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152 Cards in this Set
- Front
- Back
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what is random movement of gas molecules due to kinetic energy?
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brownian
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what is pressure?
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force/area
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what are the units of gas pressure?
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mm Hg
cm H2O psi Pa atm |
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total gas pressure is proportional to what?
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total concentration of gas molecules
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what is the partial pressure of the gas proportional to?
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its fractional concentration in the mixture
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what is henry's law?
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the pressure of a gas in solution it proportional to its concentration
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what does alpha stand for?
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solubitily coefficient
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what is alpha of oxygen?
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0.024
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what is alpha of carbon dioxide?
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0.57
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what is alpha of CO?
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0.018
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what is alpha of nitrogen?
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0.012
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what is alpha of helium?
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0.008
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what is fick's law?
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flux is proportional to change gas pressure x area x solubility/ d x MW1/2
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what is the diffusivity of oxygen?
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1.0
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diffusivity of CO2?
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20.3
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diffusivity of CO?
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0.81
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diffusivity of nitrogen?
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0.53
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diffusivity of helium?
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0.95
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how many mL of new air is delivered to the alveoli with each normal breath?
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350
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how much of total alveolar gas is replaced by new air?
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1/7
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why isn't all of alveoli gas replaced?
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to prevent sudden changes in blood gas concentration
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what is alveolar partial pressure of oxygen determined by??
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balance between oxygen delivery and oxygen absorption
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when a person is breathing normal atm air at sea level PAO2 cannot exceed _______ unless ______?
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150 mm Hg - unless breathing gas with a higher PO2
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what are the conditions when alveolar PCO2 is 40 mm Hg?
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CO2 production/excretion rate of 200 mL/min and alveolar ventilation of 4.2 L/min
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What is PACO2 inversely r/t?
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alveolar ventilation
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what is saturated vapor pressure of water at body temperature?
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47 mm Hg
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humidification highers or lowers the partial pressures of inspired oxygen and nitrogen?
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lowers
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what is a combination of dead space gas and alveolar gas?
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expired gas
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what is the average thickness of the respiratory membrane?
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0.6 nanometers
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what is included in the respiratory membrane?
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fluid lining of the alveolus
type 1 epithelial cells epithelial basement membrane interstitial space capillary basement membrane capillary endothelium |
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what is the total surface area of the respiratory membrane?
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50-100 square meters
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what is the total amount of blood in the pulmonary capillaries at any time?
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60-140 mL
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what are the four factors affecting the rate of gas diffusion across the respiratory membrane?
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thickness of resp membrane
surface area of resp membrane diffusivity of the gas in the resp membrane difference in gas partial pressure across the resp membrane |
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rate of diffusion is inversely related to?
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thickness
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what can increase the thickness of the resp membrane and impair gas exchange?
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pulmonary interstitial edema and fibrosis
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rate of diffusion is directly related to what?
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surface area
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what reduces surface area?
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surgical removal of lung tissue
certain pulm diseases (emphysema) |
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diffusivity is directly r/t? and inversely r/t?
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gas solubility and molecular weight of the gas
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how much faster does CO2 diffuse through the membrane than oxygen? and nitrogen?
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20x faster than O2
40x faster than nitrogen |
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what is volume of a gas that diffuses across the membrane per minute in response to a partial pressure difference of 1 mmHg?
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diffusion capacity
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what is the diffusion capacity of O2 at rest?
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21 mL/ min x mmHg
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what is max O2 diffusion capacity?
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65 mL/min x mmHg
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how can max O2 diffusion capacity be achieved?
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opening of dormant capillaries
better ventilation-perfusion matching |
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what is the diffusion capacity of CO2?
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technical difficulties preclude direct measurement
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what is the estimated diffusion capacity of CO2?
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400-450 mL/min x mmHg at rest and 1200-1300 mL/min xmmHg maximum
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what is the transit time of blood in the pulmonary capillary?
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0.75 seconds
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what is PO2 of blood entering the capillary?
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40 mmHg
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What is PAO2 of blood entering the capillary?
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100 mmHg
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when does diffusion equilibrium of alveolar gas occur?
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about 1/3 the length of the capillary (0.25 sec)
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when can diffusion impairment occur?
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patient with thickened resp membrane
exercise @ high altitude |
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what is PCO2 of blood entering the pulmonary capillary?
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45 mmHg
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What is PACO2 of blood entering the pulm capillary?
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40 mmHg
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when can diffusion impairment create a difference between end-capillary PCO2 and PACO2?
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during exercise
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what is uptake of oxygen by the pulm capillary blood driven by?
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difference in PO2 between alveolar gas and capillary blood
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What is PAO2?
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100-104 mmHg
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PO2 of mixed venous blood entering the capillary is?
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40 mmHg
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blood leaving the lungs and traveling to the left side of the heart has a PO2 of?
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95 to 100 mmHg
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Why is PO2 less when traveling to the left side of the heart?
