# Gas Exchange and Transport Quiz 5.txt

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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
 Author: coreygloudeman ID: 135208 Card Set: Gas Exchange and Transport Quiz 5.txt Updated: 2012-02-16 06:56:43 Tags: CRAFTON HILLS COLLEGE RESP 135 Gas Exchange Transport Quiz Folders: Description: CRAFTON HILLS COLLEGE RESP 135 Gas Exchange and Transport Quiz 5 Show Answers: