# Gas Exchange and Transport Exam.txt

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1. What is the difference between the normal gradients in oxygen and carbon dioxide partial pressures between the atmospher and tissues?
• Simple diffusion. For oxygen, it is a decreasing amount of tension from atmospheric to the cells.
• For CO2 it is opposite, from greatest amount at the cell to the least amount in the atmosphere. This aids the lungs in gettings rid of CO2
2. Why are partial pressure gradients for oxygen and carbon dioxide important within the body?
Because they are what allow for gas flow in and out of the lungs
3. How do you determine alveolar oxygen and carbon dioxide partial pressures?
• PACO2 = VCO2 x 0.863 / VA
• Normal value is 200 ml/min and VA is alveolar ventilation which is normally 4.3 L, so...
• PACO2 = 200 mL/min x 0.863 / 4.3 L/min = (approx) 40 mmHg
4. How is PACO2 maintained?
by increasing or decreasing the rate of breathing
5. How do you apply the air equation in determining PAO2?
• PAO2 = FiO2 x (PB - PH20) - PACO2/R
• IF the FIO2 is 60% or greater the correction for R can be dropped
• FiO2 = fractional concentration of inspired oxygen
• PB = barometric pressure
• PH20 = water vapor tension (47 mmHg at 37 C)
• PACO2 = alveolar partial pressure of carbon dioxide
• R = respiratory exchange ratio (nomarl value is 0.8) which is the ratio of carbon dioxide excretion to oxygen uptake.
• Example: PAO2 = 0.21 (760 - 47) � 40 / 0.8 = 100 mmHg
6. How do you compute the alveolar-arterial PO2 difference and the a/A ratio?
• Egan's pg. 239
• Normal difference is small, only 5 to 10 torr while breathing air and no more than 65 torr when breathing 100% O2
• P(A-a)O2 = PAO2 - PaO2
• Example: P(A-a)O2 = 449 - 50
• P(A-a)O2 ~ 400 torr
• Abnormal; 400 torr is very high.

• a/A = PaO2/PAO2
• Example: a/A = 50/449
• a/A = 0.11
• Abnormal; should be atleast 90%
7. What is the relationship of oxygen and carbon dioxide in the lungs?
As Oxygen goes up, Carbon dioxide goes down, and vice versa.
8. How do you calculate alveolar nitrogen partial pressure?
• PAN2 = PB - (PAO2 + PACO2 + PH20)
• Example:
• PAN2 = 760mmHg - (100 mmHg + 40mmHg + 47mmHg)
• PAN2 - 760 mmHg - 187 mmHg
• PAN2 = 573 mmHg
9. What are the pertinent physical laws in the determination of factors affecting diffusion at the alveolar-capillary membrane?
Fick's first law
10. What are the barriers to diffusion from lungs to the blood?
• 1. Surfacant
• 2. ALVEOLAR MEMBRANE
• 3. INTERSTITIAL SPACE (FLUID)
• 4. CAPILLARY MEMBRANE
• 5. Red blood cells
11. What is Fick's first law of diffusion?
• Vgas = A x D / T * (P1-P2)
• A is the cross-sectional area available for diffusion
• D is the diffusion coefficient of the gas
• T is the thickness of the membrane
• (P1-P2) is the partial pressure gradient across the membrane
12. If you have a greater surface area, diffusion coefficient, partial pressure gradient and minimal thickness; is the diffuision increased or decreased?
Increased
13. If you have less of an area, a lower diffusion coefficient, less of a pressure gradient and a greater thickness or distance; is the diffuision increased or decreased?
Decreased
14. What are the partial pressure gradients for O2 and CO2 from mixed venous blood to the alveolus?
• Normal arterial: 40-100
• Normal venous: 46-40
15. What is the diffusion coefficient?
Constant of how well a gas will diffuse
16. What is the solubility coefficients for O2 and CO2 and explain how this affects diffusion?
0.003 is the solubility coefficient of oxygen at 1 mmHg in 100ml of plasma
17. How do time limitations affect diffusion?
Rapid blood flow with a diffusion defect will cause inadequate oxygenation
18. What is diffusion capacity?
DL is the diffusing capacity of the lung measured as the amount of gas (ml/min) that diffuses into the blood for each 1 mm Hg difference in the pressure gradient
19. What is the normal DLCO?
• 25 ml/min/mm Hg for a steady state test
• for a single breath test is 40 ml/min/mm Hg
20. What are systemic diffusion gradients?
• PO2 of 100 mmHg (tissue capillary) --> PO2 <40 mmHg (cells)
• PCO2 >46 mmHg (cells) --> PCO2 of 40 mmHg (capillary blood)
• Venous blood has a PO2 of about 40 mmHg and a PCO2 of about 46 mmHg
21. What are the normal variations between ventilation and perfusion in the healthy lung and its effect on local gas tensions?
• 1. Right-to-left shunts in the pulmonary and cardiac circulation
• 2. Regional differences in pulmonary ventilation and blood flow
22. What is the difference between alveolar and arterial oxygen tensions?
PaO2 of healthy individuals breathing air at sea level is always about 5 to 10 mmHg less than the calculated PAO2
23. What is an anatomic shunt?
perfusion without ventilation
24. What is the value for the normal anatomic shunt?
3-5%
25. What is the normal respiratory exchange ratio?
0.8
26. How can the normal respiratory exchange ratio be altered?
Changes in blood flow
27. What is the ventilation to perfusion ratio?
• Comparison of PAO2 to PACO2.
• ideal ratio is 1.0 and indicates that ventilation and perfusion are in perfect balance. (ex. 10/10 = 1)
28. What is a high V/Q and a low V/Q?
• high V/Q indicates that ventilation is greater than perfusion. (ex. 10/5 = 2
• Here the PAO2 is higher and the PACO2 is lower than normal
• A low V/Q indicates that perfusion is greater than ventilation. (ex. 5/10 = 0.5)
• Here the PAO2 is lower, and the PACO2 is higher than normal
29. What are the effects of alterations of V/Q?
• High V/Q (to the right), R increases, PAO2 increases and PACO2 decreases. Gases in dead space areas are similar to that of inspired air.
• Low V/Q (curve to the left), R decreases, PAO2 decreases, and PACO2 increases. Gases in the shunt range are like that of mixed venous blood.
30. What are alveolar shunts and how do they compare to dead space?
• Alveolar shunts are exchange units with a V/Q of 0. They are not normal.
• Dead space has exchange units with a V/Q greater than 1, so if a shunt occurs, there is no ventilation, but normal perfusion
31. What are the normal regional differences that occur in the lung?
• Due mainly to gravity and thus are most evident in the upright posture
• Blood flow is 20 times greater at the base than at the apices
32. What are the perfusion variations?
both blood flow and ventilation increase from the top to the bottom of the lung, but blood flow increases proportionately more than ventilation
33. What are the ventilation variations?
With ventilation, the bases have about four times as much ventilation as the apices due to gravity's effect on pleural pressures
34. What are the differences between the mechanisms by which oxygen and carbon dioxide are transported in the blood?
• Blood carries oxygen in two forms:
• 1. dissolved in the plasma and erythrocyte intracellular fluid
• 2. combined with hemoglobin in the red blood cell (RBC): MAJORITY IS CARRIED HERE!

• Gaseous oxygen diffuses into the blood and dissolves in the plasma and erythrocyte fluid
• Most blood oxygen is transported in chemical combination with hemoglobin (Hb) in the erythrocytes
35. How do you calculate dissolved oxygen in the plasma?
• Dissolved oxygen (ml/dl) = PO2 X 0.003
• 0.003 is the solubility coefficient of oxygen at 1 mmHg in 100ml of plasma
36. Describe and calculate oxygen carrying capacity of hemoglobin.
• In whole blood, each gram of Hb can carry about 1.34 ml of oxygen.
• Average Hb is about 15 g/dl
• To compute the oxygen-carrying capacity of the blood we use the following formula:
• 1.34 ml/g X Hb = Hb O2 carrying capacity
• 1.34 ml/g X 15 g/dl = 20.1ml/dl
37. Define and compute oxygen saturation of hemoglobin.
• Saturation is a measure of the amount of available hemoglobin that is actually carrying oxygen.
• It is content (HbO2) divided by capacity (total hemoglobin) expressed as a percentage.
