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how many mmHg difference of the apex-base lies above the level of the heart, and how many mmHg difference lies below the heart?
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15mmHg above the heart
8mmHg lies below the heart |
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lung level= apex and what is pulm artery pressure systolic, diastolic and mean?
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sys= 10mmHg
diastolic=-7mmHg mean= -1.3mmHg |
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lung level=heart what is pulm artery pressure sys, diastolic, and mean?
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sys= 25mmHg
diastolic= 8mmHg mean=15mmHg |
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lung level= base what is pulm artery pressure sys, diastolic, base?
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sys= 33mmHg
diastolic= 16mmHg mean= 22mmHg |
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in the upright lung blood flow is greatest where, and least where?
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greatest in the base, and least in the apex
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T or F pulmonary capillaries have internal and external pressure.
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True
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for blood flow to occcur in the region of the lung what must be true?
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Pcap must exceed Palv
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what is zone 1 pulm perfusion?
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Palv>Pcap; no blood flow
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What is zone 2 pulm perfusion?
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Pcap>Palv during systole-blood flow occurs:
Palv>Pcap during diastole no blood flow -zone 2 is intermittent |
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What is zone 3 pulm perfusion?
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Pcap> Palv continuous blood flow
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in the supine position what zone of blood flow occurs?
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zone 3-blood flow occurs in all parts of the lung
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when may zone 1 occur?
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normally not occur in lungs; but may occur in lung apex when Palv is increased and/or when pulm arterial pressure is decreased
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zone 1 creates what?
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alveolar dead space
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the tip of the pulm artery catheter should be in what zone?
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zone 3
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fluid moves into interstitial space how many ml per hr?
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20ml/hr
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T or F Net filtration of fluid normally occurs in lung capillaries
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True
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fluid and protein that enter the interstitial space are removed by what?
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lymphatic flow-critical to prevent pulm edema
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when does interstitial edema occur?
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when normal capillary fluid dynamics are disrupted, causing fluid accumulation in the interstitial space
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what can cause a lg increase in pulm Pcap?
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Left heart failure or mitral valve disease
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what increases Kf?
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damage to pulm capillary membrane; ex infections-pneumonia, inhalation of noxious substances)
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negative pressure pulm edema can occur when?
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secondary to laryngospasm or airway obstruction
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what are the safety factors to resist formation of pulm edema?
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-increased lymph flow
-dilution of interstitial protein |
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because of the safety factors Pcap needs to increase to what before significant pulm edema occurs?
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25-30mmHg
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what are 2 other funciton s of pulm circulation?
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1-behave as a blood reservoir
2-Filter; removal of thrombi before they can reach the heart or brain |
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what are the metabolic functions of the lung?
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1-production of pulm surfactant
2-protein synthesis: collagen and elastin 3-metabolism of vasoactive substances 4-extraction of some drugs ex fentanyl, lidocaine, propranolol |
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what is the enzyme that is located in the pulm endothelium?
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angiotensin converting enzyme- conversion of angiotensin I to angiotensin II
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What inhibits angiotensin converting enzyme?
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ACE inhibitors such as captopril or enalapril
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what else does ACE do?
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inactivation of some circulating vasoactive substances; prostaglandins and bradykinin
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lungs can produce synthesis and release of vasoactive substances such as what?
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histamine and leukotrienes
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