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76 Cards in this Set
- Front
- Back
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What is the function of the respiratory system? (2 parts)
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1. Oxygenation of blood
2. Elimination of CO2 |
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V
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gas volume
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Q
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Blood volume
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P
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pressure of a gas in a gas or in a liquid
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F
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Concentration of a gas in a gas phase (fraction/percent)
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C
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Concentration of a gas in a liquid, either in chemical equilibrium or dissolved.
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S
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% saturation of hemoglobin with oxygen
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f
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Breathing frequency - breaths/min
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Eupnea
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Normal breathing at rest
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Hyperpnea
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Increased breathing
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Hypopnea
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Decreased breathing
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Dyspnea
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Awareness of breathing
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Tachypnea
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Increased freq of breathing
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Hyperventilation
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Breathing in excess of requirements of metabolism resulting in decreased PaCO2
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Hypoventilation
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Breathing insufficient for requirements of metabolism resulting in increased PCo2
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Hypoxia
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Reduced oxygen in inspired air
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Hypoxemia
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Reduced oxygen in arterial blood
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Hypercapnia
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Increased PaCO2 or PACO2
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Apnea
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Cessation of breathing
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Periodic Breathing
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Alternate periods of increased and decreased breathing
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Avagadro's hypothesis for gas behavior:
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For all gases, an equal # of molecules in the same space and at the same Temp will exert the same Pressure
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Dalton's Law for gas behavior:
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In a gas mixture, the pressure exerted by each individual gas in a space is independent of the pressures of other gases in the mixture.
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Boyle's Law for gas behavior:
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As a gas is compressed, its volume decreases in proportion to its pressure increase.
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Charles Law:
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If a vol of gas is kept constant, the pressure of the gas is proportional to temp.
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Ideal Gas Law:
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PV = nRT
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Henry's Law:
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The conc of a dissolved gas is equal to the partial pressure of the gas times the solubility coefficient.
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How many molecules of gas are in a mole, and how much volume will they occupy? At what pressure?
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6 x 10^23 molecules in a vol of 22.4 L at a temp of 0'C and pressure of 760 mm Hg.
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Define Breathing:
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Movement of air from the Atmosphere to the lungs and alveoli
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What is V(E)?
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Pulmonary ventilation
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What is V(A)?
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Alveolar ventilation
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What is V(D)?
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Dead space ventilation
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What 2 things affect breathing?
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-Mechanics
-Control |
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What structure mainly controls breathing?
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The brainstem
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What happens after air enters the lungs/alveoli via breathing?
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Alveolar-Capillary exchange
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What 2 factors determine or influene alveolar-capillary exchange?
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-Diffusing capacity
-Ventilation-perfusion matching |
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How is oxygen transported in the blood?
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By the action of the heart pumping.
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2 factors that determine how blood gas is transported:
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-How much gas is DISSOLVED
-How much gas is bound to HEMOGLOBIN |
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What happens after blood transport of gases?
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Capillary-tissue exchange.
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2 factors that influence Capillary-Tissue exchange:
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-Diffusion
-Pressure gradients |
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What % of gas in the atmosphere is oxygen?
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21%
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What is the concentration of O2 in the atmosphere?
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21% x 760 mm Hg = 150 mm Hg
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What is the normal pressure of O2 in alveoli and arterial blood?
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~100 mm Mg
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What is the normal mixed venous Po2?
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about 45 mm Hg
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What is the normal atmospheric PCo2?
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0 mm Hg
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What is the normal alveolar and arterial PCo2?
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40 mm Hg
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What is the normal mixed venous PCo2?
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A little above 40 mm Hg
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Why do Alveolar PO2 and PCo2 levels differ from atmospheric values? Why not the same?
(3 reasons) |
1. Dead space
2. Functional residual volume 3. Continuous O2 usage and CO2 production |
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Why is arterial PO2 slightly less than alveolar PO2?