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due to shunt flow of the bronchial circulation and poorly ventilated and nonventilated aveoli
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what is the concentration of dissolved oxygen in arterial blood with a PO2 of 100 mm Hg?
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0.3%
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with a normal PO2 of 95-100 mmHg, how much of the total oxygen carried in arterial blood is bound to hemoglobin?
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97-98%
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what is the chemistry of hemoglobin?
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heme group bound to the polypeptide globin
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how many subunits combine to for the Hb molecule?
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4
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which Hb is the most common?
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HbA
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What is the MW of Hba?
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64,000
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what does the heme group contain that binds an oxygen molecule?
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iron ion (fe++)
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Hb molecule can bind a maximum of how many O2 molecules?
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4
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normal blood Hb concentration is?
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15g/100 mL blood
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one gram of pure Hb can combine with?
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1.39 mL of oxygen
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what is the quantity of oxygen bound to Hb at a PaO2 of 95-100 mmHg?
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19.5 mL/100 mL blood
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at a mixed venous PO2 of 40 mmHg, oxygen saturation of Hb is? and the quantity of oxygen bound is?
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75% - 14.5 mL/100mL of blood
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what does the flat upper portion of the oxyhemoglobin dissociation curve mean?
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provides some protection against hypoxemia - even @ a PaO2 of 70 mmHg, Hb saturation is more than 90%
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what does the steep lower portion of the oxyhemoglobin dissociation curve mean?
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permits unloading of large amounts of oxygen to the tissues as PO2 falls to 40 mmHg in the systemic capillaries
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what is a frequently used indicator of the position of the curve along the x-axis?
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P50
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The Po2 @ 50% saturation - what is the normal value of P50?
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27 mmHg
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what factors shift the OD curve to the right?
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increased PCO2 and hydrogen ion concentration
increased RBC 2,3 diphosgylcerate hyperthermia inhaled anesthetics |
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What does it mean when the OD curve shifts to the right?
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facilitate oxygen unloading and thus may permit normal oxygen supply to cells despite reduced tissue perfusion
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What does it mean when the OD shifts to the left?
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impair oxygen unloading - thus increased tissue perfusion may be necessary to provide adequate oxygen supply to cells
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What conditions shift the OD curve to the left?
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alkalosis
hypothermia decreased 2,3 DPG (banked whole blood) carboxyhemoglobin |
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what is the oxygen concentration of the blood equation?
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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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5 mL/100 mL
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an arteriovenous oxygen content value greater than 5 mL/100mL suggests?
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reduced CO
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arteriovenous oxygen content less than 5 mL/100mL may be caused by?
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arteriovenous shunts - such as occur during hyperdynamic sepsis
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CO combines with _______ to form ________?
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hb, carboxygemoglobin
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how much higher is the affinity of CO for Hb than that of O2 to Hb?
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240x
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CoHb shifts the oxyhemoglobin dissociation curve to the ______, interfering with ________?
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left, oxygen unloading
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What are the three forms of transport of CO2 in the blood?
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CO2 dissolved in plasma water
bicarbonate ion carbinohemoglobin |
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which transport of CO2 in blood obeys henry's law?
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CO2 dissolved in plasma water
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At venous blood PCo2 of 45 mmhg the amount of dissolved CO2 is?
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2.7 mL/100 mL
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What percentage of blood is CO2 transport by dissolving in plasma water?
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7%
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How does a bicarbonate ion transport CO2?
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CO2 reacts with water inside RBCs to form carbonic acid - rxn catalyzed by the enzyme carbonic anhydrase present inside RBCs
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what does carbonic acid ionized to?
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hydrogen and bicarbonate ions
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what is H+ buffered by?
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hb
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What is it called when HCO3 diffuses out of the RBC in exchange for Cl?
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Chloride shift or Hamburger's phenomenon
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how much of blood CO2 is transported as bicarbonate?
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70%
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what does CO2 react reversibly with to form carbaminohemoglobin?
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terminal amine group of the hemoglobin molecule
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how much of blood CO2 is transported in carbaminohemoglobin?
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23%
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What is the CO2 "dissociation" curve?
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relates total CO2 in the blood to PCO2
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What is the Haldane effect?
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shifts the CO2 dissociation curve to the right, relative to its position in the tissues
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binding of O2 to Hb causes what?
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Hb to become a stronger acid
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What is respiratory quotient?
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the ratio of CO2 production to O2 consumption
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CO2 excretion is normally about _____ of oxygen uptake and RQ is _____?
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80%, 0.8
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If a person were using only carbohydrates for metabolism, R is?
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1.0
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if a person were using only fatty acids for metabolism, R is?
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0.70
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For a person consuming a normal diet consisting of CHO, fat, and protein, R is?
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0.80
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What is characteristic of pulmonary arteries?
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thin-walled vessels with relatively large diameters and little smooth muscle
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What can help to prevent pulmonary edema in pulmonary veins?
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reservior function - the distention minimizes an increase in pulmonary capillary pressure
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Where is pulmonary lymph flow primarily directed to?
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right lymphatic duct and from there to the venous side of the systemic circulation
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What is SP @ level of the heart?
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25 mmHg
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DP @ level of heart?
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8 mmHg
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Mean PAP @ level of heart?
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15 mmHg
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Pulse pressure @ level of heart?
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17 mmHg
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Why does the pulmonary arterial system have low pressures?
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low pressure chamber (right ventricle)
properties of the pulmonary arteries (thin-walled, large-diameter, high compliance vessels) |
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What is pulmonary capillary pressure @ the level of the heart?
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7 mmHg
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Pulm venous pressure, Left atrial pressure, and LVEDP can be estimated by measuring what?
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pulm artery wedge pressure
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what effect occurs in the pulm arterial and capillary pressures with modest increases in left atrial pressures?
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little effect
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When is pulmonary edema likely?
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when left atrial pressure rises about 25-30 mmHg
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PVR is _______ that of systemic vascular resistance?
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1/10
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What is PVR primarily determined by?
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passive factors - levels of pulmonary and venous blood pressures and lung volumes
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decrease in pulmonary arterial or venous pressures does what to PVR?
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increases
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increases in pulmonary arterial or venous blood pressures does what to PVR?
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decreases PVR through distension and recruitment of pulmonary capillaries
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at rest, the lungs contain how much blood and how much is contained in the pulm capillaries?
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450 mL of blood (9% of total blood vol), 70 mL is pulm caps
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left heart failure or mitral valve dysfunction does what to pulm blood volume and pulm vascular pressure?
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greatly increases
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What is hypoxic pulmonary vasoconstriction?
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if alveolar PO2 is reduced (less than 70) due to insufficient ventilation of a lung region, contraction of smooth muscle occurs in small arterioles in the hypoxic area, reducing blood flow to the area
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What is the PAO2 sensor in arteriolar smooth muscle cells?
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mitochondrial electron transport chain
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what are the fxns of HPV?
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diversion of blood flow away from poorly ventilated alveoli to areas that are better ventilated
fetal circulation |
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Does the ANS exert influence on pulmonary arterial resistance?
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little influence
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in what cases can the SNS strongly constrict the pulm veins and displace blood to the systemic circulation?
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hemorrhage or shock
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What situations can enhance HPV?
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hypercapnia and acidemia
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In a column of blood, hydrostatic pressure occurs where due to what?
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occurs at any level due to weight of the blood above that level
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a column of blood 100 cm in height has a hydrostatic pressure of what at its base?
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100 cm H20
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what is the distance from apex to base in an adult lung?
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30 cm
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what is the hydrostatic pressure difference that exists between the apex and the base of the upright lung?
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30 cm H20 (23 mmHg)
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how many mmHg of the apex-to base difference lies above the level of the heart?
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15 mmHg
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how many mmHg of the apex-to base difference lies below the level of the heart?
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8 mmHg
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in the upright lung, where is blood flow the greatest?
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in the base
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What happens in Zone 1?
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Palv > Pcap - no blood flow
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what happens in zone 2?
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Pcap > Palv during systole, blood flow occurs
Palv > Pcap during diastole, no blood flow (flow is intermittent) |
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For blood flow to occur in a region of a lung what must occur?
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Pcap must exceed Palv
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What happens in zone 3?
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Pcap > Palv at all times, continuous blood flow
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What happens when a person is in the supine position (in terms of blood flow)?
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zone 3 blood flow occurs in all parts of the lung
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Does Zone 1 normally occur in the lungs?
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no
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When can Zone 1 blood flow occur?
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in the lung apex when Palv is increased (positive pressure ventilation) or when pulm arterial blood pressure is decreased (hypovolemia)
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What does zone 1 create?
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alveolar dead space
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where should the tip of the PAP catheter be placed?
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in zone 3 to measure LVEDP
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how much fluid continually moves into the interstitial space?
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20 mL/hr in normal conditions
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what is critical for maintenance of normal fluid dynamics across the pulm capillary walls?
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fluid and protein that enter the interstitial space are removed by lymphatic flow
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How does pulm edema occur?
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when normal capillary fluid dynamics are disrupted, causing a fluid accumulation in the interstitial space
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what is pulm edema caused by?
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LHF
MVI damage to capillary membrane (infections, pneumonia, inhalation of noxious substances) negative pressure pulm edema secondary to laryngospasm or airway obstruction |
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How much can Pcap increase before significant pulmonary edema occurs?
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25-30 mmHg
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What are other functions of the pulm circulation?
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blood reservior
filter - removal of thrombi before they reach heart or brain |
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what are the metabolic functions of the lung?
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production of pulm surfactant
protein synthesis (collagen and elastin) metabolism of vasoactive substances extraction of some drugs (fentanyl, lidocaine, propanolol) |
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what inhibits angiontensin converting enzyme?
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ACE inhibitors - captopril and enalapril
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