Term
| What is the major factor affecting the distribution of blood flow in the upright individual? |
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Definition
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Term
| What causes the A-a difference? |
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Definition
| The normal mismatching of perfusion and ventilation over the entire span of alveoli will lead to a lower PaO2 compared to a PAO2. |
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Term
| What is the pressure difference between the apex of the lung and the base for a standing individual? |
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Definition
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Term
| In what region of the lung is vascular pressure the highest? |
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Definition
| The bottom, due to gravity. |
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Term
| What is the cause of the increased resistance at low lung volumes? |
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Definition
| This is due to the compression of extra-alveolar vessels caused by increased pleural pressures and decreased traction of vessel connective tissue. Usually around 80 cm H2O/L/min. |
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Term
| What is the cause of increased resistance during high lung volumes? |
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Definition
| Increased alveolar pressure and compression of alveolar capillaries. Around 120 cm H2O/L/min. |
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Term
| What region of the lung has the highest level of blood flow? |
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Definition
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Term
| What determines the blood flow through the pulmonary capillaries? |
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Definition
| Determined by pressure differential between arterial and venous side as well as the alveolar pressure. |
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Term
| What is characteristic of Zone I? |
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Definition
PA>Pa>Pv
These areas rarely exist and if they do are considered dead space due to lack of perfusion. |
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Term
| What is characteristic of Zone II? |
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Definition
Pa>PA>Pv
Flow is determined by the difference between pulmonary artery pressure and alveolar pressure, independent of Pv. |
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Term
| What is characterstic of Zone III? |
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Definition
Pa>Pv>PA
Pulmonary venous pressure is greatest. Flow is determined by the usual intravascular pressure gradient (Pa-Pv). Capillaries have low resistance. |
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Term
| In the supine position the majority of the lung will be in Zone ___? |
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Definition
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Term
| With exercise and increased CO, what happens to perfusion throughout the lung? |
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Definition
| With increased perfusion come recruitment of more blood vessels in the upper portion of the lung which creates a more uniform blood flow throughout the lung. |
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Term
| What effect does increased pulmonary venous pressure have on distribution of blood flow in the lungs? |
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Definition
| Increases recruitment and distention of vessels in zones I and II. This leads to an overall more uniform perfusion throught the lungs. |
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Term
| What are the pressure relationships during inhalation and exhalation? |
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Definition
Inhalation - Thoracic cage volume increases, pleural pressure becomes more negative, alveolar pressure becomes negative
Exhalation - Thoracic cage volume decreases, pleural volume becomes less negative, alveolar pressure becomes positive |
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Term
| Where is ventilation most efficient? |
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Definition
| Base of the lung. This is because there is more lung tissue at the base as compared to the middle or apex. |
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Term
| Which is more affected by gravity: ventilation or perfusion? |
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Definition
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Term
| Progressing from the top of the lung to the bottom the pleural pressure becomes _______ negative. |
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Definition
| Less. (-10, -5, -2.5) going from top to bottom |
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Term
| Where are alveoli larger: base or apex? |
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Definition
| Alveoli are larger at the top of the lung since pleural pressures become less negative toward the base. Thus there is a larger gradient between atmosphere and alveoli at the top of the lungs. |
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Term
| What portion of the lung will receive the initial part of a tidal breath? |
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Definition
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Term
T/F
1. Ventilation increases 2 fold from top to bottom
2. Perfusion increases 1.5 fold from top to bottom
3. Top of the lung has a low V/Q ratio
4. Difference in V/Q ratios within the lung cause the A-a oxygen difference. |
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Definition
1. True
2. False. It increases 5 fold. Gravity has more effect on perfusion than ventilation
3. False. Has a higher V/Q ratio
4. True
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Term
| Why does tuberculosis re-activate in the apex of the lung? |
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Definition
| Because of the higher V/Q ratios, the apex has a higher PO2 which is preferential for TB proliferation. |
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Term
| What areas of the lung does emphysema cause the most damage? |
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Definition
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