#1 Zhu - Principles of Pulmonary Gas Transport Flashcards
What does Fick’s law measure?
What are the 5 components of Fick’s law?
DIFFUSION RATE Pressure Gradient Area Solubility (Intrinsic property of gas) Distance Molecular Weight FICK = FIVE
Which components of Fick’s law are inversely related to the diffusion rate?
Distance
Molecular Weight
What is the diffusion constant?
Solubility/(sqrt of Molecular Weight)
What does the diffusion capacity determine?
The diffusion capacity determines the ability of the respiratory membrane to transport a gas into and out of the blood.
What are the components of the diffusion capacity?
Area Solubility Distance Molecular Weight It can change due to change in area and/or change in distance.
Where does gas exchange happen?
Respiratory Unit
- Respiratory Bronchioles
- Alveolar Duct
- Alveolar Sac
In emphysema, what would you expect to happen to the diffusion rate and why?
Decreased diffusion rate due to decreased area.
In interstitial edema, what would you expect to happen to the diffusion rate and why?
Decreased diffusion rate due to increased distance.
In fibrosis, what would you expect to happen to the diffusion rate and why?
Decreased diffusion rate due to increased distance.
What is the vapor pressure based on a body temperature of 37 degrees Celsius?
47 mmHg
What is the PO2 of humidified air?
150 mmHg
(760-47) * 0.21
What is the PN2 of humidified air?
563 mmHg
(760-47) *0.79
What is the PO2 of alveolar air?
104 mmHg
What is the PCO2 of alveolar air?
40 mmHg
What is the PO2 in the arterial end of the capillary in the lung?
40 mmHg
What is the PO2 in the venous end of the capillary in the lung?
104 mmHg
What is the PO2 in the systemic arteries and why?
95 mmHg
Bronchial Circulation contamination
What is the PO2 in the arterial end of the capillaries in the peripheral tissue?
95 mmHg
What is the PO2 in the venous end of the capillaries in the peripheral tissue?
40 mmHg
How is O2 transported in the blood?
Dissolved (3%)
Hemoglobin (97%)
Hemoglobin F causes what kind of shift in the Oxygen-Hemoglobin Dissociation Curve?
Left shift
Easier to load O2
Increased Affinity
Hemoglobin S causes what kind of shift in the Oxygen-Hemoglobin Dissociation Curve?
Right shift
Easier to UNload O2
Decreased Affinity
A right shift in the Oxygen-Hemoglobin Dissociation Curve can be induced by?
1 - Increased H+
2 - Increased CO2
3 - Increased temperature
4 - Increased BPG (end product of RBC metabolism, increased in chronic hypoxia)
A left shift in the Oxygen-Hemoglobin Dissociation Curve can be induced by?
1 - Decreased H+
2 - Decreased CO2
3 - Decreased temperature
4 - Decreased BPG
What is the Bohr Effect and its components?
The Bohr Effect influences the binding of O2.
H+
CO2
What is the PCO2 at the arterial end of the pulmonary capillary?
45 mmHg
What is the PCO2 at the venous end of the pulmonary capillary?
40 mmHg
What is the PCO2 at the arterial end of the capillary in the peripheral tissue?
40 Hg
What is the PCO2 at the venous end of the capillary in the peripheral tissue?
45 mmHg
How is CO2 transported in the blood?
Dissolved (7%)
Hemoglobin (23%)
HCO3 (70%)
What maintains the electrical neutrality in the RBC when HCO3 diffuses out of the RBC?
Cl- diffusing into the RBC
This is referred to as the chloride shift.
How would exercise change the chloride shift?
increase
How do you calculate the alveolar ventilation?
Ventilation = Frequency (Tidal volume - Dead space)
4200 mL = 12 (500-350)
What determines the PO2 and PCO2 in alveolar air?
- Alveolar ventilation
2. Rate of O2 absorption and CO2 excretion
Describe the Haldane Effect.
Deoxygenation of the blood increases its ability to carry CO2.
What is the ventilation-perfusion ratio?
Alveolar Ventilation / Cardiac Output
4.2 L/min / 5.0 L/min = 0.8
When ventilation exceeds blood flow, the ventilation-perfusion ratio is (less than/greater than) 0.8.
Greater than 0.8 The space (the volume of air) does not participate in gas exchange.
What physiological factors would create a ventilation-perfusion ratio > 0.8? Pathophysiological?
Physiological: upper part of the upright lung
Pathophysiological: Obstruction or loss of blood flow
What physiological factors would create a ventilation-perfusion ratio less than 0.8? Pathophysiological?
Physiological: lower part of the upright lung
Pathophysiological: Obstruction to air flow
When blood flow exceeds ventilation, the ventilation-perfustion ratio is (less than/greater than) 0.8?
Less than 0.8
“Blood enters the arterial system without going through ventilated areas of the lung.”