• SaO2 = [HbO2]___ x 100
• Total Hb

• Example: Total Hb = 15 g/dl and HbO2 = 7.5g/dl
• SaO2 (%) = 7.5____ X 100 = 50%
• 15
• This hemoglobin is 50% saturated so it is only carrying half its oxygen
38. What is the relationship of HbO2 and PO2 and the oxygen dissociation curve?
• Hb saturation with oxygen varies with changes in PO2
• Below 60mmHg, the curve steepens. Here, a small drop in PO2 causes a large drop in SaO2 indicating a lessening affinity for oxygen
39. How do you calculate total oxygen content of the blood?
• Must have three variables; (1) PO2, (2) total hemoglobin content (g/dl), and (3) hemoglobin saturation.
• CxO2 = (0.003 X PxO2) + (Hbtot x 1.34 X SxO2)
• CaO2 = (0.003 X 100) + 15 X 1.34 X 0.97
• CaO2 = (0.3) + (19.5)
• CaO2 = 19.8 ml/dl
40. What is normal arterial SaO2?
97 %
41. What is normal venous SvO2?
75%
42. What values occur at loading point for oxygen to hemoglobin occur?
PaO2 of 100 mmHg and SaO2 of 97%
43. What values occur at unloading point for oxygen to hemoglobin occur?
PvO2 of 40 mmHg and SvO2 of 73%
44. What is the normal arterial-venous oxygen content difference and what is its significance?
• 4-8, or 5 ml/dl and is the amount of oxygen given up by every 100 mls of blood on each pass through the tissues
• The C(a-v)O2 indicates the amount of oxygen removed in relation to blood flow
45. What are normal values for oxygen content of arterial and venous blood?
• Combined O2 (1.34 x 15 X SO2) 19.5 14.7
• Dissolved O2(PO2 X 0.003) 0.3 0.1
• Total O2 content 19.8 14.8 (difference of 5)
46. What is Fick's equation for calculating cardiac output?
• Qt = VO2______
• C(a-v)O2 X 10

• Qt is cardiac output (L/min)
• VO2 is whole-body consumption (ml/min)
• C(a-v)O2 is the arteriovenous oxygen contents difference (ml/dl)
• 10 converts ml/dl to ml/L

• Using a normal VO2 of 250 ml/min and a normal C(a-v)O2 of 5 ml/dl you can calculate the cardiac output:
• Qt = VO2___
• C(a-v)O2 X 10
• Qt = 250 ml/min________
• 5 ml/dl X 10
• Qt = 250 ml/min________
• 50 ml/L
• Qt = 5.0 L/min
47. What is normal VO2 value and normal C(a-v)o2?
250 ml/min; 5 ml/dl
48. What is the Significance of the C(a-v)O2?
If the oxygen consumption remains constant, a decrease in cardiac output will increase the C(a-v)O2 and if the cardiac output rises, the C(a-v)O2 will fall proportionately.
• blood pH,
• body temperature,
• erythrocyte concentration of certain organic phosphates (2,3 DPG),
• Hb structure variations
• Other substances combining with Hb (ex. carboxyhemoglobin)
50. How does a low pH (acidity) shift the oxyhemoglobin dissasociation curve and what happens from that shift?
• Right;
• When the curve shifts to the right, the % Hb sat for a given PO2 falls (decreased affinity for oxygen)
51. How does a high pH (alkalinity) shift the oxyhemoglobin dissasociation curve and what happens from that shift?
• Left;
• As the curve shifts to the left, the % Hb sat for a given PO2 rises (increased affinity of Hb for oxygen).
52. What is the Bohr effect?
alters the position of the HbO2 dissociation curve due to changes in blood pH. These changes enhance oxygen loading in the lungs and oxygen unloading in the tissues. As blood in the tissues picks up CO2, pH falls, the curve shifts to the right. With lower affinity for oxygen, Hb more readily gives up its oxygen to the tissues. Venous blood returning to the lungs, pH goes up to 7.40 and shifts the HbO2 curve back to the left to aid loading at the lungs.
55. What is P50?
• the partial pressure of oxygen at which the Hb is 50% saturated, at 7.40 pH
• Normal P50 is about 27 (26.6)mmHg
56. Where is 2,3-diphosphoglycerate (2,3-DPG) found, and what does it do?
found in the red blood cells. It stabilizes the deoxygenated Hb molecule, reducing its affinity for oxygen. Without 2,3-DPG normal oxygen unloading would be impossible
57. What does an increased 2,3-DPG cause and what causes an increase in it?
• shifts the HbO2 curve to the right, increased oxygen unloading or decreased affinity of Hb for oxygen
• Things that cause it:
• alkalosis
• chronic hypoxemia
• anemia
58. What does a decreased 2,3-DPG cause and what causes a decrease in it?
• shift the curve to the left, increased affinity of Hb for oxygen (loading)
• What causes this:
• acidosis
• banked blood-(stored blood)
59. What does increased P50 mean?
the curve is shifted to the right, increased unloading, decreased affinity of Hb for O2.
60. What does decreased P50 mean?
the curve is shifted to the left, increased affinity of Hb for O2 and decreased unloading
61. How many different abnormal hemoglobins are there and what percents are usually found in a healthy individual?
120; 15-40%
62. What causes methemoglobinemia and what are common symptoms?
nitrite poisioning; Blood looks brownish in color, and skin color is grayish
63. How much stronger is the affinity for CO than Oxygen?
200 times
64. Where does HbCO shift the HbO2 curve and how do we treat it?
• increasing oxygen concentration to decrease the half life of CO and to supersaturate the plasma to keep oxygen going to the tissues. Hyperbaric oxygen (HBO) is recommended for use, usually with patients of 25% or greater HbCO
65. What things will shift the HbO2 curve to the right?
• low pH (acidity)
• increase in body temperature
• increased 2,3-DPG
• increased P50
66. What things will shift the HbO2 curve to the left?
• high pH (alkalinity)
• decrease in body temperature
• decrease 2,3-DPG
• decreased P50
• HbCO
67. What things cause a decrease for affinity of O2?
• low pH (acidity)
• increase in body temperature
• increased 2,3-DPG
• increased P50
68. What things cause a increase for affinity of O2?
• high pH (alkalinity)
• decrease in body temperature
• decrease 2,3-DPG
• decreased P50
Opposite, if one is increase, the other will be decreased
70. In what forms is carbon dioxide transported in the blood and how much of it is usually transported?
• 3 forms:
• 1. dissolved in physical solution
• 2. chemically combined with protein
• 3. ionized as bicarbonate

Approximately 45 to 55 ml/dl
71. Hamburger phenomenon is the same as what?
Chloride shift
72. What is the Chloride shift?
the shifting of chloride ions (Cl-) from the plasma into the erythrocyte
73. Which form of carbon dioxide transport accounts for the highest amount of CO2 transported?
ionized as bicarbonate, 80%
74. How much carbon dioxide is transported as Carbaminohemoglobin?
12%
75. How much does dissolved carbon dioxide account for total carbon dioxide expelled from the lungs?
8%
76. What is significant of the Carbon Dioxide curve as opposed to the HbO2 Curve?
there is more direct relationship between partial pressure of CO2 and the amount of CO2 content in the blood
77. What is the Haldane effect?
the influence of oxyhemoglobin saturation on CO2 dissociation curve
78. The CO2 dissociation curve occurs along a linear or curved line?
linear
79. High SaO2 ________ the blood�s capacity to hold CO2, helping it unload at the lungs.
decreases
80. Lower SvO2 ________ the bloods capacity for CO2 aiding uptake at the tissues
increases
81. Hypoxia occurs when DO2 falls short of cellular needs due to what?
• (1) decreased of arterial blood content (hypoxemia),
• (2) decreased cardiac output or perfusion (shock or ischemia),
• (3) Abnormal cellular function prevents proper uptake of O2 (dysoxia)
82. What is the equation for Impaired Oxygen Delivery?
DO2 = CaO2 x Qt
83. What is hypoxia?
When oxygen delivery falls short of cellular needs
84. When does hypoxia occur?
• occurs when DO2 falls short of cellular needs. This is
• due to:
• (1) decreased of arterial blood content (hypoxemia),
• (2) decreased cardiac output or perfusion (shock or ischemia),
• (3) Abnormal cellular function prevents proper uptake of O2 (dysoxia)
85. What is hypoxemia?
when the partial pressure of oxygen in the arterial blood (PaO2)is decreased to lower than the predicted normal based on the age of the patient. It can also occur when there is an Impaired oxygen delivery also occurs in the presence of abnor-malities that prevent saturation of the Hb with oxygen.