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Because of bronchial venous admixture
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Why is mixed venous PO2 less than arterial PO2?
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Because of O2 utilization (duh)
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Why aren't the changes in PCo2 in arterial and mixed venous as significant as the changes in PO2 values?
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Because the O2 and CO2 hemoglobin dissociation curves have different shapes.
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How many CO2's are produced for every 10 O2 used normally?
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~8
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What does/doesn't determine arterial and alveolar PO2 and PCO2?
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The RESPIRATORY SYSTEM - not hemoglobin.
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What does hemoglobin determine?
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Mixed venous PO2 levels - after oxygen has been dissociated from hemoglobin.
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So how will the pressure gradients in an anemic individual compare to normal?
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All same except MIXED VENOUS PO2 levels will be lower.
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Why are mixed venous PO2 and PCO2 gas pressures different in the anemic individual?
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Because each unit of blood carries less O2 and CO2 in bound form.
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What is the mixed venous O2 level in an anemic individual compared to normal?
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about 20 instead of 45 mm Hg.
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What is the single most best way to assess whether the lung system is meeting its objective?
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Look at alveolar and arterial PCO2
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How do PO2 levels in a person at high altitude compare to those in a normal person?
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They will be much lower at each step in the transfer path.
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Why are PO2 levels lower when at high altitude?
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Because there are fewer O2 molecules in the atmosphere at high altitude compared to sea level.
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What is the atmospheric PO2 at pike's peak?
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~80 mm Hg (instead of 150!)
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What are the alveolar, arterial, and mixed venous Po2 levels in a person at pike's peak?
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Alveolar = 60 mm Hg
Arterial = 50 mm Hg Mixed Venous = 35 mm Hg |
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How come the difference in alveolar PO2 is not as striking even though Atmospheric PO2 is much lower than at normal sea level?
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Because the chemoreceptors are stimulated to hyperventilate and compensate for hypoxia
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Why is the drop from arterial PO2 to Mixed venous PO2 less than normal?
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Because the Hb-O2 dissociation curve shifts to increase delivery.
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Why is PCO2 decreased at high altitude?
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Due to hyperventilation - blowing off more CO2.
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What are the arterial and alveolar PCO2 levels in a resident of Pike's peak?
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~20 mm Hg (instead of 40)
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How would you know if a person is hypoventilating, based on comparing their PO2 and PCo2 gas gradients to normal?
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-Alveolar and arterial PO2 would be decreased to about same degree as PCO2 increase
-There would be no change in mixed venous levels - not a problem with hemoglobin. |
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When does everyone undergo hypoventilation normally?
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When sleeping.
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What is Farmer's Lung disease?
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Abnormal alveolar-capillary gas exchange
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What is the hallmark of inadequate gas exchange from alveoli to capillaries?
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A significant difference between alveolar and arterial PO2 levels
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What happens to alveolar and arterial PO2 levels in farmer's lung disease?
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-Alveolar PO2 will be increased
-Arterial PO2 will be decreased (both normally close to 100) |
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What does the reduced arterial PO2 stimulate?
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Increased breathing
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What results from the increased breathing?
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Increased ALVEOLAR PO2 and decreased PCO2 (blowing it off), but not arterial because exchange is just abnormal.
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Why isn't mixed venous PO2 reduced as much as arterial PO2 in farmer's lung disease?
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Because the Hb-O2 dissociation curve shifts to the steep portion for better release.
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What's the best way to tell whether a person is hyperventilating or hypoventilating?
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Look at alveolar/arterial PCO2 - will be increased if hypoventilating, and decreased if hyperventilating. O2 levels won't always tell the truth.
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How do PO2 levels in a person with COPD compare to normal? Why?
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All are lower - because there is poor Atm->alveolar exchange as well as alveolar->arterial.
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How do PCo2 levels in a person with COPD compare to normal? Why?
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All PCo2 levels are INCREASED b/c patient is hypoventilating - cannot increase breathing so not blowing off CO2 like farmer.
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