Gas Exchange and Transport Quiz 5.txt

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coreygloudeman
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Gas Exchange and Transport Quiz 5.txt
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2012-02-16 01:56:43
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CRAFTON HILLS COLLEGE RESP 135 Gas Exchange Transport Quiz
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CRAFTON HILLS COLLEGE RESP 135 Gas Exchange and Transport Quiz 5
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  1. What are the factors that impair carbon dioxide removal?
    • decreased alveolar ventilation (VA) relative to metabolic needs
    • Examples:
    • hypercapnia and respiratory acidosis
  2. What is the equation for Impaired CO2 removal?
    PaCO2 = VCO2 / VA
  3. A decrease in alveolar ventilation occurs when:
    • (1) The minute ventilation is inadequate
    • (2) The dead space ventilation per minute is increased
    • (3) A V/Q imbalance exists
  4. What portion of Minute Ventilation will usually cause a drop in its value?
    • Tidal Volumes
    • Examples:
    • -- Atelectasis
    • Respiratory center depression
    • Neuromuscular disorders
    • Impeded thoracic expansion:
    • - kyphoscoliosis
  5. What things will usually cause a decrease in Respiratory Rate (f), inturn causing a decrease in minute ventialtion (VE)?
    Drug Overdose
  6. What is Dead Space Ventilation?
    • ventilation without perfusion or ventilation in excess of perfusion (high V/Q)
    • (Vt - VDS) X f = VA
  7. What causes an increase in Dead Space Ventilation?
    • 1. Rapid, shallow breathing (an increase in anatomical dead space per minute)
    • Using the dead space formula:
    • Normal: (500 ml - 150 ml) X 12 = 4200 ml
    • Shallow: (250 ml - 150 ml) X 24 = 2400 ml
  8. 2. Increased physiological dead space (V/Q = 0)
    • Using the dead space formula:
    • Normal: (500 ml - 150 ml) X 12 = 4200 ml
    • DS(increased): (500 ml - 300 ml) X 12 = 2400 ml
  9. How do V/Q imbalances affect the exchange of both oxygen and carbon dioxide?
    • Greater effect on Oxygenation than CO2
    • any increase in PCO2 from low V/Q units can be corrected by a reduction in PCO2 from high V/Q units
    • But, O2 cannot be corrected as easily because the oxygen curve is nearly flat when the PO2 is above normal
  10. How do we fix a V/Q imbalance in which we have a high CO2?
    increase ventilation, if they can not then the patient will become hypercapnic
  11. What are the clinical assessments of dead space?
    • 1. Minute ventilation to arterial PCO2 disparity:
    • patient has a minute ventilation of 20 L/min and the PaCO2 is 40 mmHg, the patient has dead space
    • VE goes up, PaCO2 will go down causing dead space

    • 2. The arterial to alveolar CO2 tension gradient P(a-A)CO2):
    • As the distance between the PaCO2 and PETCO2 increases it means there is more dead space
    • Gas will be closer to ATMOSPHERIC AIR
    • It mixes with other gases from perfused areas, however the PETCO2 will be lowered

    • 3. Dead space to tidal volume ratio VD/Vt:
    • Normal VDS/Vt is about .2 to .4 (20% to 40%)
    • A patient on a ventilator it can be up to .5 (50%)
    • A 0.6 (60%) is normal for COPD patients
    • 0.6 to 0.8 (60 to 80%) SIGNIFICANT DISEASE AND THE PATIENT IS UNABLE TO MAINTAIN SPONTANEOUS VENTILATION!
    • Calculated using the modified Bohr equation:
    • VDS/Vt = PaCO2 - PECO2 / PaCO2
    • PECO2 = Partial Pressure of Exhaled CO2
    • Example: 40-28/40 = .3
  12. End tidal CO2 (PETCO2) is usually 1 to _ mmHg less than PaCO2.
    5
  13. What is Minute ventilation to arterial PCO2 disparity?
    • patient has a minute ventilation of 20 L/min and the PaCO2 is 40 mmHg, the patient has dead space
    • VE goes up, PaCO2 will go down causing dead space
  14. What is the arterial to alveolar CO2 tension gradient P(a-A)CO2)?
    • As the distance between the PaCO2 and PETCO2 increases it means there is more dead space
    • Gas will be closer to ATMOSPHERIC AIR
    • It mixes with other gases from perfused areas, however the PETCO2 will be lowered
  15. What is Dead space to tidal volume ratio VD/Vt?
    • Normal VDS/Vt is about .2 to .4 (20% to 40%)
    • A patient on a ventilator it can be up to .5 (50%)
    • A 0.6 (60%) is normal for COPD patients
    • 0.6 to 0.8 (60 to 80%) SIGNIFICANT DISEASE AND THE PATIENT IS UNABLE TO MAINTAIN SPONTANEOUS VENTILATION!
    • Calculated using the modified Bohr equation:
    • VDS/Vt = PaCO2 - PECO2 / PaCO2
    • PECO2 = Partial Pressure of Exhaled CO2
    • Example: 40-28/40 = .3

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