86. What things cause hypoxemia?
• Low PIO2
• Hypoventilation
• V/Q imbalance (Low V/Q)
• Anatomic shunt
• Physiologic shunt
• Diffusion defect
• Normal aging
87. What is the most common cause of hypoxemia in patients with lung disease?
Low V/Q�s
88. What is Refractory hypoxemia?
an abnormal deficiency of oxygen in the arterial blood that is resistant to treatment; usually indicates the presence of right-to-left shunting
89. What is Responsive hypoxemia?
Hypoxemia that shows a significant increase in PaO2 from an increase in FIO2.
90. One may estimate the expected PaO2 in older adults by using the following formula: Expected PaO2 =
100.1 - (0.323 X Age in years)
91. Decreased of arterial blood content (hypoxemia).
factor that impairs oxygen delivery to the tissues
92. Decreased cardiac output or perfusion (shock or ischemia).
factor that impairs oxygen delivery to the tissues
93. Abnormal cellular function prevents proper uptake of O2 (dysoxia).
factor that impairs oxygen delivery to the tissues
94. What is diffusion defect?
thickening of the alveolar-capillary membrane, gas exchange is impeded
95. What causes diffusion defect?
Disorders of the alveolar-capillary membrane such as; pulmonary fibrosis, interstitial edema, and interstitial lung disease
96. What indicates diffusion defect and how can it be fixed?
• Low PaO2
• High P(A-a)O2 on air; resolves with O2
97. For low PiO2 (hypoxia), what is the lab assessment for it?
• PaO2 is low
• P(A-a)O2 gradient on room air and supplemental O2 are normal
• CaO2 is low
• CvO2 is normal (if cardiac output increases to compensate)
• Example: is travel to high altitudes; low barometric pressure, creating mountain sickness.
98. For hypoventilation (hypoxia), what is the lab assessment for it?
• PaO2 decreased
• Normal P(A-a)O2 on room air and supplemental O2
• CaO2 decreased
• CvO2 normal (if cardiac output increases to compensate)
99. What is VENTILATION/PERFUSION IMBALANCES (Low V/Q) caused by?
Perfusion in excess of ventilation; such as with bronchospasm, secretions in airway, and low volumes
100. What are the primary indicators for VENTILATION/PERFUSION IMBALANCES (Low V/Q)?
• Low PaO2
• High P(A-a)O2 on air; decreases with O2 :)
101. For VENTILATION/PERFUSION IMBALANCES (Low V/Q [hypoxia]), what is the lab assessment for it?
• PaO2 decreased
• P(A-a)O2 widened on room air but decreased widening with supplemental oxygen
• CaO2 is decreased
• CvO2 is normal (if cardiac output increases to compensate)
102. How can a Low V/Q be fixed?
supplemental O2
103. What is an Anatomical shunt?
• This is considered to be a true shunt
• Caused by:
• Blood flow between right and left sides of circulation; congenital heart disease
104. What are the primary indicators of Anatomical shunt?
• Low PaO2
• High P(A-a)O2 on room air; does not resolve with O2 :(
105. For Anatomical shunt (hypoxia), what is the lab assessment for it?
• PaO2 will be very low (if over 25-30% shunt)
• P(A-a)O2 is very wide and widens even further with supplemental oxygen (if over 25-30% shunt)
• CaO2 is decreased
• CvO2 is normal (if cardiac output increases to compensate)
106. As the shunted blood increases to 30%; it becomes ___________ to make up the oxygen of blood going by totally unventilated alveoli
impossible
107. What is a Physiologic shunt, what are the indicators, and can it be fixed with O2?
• Perfusion without ventilation; atelectasis, pneumonia, and pulmonary edema
• Low PaO2 High P(A-a)O2 on air; does not resolve with O2 :(
108. For Physiologic shunt (hypoxia), what is the lab assessment for it?
• Extremely low PaO2 (as % shunt increases)
• P(A-a)O2 widened with increased widening with supplemental O2 (as % shunt increases)
• CaO2 is low
• CvO2 is normal (if cardiac output increases to compensate)
109. What is the 50/50 rule of thumb?
If the oxygen concentration is more than 50% and the PaO2 is less than 50 mmHg, significant shunting is present; otherwise the hypoxemia is mainly due to a simple V/Q imbalance
110. What is HEMOGLOBIN DEFICIENCIES ABSOLUTE, and what are the primary indicators for it?
• Loss of hemoglobin (Hb) anemia; due to hemorrhage or inadequate erythropoiesis
• Low Hb content, Reduced CaO2
111. For HEMOGLOBIN DEFICIENCIES ABSOLUTE (hypoxia), what is the lab assessment for it?
• PaO2 may be normal or low
• P(A-a)O2 is normal both on and off oxygen
• CaO2 is low
• CvO2 is low
112. Progressive decreases in Hb causes large or small drops in CaO2?
large
113. What is HEMOGLOBIN DEFICIENCIES RELATIVE, and what are the primary indicators for it?
Abnormal hemoglobin; carboxyhemoglobin, methemoglobin, and abnormal hemoglobin (those causing left shift of oxyhemoglobin dissociation curve)

Abnormal SaO2 (done by co-oximeter), Reduced CaO2
114. For HEMOGLOBIN DEFICIENCIES ABSOLUTE (hypoxia), what is the lab assessment for it?
• PaO2 may be normal or decreased
• P(A-a)O2 gradient is normal on room air and oxygen
• CaO2 is reduced (co-oximeter)
• CvO2 is reduced (co-oximeter)
115. What is the difference between HEMOGLOBIN DEFICIENCIES ABSOLUTE, and RELATIVE?
absolute refers to a loss of Hb (anemia), relative refers to abnormal hemoglobins that cause a left shift of HbO2 curve
116. What is REDUCED BLOOD FLOW, and what are the primary indicators for it?
Decreased perfusion; (1) circulatory failure (shock) and (2) local reduction in perfusion such as MI, CVA (ischemia)

Increased (widened) C(a-v)O2, Decreased CvO2
117. For REDUCED BLOOD FLOW (hypoxia), what is the lab assessment for it?
• PaO2 is normal
• P(A-a)O2 is normal on room air and on oxygen
• CaO2 is normal
• CvO2 is decreased
• C(a-v)O2 is widened (increased)
118. What is DYSOXIA, and what are the primary indicators for it?
Dysoxia is a form of hypoxia in which the cellular uptake of oxygen is abnormally decreased. Cyanide poisoning (disruption of cellular enzymes) and tissue oxygen consumption dependent on oxygen delivery

Normal CaO2, Increased CvO2
119. For DYSOXIA (hypoxia), what is the lab assessment for it?
• PaO2 is normal
• P(A-a)O2 on room air and supplemental oxygen is normal
• CaO2 is normal
• CvO2 is increased
120. What is the primary goal of treating hypoxia?
to give sufficient oxygen to ensure that the patient is safe and his or her condition does not deteriorate
121. What is the treatment for various types of hypoxia?
• most can be solved with oxygen the only kind that can't are:
• Physiologic shunt
• Anatomical shunt
122. What causes for hypoxia have an extremely low PaO2 value attained from assessment?
Anatomical shunt (if over 25-30% shunt), and Physiologic shunt (as % shunt increases)
123. What causes for hypoxia have a normal OR low PaO2 value attained from assessment?
HEMOGLOBIN DEFICIENCIES ABSOLUTE and RELATIVE
124. What causes for hypoxia have a normal PaO2 value attained from assessment?
REDUCED BLOOD FLOW and DYSOXIA
125. What are the factors that impair carbon dioxide removal?
• decreased alveolar ventilation (VA) relative to metabolic needs
• Examples:
• hypercapnia and respiratory acidosis
126. What is the equation for Impaired CO2 removal?
PaCO2 = VCO2 / VA
127. 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
128. 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
129. What things will usually cause a decrease in Respiratory Rate (f), inturn causing a decrease in minute ventialtion (VE)?
Drug Overdose
130. What is Dead Space Ventilation?
• ventilation without perfusion or ventilation in excess of perfusion (high V/Q)
• (Vt - VDS) X f = VA
131. 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
132. 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
133. 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
134. 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
135. 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
136. End tidal CO2 (PETCO2) is usually 1 to _ mmHg less than PaCO2.
5
137. 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
138. 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
139. 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: 135209 Card Set: Gas Exchange and Transport Exam.txt Updated: 2012-02-16 17:39:17 Tags: CRAFTON HILLS COLLEGE RESP 135 Gas Exchange Transport Exam Folders: Description: CRAFTON HILLS COLLEGE RESP 135 Gas Exchange and Transport Exam Show Answers: